RBRC Events

Hosted by: Vivian Stojanoff

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Hosted by: Yacine Mehtar-Tani

Abstract: Recent work has found that entanglement minimization in low-energy baryon-baryon scattering leads to enhanced symmetry, which is distinct from large-N QCD expectations, and which is confirmed in lattice QCD simulations. I will review these developments and then I will present very recent work which considers implications of entanglement minimization for pion-pion and pion-baryon scattering.

Hosted by: Semeon Valgushev

Abstract: I will talk about three approaches to deepen our understanding of the high-baryon state of matter: The first one is the pQCD analysis with the effect of resummation. It is said that the pQCD EoS is uncertain unless the baryon density is unphysically large, but this is caused by an improper choice of small scale. A simple resummation can change the situation drastically to narrow the uncertainty band. The second one is the interacting hadronic model that complements the pQCD analysis, but an excluded volume effect with hard core would easily violate the causality. I will discuss that the Carnahan-Starling implementation of the smeared interacting core works well with phenomenology. Finally, I will introduce a bit of academic thinking about nuclear matter under strong magnetic fields described by the Skyrme model, which is however rather model independent in a sense that the important physics is brought in by the anomalous coupling between the density and the magnetic field.

Hosted by: Julia Gehrlein

Abstract: While the LHC has not discovered any new particles directly yet, hints for the violation of lepton flavour universality (satisfied within the SM) accumulated in recent years. In particular, deviations from the SM predictions were observed in semi-leptonic B decays (b->sll and b->ctau), in the anomalous magnetic moment of the muon (g-2), in leptonic tau decays and di-electron searches. Furthermore, also the deficit in first row CKM unitarity, known as the Cabibbo Angle Anomaly, can be interpreted as a sign of lepton flavour universality violation. In this talk I review the status of these anomalies and give an overview of the possible interpretations in terms of new physics models.

Hosted by: Yoshitaka Hatta

Abstract: This is not a lattice talk. Instead, I will present our recent development on how to formulate the quark Sivers function on Lattice based on the so-called large momentum effective theory. In particular, we argue the spin asymmetry defined as the ratio of the quark Sivers function over the spin averaged distribution can be directly calculated in terms of the relevant quasi distributions with the soft functions and perturbative matching kernels cancelling out. We will give explicit results at one-loop order, which reduces to a collinear expansion at twist-three level. This may lead to an alternative way to simulate the quark-gluon-quark correlation function (twist-3 distribution) on lattice. Reference: 2011.13397 [hep-ph]

Hosted by: Yacine Mehtar-Tani

Abstract: Any plasma in thermal equilibrium emits gravitational waves. In this talk, I show that, for wavelengths longer than the microscopic mean free path, the production is sourced by hydrodynamic fluctuations, while for wavelengths of the order of the inverse temperature it is sourced by scatterings. This latter mechanism is the leading one and I will show a consistent computation for a Standard Model plasma to leading order in coupling constants. I will show how the energy density of these thermally produced gravitational waves accumulates over the thermal history of the universe, contributes to the Neff parameter and constrains the highest temperature of the universe. The current theoretical uncertainty ?Neff ≤ 0.001 corresponds to Tmax ≤ 2e17 GeV. I will show throughout the presentation how the methods and physical picture are related to analogous calculations for the QCD plasma.

Hosted by: Julia Gehrlein

Abstract: The unitary PMNS matrix is the parametrization used for mixing of three active neutrinos. In case there are extra neutrinos which are heavy iso-singlets, the effective mixing matrix for the three active neutrinos will be non-unitary. As a result, the oscillation probabilities between the active neutrinos are modified from the probabilities obtained using the PMNS matrix. Long baseline neutrino experiments can probe the non-unitarity and constrain parameters of the model. We have analyzed the latest data from the NOvA and T2K experiments using both the unitary and non-unitary mixing scenarios. In this talk I will present results from our analysis and show that the tension between the oscillation data from these two experiments can be reduced when analyzing with non-unitary mixing of the neutrinos.

Hosted by: Yoshitaka Hatta

Abstract: Holographic description of QCD is capable of reproducing various hadronic observables. In this talk I will apply the holographic principle to multi-baryon systems, and attempt to derive important disciplines of nuclear physics: nuclear density saturation, nuclear binding energy and nuclear magic numbers.

Hosted by: Julia Gehrlein

Abstract: Axions and axion-like particles (ALPs) appear in many well-motivated extensions of the Standard Model (SM). Their couplings to SM particles can be described in a model-independent way using effective Lagrangians. I will discuss the RG evolution of these couplings from the new-physics scale down to low energies, as well as the first consistent matching of a generic ALP model onto the weak chiral Lagrangian. Phenomenological implications for flavor physics and for the anomalous magnetic moment of the muon will also be presented. Finally, I will describe how even a light ALP necessarily affects the RG evolution of the dimension-6 operators in the SMEFT starting at a high scale, and how this ALP-SMEFT interference can be used to systematically search for indirect ALP effects on precision observables.

Hosted by: Julia Gehrlein

Abstract: We compute the leading order hadronic vacuum polarization contribution to the muon magnetic moment from lattice QCD. The result is somewhat larger, than the traditional experimental data-driven determination (R-ratio method). The recent Fermi National Laboratory measurement of the muon magnetic moment, which has been claiming strong hint of new physics beyond the Standard Model, is now put into a different perspective. Our result is compatible with the no new physics scenario.

Hosted by: Julia Gehrlein

Abstract: The precise determination of the properties of the Higgs boson—the first and only elementary scalar particle we have observed—is among the highest priorities of the LHC programme and possible future colliders. I will present state-of-the-art precision calculations for Higgs production in the gluon-fusion process and discuss their impact on the interpretation of hadron-collider data.

Hosted by: Semeon Valgushev

Abstract: Gradient flow is a smoothing procedure that suppresses ultraviolet fluctuations of gauge fields. It is often used for high-precision scale setting and renormalization of operators in lattice QCD calculations. The gradient flow equation is defined on the SU(3) manifold and therefore requires geometric, or structure-preserving, integration methods to obtain its numerical solutions. I discuss the properties of the three-stage third-order Runge-Kutta integrator introduced by Luescher (that became almost the default choice in lattice QCD applications) and its relation to structure-preserving integrators available in the literature. I demonstrate how classical low-storage Runge-Kutta methods can be turned into structure-preserving integration methods and how schemes of order higher than three can be built. Based on the properties of the low-storage schemes I discuss how the methods can be tuned for optimal performance in lattice QCD or any other applications.

Hosted by: Julia Gehrlein

Abstract: The smallness of the cosmological constant has yet to be understood in our current theories of nature. I will argue that a dynamical (and non-antropic) explanation suggests that today's dark energy has a dynamical component. I will show that if dark energy evolves in time, its dynamical component could be dominated by a bath of dark radiation. Within current constraints this radiation could have up to ∼103 times more energy density than the cosmic microwave background. I will show models that produce different forms of dark radiation such as hidden photons, milli-charged particles and even Standard Model neutrinos. I will also show that the late-time cosmology is potentially distinguishable from a cosmological constant or normal quintessence. If the radiation couples to the standard model, it may be directly testable in laboratory experiments!

Hosted by: Julia Gehrlein

Abstract: The production of dark matter via thermal decoupling from the primordial plasma, and the direct, indirect and collider signals associated with this mechanism, have been the pillars of dark matter phenomenology in the past decades. In sharp contrast to the sub-TeV regime, the interactions of thermal-relic dark matter with multi-TeV or larger mass manifest as long-range. This is supported by unitarity arguments, and shown by explicit calculations in WIMP and other models. The long-range nature of the interactions gives rise to non-perturbative effects, with the most prominent being the existence of bound states. The formation and decay of unstable bound states in the early universe decrease the dark matter density, thereby changing its predicted mass and/or couplings. This can have severe implications for all experimental probes, particularly for collider and indirect searches.

Hosted by: Yacine Mehtar-Tani

Abstract: High-energy Operator Product Expansion is a formalism to study scattering amplitudes at high-energy (Regge limit) in perturbation theory. When it is applied to the product of two electromagnetic currents, we may write the unpolarized DIS amplitude as a convolution of coefficient functions and matrix elements of Wilson lines. The energy dependence of the cross-section is encoded in the Balitsky-Kovchegov evolution equation. To study polarized scattering processes one has to include sub-eikonal corrections into the OPE formalism. I will discuss the OPE of two electromagnetic currents with sub-eikonal terms: I will present new impact factors, matrix elements of new operators which are parametrized by new quark and gluon distributions, and present new high-energy evolution equations.

Hosted by: Julia Gehrlein

Abstract: Recent results from LHCb and B-factories hint at violation of Lepton Flavor Universality (LFU) in both tree-level and loop-induced B-meson decays. After a brief review of the status of these anomalies, we will discuss the minimalistic scenarios of New Physics at the O(TeV) scale which involve one leptoquark state (LQ) and which are consistent with a number of measured low energy flavor physics observables, as well as with the direct searches at the LHC. We will show which LQ can provide acceptable solution to these anomalies, and make predictions regarding the lepton flavor violating decay modes that can be probed experimentally and therefore test the validity of the proposed scenarios.

Hosted by: Yacine Mehtar-Tani

Abstract: We review and revisit the concept of charge distribution in the relativistic context. Adopting a phase-space perspective allows us to discuss the momentum dependence of these distributions and to connect the well-known pictures in both the Breit frame and the infinite-momentum frame. In particular, we explain why the center of the neutron charge distribution appears to be negative in the infinite-momentum frame and positive in the Breit frame.

Hosted by: Julia Gehrlein

Abstract: As we all eagerly await the results of the Fermilab g-2 experiment, I will entertain the possibility that the long-standing discrepancy between the theoretical and experimental values of the muon anomalous magnetic moment arises from new physics. I will argue that the value of the discrepancy imposes a firm boundary on the parameter space of any new physics explanation, such that observables which confirm the anomaly are guaranteed through a combination of muon fixed-target and collider experiments up to 30 TeV center of mass energy. I will further explain that if new particles are not seen directly (either through missing energy or new charged tracks) at a 30 TeV muon collider, this would indicate an explicit fine-tuning problem in the Higgs potential arising from finite, well-defined quantum corrections and would provide persuasive evidence that nature is fine-tuned.

Hosted by: Yoshitaka Hatta

Abstract: Due to the discovery of renormalon cancelation, understanding of the heavy quark mass and interquark force was improved drastically around 1998. I overview what was understood then and theoretical progress that took place after it. We show how to extract genuine UV part of the leading Wilson coefficient in OPE of the static QCD potential and how it improves the theory prediction in the range r*Lambda_QCD

Hosted by: Julia Gehrlein

Abstract:Measuring the mass of the W boson is an important check on the consistency of the Standard Model. The target precision for measurements of the W boson mass at the Large Hadron Collider is O(10 MeV), i.e. about 0.1 per mille. Achieving this degree of precision will require extremely good theoretical control on all aspects of vector boson production, including the simultaneous effects of QCD and electroweak corrections. I will describe a recent calculation of these mixed QCD-EW corrections to W and Z boson production, and discuss their impact on the measurement of the W boson mass.

Hosted by: Julia Gehrlein

Abstract: Hawking radiation offers a unique method of neutrino production, unlike any weak interaction process. Moreover, black hole evaporation depends on whether neutrinos are Dirac or Majorana, providing a different phenomenology in each case. If neutrinos are Dirac particles, the emission of the light right-handed states does not suffer from the helicity suppression present in weak interactions. Hence, it is possible to have a significant fraction of such states as relics from the Early Universe. On the other hand, if neutrinos are Majorana, heavy right-handed states like those appearing in the seesaw mechanism can be produced by a black hole, altering thermal leptogenesis and thus the baryon asymmetry. In this talk, we will explore these two different possibilities.

Hosted by: Yoshitaka Hatta

Abstract: I will discuss issues related to the proton mass decomposition and in particular, the role played by the anomalous term. I will first show that the form of the mass decomposition crucially depends on the regularization scheme, or more precisely , depends on whether there is a cutoff in temporal direction. I will show that in symmetric cutoff theory, the existence of an anomalous term is manifest and can be traced back to the construction of isotropic cutoff theory. Then I will use 1+1 non-linear sigma model in large N limit as an example to demonstrate the above points by studying the mass structure in various cutoff schemes. I will argue that the mass generation through trace anomaly can be viewed as dynamical higgs effect. Finally, I will comment on the possibility of probing the gluon content of nucleon through photo production of Ji/Psi.

Hosted by: Julia Gehrlein

Abstract: Drell-Yan production of a charged lepton pair is a key process at the Large Hadron Collider. The region of large invariant mass region is of particular interest for new physics searches, which motivates precise theory predictions at energies well above the Z resonance. In this talk, I discuss our recent calculation of the mixed electroweak-QCD two-loop amplitudes for the process qq->l+l- as a further step in this direction. I present the calculation in two different approaches, the 't Hooft-Veltman-Breitenlohner-Maison (HVBM) gamma5 scheme and Kreimer's anticommuting gamma5 scheme, and discuss how one arrives at scheme-independent results. Solving the master integrals in terms of multiple polylogarithms of algebraic arguments, we obtain fully analytic results for the helicity amplitudes, which allow for fast and robust numerical evaluations in Monte-Carlo programs.

Hosted by: Akio Tomiya

Abstract: Jet substructure techniques are powerful tools to probe the perturbative regime of jet evolution in proton-proton and heavy-ion collisions. Over the past few years, a wide variety of substructure observables have been proposed in order to pin down specific aspects of jet dynamics in a quark-gluon plasma. In this talk, I will review some of them, such as Soft Drop, Lund plane and Dynamical Grooming observables. Within a factorized picture for jet radiations in a dense medium, I will try to highlight the main perturbative mechanisms which drive the medium modifications of these observables.

Hosted by: Yoshitaka Hatta

Abstract: The D-term is, like mass and spin, one of the particle properties directly related to the matrix element of the energy-momentum tensor. But, unlike mass and spin, nearly nothing is known about this property experimentally. This fact as well as the physically appealing interpretation of the D-term form factor in terms of the mechanical forces inside hadrons has triggered a lot of interest in literature. Recent theoretical, phenomenological and experimental advances are presented.

Hosted by: Peter Boyle

Abstract: The Monte Carlo methods used in Lattice QCD simulations rely on the rotation of the path integral to Euclidean metric. Unfortunately, the limited knowledge of correlation functions on finite subsets of points prevents a direct analytic continuation to Minkowski signature. In their seminal publication of 1990, Maiani and Testa showed that physical amplitudes away from threshold cannot be directly extracted, ie without an inverse problem, from Euclidean correlators, due to off-shell contaminations. In this presentation, I revisit and extend their original work, and explore the connection with recent developments on the inverse problem in Lattice QCD.

Hosted by: Yacine Mehtar-Tani

Abstract: The quark-gluon plasma (QGP) created in high-energy heavy-ion collisions at RHIC and LHC is opaque to energetic and heavy particles that are created in short-distance particle scattering. Jets, aligned collections of energetic hadrons resulting from the fragmentation of fundamental quarks and gluons that are collected within a cone of radius R, are of special interest since they develop on time-scales comparable to the lifetime of the plasma. Jet ``quenching'', or the suppression of the jet yield at large transverse momentum, is therefore a probe not only of the elastic and inelastic interactions with the medium, but also of the medium's capability to resolve correlated QCD color charges. The energy removed from the jet is redistributed in modes that span hard collinear gluon radiation (bremsstrahlung) to softer excitations that ultimately thermalize with the surrounding medium. The radius dependence of the jet spectrum is particularly sensitive to the rich physics outlined above. In the first part of the talk, I will present a recent calculation of the jet spectrum in heavy-ion collisions where the medium parameters are sampled from a realistic hydrodynamic evolution of the QGP. Up to relatively large radii R~0.6, the suppression is dominated by perturbative physics while non-perturbative effects, related to the details of thermalization, start to dominate at R~1. This provides, for the first time, a solid basis for higher-order precision calculations of the jet spectrum that are paramount to realize the potential of hard probes as precision tools to extract the properties of the QGP. However, jets are rare events and their spectrum drops rapidly with transverse momentum. This induces a strong bias on any process happening in the medium and makes it hard to dig out rare events where heavy-ion jets were substantially modified. In the second part of my talk, I will report on a recent attempt to extract the jet energy before quenching using machine learning. This allows to reduce the biases and enhance the signal of medium modifications. It also allows to better constrain jets as tomographic tools of the medium.

Hosted by: Julia Gehrlein

Abstract: Determining the thermal history of electroweak symmetry breaking (EWSB) is a key task for particle physics and cosmology. In the Standard Model, EWSB occurs via a crossover transition. In many scenarios for beyond the Standard Model (BSM) physics, however, the nature of the transition and pattern can differ, with important implications for baryogenesis and gravitational wave generation. I give generic arguments for why most BSM physics that leads to such an alternate history will be accessible at the LHC and next generation colliders. I also discuss recent developments in effective field theory and nonperturbative computations that are essential for a robust confrontation of theory with experiment.

Hosted by: Akio Tomiya

Abstract: We employ the functional renormalization group approach formulated on the Schwinger-Keldysh contour to calculate real-time correlation functions in scalar field theories. We provide a detailed description of the formalism, discuss suitable truncation schemes for real-time calculations as well as the numerical procedure to self-consistently solve the flow equations for the spectral function. Subsequently, we discuss the relations to other perturbative and non-perturbative approaches to calculate spectral functions, and present a detailed comparison and benchmark in d=0+1dimensions.

Hosted by: Semeon Valgushev

Abstract: It has been over three decades since the first two-baryon studies from lattice QCD were performed. Despite algorithmic improvements and increases in computational resources since then, there remains disagreement on results from various groups in the lattice community. A major barrier in resolving these discrepancies is the poor signal-to-noise ratio for baryons, which needs to be overcome with modern methods. In this seminar, I will begin by covering various techniques and formalism that have become standard in lattice spectroscopy. This will include the use of distillation (and its stochastic variant) to treat all-to-all quark propagation; a variational method, which can help to reduce unwanted excited states while allowing for several desired states to be extracted; and the L\"uscher two-particle formalism, which relates finite-volume energies to infinite-volume scattering amplitudes. I will then present our recent results for two nucleon S-wave interactions in both isospin channels, computed at the SU(3)-flavor-symmetric point corresponding to mπ≈714 MeV. These results strongly disfavor the presence of any bound states at this pion mass, which contradicts some of the calculations in the literature. Further, our recent results for the H dibaryon—-also using an SU(3)-symmetric setup, but corresponding to mπ≈420 MeV—-show appreciable dependence on the lattice spacing. This could explain some of the discrepancies in the literature. However, I will discuss other possibilities, as well as future directions for spectroscopy.

Hosted by: Akio Tomiya

Abstract: Recent advances in machine learning have begun creating new bridges to physics and mathematics that have traditionally existed between the latter two. Given this progress, I will speculate about where we are and where things might be headed, including through the recently launched NSF AI Institute for Artificial Intelligence and Fundamental Interactions. Specifically, I'll survey well-known machine learning results in supervised learning, reinforcement learning, and generative models, and explain cases where these techniques are already impacting physics and math. In more detail, I will explain some remarkable similarities between neural networks and quantum field theory that might point towards a theoretical understanding of deep learning, and also how an AI agent's ability to unknot headphones might provide useful in cracking a foundational problem in topology.

Hosted by: Yacine Mehtar-Tani

Abstract: The Drell-Yan hadronic tensor for electromagnetic (EM) current is calculated in the Sudakov region s»Q2»q2⊥ with 1Q2 accuracy, first at the tree level and then with the double-log accuracy. It is demonstrated that in the leading order in Nc the higher-twist quark-quark-gluon TMDs reduce to leading-twist TMDs due to QCD equation of motion. The resulting tensor for unpolarized hadrons is EM gauge-invariant and depends on two leading-twist TMDs: f1 responsible for total DY cross section, and Boer-Mulders function h⊥1. The order-of-magnitude estimates of angular distributions for DY process seem to agree with LHC results at corresponding kinematics.

Hosted by: Yoshitaka Hatta

Abstract: I develop an Effective Field Theory (EFT) framework to compute jet substructure observables for heavy ion collision experiments. I consider dijet events that accompany the formation of a Quark Gluon Plasma(QGP) medium in a heavy ion collision and look at the simultaneous measurement of jet mass along with the transverse momentum imbalance between the jets accounting for both vacuum and medium evolution. Treating the energetic jet as an open quantum system interacting with a QGP bath, I write down a factorization formula within the SCET(Soft Collinear Effective Theory) framework for the reduced density matrix of the jet in the Markovian approximation. This allows a resummation of large logarithms that arise due to the final state measurements imposed while simultaneously summing over multiple interactions of the jet with the medium. I will discuss the novel IR structure of the medium modified jet function that arises in this factorization approach.

Hosted by: Julia Gehrlein

Abstract: Neutrino oscillations are precision probes of new physics. Apart from neutrino masses and mixings, they are also sensitive to possible deviations of low-energy interactions between quarks and leptons from the Standard Model predictions. I will present a systematic description of such non-standard interactions (NSI) in oscillation experiments using an Effective Field Theory (EFT) approach. The relation with the traditional NSI formalism will be clarified. As a phenomenological example, I will discuss the application of this framework to short baseline reactor experiments such as Daya Bay. Bounds on operators of the Standard Model EFT will be extracted and compared with other probes.

Hosted by: Akio Tomiya

Abstract: The weak value, proposed by Aharonov et al. in 1988, has been applied for various fields of physics for the purpose of precision measurement, which is made possible with the help of the 'postselection' specifying actively the final state in the physical process. Here we have considered the feasibility of applying the weak measurement in high energy particle physics, especially in measuring the CP-violating parameters in B meson decays, where the effective lifetime of the decay mode is expected to be prolonged statistically due to the postselection. Our analysis shows that, when adopted in the Belle II experiment at the SuperKEKB collider, the effective lifetime may be prolonged up to 2.6 times, and that the measurement precision of the CP-violating parameters may be improved by about 20%.

Hosted by: Akio Tomiya

Abstract: How axial anomaly manifests itself in the two-point correlation functions of iso-triplet scalar and pseudo-scalar mesons affects the nature of chiral phase transition. In this talk we first review current status on the fate of UA(1) anomaly in the finite temperature lattice QCD, and then present a first continuum and chiral extrapolation of two UA(1) measures in (2+1)-flavor lattice QCD at 1.6Tc. After continuum and chiral extrapolations we find that axial anomaly remains manifested in the 2-point correlation functions of scalar and pseudo-scalar mesons in the chiral limit. To study the origin of the axial anomaly we propose novel relations between the quark mass derivatives of Dirac eigenvalue spectrum ρ and correlation functions among eigenvalues. We find that the peak structure developed in ρ in the infrared region with its height proportional to quark mass squared is responsible for the manifestation of axial anomaly. These findings suggest that the axial anomaly is driven by the weakly interacting (quasi-)instanton gas motived ρ at T>1.6Tc and the chiral phase transition belongs to 3-d O(4) universality class. The talk is based on https://arxiv.org/abs/2010.14836.

Hosted by: Semeon Valgushev

Abstract: It has been widely believed that the relativistic Navier-Stokes equations violate the basic physical requirements of equilibrium stability and causality, and therefore can not be used for practical simulations of relativistic fluids. In this talk, I will discuss why this belief is unfounded. There is not one, but infinitely many Navier-Stokes equations because there are infinitely many conventions that can be used to define what one means by "fluid temperature", "fluid velocity" etc. out of equilibrium. The early works on relativistic hydrodynamics (Eckart, Landau-Lifshitz) have indeed adopted conventions that lead to unphysical predictions. On the other hand, when one adopts physically sensible conventions, the resulting relativistic Navier-Stokes equations are both stable and causal.

Hosted by: Akio Tomiya

Abstract: Using the CGC effective theory together with the hybrid factorisation, we study forward dijet production in proton-nucleus collisions beyond leading order. In this paper, we compute the "real" next-to-leading order (NLO) corrections, i.e. the radiative corrections associated with a three-parton final state, out of which only two are being measured. To that aim, we start by revisiting our previous results for the three-parton cross-section presented in our previous paper. After some reshuffling of terms, we deduce new expressions for these results, which not only look considerably simpler, but are also physically more transparent. We also correct several errors in this process. The real NLO corrections to inclusive dijet production are then obtained by integrating out the kinematics of any of the three final partons. We explicitly work out the interesting limits where the unmeasured parton is either a soft gluon, or the product of a collinear splitting. We find the expected results in both limits: the B-JIMWLK evolution of the leading-order dijet cross-section in the first case (soft gluon) and, respectively, the DGLAP evolution of the initial and final states in the second case (collinear splitting). The "virtual" NLO corrections to dijet production will be presented in a subsequent publication.

Hosted by: Semeon Valgushev

Abstract: The observed mass and radius relations of neutron stars can be explained remarkably well using a model of dense matter known as quarkyonic matter. I describe how the quarkyonic model can arise dynamically from an excluded volume model for nuclear interactions. I also discuss how thermal effects can be incorporated in such a model.

Hosted by: Akio Tomiya

Abstract: Deeply virtual Compton scattering (DVCS) is a powerful channel to study the spatial structure of protons and nuclei at the future Electron-Ion Collider (EIC). In the collinear framework, DVCS is dependent on the quark and gluon generalized parton distributions (GPDs). At small x, these objects are closely related to the dipole correlator of Wilson Lines [1]. It is well known that the transverse momentum spectrum of DVCS at small x gives access to the impact parameter dependence of the dipole correlator. In [2], it was shown that by studying the azimuthal anisotropies of the final state photon with the electron plane in DIS one could also access the angular dependence of the dipole correlator. This information is crucial to unveil the structure of the orbital angular momentum carried by gluons inside hadrons and nuclei. In this talk, I will review the computation of DVCS at leading order in the CGC EFT, including the azimuthal angular correlations with respect to the electron plane. Then, I will show how to obtain similar expressions for exclusive vector meson production. I will then present our predictions for these anisotropies in electron-proton and electron-gold collisions for the kinematics of the future EIC. Finally, I will discuss the potential to measure the angular structure of color charge and geometric fluctuations in incoherent diffractive production. This talk is based on [3]. References: [1] Probing the Small-x Gluon Tomography in Correlated Hard Diffractive Dijet Production in DIS. arXiv:1601.01585 [2] Gluon Tomography from Deeply Virtual Compton Scattering at Small-x. Y. Hatta, B-W. Xiao, and F. Yuan. arXiv:1703.02085 [3] Gluon imaging using azimuthal correlations in diffractive scattering at the Electron-Ion Collider. H. Mäntysaari, K. Roy, F. Salazar, and B. Schenke. arXiv:2011.0246.

Hosted by: Yacine Mehtar-Tani

Collisions between heavy atomic nuclei at ultra-relativistic energies are carried out at particle colliders to produce a state of matter where quarks and gluons, the color degrees of freedom, are not bound - the quark–gluon plasma. This state is thought to be produced as a transient phenomenon before it fragments into thousands of particles that reach the particle detectors. I show how the thermodynamic properties of this transient state can be reconstructed from the information collected in detectors: The matter created in lead–lead collisions at the Large Hadron Collider at CERN is found to reach a temperature as high as 2.6 trillion degrees, the highest ever recorded in the laboratory. The value of the entropy density at this temperature, estimated from experimental data, agrees quantitatively with first-principles calculations from quantum chromodynamics. These results confirm that a deconfined phase of matter is indeed produced, in which sound waves propagate at half the speed of light.

Hosted by: Akio Tomiya

We investigate the axial U(1) anomaly of two-flavor QCD at temperatures 190–330 MeV. In order to preserve precise chiral symmetry on the lattice, we employ the M¨obius domain-wall fermion action as well as overlap fermion action implemented with a stochastic reweighting technique. Compared to our previous studies, we reduce the lattice spacing to 0.07 fm, simulate larger multiple volumes to estimate finite size effect, and take more than four quark mass points, including one below physical point to investigate the chiral limit. We measure the topological susceptibility, axial U(1) susceptibility, and examine the degeneracy of U(1) partners in meson and baryon correlators. All the data above the critical temperature indicate that the axial U(1) violation is consistent with zero within statistical errors. The quark mass dependence suggests disappearance of the U(1) anomaly at a rate comparable to that of the SU(2)L × SU(2)R symmetry breaking. This talk is based on a work in JLQCD collaboration, arXiv:2011.01499.

Hosted by: Yacine Mehtar-Tani

Abstract: I will discuss the conditions under which Higgs and confining regimes in gauge theories with fundamental representation matter fields can be sharply distinguished. It is widely believed that these regimes are smoothly connected unless they are distinguished by the realization of global symmetries. However, I will show that when a U(1) global symmetry is spontaneously broken in both the confining and Higgs regimes, the two phases can be separated by a phase boundary. The phase transition between the two regimes may be detected by a novel topological vortex order parameter. I'll illustrate these ideas by explicit calculations in gauge theories in three spacetime dimensions, and then explain the generalization to four dimensions. One important implication of our results is that nuclear matter and quark matter are sharply distinct phases of QCD with an approximate SU(3) flavor symmetry.

Hosted by: Akio Tomiya

The usual calculation method of field theory relies on Lagrangian under a certain symmetry. Then, one can obtain amplitudes by using Feynman rules and diagrams. In contrast, a method called "scattering amplitudes" (on-shell amplitudes, modern amplitude method, or spinor-helicity formalism) provides the amplitudes directly from symmetries without relying on Lagrangian. For example, a calculation of gluon n-point scattering amplitudes can be greatly reduced in this method. The scattering amplitude approach is expected to extract some essences in field theory, which are not obvious in the usual Feynman methods. Conventional scattering amplitude methods are the theory for massless particles, basically. In 2017, this method was generalized to involve massive particles by Nima Arkani-Hamed group. In this talk, first, I will provide a brief review of the scattering amplitudes. Next, I will introduce the scattering amplitude calculations connected with electroweak symmetry breaking, which are related to masses, vev, and longitudinal waves, by using the generalized method. In particular, we do not use Lagrangian. We derived (strictly speaking, re-derived) several equations for electroweak symmetry breaking that are supposed to be inherent in field theory. This talk is based on arXiv:1909.10551 and arXiv:2008.09652.

Hosted by: Yoshitaka Hatta

Abstract: This talk discusses some recent results in the thermodynamics of QCD in the limit where the number of colors,Nc, is large. It has long been known that there are very strong reasons to believe that large Nc QCD, unlike QCD with Nc=3, has a first order phase transition at zero chemical potential. This implies the existence of metastable superheated and supercooled regimes. Recently some remarkable properties of these phases have been elucidated, most dramatically the fact that the metastable supercoloed plasma phase at large Nc will have negative absolute pressure—a pressure below that of the vacuum.

Hosted by: Akio Tomiya

Abstract: How axial anomaly manifests itself in the two-point correlation functions of iso-triplet scalar and pseudo-scalar mesons affects the nature of chiral phase transition. In this talk we first review current status on the fate of UA(1) anomaly in the finite temperature lattice QCD, and then present a first continuum and chiral extrapolation of two UA(1) measures in (2+1)-flavor lattice QCD at 1.6Tc. After continuum and chiral extrapolations we find that axial anomaly remains manifested in the 2-point correlation functions of scalar and pseudo-scalar mesons in the chiral limit. To study the origin of the axial anomaly we propose novel relations between the quark mass derivatives of Dirac eigenvalue spectrum ρ and correlation functions among eigenvalues. We find that the peak structure developed in ρ in the infrared region with its height proportional to quark mass squared is responsible for the manifestation of axial anomaly. These findings suggest that the axial anomaly is driven by the weakly interacting (quasi-)instanton gas motived ρ at T>1.6Tc and the chiral phase transition belongs to 3-d O(4) universality class. The talk is based on https://arxiv.org/abs/2010.14836.

Hosted by: Yoshitaka Hatta

In this talk I will report our recent results on the computation of the heavy quark momentum diffusion coefficient from the correlator of two chromoelectric fields attached to a Polyakov loop in pure SU(3) gauge theory on lattice. We measured the diffusion coefficient on very wide range of temparatures from 1.1Tc to 10^4Tc. We see an agreement to perturbation theory at very high temperatures and can for the first time fit a temperature dependence of this quantity.

Hosted by: Yoshitaka Hatta

Abstract:Fluctuations are important measures in relativistic heavy-ion collisions, in particular near the QCD critical point. In this talk, I will discuss the state-of-the-art formalism for the deterministic fluctuating hydrodynamics, and connect it to the ongoing Beam Energy Scan Program at RHIC. I will also address recent progress in the dynamics of non-Gaussian fluctuations.

Hosted by: Akio Tomiya

Abstract: We study the fragmentation (far forward/backward) region of heavy-ion collisions by considering an at-rest nucleus which is struck by a relativistic sheet of colored glass. By means of a simple classical model, we calculate the subsequent evolution of baryons and the associated radiation. We confirm that the struck nucleus undergoes compression and that the dynamics of the early times of the collision are best described by two separate fluids as the produced radiation's velocity distribution is very different to the velocity distribution of the matter in the struck nucleus. (Based on https://arxiv.org/abs/2009.05680)

Hosted by: Yoshitaka Hatta

Abstract: I will discuss what we have so far learned about the QCD phase diagram by studying correlations and fluctuations. I will also address recent progress in relating lattice QCD results to actual measurements.

Hosted by: Yoshitaka Hatta

Abstract: Symmetries of the weak sector of the Standard Model and its completeness find an exact mathematical realization in the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) quark mixing matrix. Of various relations among its elements, the top-row unitarity relation is by far the one known with the highest precision. The last few years have seen a rapid development in both the theory and experiments related to the extraction of the top-row CKM matrix elements and the respective unitarity relation, as quoted in the 2020 PDG: |V_{ud}|^2+|V_{us}|^2+|V_{ub}|^2=0.9985(3)_{V_{ud}}(4)_{V_{us}}. The apparent 3sigma deviation from unitarity points towards the possibility of BSM physics. Therefore, it is important to further reduce all the SM uncertainties in both V_{ud} and V_{us} in order to reach a level sufficient to claim a discovery. This involves a better understanding of various QCD matrix elements that enter the beta decays of neutron, nuclei and kaon, in particular those governing the electromagnetic radiative corrections (EMRC) in such processes. In this talk I will briefly describe the recent progress along this direction and discuss possible improvements in the future.

Hosted by: Yacine Mehtar-Tani

Abstract: With the future electron-ion collider data estimated to arrive in a decade, the need for theoretical and phenomenological tools to understand deep inelastic scattering (DIS) events has never been more urgent. In this seminar I will discuss early steps towards this direction. Specifically, I will focus on the adaptation to DIS of: i) the modified MassDrop Tagger grooming algorithm (mMDT) ii) and energy-energy correlation (EEC) event shape. Our adaptation relies on the geometrical separation of initial and final state radiation in the Breit frame, where I will establish the definitions of the proposed observables. The novel grooming procedure, although similar to mMDT, employs the Centauro measure used in the novel jet algorithm tailored to the needs of DIS. The groomed 1-jettiness will also be discussed.

Hosted by: Semeon Valgushev

Confirming or ruling out the existence of deconfined quark matter inside neutron stars is one of the most prominent open problems in nuclear astrophysics. While the ultimate goal continues to be the observation of a smoking gun signal directly indicating the presence or creation of quark matter, a more indirect approach to the problem has lately become feasible. By combining ab-initio theoretical results for the microscopic properties of dense QCD matter with the latest astrophysical measurements of neutron star properties, it is possible to build stringent model-independent constraints for the material properties of neutron-star matter at different densities. Presenting results from a very recent analysis of this kind, we argue that matter in the cores of the heaviest stable neutron stars has characteristics considerably closer to the predicted properties of deconfined quark matter than those of nuclear matter. The implications of this finding as well as potential ways of improving its accuracy are also discussed.

Hosted by: Yoshitaka Hatta

With data for small system collectivity getting ever more precise and diverse, and new experiments such as the EIC promise data with unprecedented geometric control, Monte Carlo generators face the requirement of a space-time picture of the initial state, to complement the more traditional momentum-space one. In this seminar I will present how the Muller dipole model has been used to that effect, previously in the DIPSY event generator, and is now being used in PYTHIA as well. Since all parameters of the model can be fitted to inclusive quantities, it offers a solid starting point for such efforts. Furthermore, since the model calculates projectile and target Fock states event-by-event, color fluctuations of the nucleon-nucleon, or γ*-nucleon, cross-section comes about as a by-product. Finally, once there is an initial space-time structure, a mechanism is needed to transport initial state anisotropies to the final state. Over the past years we have developed a model based on interacting strings, with exactly this aim. I will discuss recent developments, with a focus on response to initial state geometry, and similarities to hydro.

Hosted by: Yoshitaka Hatta

We present a reformulation of an SU(2) Hamiltonian lattice gauge theory—-a loop-string-hadron (LSH) formulation—-that characterizes dynamics directly in terms of its loop, string, and hadronic degrees of freedom, while alleviating several apparent disadvantages of quantumly simulating the Kogut-Susskind formulation. This LSH formulation, derived from Schwinger bosons, extends the local loop formulation of (d+1)-dimensional lattice gauge theories by incorporating staggered quarks, furnishing the algebra of gauge-singlet operators, and succinctly encoding the dynamics among states having Gauss's law built in to them. LSH operators are factored into explicit products of "normalized'' ladder operators and diagonal matrices, priming them for applications in quantum algorithms. Self-contained translations of the Hamiltonian are given and I comment on the next steps for this framework.

Hosted by: Yoshitaka Hatta

We present [hep-ph/2006.06726] a framework that resums threshold enhanced large logarithms to all orders in perturbation theory for inclusive processes such as the production of a pair of leptons in Drell-Yan process and of Higgs boson in gluon fusion as well as in bottom quark annihilation at the hadron colliders. In addition, we apply [hep-ph/2007.12214] this to Deep Inelastic Scattering (DIS) and hadron production in Semi-Inclusive Annihilation (SIA) of electron positron colliders. These logarithms include the distributions P(log?^i (1−z))/1−z)) resulting from soft plus virtual (SV) and the logarithms log?^i (1−z) from next to SV contributions. We use collinear factorisation and renormalisation group invariance to achieve this. We find that the resummed result is a solution to Sudakov type differential equation and hence it can predict soft plus virtual contributions as well as next to SV contributions to all orders in strong coupling constant to the partonic coefficient function in terms of infrared anomalous dimensions and process independent functions. The z space resummed result is shown to have integral representation which allows us to resum the large logarithms of the form log?i(N) retaining 1/N corrections resulting from next to SV terms. We show that in N space, tower of logarithms are summed to all orders in strong coupling constant.

Hosted by: Yoshitaka Hatta

In this talk, I will talk about several interesting and peculiar aspects of the photon in high energy scatterings. First, I will review the history of Weizsacker-Williams photon distribution in a relativistic moving charged particle in the so-called equivalent photon approximation (EPA), and discuss the extension of this method towards the photon Wigner distribution. These methods can be applied to the dilepton productions recently measured by STAR, ATLAS and CMS collaborations. In the end, I will also mention the rich QCD structure of the photon and its implication on the collective phenomenon at the future EIC. https://bluejeans.com/429607848

Hosted by: Nikhil Karthik

Extracting the shear viscosity of quark-gluon plasma from experimental data has been one of the major goals of heavy-ion physics, leading to very low values of eta/s = 1-2/4pi. Most of these works have been done using by now outdated EoS parametrization, and I'll discuss how and whether the use of contemporary EoS affects the extracted EoS in a full-fledged Bayesian analysis. I will also discuss whether the minimum value of eta/s depends on how the temperature dependence of eta/s is parametrised. bluejeans: https://bluejeans.com/826383959

Hosted by: Nikhil Karthik

We consider a class of quantum field theories and quantum mechanics, which we couple to topological QFTs, in order to classify non-perturbative effects in the original theory. The TQFT structure arises naturally from turning on a classical background field for a discrete 0- or 1-form global symmetry present in the theory. By using this method, I prove that the the non-perturbative expansion parameter is exp[-S_I/N]= \exp[-{8 \pi^2}/{g^2N}], both in the semi-classical weak coupling domain and strong coupling domain, corresponding to a fractional topological charge configurations. To classify the non-perturbative effects in original SU(N) theory, we must use PSU(N) bundle and lift configurations (critical points at infinity) for which there is no obstruction back to SU(N). These provide a refinement of instanton sums: integer topological charge, but crucially fractional action configurations contribute.

Hosted by: Yuta Kikuchi

Quarkonium production and polarization in the color evaporation model Abstract: One of the best ways to understand hadronization in QCD is to study the production of quarkonium. The color evaporation model (CEM) and Nonrelativistic QCD (NRQCD) can describe production yields rather well but spin-related measurements like the polarization are stronger tests. In this talk, I will outline the quarkonium polarization puzzle and present recent attempts to use the color evaporation model to describe the polarization of quarkonium production.

Hosted by: Nikhil Karthik

We present a precise definition of a conserved quantity from an arbitrary covariantly conserved current available in a general curved spacetime. This definition enables us to define energy and momentum for matter by the volume integral. As a result we can compute charges of well-known black holes just as an electric charge of an electron in electromagnetism by the volume integration of a delta function singularity. As a byproduct we show that the definition leads to a correction to the known mass formula of a compact star in the Oppenheimer-Volkoff equation. Bluejeans link: https://bnl.bluejeans.com/726276981

Hosted by: Nikhil Karthik

The physics of gluon saturation or color glass condensate (CGC) has been one of the main driving forces for the future Electron Ion Collider. Significant progress has been made in the theory and phenomenology for computing physics observables measured at RHIC and LHC in the past decades. However, the higher-order perturbative calculations in the CGC formalism still remains a bit elusive, especially in comparison with the conventional QCD collinear factorization in the dilute regime. In this talk, using single hadron production in proton-nucleus collisions as an example, I point out some of the interesting difficulties and demonstrate how this can be solved. For example, in the standard collinear factorization, the natural hard scale will automatically arise from a higher-order calculation, while choosing the natural rapidity scale for small-x remains quite tricky even with explicit higher-order calculation. I further show how to perform threshold resummation and demonstrate how this would solve the well-known negative cross section problem for this process.

Hosted by: Akio Tomiya

The method of matrix product states (MPS), as one of the tensor-network (TN) approaches, has been shown to be applicable to study 1+1 dimensional quantum field theories in the canonical formalism. In this talk, I present our work on the massive Thirring model using the MPS technique. Our work shows that the MPS method can be used to identify a Berezinskii-Kosterlitz-Thouless phase transition in the Thirring model. I will also discuss our exploratory results for real-time dynamics and dynamical phase transition. BJ link https://bluejeans.com/871723105

Hosted by: Nikhil Karthik

We determine a previously unknown universal quantity, the location of the Yang-Lee edge singularity for the O(N) theories in a wide range of N and various dimensions. At large N, we reproduce the N\to\infty analytical result on the location of the singularity and, additionally, we obtain the mean-field result for the location in d=4 dimensions. In order to capture the nonperturbative physics for arbitrary N, d and complex-valued external fields, we use the functional renormalization group approach. Bluejeans link: https://bnl.bluejeans.com/726276981

Hosted by: Yuta Kikuchi

Due to the light-cone separation, straightforward calculation of Patron Distribution Function (PDF) is not possible using lattice QCD. The Large Momentum Effective Theory (LaMET) provides a systematic way to relate the quasi-PDF, defined by equal-time correlators at large hadron momentum state, to the PDF order by order in perturbation theory. Within the framework of LaMET, we study the pion valence PDF and the nucleon iso-vector PDFs. Our analysis use both RI-MOM and ratio-based schemes to renormalize the quasi-PDF matrix elements. We reconstruct the x-dependent, as well as infer the first few moments of the pion valence PDF. We compare nucleon iso-vector quasi-PDF matrix elements with the corresponding results of the global fits in coordinate space.

Hosted by: Nikhil Karthik

Bluejeans link: https://bnl.bluejeans.com/726276981

Hosted by: Nikhil Karthik

Jets are hard probes that originate from initial hard scatterings of the nuclei in heavy ion collisions. They acquire transverse momentum broadening through interaction with the evolving quark-gluon plasma. However, already the pre-equilibrium Glasma stage can contribute to transverse momentum broadening. In this talk, I present our recent work [1] where we calculate the contribution to transverse momentum broadening from the Glasma phase. We base our calculation on the boost-invariant 2+1D Glasma description which builds upon the Color Glass Condensate framework. Interestingly, we find strong time-dependence and anisotropic results with larger momentum broadening in the direction along the beam axis. [1] https://arxiv.org/abs/2001.10001 Bluejeans link: https://bnl.bluejeans.com/726276981

Hosted by: Nikhil Karthik

With the first detection of gravitational waves from a binary system of neutron stars, GW170817, a new window was opened to study the properties of matter at and above nuclear-saturation density. Reaching densities a few times that of nuclear matter and temperatures up to 100 MeV, such mergers represent potential sites for a phase transition from confined hadronic to deconfined quark matter. While for GW170817 the postmerger signal could not be detected, such a signal will be a powerful observable in the near future. In this seminar I will present the possible scenarios of how a phase transition to quark-gluon plasma can take place in the postmerger phase of a binary neutron star merger. I will focus on the most recently explored scenario of a so-called ``delayed phase transition'', where the merger remnant transitions from a purely hadronic hypermassive neutron star to a meta-stable hypermassive hybrid star with a dense quark core. This process promises to yield the strongest signature in the gravitational-wave signal for the production of quark matter in the present Universe. Bluejeans link: https://bnl.bluejeans.com/726276981

Hosted by: Akio Tomiya

We discuss the violation of quark-flavor symmetry at high temperatures, induced from axial anomaly and nonperturbative thermal loop corrections. To perform the nonperturbative analysis, we employ a three-flavor linear-sigma model based on the Cornwall-Jackiw-Tomboulis formalism, in which the flavor breaking induced by the axial anomaly plays a significant role in the light scalar meson spectrum and the vacuum structure of the chiral symmetry. In this talk, we will show the flavor breaking effects on the quark condensates and the meson spectroscopy. The critical flavor violation in the topological susceptibility will be also presented. BJ link: https://bluejeans.com/871723105

Hosted by: Nikhil Karthik

The direct photon emission model in relativistic nuclear colliders has been improved in recent years for reducing the discrepancy between theoretical estimations and experimental data and for understanding the properties of the QCD matter. In this talk, the contribution of pre-equilibrium photons are investigated in addition to those of prompt and thermal photons in the framework of a relativistic hydrodynamic model. The numerical simulations at an LHC energy suggest that the pre-equilibrium photons may be relevant at intermediate transverse momentum near the saturation momentum scale, increasing particle spectra and reducing elliptic flow of direct photons. Bluejeans link: https://bnl.bluejeans.com/726276981

Hosted by: Nikhil Karthik

Based on the AdS/CFT correspondence, we build up a simple deep neural network to learn the black-hole metrics from the complex frequency-dependent shear viscosity. The network architecture provides a discretized representation of the holographic renormalization group flow of the shear viscosity and is applicable for a large class of strongly coupled field theories. Given the existence of the horizon and guided by the smoothness of spacetimes, we show that the Schwarzschild and Reissner-Nordstrom metrics can be learned accurately. Moreover, we illustrate that the generalization ability of the deep neural network can be excellent, which indicates that using the black hole spacetime as a hidden data structure, a wide spectrum of the shear viscosity can be generated from a narrow frequency range. Our work might not only suggest a data-driven way to study holographic transports, but also shed new light on the emergence mechanism of black hole spacetimes from field theories.

Hosted by: Nikhil Karthik

Monte Carlo event generators are among the most used tools in high-energy physics today. As an introduction, I will explain what is their role in modern collider phenomenology. The talk will focus on a central part of Monte Carlo generators, the parton shower, which essentially covers all the scales between the hard scale of the collision and the non-perturbative scale. I will describe how typical parton-shower algorithms are built. I will then report on a recent work (arXiv:2020:11114) where we introduced a new set of parton showers aimed at achieving an unprecedented (logarithmic) accuracy. https://bnl.bluejeans.com/726276981

Hosted by: Yuta Kikuchi

I will discuss the evolution of hydrodynamic fluctuations for QCD matter below T_c in the chiral limit. The theoretical description is ordinary hydrodynamics at long distances and superfluid-like at short distances. The latter is represented by pions (the Goldstone modes), reflecting the broken SU(2)_L x SU(2)_R symmetry. The superfluid degrees of freedom contribute to the transport coefficients of the ordinary theory at long distances. This determines the leading dependence of some transport parameters of QCD on the pion mass. I will make some comments on the predictions of this computation near the O(4) critical point. https://bluejeans.com/724325293

Hosted by: Akio Tomiya

I will discuss the status and future of lattice Quantum Chromodynamics (QCD) calculations for nuclear physics. With advances in supercomputing, we are beginning to quantitatively understand nuclear structure and interactions directly from the fundamental quark and gluon degrees of freedom of the Standard Model. Recent studies provide insight into the neutrino-nucleus interactions relevant to long-baseline neutrino experiments, double beta decay, and nuclear sigma terms needed for theory predictions of dark matter cross-sections at underground detectors. The rapid progress in this field has been possible because of new algorithms but challenges still remain to reach the large nuclei used in many of these experiments. Recently, machine learning tools have been shown to provide a potentially revolutionary way to address these challenges and allow a Standard Model understanding of the physics of nuclei. Bluejeans link: https://bluejeans.com/806818825

Hosted by: Nikhil Karthik

Bluejeans link: https://bnl.bluejeans.com/726276981

Hosted by: Akio Tomiya

The tempered Lefschetz thimble method (TLTM) [arXiv:1703.00861] is a parallel-tempering algorithm towards solving the numerical sign problem. It uses the deformation parameter of integration surface (the flow time of the antiholomorphic gradient flow) as a tempering parameter, and is expected to tame both the sign and ergodicity problems simultaneously that exist intrinsically in thimble methods. In this talk, I explain the basics of TLTM, and apply the method to various problems, including the quantum Monte Carlo simulation of the Hubbard model away from half filling and the chiral random matrix models with finite temperature and finite chemical potential. This talk is based on collaboration with Nobuyuki Matsumoto and Naoya Umeda [arXiv: 1703.00861, 1906.04243, 1912.13303]. Bluejeans Link: https://bluejeans.com/871723105

Hosted by: Nikhil Karthik

Studies of the composition of the fireball produced in very high energy heavy-ion collisions show that the composition is that of an equilibrium gas of hadrons at a temperature of about 155 MeV, and zero chemical potential. At the same time, lattice computations show that the chiral cross over of QCD occurs at a temperature of about 155 MeV. The composition of the fireball is a question of the dynamics of hadron reactions, whereas the location of a cross over is a question about the equilibrium free energy density. I describe a computation which shows why they coincide. Bluejeans link: https://bnl.bluejeans.com/726276981

Hosted by: Yuta Kikuchi

Topological gauge field configurations play an important role in the phenomenology of QCD. The axial anomaly is inextricably linked to topological effects. They give rise to anomalous meson masses, affect the order of the chiral phase transition, and lead to the chiral magnetic effect which is relevant for condensed matter and heavy-ion physics. On the flip side, topological gauge field configurations can also give rise to CP violating effects in QCD. A potential resolution of this strong CP problem involves a new particle, the axion. Incidentally, axions are also viable dark matter candidates and their properties are largely determined by the distribution of topological charge in QCD. At high energies in the deconfined regime, the topological structure of QCD is well described by a dilute gas of instantons. In this regime all the effects mentioned above are typically studied based on instantons of unit topological charge. As discussed in this talk, there are also effects uniquely related to instantons of higher topological charge. On the one hand, they give rise to higher-order anomalous quark correlations which manifest themselves in anomalous hadronic interactions. On the other hand, they modify the distribution of topological charge. This, in turn, affects the properties of axions and can lead to a topological mechanism to increase the amount of axion dark matter.

Hosted by: Nikhil Karthik

Motivated by the fermion bag approach—a quantum Monte Carlo approach that takes advantage of grouped local degrees of freedom—we consider a new class of Hamiltonian lattice field theories that can help us study fermionic quantum critical points. We construct the partition function of a lattice Hamiltonian in 2+1 dimensions in discrete time, with a temporal lattice spacing \varepsilon. When \varepsilon \rightarrow 0, we obtain the partition function of the original lattice Hamiltonian. But when \varepsilon = 1, we obtain a new type of space-time lattice field theory which treats space and time differently, but still lacks fermion doubling in the time dimension, in contrast to Lagrangian lattice field theories. Here we show that both continuous-time and discrete-time lattice field theories derived from the t-V model have a fermionic quantum critical point with critical exponents that match within errors. The fermion bag algorithms run relatively faster on the discrete-time model and allow us to compute quantities even on 100^3 lattices near the quantum critical point. Bluejeans link: https://bnl.bluejeans.com/726276981

Hosted by: Nikhil Karthik

In this talk, I will outline a formalism to study open quantum field theories using holographic methods. More precisely, I will consider a quantum field theory (the system) coupled to a holographic field theory at finite temperature (the environment). The aim here is to integrate out the holographic environment with an aim of obtaining an effective dynamics for the resulting open quantum field theory. This is done using semiclassical gravitational Schwinger-Keldysh saddle geometries obtained by complexifying black hole spacetimes. In addition to shedding light on open quantum systems coupled to strongly correlated thermal environments, these results also provide a principled computation of Schwinger-Keldysh observables in gravity and holography. In particular, these influence functionals capture both the dissipative physics of black hole quasinormal modes, as well as that of the fluctuations encoded in outgoing Hawking quanta, and interactions between them. This talk will be based on https://arxiv.org/abs/2004.02888 Bluejeans link: https://bnl.bluejeans.com/726276981

Hosted by: Nikhil Karthik

Transverse momentum distributions (TMDs) allow one to map the hadronic structure in a three-dimensional momentum space, exploring all the possible spin and momentum correlations between a hadron and its elementary constituents. I will discuss their predictive power as a function of the kinematics and, in particular, I will show that the flavor structure of the TMDs can have an impact on the determination of the W boson mass at the Large Hadron Collider, providing a new connection between 3D hadron tomography and high-energy physics. Bluejeans link: https://bnl.bluejeans.com/726276981

Hosted by: Nikhil Karthik

The TMD Topical Collaboration, funded by the DOE Office of Nuclear Physics, was formed by pulling together expertise in QCD theory, phenomenology and lattice QCD from 10 universities and 4 national labs to address the challenge to develop new theoretical and phenomenological tools that are urgently needed for precision extraction of 3D tomography of parton motion inside hadrons from current and future data. In this talk, I will briefly summarize the challenge to extract the true parton motion inside a bound hadron once it is broken by the collisions, and how the TMD Collaboration integrates our knowledge in QCD theory, phenomenology and lattice QCD to overcome the challenge.

Hosted by: Nikhil Karthik

QCD has been extensively studied in various regimes and using various methodologies. While the lattice regularized version is the most popular ab-initio version, this approach has problems dealing with dense, as well as non-equilibrium QCD matter. In this talk, I will introduce the so-called Quantum Link Models, which offer a different approach to the problem. We will explore some qualitative aspects of QCD and nuclear physics using these models.

Hosted by: Nikhil Karthik

Hosted by: Nikhil Karthik

Hosted by: Yuta Kikuchi

Ioffe time essentially quantifies the distance along the lightcone that the quark fields that enter the correlator describing the Parton Distribution Function (PDF) are separated by. In this sense, it is a natural candidate for clearly separating the short and long distance physics. We study how the behavior of the parton distribution in Ioffe time can be mapped out given its Mellin moments. Pseudo PDFs describe the nucleon matrix elements of quark field operators separated by a space like distance z. These are calculable in lattice QCD and as z^2 approaches zero, pseudo PDFs approach the actual PDFs. Complimentary to lattice efforts, we study the behavior of of pseudo PDFs as a function of z in a spectator diquark model. We also extend the study to Generalized Parton Distributions (GPDs), which involves taking into account an extra degree of freedom because of the non diagonal nature of the hadronic matrix element in the case of GPDs.

Hosted by: Akio Tomiya

The transverse momentum dependent parton distribution functions (TMDPDFs) measure the transverse momentum of partons in a fast moving hadron, and is an important observable for the Electron-Ion Collider. The energy evolution of TMDPDFs is given by the Collins-Soper (CS) anomalous dimension, or the CS kernel, which is essential to the fitting of TMDPDFs from global cross section data at different energies. At small transverse momentum, the CS kernel is nonperturbative and can only be determined from global fitting or first principle calculations. In this talk, I present an exploratory calculation of the CS kernel from lattice QCD using the large-momentum effective theory, which is a systematic approach to extract light-cone parton physics. Our preliminary results show that it is promising to achieve precision calculation with currently available computing resources, which has the potential to be used in the global fitting of TMDPDFs in the future.

Hosted by: Nikhil Karthik

Hosted by: Nikhil Karthik

We develop two approaches to the problem of soft fragmentation of hadrons in a gauge theory for high energy processes. The first approach directly adapts the standard resummation of the parton distribution function's anomalous dimension (that of twist-two local operators) in the forward scattering regime, using kT-factorization and BFKL theory, to the case of fragmentation function by exploiting the mapping between the dynamics of eikonal lines on transverse-plane to the celestial-sphere. Critically, to correctly resum the anomalous dimension of the fragmentation function under this mapping, one must pay careful attention to the role of regularization, despite the manifest collinear or infra- red finiteness of the BFKL equation. The anomalous dependence on energy in the celestial case, arising due to the mismatch of dimensionality between positions and angles, drives the differences between the space-like and time-like anomalous dimension of parton densities, even in a conformal theory. The second approach adapts an angular-ordered evolution equation, but working in 4 − 2epsilon dimensions at all angles. The two approaches are united by demanding that the anomalous dimension in 4 − 2epsilon dimensions for the PDF determines the kernel for the angular-ordered evolution to all orders.

Hosted by: Akio Tomiya

It is known that quantum phase transitions occur in the process of quantum annealing. The order of phase transition and computational efficiency are closely related with each other. Quantum computation starts with a non-entangled state and evolves into some entangled states, due to many body interactions and the dynamical delocalization of quantum information over an entire system's degrees of freedom (information scrambling). It is common to diagnose scrambling by observing the time evolution of single qubit Pauli operators with an out-of-timeorder correlator (OTOC). We aim at establishing a method to clarify those relations between phase transitions and scrambling by OTOCs. Using the p-spin model, we diagnose quantum phase transitions associated with quantum annealing and reverse annealing. In addition we provide a novel Majorana fermion model in which non-stoquastic dynamics of annealing can turn a first-order phase transition into a second-order phase transition. We also show that these phase transitions can be diagnosed by the OTOCs.

Hosted by: Nikhil Karthik

In this talk we review indications of an infrared gluon mass in different nonperturbative approaches and discuss its dynamical generation in a Gribov-Zwanziger model. We compute in particular the one-loop effective potential of the model in the recently-established BRST-invariant setup which guarantees gauge-parameter independence of the generated mass scales.

Hosted by: Nikhil Karthik

Current heavy-ion collision experiments might lead to the discovery of a first-order chiral symmetry breaking phase-transition line, ending in a second-order critical point. Nevertheless, the extraction of information about the equilibrium thermodynamic properties of baryonic matter from the highly dynamic, small, noisy and fluctuating environment formed in such collisions is an extremely challenging task. We address some of the limitations present in the experimental search for the QCD critical point.

Hosted by: Nikhil Karthik

New measurements of jet quenching observables at RHIC and at the LHC, such as jet substructure observables, demand an increased precision in the theory calculations describing medium-induced radiation of gluons. Closed expressions for the gluon spectrum including an arbitrary number of multiple scatterings have been known for the past 20 years, but analytical calculations have failed to evaluate this spectrum using realistic models for parton-medium interactions. We show a flexible method which allows us to write the analytical expressions for the full in-medium spectrum, including the resummation of all multiple scatterings, in a form where the numerical evaluation can be easily performed without the need of the usually employed harmonic or first opacity approximation. We present the transverse momentum and energy-dependent medium-induced gluon emission distributions for known realistic interaction models to illustrate how our framework can be applied beyond the limited kinematic regions of previous calculations.

Hosted by: Yuta Kikuchi

Photons and dileptons offer themselves as 'clean' probes of the quark-gluon plasma because they are unlikely to reinteract once produced. Their emission rates are given via the vector channel spectral function, an object that can ultimately be reconstructed by analytic continuation of lattice data. To confront perturbative results with that data, the NLO corrections are needed in all domains that affect the associated imaginary-time correlator, namely for energies above, below and in the vicinity of the light cone. We summarize recent progress here and, to control an unavoidable snag, we also determine these corrections for the transverse and longitudinal polarizations separately. Our results should help to scrutinize direct spectral reconstruction attempts from lattice QCD.

Hosted by: Nikhil Karthik

Hosted by: Nikhil Karthik

I discuss three new methods for the quantum many-body problem. The first is the pinhole trace algorithm for first principles calculations of nuclear thermodynamics. I will present lattice Monte Carlo results for the liquid-vapor critical point. The second is the eigenvector continuation method for extrapolation and interpolation of quantum wave functions. I will show how it can be used as a fast emulator for quantum many-body calculations and as a resummation method for divergent perturbative expansions. The third is the projected cooling algorithm for quantum computers. This method is able to construct the localized ground state of any Hamiltonian with a translationally-invariant kinetic energy and interactions that vanish at infinity.

Hosted by: Niklas Mueller

Experimental analyses during the high-luminosity era of the LHC will call for an unprecedented level of precision in event simulation. With the computation of hard cross sections at next-to-leading order accuracy a solved problem, the focus of development has now shifted towards automated precision resummation, i.e. the extension of parton-showers to next-to-leading order accuracy and beyond the leading-color approximation. At the same time, seemingly mundane problems like the consistent matching of four- and five-flavor calculations at next-to-leading order accuracy need to be tackled in order to make precision forecasts for the measurement of b-jet associated processes such as ttbb. I will discuss the theoretical foundations and practical implications of new algorithms that solve these problems and briefly touch on the readiness of event generators for the next generation high-performance computers.

Hosted by: Yuta Kikuchi

We present the first computation of the NLO photon+dijet impact factor in e+A DIS at small x. When combined with the extant results for the JIMWLK small x evolution to NLLx accuracy, this result provides us with a prediction of the photon+dijet cross-section in e+A DIS to O( (\alpha_S)^3 ln(1/x) ) accuracy. The comparison of this result with photon+dijet measurements at a future EIC therefore provides a precision test of the systematics of gluon saturation. In the soft photon limit, one obtains a compact representation of the state-of-the art results for fully inclusive DIS. The novel techniques developed in this computation can also be applied to promote existing LO computations of photon+dijet production in p+A collisions to NLO+NLLx accuracy.

Hosted by: Nikhil Karthik

Quantum computers provide a unique way of computing real-time correlators from first principles, a task not yet achievable on classical computers due to the sign problem. The determination of the hadronic tensor on the Euclidean lattice is obstructed by the difficulty of converting Euclidean correlators to real-time correlators. This is a match made in heaven: a lattice field theory simulation on a quantum computer may provide access to PDFs. In this talk we discuss the way in which a quantum computer may naturally solve this problem, outline recent progress on simulating field theories on a quantum computer, and detail the resources needed to perform such a calculation.

Hosted by: Nikhil Karthik

The small-x evolution equations for the quark and gluon helicity distribution have recently been constructed by finding sub-eikonal corrections to the eikonal shock wave formalism. Those equations are written for correlators of infinite light-cone Wilson lines along with the so-called polarized Wilson lines. Those equations close in the large N_c-limit (N_c is the number of quark colors), but also in the large N_c & N_f-limit (N_f is the number of quark flavors). However, in the shock wave formalism, no closed form can be obtained for arbitrary value of N_c and N_f. For the unpolarized case, the generalization of the Balitsky-Kovchegov equation is done by the Jalilian-Marian—Iancu—McLerran—Weigert—Leonidov—Kovner (JIMWLK) functional evolution equation. Such an approach for the small-x evolution of the helicity is beneficial for numerical evaluation at finite N_c and N_f (beyond previously used limit), and for the evaluation of helicity-dependent operator with an arbitrary number of Wilson lines. We derive an analogue of the JIMWLK evolution equation for the small-x evolution of helicity distributions and obtain an evolution equation for the target weight functional.

Hosted by: Nikhil Karthik

In the study of the quark-gluon plasma (QGP) in high-energy heavy-ion collisions, jet quenching plays an essential role as hard probes of the properties of the dense strongly interacting matter. In this talk, we present an attempt to probe the underlying structure of the quark-gluon plasma (QGP) at high resolution, based on the extracted jet transport coefficient \hat{q}. We argue that the exchanged momentum k between the hard parton and the medium varies over a range of scales, and for k ≥ 1 GeV, \hat{q} can be expressed in terms of a parton distribution function (PDF). Calculations, based on this reconstructed \hat{q} are compared to data sensitive to the hardcore of jets i.e., the single hadron suppression in terms of the nuclear modification factor R_{AA} and the azimuthal anisotropy parameter v_{2}, as a function of transverse momentum p_{T}, centrality and energy of the collision. It is demonstrated that the scale evolution of the QGP-PDF is responsible for the reduction in the normalization of \hat{q} between fits to Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC) data; a puzzle, first discovered by the JET collaboration.

Hosted by: Nikhil Karthik

The knowledge of all elementary correlation functions in a theory is sufficient to access all possible observables. The computation of these correlation functions in QCD within the Functional Renormalization Group is outlined. For applications, the shear and bulk viscosity in Yang-Mills, as well as diffusive transport for the critical mode in a Low-Energy Effective Theory of QCD are discussed.

Hosted by: Niklas Karthik

Hosted by: Yuta Kikuchi

Photons and dileptons offer themselves as 'clean' probes of the quark-gluon plasma because they are unlikely to reinteract once produced. Their emission rates are given via the vector channel spectral function, an object that can ultimately be reconstructed by analytic continuation of lattice data. To confront perturbative results with that data, the NLO corrections are needed in all domains that affect the associated imaginary-time correlator, namely for energies above, below and in the vicinity of the light cone. We summarize recent progress here and, to control an unavoidable snag, we also determine these corrections for the transverse and longitudinal polarizations separately. Our results should help to scrutinize direct spectral reconstruction attempts from lattice QCD.

Hosted by: Yuta Kikuchi

During the spring of 2018, the Relativistic Heavy-Ion Collider carried out an isobar run consisting of Ru+Ru and Zr+Zr collisions at 200 GeV. The main objective of such experimental program was the unambiguous observation of a Chiral Magnetic Effect-driven charge separation. In this talk, I will demonstrate how an experimentally confirmed property of the nuclear structure of Zr, i.e. its neutron skin, significantly reduces the feasibility of such a finding. This study provides a much needed theoretical baseline to meaningfully interpret the recorded experimental data by combining state-of-the art nuclear structure techniques with a dynamical description of heavy-ion collisions in terms of a novel transport model, SMASH.

Hosted by: Nikhil Karthik

Hosted by: Nikhil Karthik

There is as yet no firm evidence for quark matter in neutron stars. This is mainly because of the lack of direct probes of the opaque neutron star interior, and the lack of clear qualitative difference between hadronic and quark phases. The detection of GW170817 has offered a first example of how gravitational waves can be used to constrain the equation of state (EoS) of ultra-dense matter. We shall discuss taking into account currently available information how to reveal possible phase transitions in neutron stars: the steadily growing body of astrophysical data and supported laboratory experiments should eventually allow us to narrow down the options by combining these various observations. We survey the proposed signatures of exotic matter, and emphasize the importance of data from neutron star mergers.

In the chiral limit, the long distance effective theory of QCD at finite temperature is not hydrodynamics but a kind of non-abelian superfluid hydrodynamics. We describe this theory and its viscous corrections, including also a correction due to the finite quark mass. At finite quark mass, the long distance theory is ordinary hydrodynamics, and the superfluid theory then just determines non-analytic in the quark mass corrections to the transport coefficients of QCD, akin to the "long time tails" of hydro. We show how this works out for the bulk viscosity. In chiral perturbation theory the dissipative parameters of the superfluid theory can be computed diagrammatically, and we do this. These results then determine the leading order the bulk viscosity of the pion gas close to the chiral limit.

Hosted by: Yuta Kikuchi

Using novel lattice (non-relativistic) QCD techniques, for the first time, we will present results pertaining to the fate of Υ(1S), Υ(2S) and Υ(3S) in QGP. We will present results on how the masses of these states change with temperature, as well as how their spatial sizes change. Finally, we will also show new lattice QCD results on excited P-wave bottomonia in QGP.

Hosted by: Niklas Mueller

In this talk, I will examine the status of the JIMWLK evolution equation in relation to the effective density matrix of a high energy hadronic system. The high energy evolution of this density matrix which is associated with the Hilbert space completely spanned by color charge density operators has the form of Lindblad equation. The JIMWLK equation is reproduced by mapping this Lindblad type quantum mechanical equation onto the classical phase space of the system using Weyl's correspondence rules.

Hosted by: Niklas Mueller

I will review the basic ideas behind the connections between resurgent asymptotics and physics, and report on current applications to quantum field theory and phase transitions.

Hosted by: Yuta Kikuchi

The chiral anomaly present in the standard model can have important phenomenological consequences, especially in cosmology and heavy-ions physics. In this talk, I will focus on the contribution from the Abelian gauge fields. Despite an absence of topologically distinct sectors, they have a surprisingly rich vacuum dynamics, partly because of the chiral anomaly. I will present results obtained from real-time classical lattice simulations of a U(1) gauge field in the presence of a chiral chemical potential. They account for short distance fluctuations, contrary to effective descriptions such as Magneto-Hydrodynamics (MHD). I will discuss various phenomena, like inverse magnetic cascade, which occur in this system. In particular, in presence of a background magnetic field, the chemical potential exponentially decays. The associated chiral decay rate is related to the diffusion of the Abelian Chern-Simons number in a magnetic background, in the absence of chemical potential. The rate obtained from the simulations is an order of magnitude larger than the one predicted by MHD. If this result is shown to be robust under corrections such as Hard Thermal Loops, it will call for a revision of the implications of fermion number and chiral number non-conservation in Abelian theory at finite temperature.

Hosted by: Niklas Mueller

The geometry of overlap between two nuclei interacting at high energy determines many of the observables typically investigated in heavy-ion-collision analyses, such as average transverse momenta () and azimuthal anisotropies of the emitted particle distributions. If the colliding nuclei are non-spherical, e.g., if they present a quadrupole deformation and look like ellipsoids, the geometry of interaction experiences nontrivial fluctuations due to the random orientation of the colliding bodies. I introduce an 'event-shape engineering' procedure that allows one to probe the quadrupole deformation of the colliding ions. The method is straightforward. One selects a batch of high-multiplicity (ultracentral) collisions, and within this batch looks at events that present an abnormally large or small of the produced hadrons. I show that these events correspond to configurations in which the colliding nuclei are overlapping along the longer (shorter) side of the prolate (oblate) ellipsoids. In these events, the interaction region has an elliptical shape, whose eccentricity is closely related to the quadrupole deformation of the considered nuclei. Therefore, for collisions of nuclei that are significantly deformed (e.g. 238U and 129Xe nuclei collided at RHIC and LHC) I predict a strong enhancement of elliptic flow in the tails of the distributions of ultracentral events. If validated by experimental data, this method would provide a robust tool to observe the deformations of nuclear ground states at particle colliders (in particular at RHIC).

Hosted by: Yuta Kikuchi

Unequal rapidity correlations can be studied within the stochastic Langevin picture of JIMWLK evolution in the Colour Glass Condensate effective field theory. By evolving the classical field in the direct and complex conjugate amplitudes, the Langevin formalism can be used to study two-particle production at large rapidity separations. We show how the evolution between the rapidities of the two produced particles can be expressed as a linear equation, even in the full nonlinear limit. In addition, we show how the Langevin formalism for two-particle correlations reduces to a BFKL picture in the dilute limit and in momentum space, providing an interpretation of BFKL evolution as a stochastic process for colour charges.

Hosted by: Niklas Mueller

In the chiral limit, the long distance effective theory of QCD at finite temperature is not hydrodynamics but a kind of non-abelian superfluid hydrodynamics. We describe this theory and its viscous corrections, including also a correction due to the finite quark mass. At finite quark mass, the long distance theory is ordinary hydrodynamics, and the superfluid theory then just determines non-analytic in the quark mass corrections to the transport coefficients of QCD, akin to the "long time tails" of hydro. We show how this works out for the bulk viscosity. In chiral perturbation theory the dissipative parameters of the superfluid theory can be computed diagrammatically, and we do this. These results then determine the leading order the bulk viscosity of the pion gas close to the chiral limit.

Hosted by: Niklas Mueller

In the chiral limit, the long distance effective theory of QCD at finite temperature is not hydrodynamics but a kind of non-abelian superfluid hydrodynamics. We describe this theory and its viscous corrections, including also a correction due to the finite quark mass. At finite quark mass, the long distance theory is ordinary hydrodynamics, and the superfluid theory then just determines non-analytic in the quark mass corrections to the transport coefficients of QCD, akin to the "long time tails" of hydro. We show how this works out for the bulk viscosity. In chiral perturbation theory the dissipative parameters of the superfluid theory can be computed diagrammatically, and we do this. These results then determine the leading order the bulk viscosity of the pion gas close to the chiral limit.

Hosted by: Yuta Kikuchi

Computation of DIS structure functions from first principles is an outstanding problem in Quantum Chromodynamics (QCD) as it involves matrix elements of products of electromagnetic currents that are light-like separated in Minkowski spacetime. Since Monte Carlo computations in lattice QCD are only robust in Euclidean spacetime, it is worthwhile to ask whether simulations on a quantum computer can be beneficial. In my talk I will outline a strategy to compute deeply inelastic scattering structure functions on a hybrid quantum computer which is based on representation of the fermion determinant in the QCD effective action as a quantum mechanical "worldline" path integral over fermionic and bosonic degrees of freedom. The proper time evolution of these worldlines can be determined on a quantum computer. While extremely challenging in general, the problem simplifies in the Regge limit of QCD, where the interaction of the worldlines with gauge fields is strongly localized in proper time and the corresponding quantum circuits can be written down. As a first application, we employ the Color Glass Condensate effective theory to construct the quantum algorithm for a simple dipole model of the F2 structure function. We outline further how this computation scales up in complexity and extends in scope to other real-time correlation functions.

Hosted by: Niklas Mueller

Motivated by the desire to study quantum field theories on a quantum computer, we propose a new type of regularization of quantum field theories where in addition to the usual lattice regularization, quantum field theories are constructed with a finite dimensional Hilbert space per lattice site. This is particularly relevant for studying bosonic field theories using a quantum computer since traditional lattice regularization assumes an infinite dimensional Hilbert space per lattice site and hence difficult to formulate on a quantum computer. Here we show that a two qubit model is sufficient to recover the 3d Wilson-Fisher fixed point and the 4d Gaussian fixed point of the O(3) sigma model. On the other hand in 2d, our qubit model does not seem to have a continuum limit although we have to study large lattices to establish this fact. We discuss modifications of our model that could perhaps yield a continuum limit.

Hosted by: Yuta Kikuchi

I will talk about supersymmetric index of 4d N=1 supersymmetric theories on S^1xM_3 which counts supersymmetric states. In the first part, I will discuss a general formula to describe an asymptotic behaviour of the index in the limit of shrinking S^1 which we refer to as 4d (refined) supersymmetric Cardy formula. This part is based on arXiv:1611.00380 with Lorenzo Di Pietro. In the second part, I will apply this formula to black hole physics. I will mainly focus on superconformal index of SU(N) N=4 super Yang-Mills theory which is expected to be dual to type IIB superstring theory on AdS_5 x S^5. We will see that the index in the large-N limit reproduces the Bekenstein-Hawking entropy of rotating charged BPS black hole on the gravity side. Our result for finite N makes a prediction to the black hole entropy with full quantum corrections. The second part is based on arXiv:1901.08091.

Hosted by: Niklas Mueller

It has long been suspected that symmetries in quantum gravity are highly constrained. In this talk I will describe joint work with Hirosi Ooguri, where we use the power of the AdS/CFT correspondence to prove three conjectures of this type: that there are no global symmetries, that there must be objects transforming in all representations of any gauge symmetry, and that any gauge group must be compact. Real world implications include the existence of magnetic monopoles and neutrinoless double beta decay, although we so far are unable to give estimates for when these should be seen. An important point, which we dwell on at length, is the proper definition of gauge and global symmetries in quantum field theory.

Hosted by: Niklas Mueller

The shear and bulk viscosities of QCD are understood to have non-trivial temperature dependence. The quark-gluon plasma created at RHIC and the LHC provides a unique probe of this temperature dependence for temperatures ranging from ∼150 ~MeV to ∼400−600 MeV. Values of viscosities commonly quoted for the quark-gluon plasma, e.g. η/s∼0.1−0.2 for the shear viscosity to entropy density ratio, are understood to represent ``effective viscosities'', which combine the actual temperature-dependence of the transport coefficient with the complex temperature profile of the quark-gluon plasma. Using 0+1D Bjorken hydrodynamics as starting point, we provide a precise definition of effective viscosity for first-order (Navier-Stokes) hydrodynamics. We examine the role of the equation of state by comparing a QCD fluid with a conformal one. We use this definition of effective viscosity to obtain families of bulk viscosities ζ/s(T) that have different temperature dependence but nevertheless produce matching temperature evolutions in 0+1D hydrodynamics. We further extend the definition of effective viscosity to second-order (Israel-Stewart) Bjorken hydrodynamics. We express the second-order effective viscosity in terms of the initial bulk pressure of the system and its first-order effective viscosity, and quantify the approximate degeneracy of these latter two quantities in Bjorken hydrodynamics. We discuss extensions of this work beyond 0+1D, and review implications for phenomenological studies of heavy ion collisions.

Hosted by: Akio Tomiya

Hosted by: Yuta Kikuchi

We consider deep inelastic scattering (DIS) on a dense nucleus described as an extremal RN-AdS black hole with holographic quantum fermions in the bulk. We find that the R-ratio (the ratio of the structure function of the black hole to proton) exhibit shadowing for x < 0.1, anti-shadowing for 0.1 < x < 0.3, EMC-like effect for 0.3 < x < 0.8 and Fermi motion for x > 0.8 in a qualitative agreement with the experimental observation of the ratio for DIS on nucleus for all range of x. We also take the dilute limit of the black hole and show that its R-ratio exhibits EMC-like effect for 0.2 < x < 0.8 and the Fermi motion for x > 0.8, and no shadowing is observed in the dilute limit.

Hosted by: Niklas Mueller

A purely analytical approach to non-perturbative QCD is discussed. The exact, gauge-fixed, Faddeev-Popov Lagrangian of Yang-Mills theory is studied by the screened massive expansion which emerges from a mere change of the expansion point of ordinary perturbation theory. The gluon propagator has gauge-invariant complex conjugated poles which might give a direct dynamical proof of gluon confinement. Their genuine nature is discussed. Because of BRST symmetry, the analytic properties and the poles are shown to play a central role in the optimization of the expansion, which becomes a very predictive and ab initio tool. While in excellent agreement with the lattice data in the Euclidean space, the expansion provides valuable information in sectors which are not easily explored on the lattice, like Minkowski space and a generic covariant gauge. Moreover, even in the Euclidean space, the method gives a lattice-independent estimate of the running coupling in the continuum limit.

Hosted by: Yuta Kikuchi

Hosted by: Niklas Mueller

Topological superconductivity hosts exotic quasi-particle excitations including Majorana bound states which hold promise for fault-tolerant quantum computing. The theory predicts emergence of Majorana bound states is accompanied by a topological phase transition. We show experimentally in epitaxial Al/InAs Josephson junctions a transition between trivial and topological superconductivity. We observe a minimum of the critical current at the topological transition, indicating a closing and reopening of the superconducting gap induced in InAs, with increasing magnetic field. By embedding the Josephson junction in a phase-sensitive loop geometry, we measure a π-jump in the superconducting phase across the junction when the system is driven through the topological transition. We present a scalable topological qubit architecture to study coherence for computing applications. Funded by DARPA TEE program.

Hosted by: Niklas Mueller

In this talk I will explain how to calculate the D meson mixing parameters x and y in the Standard Model. Charm physics is notoriously difficult, because most effective theories and perturbation theories do not apply well. I propose to study the D meson mixing via a dispersion relation, which relates low mass dynamics to high mass one. Taking heavy quark results as inputs in the high mass region, we obtain x and y consistent with experimental data at least in order of magnitude.

Hosted by: Yuta Kikuchi

In this talk, I would like to talk about my works with machine learning. I plan to introduce my works which related to lattice QCD research: detection of phase transition in classical spin systems [arXiv 1609.09087, 1812.01522], configuration generation [1712.03893 + some]

Hosted by: Niklas Mueller

The advent of quantum computing for scientific research presents the possibility of calculating time-dependent observables like viscosity and parton distributions from QCD. In order to utilize this new tool, a number of theoretical and practical issues must be addressed related to efficiently digitize, initialize, propagate, and evaluate quantum field theory. In this talk, I will discuss a number of projects being undertaken by the NuQS collaboration to realize calculations on NISQ era and beyond quantum computers.

Hosted by: Yuta Kikuchi

In this talk, we discuss the physical role of complex saddle points of path integrals. In the first case study, we analyze saddle point structure of two-dimensional lattice gauge theory represented as Gross-Witten-Wadia unitary matrix model. We find that non-perturbative physics in the strong coupling phase can be understood in terms of new family of complex saddle points those properties are connected to resurgent structure of the 1/N expansion. In the second case study, we discuss the sign problem in fermionic systems at finite density and the possibility to alleviate it with the help of defomations of integration contour into complex space on the example of two-dimensional Hubbard model.

Hosted by: Niklas Mueller

Hosted by: Yuta Kikuchi

The search for an understanding of fundamental particle physics that goes beyond the Standard Model (SM) has grown into a worldwide titanic effort. Low-energy precision experiments are complementary to collider searches and, in certain cases, can even probe higher energy scales directly. However, the interpretation of a potential signal, or lack thereof, is complicated because of the non-perturbative nature of low-energy QCD. I will use the search for electric dipole moments (EDMs), which aims to discover beyond-the-SM CP violation, as an example to illustrate these difficulties and how they can be overcome by combining (chiral) effective field theory and lattice QCD. I discuss how EDM experiments involving complex systems like nucleons, nuclei, atoms, and molecules constrain possible CP-violating interactions involving the Higgs boson, how these constraints match up to direct LHC searches, and the relevance of and strategies for the improvement of the hadronic and nuclear theory.

Hosted by: Niklas Mueller

We present a general systematic formalism for describing dynamics of fluctuations in an arbitrary relativistic hydrodynamic flow, including their feedback (known as long-time hydrodynamic tails) in a deterministic way. The fluctuations are described by two-point equal-time correlation functions. We introduce a definition of equal time in a situation where the local rest frame is determined by the local flow velocity, and a method of taking derivatives and Wigner transforms of such equal-time correlation functions, which we call confluent. The Wigner functions satisfy evolution equations that describes the relaxation of the out-of-equilibrium modes. We find that the equations for confluent Wigner functions nontrivially match with the kinetic equation for phonons propagating on an arbitrary background, including relativistic inertial and Coriolis forces due to acceleration and vorticity of the flow. We also describe the procedure of renormalization of short-distance singularities which eliminates cutoff dependence, allowing efficient numerical implementation of these equations.

Hosted by: Yuta Kikuchi

The quantum chiral anomaly enables a nearly dissipationless current in the presence of chirality imbalance and magnetic field – this is the Chiral Magnetic Effect (CME), observed recently in Dirac and Weyl semimetals. We propose to utilize the CME for the design of qubits potentially capable of operating at THz frequency, room temperature, and the coherence time to gate time ratio of about 10^4 . The proposed "Chiral Qubit" is a micron-scale ring made of a Weyl or Dirac semimetal, with the |0> and |1> quantum states corresponding to the symmetric and antisymmetric superpositions of quantum states describing chiral fermions circulating along the ring clockwise and counter-clockwise. A fractional magnetic flux through the ring induces a quantum superposition of the |0> and |1> quantum states. The entanglement of qubits can be implemented through the near-field THz frequency electromagnetic fields.

Hosted by: Yuta Kikuchi

Hosted by: Niklas Mueller

To extract parton distributions from the lattice simulations, one needs to consider matrix elements M(z,p) of bilocal correlators of parton fields [generically written as φ(0)φ(z)] at spacelike separations z=(0,0,0,z_3). A transition to PDFs may be proceeded by taking a Fourier transform either with respect to z_3 for fixed p_3 (which gives X. Ji's quasi-PDFs), or with respect to the Lorentz-invariant variable ν=-(zp) for fixed values of another Lorentz invariant z^2 [which results in pseudo-PDFs].These functions are interesting on their own, and I will discuss, in the continuum case, their general properties, the connection between the two types of functions, and their relation with the usual light-cone PDFs. I will outline the algorithm of extracting the PDFs through the use of the so-called "reduced Ioffe-time distributions",and illustrate this pseudo-PDF-oriented approach on the example of exploratory lattice simulations performed by Orginos et al.

Hosted by: Niklas Mueller

The famous "sign problem" is the main roadblock in the path to a Monte Carlo solution of QCD at finite densities and the study of real time dynamics. We review a recent developed approach to this problem based on deforming the domain of integration of the oath integral into complex field space. After discussing the math involved in the complex analysis of multidimensional spaces we will talk about the advantages/disadvantages of using Lefschetz thimbles, "learnifolds" and "optimized manifolds" as the alternative integration manifold as well as the algorithms that go with them. Several examples of lower dimensional field theories will be presented.

Hosted by: Niklas Mueller

We introduce the notion of the Color Glass Condensate (CGC) density matrix ρ̂ . This generalizes the concept of probability density for the distribution of the color charges in the hadronic wave function and is consistent with understanding the CGC as an effective theory after integration of part of the hadronic degrees of freedom. We derive the evolution equations for the density matrix and show that it has the celebrated Kossakowsky-Lindblad form describing the non-unitary evolution of the density matrix of an open system. Additionally, we consider the dilute limit and demonstrate that, at large rapidity, the entanglement entropy of the density matrix grows linearly with rapidity according to dSe/dy=γ, where γ is the leading BFKL eigenvalue. We also discuss the evolution of ρ̂ in the saturated regime and relate it to the Levin-Tuchin law and find that the entropy again grows linearly with rapidity, but at a slower rate. Finally we introduce the Wigner functional derived from this density matrix and discuss how it can be used to determine the distribution of color currents, which may be instrumental in understanding dynamical features of QCD at high energy.

Hosted by: Niklas Mueller

Inclusive particle production at high p_t is successfully described by perturbative QCD using collinear factorization formalism with DGLAP evolution of the parton distribution functions. This formalism breaks down at small Bjorken x (high energy) due to high gluon density (gluon saturation) effects. The Color Glass Condensate (CGC) formalism is an effective action approach to particle production at small Bjorken x (low p_t) which includes gluon saturation. The CGC formalism nevertheless breaks down at intermediate/large Bjorken x, corresponding to the high p_t kinematic region in high energy collisions. Here we describe the first steps taken towards the derivation of a new formalism, with the ultimate goal of having a unified formalism for particle production at both low and high p_t in high energy hadronic/heavy ion collisions.

Hosted by: Sally Dawson

Hosted by: Sally Dawson

Hosted by: Sally Dawson

Hosted by: Niklas Mueller

Hosted by: Niklas Mueller

We revisit the problem of baryons in the large N limit of Quantum Chromodynamics. A special case in which the theory of Skyrmions is inapplicable is one-flavor QCD, where there are no light pions to construct the baryon from. More generally, the description of baryons made out of predominantly one flavor within the Skyrmion model is unsatisfactory. We propose a model for such baryons, where the baryons are interpreted as quantum Hall droplets. An important element in our construction is an extended, 2+1 dimensional, meta-stable configuration of the η′ particle. Baryon number is identified with a magnetic symmetry on the 2+1 dimensional sheet. If the sheet has a boundary, there are finite energy chiral excitations which carry baryon number. These chiral excitations are analogous to the electron in the fractional quantum Hall effect. Studying the chiral vertex operators we are able to determine the spin, isospin, and certain excitations of the droplet. In addition, balancing the tension of the droplet against the energy stored at the boundary we estimate the size and mass of the baryons. The mass, size, spin, isospin, and excitations that we find agree with phenomenological expectations.

Hosted by: Niklas Mueller

Hosted by: Niklas Mueller

The Sachdev-Ye-Kitaev (SYK) model has a long history in nuclear physics where its precursor was introduced as a model for the two-body nuclear interaction to describe the spectra of complex nuclei. Most notably, its level density is given by the Bethe formula and its level correlations are consistent with chaotic motion of the nucleons. Recently, this model received a great of attention as a solvable model for the quantum states of a black hole, exactly because of these properties. In this lecture we introduce the SYK model from a nuclear physics perspective and discuss its chaotic nature and its relation with black hole physics. We end with a summary of recent work on two SYK models coupled by a spin-spin interaction as a model for wormholes.

Hosted by: Yuta Kikuchi

Recently, chiral photocurrents have been observed in Weyl materials. We propose a new mechanism for photocurrents in Dirac materials in the presence of magnetic fields, that does not depend on any asymmetries of the crystal. This Chiral Magnetic Photocurrent would be an independent probe of the chiral anomaly. We also also discuss an observation of terahertz emission in the Weyl material TaAs with tunable ellipticity, due to chiral photocurrents induced by an ultrafast near infrared laser.

Hosted by: Niklas Mueller

Experimental verification of relativistic field theory models requires accelerator experiments. A possible pathway that could help understanding the dynamics of such models for bosons or fermions is the use of quantum technology in the form of quantum analog simulators. In this talk we will explore the possibility of generating nonlinear Dirac-type Hamiltonians using coherent superpositions of photons and spin wave excitations of atoms. Our realization uses a driven slow-light setup, where photons mimic the Dirac fields and different dynamics can be implemented and tuned by adjusting optical parameters. We will show our progress tin building a quantum simulator of the Jackiw-Rebbi model using highly-interacting photons strongly coupled to a room temperature atomic ensemble. We have identified suitable conditions in which the input photons dispersion relations can be tuned to a spinor of light configuration, mimicking the Dirac regime and providing a framework to create tunable interactions and varying mass terms. Lastly, we will show our vision to scale these ideas to multiple interacting fermions.

Hosted by: Enrico Rinaldi

The scalar-isoscalar mode of QCD becomes lighter/nearly massless close to the chiral transition/second-order critical point. This mode is the main responsible for the attractive part of the nucleon-nucleon potential at distances of 1-2 fm. Therefore, a long-range strong attraction among nucleons is predicted to develop close to the QCD critical point. Using the Walecka-Serot model for the NN potential we study the effects of the critical mode in a system of nucleons and mesons using a Molecular Dynamics+Langevin equations for the freeze-out conditions of heavy-ion collisions. Beyond mean field, we observe strong nucleon correlations leading to baryon clustering. We propose that light-nuclei formation, together with an enhancement of cumulants of the proton distribution can signal the presence of the QCD critical point.

Hosted by: Enrico Rinaldi

We introduce a new "quantile'' analysis strategy to study the modification of jets as they traverse through a droplet of quark-gluon plasma. To date, most jet modification studies have been based on comparing the jet properties measured in heavy-ion collisions to a proton-proton baseline at the same reconstructed jet transverse momentum pT. It is well known, however, that the quenching of jets from their interaction with the medium leads to a migration of jets from higher to lower pT, making it challenging to directly infer the degree and mechanism of jet energy loss. Our proposed quantile matching procedure is inspired by (but not reliant on) the approximate monotonicity of energy loss in the jet pT. In this strategy, jets in heavy-ion collisions ordered by pT are viewed as modified versions of the same number of highest-energy jets in proton-proton collisions. Despite non-monotonic fluctuations in the energy loss, we use an event generator to validate the strong correlation between the pT of the parton that initiates a heavy-ion jet and the pT of the vacuum jet which corresponds to it via the quantile procedure. We demonstrate that this strategy both provides a complementary way to study jet modification and mitigates the effect of pT migration in heavy-ion collisions.

Hosted by: Niklas Mueller

I will give an overview of our work on developing an effective field theory of dissipative hydrodynamics. The formulation is based on the Schwinger-Keldysh formalism, which provides a functional approach that naturally includes dissipation and fluctuations. Hydrodynamics is implemented by introducing suitable degrees of freedom and symmetries. I will then discuss two important by-products. First, the second law of thermodynamics, which in the traditional approach is imposed at phenomenological level, is here obtained from a basic symmetry principle together with constraints from unitarity. Second, I will show consistency with unitarity and causality of the hydrodynamic path-integral at all loops, which leads to the first systematic framework to compute hydrodynamic fluctuations.

Hosted by: Yuta Kikuchi

In this talk, I will present a connection between two approaches of studying quarkonium dynamics inside quark-gluon plasma: the open quantum system formalism and the transport equation. I will discuss insights from the perspective of quantum information. I will show that under the weak coupling and Markovian approximations, the Lindblad equation turns to a Boltzmann transport equation after a Wigner transform is applied to the system density matrix. I will demonstrate how the separation of physical scales justifies the approximations, by using effective field theory of QCD. Finally, I will show some phenomenological results based on the derived transport equation.

Hosted by: Niklas Mueller

Chiral effects attracted significant attention in the literature. Recently, a generalization of chiral vortical effect (CVE) to systems of photons was suggested. In this talk I will discuss the relation of this new transport to the topological phase of photons and show that, in general, CVE can take place in rotating systems of massless particles with any spin.

Hosted by: Enrico Rinaldi

Proton decay is one of possible signatures of baryon number violation, which has to exist to explain the baryon asymmetry and the existence of nuclear matter. Proton decay is one of natural implications of the Grand Unification Theory. After integrating out the high energy degrees of freedom, the baryon number violation operator that mediates proton decay can be found as the composite operator of standard model fields. We discuss the hadronic matrix elements of this BV operator made of three quarks and a lepton. We will start from the current experimental bound of proton lifetime. We present preliminary results of matrix element calculation done with the 2+1 dynamical flavor domain wall fermions at the physical point. We will discuss the proton decay channels that no matrix element has been calculated on the lattice.

Hosted by: Yuta Kikuchi

Hosted by: Niklas Mueller

Experimental detection of fundamental symmetry violation would provide a clear signal for new physics, but theoretical predictions that can be compared with data are needed in order to interpret experimental results as measurements or constraints of beyond the Standard Model physics parameters. For low-energy experiments involving protons, neutrons, and nuclei, reliable theoretical predictions must include the strong interactions of QCD that confine quarks and gluons. I will discuss experimental searches for neutron-antineutron oscillations that test beyond the Standard Model theories of matter-antimatter asymmetry with low-scale baryon-number violation. Lattice QCD can be used to calculate the neutron-antineutron transition rate using a complete basis of six-quark operators describing neutron-antineutron oscillations in effective field theory, and I will present the first lattice QCD results for neutron-antineutron oscillations using physical quark mass simulations and fully quantified uncertainties. Other experiments searching for neutrinoless double-beta decay and dark matter direct detection use large nuclear targets that are more difficult to simulate in lattice QCD because of an exponentially difficult sign(al-to-noise) problem. I will briefly describe the state-of-the-art for lattice QCD calculations of axial, scalar, and tensor matrix elements relevant to new physics searches with nuclei and outline my ongoing efforts to improve signal-to-noise problems using phase unwrapping.

Hosted by: Yuta Kikuchi

Hosted by: Niklas Mueller

The small Bjorken-x regime of QCD is of great interest since a variety of different phenomena are known or expected to emerge, from BFKL small-x effects and non-linear and saturation dynamics to shadowing corrections in heavy nuclei. In this talk we present recent developments in our understanding of perturbative and non-perturbative QCD at small-x: the evidence for BFKL dynamics in the HERA structure function data, the precision determination of collinear PDFs from charm production at LHCb, and the first results on neural-network based fits of nuclear PDFs. We also highlight the remarkable connection between small-x QCD and high-energy astrophysics, in particular for the theoretical predictions of signal and background event rates at neutrino telescopes such as IceCube and KM3NET

Hosted by: Niklas Mueller

We consider the Casimir effect in a gauge-invariant Hamiltonian formulation of nonabelian gauge theories in $(2+1)$ dimensions. We compare our analytical results with recent lattice simulations.

Hosted by: Yuta Kikuchi

We will focus on the theoretical description of exclusive ρ meson production in eA collisions, using a hybrid factorization scheme which involves Balitsky's shockwave description of the Color Glass Condensate in the t channel, and Distribution Amplitudes (DAs) in the s channel. We will first give a quick introduction to the shockwave framework and to collinear factorization up to twist 3 for DAs, then we will apply these framweworks to the production of a longitudinal meson at NLO accuracy, and to the production of a transverse meson at twist 3 accuracy. We will insist on the experimental applications, and on several theoretical questions raised by our results: the dilute BFKL limit at NLO for diffraction, and collinear factorization breaking at twist 3.

Hosted by: Niklas Mueller

Exotic phases of QCD exhibiting strong correlations exist at very high baryon density and relatively low temperatures. Examples of such phases range from nucleon superfluid phases expected to occur in the interior of neutron stars, to possible color superconducting phases, which may occur in the core of a neutron stars. Some of these phases may also occur in relativistic heavy ion collisions in the high baryon density regime, e.g. at RHIC (BES), FAIR, and NICA. We discuss the possibilities of detecting them in heavy ion collisions focusing on the universal aspects of associated phase transitions.

Hosted by: Niklas Mueller

Hosted by: Yuta Kikuchi

Hosted by: Niklas Mueller

In relativistic heavy nucleus collisions an ultra-dense, high-temperature state of nuclear matter is created with de-confined quarks and gluons. Understanding how the non-equilibrium Quark-Gluon Plasma thermalizes is important in connecting the initial state physics with the emergent hydrodynamic behavior of the QGP at later times. In this talk, I will use weakly coupled QCD kinetic theory with quark and gluon degrees of freedom to study the QGP evolution in the far-from-equilibrium regime, where it exhibits universal scaling, and its approach to thermal and chemical equilibrium.

Hosted by: Yuya Tanizaki

Hosted by: Sally Dawson

Hosted by: Chun Shen

Next-generation neutrinoless double-beta decay experiments aim to discover lepton-number violation in order to shed light on the nature of neutrino masses. A non-zero signal would have profound implications by demonstrating the existence of elementary Majorana particles and possibly pointing towards a solution of matter-antimatter asymmetry in the universe. However, the interpretation of the experimental signal (or lack thereof) requires care. First of all, a single nonzero measurement would indicate lepton-number violation but will not identify the underlying source. Second, complicated hadronic and nuclear input is required to connect the experimental data to a fundamental description of lepton-number violation. In this talk, I will use effective field theories to connect neutrinoless double-beta decay measurements to the fundamental lepton-number-violating source.

Hosted by: Andrey Tarasov

Pythia 8 is a general-purpose Monte-Carlo event generator widely used to simulate high-energy proton-proton collisions at the LHC. Recently it has been extended to handle also other collision systems involving lepton and heavy-ion beams. In this seminar I will review the current Pythia 8 capabilities in processes relevant to an Electron-Ion Collider (EIC) and discuss about the projected future improvements. The relevant processes can be divided into two regions based on the virtuality of the intermediate photon: deeply inelastic scattering (DIS) at high virtualities and photoproduction at low virtualities. I will begin with an introduction of the event generation steps in Pythia 8 and then briefly discuss how the DIS processes can be simulated. Then I present our photoproduction framework and compare the results to the HERA data for charged-hadron and dijet production in lepton-proton collisions. In particular I discuss about the role of multiparton interactions in photon-proton interactions with resolved photons and how these can be constrained with the existing HERA data. Then I discuss how the same framework can be applied to ultra-peripheral heavy-ion collisions at the LHC where one can study high-energy photon-nucleus interactions in a kinematic region comparable to EIC. Finally I will show our first predictions for dijet production in these events and quantify the contribution of diffractive events according to the hard diffractionmodel that has been recently implemented into Pythia 8.

Hosted by: Sally Dawson

Since the discovery of a Higgs boson in 2012 at CERN, accessing its properties is one of the main goals of the Large Hadron Collider (LHC) experimental collaborations. The triple Higgs coupling in particular is a primary target as it would be a direct probe of the shape of the scalar potential at the origin of the electroweak-symmetry-breaking mechanism, and is directly accessed via the production of a pair of Higgs bosons. In this view, it is of utmost importance to reach high precision in the theoretical prediction of Higgs boson pair production cross section at the LHC. I will present in this talk the calculation of the 2-loop QCD corrections to the Higgs-pair-production cross section via gluon fusion, that is the main production mechanism, including the top-quark mass effects in the loops. It will be shown that they can be significant in the Higgs-pair-mass differential distributions.

Hosted by: Rob Pisarski

I will discuss the uncertainty in quantum mechanics as a property reflecting the "quantity" (measure) on the set of possible probing outcomes. This is in contrast to the commonly used "spectral distance" (metric). An unexpected insight into the nature of quantum uncertainty (and that of measure) is obtained as a result. One of the motivations for considering measure uncertainty is that it is directly relevant for assessing the efficiency of quantum computation.

Hosted by: Rob Pisarski

Non-relativistic quantum matter, as realized in ultracold atomic gases, continues to be a remarkably versatile playground for many-body physics. Experimentalists have exquisite control over temperature, density, coupling, and shape of the trapping potential. Additionally, a wide range of properties can be measured: from simple ones like equations of state to more involved ones like the bulk viscosity and entanglement. The latter has received much attention due to its connection to quantum phase transitions, but it has proven extremely difficult to compute: stochastic methods display exponential signal-to-noise issues of a very similar nature as those due to the infamous sign problem affecting finite-density QCD. In this talk, I will present an algorithm that solves the signal-to-noise issue for entanglement, and I will show results for strongly interacting systems in three spatial dimensions that are the first of their kind. I will also present a few recent explorations of the thermodynamics of polarized matter and other cases that usually have a sign problem, using complexified stochastic quantization.

Hosted by: Enrico Rinaldi

We study the chaotic nature of classical and quantum systems. In particular, we will study the detail of the Lyapunov growth. We will show the evidence that the spectrum of Lyapunov exponents admits universal description by Random Matrix Theory, and systems dual to black holes exhibit 'strong' universality.

Hosted by: Enrico Rinaldi

Hosted by: Chun Shen

Jets are collimated spray of hadrons that are naturally produced in high energy colliders. They are powerful probes of many different aspects of QCD dynamics. In this talk, we will demonstrate how to use jets to explore the transverse momentum dependent (TMD) physics. A novel TMD framework to deal with back-to-back two particle correlations is presented, with which we could study the Sivers asymmetry for photon+jet or dijet production in transversely polarized proton-proton collisions. At the end of the talk, we also show how jet substructure could be used to explore the TMD fragmentation functions. We expect these studies to have important applications at RHIC in the future.

Hosted by: Rob Pisarski

Hosted by: Chun Shen

Comparing collision systems of different size, at near the same collision energy, offers us the opportunity to probe the scaling behavior and therefore the nature of the system itself. Recently, we made predictions for Xe-Xe collisions at 5.44 TeV using viscous hydrodynamic simulations, noting that the scaling from the larger Pb-Pb system is rather generic, and arguing that robust predictions can be made that do not depend on details of the model. Here we confront our predictions with measurements that were subsequently made in a short Xe-Xe run at the LHC by the ALICE, ATLAS, and CMS collaborations. We find that the predictions are largely confirmed, with small discrepancies that could point the way to a better understanding of the medium created in such collisions.

Hosted by: Yuya Tanizaki

We report our study on the properties of the topological structures present in the QCD medium. We use dynamical domain wall fermion configurations on lattices of size 32^3x8 and detect the topological structures through the zero modes of the overlap operator. We explicitly show that the properties of the zero modes of the QCD Dirac operator agrees well with that of calorons with non-trivial holonomy. Different profiles of the zero modes are observed, ranging from solutions that are localized in all four spacetime dimensions, to profiles that are localized in the spatial directions, and constant along the temporal extent of the lattice. This indicates towards the presence of instanton-dyons in the hot QCD medium around Tc, where the distance between dyons control the shape and extent of the zero modes.

Hosted by: Chun Shen

In this talk I violate the common wisdom "one seminar — one message" and discuss two seemingly unrelated results in the framework of the dilute-dense CGC approach: the effect of spatial eccentricity of the projectile (proton) shape on the second harmonic in double-inclusive gluon production and the theoretical description of the high gluon multiplicity tail. I will show that these two superficially unrelated results in combination may lead to unexpected consequences for the phenomenology of p-A collisions.

Hosted by: Chun Shen

An electron-ion collider can test many fundamental features of QCD for hadron and nuclear physics, including flavor-dependent antishadowing in deep inelastic electron-nucleus scattering, the breakdown of sum rules for nuclear structure functions, the role of ``hidden-color " degrees of freedom, and the effects of "color transparency" on the baryon-to-meson anomaly observed at high transverse momentum in heavy-ion collisions. I will also discuss intrinsic heavy quark phenomena and the production of exotic multiquark states at the EIC. On the theory side, I will discuss the new insights into color confinement that one obtains from light-front holography, including supersymmetric features of the meson, baryon, and tetraquark spectroscopy. The Principle of Maximum Conformality (PMC) can be used to systematically eliminate renormalization scale ambiguities and thus obtain scheme-independent pQCD predictions.

Hosted by: Co-hosted by Christoph Lehner and Taku Izubuchi

Hosted by: Mattia Bruno and Enrico Rinaldi

Quantum simulation proposes to use future quantum computers to calculate properties of quantum systems. In the context of chemistry, the target is the electronic structure problem: determination of the electronic energy given the nuclear coordinates of a molecule. Since 2006 we have been studying quantum approaches to quantum chemical problems, and such approaches must face the challenges of high, but fixed, precision requirements, and fermion antisymmetry. I will describe several algorithmic developments in this area including improvements upon the Jordan Wigner transformation, alternatives to phase estimation, adiabatic quantum computing approaches to the electronic structure problem, methods based on sparse Hamiltonian simulation techniques and the potential for experiments realizing these algorithms in the near future. I will also briefly review work by others on the analog and digital simulation of lattice gauge theories using quantum simulators.

Hosted by: Chun Shen

QCD at finite temperature and moderate densities predicts a phase transition from a chiral symmetry broken hadronic phase to a chirally restored deconfined quark-gluon plasma phase. In this talk I report on recent progress achieved basically with functional renormalization group (FRG) methods to reveal the QCD phase structure. Two and three quark flavor FRG investigations are confronted to results obtained with effective chiral low-energy models. The importance of quantum and thermal fluctuations is demonstrated and their consequences for the experimental signatures to detect possible critical endpoints in the phase diagram are discussed.

Hosted by: Chun Shen

QCD at large, but not asymptotically large, baryon density presents an enormous theoretical challenge because first-principle calculations are nearly impossible. Phenomenologically, dense QCD is of great interest for the interior of neutron stars, in particular after the recent detection of gravitational waves from neutron star mergers. I will discuss a holographic approach to dense matter, making use of the Sakai-Sugimoto model, which can account for both nuclear matter and quark matter and the transition between them. In particular, nucleons are implemented as instantons in the bulk, and I will discuss certain approximations for many-nucleon matter based on the flat-space instanton solution and present the resulting phase diagrams.

Hosted by: Yuya Tanizaki

Hosted by: Andrey Tarasov

It is well known that BFKL gives anomalous dimensions of twist-2 operators of spin j in the "BFKL limit'' $g^2\righarrow 0,\omega\equiv j-1\righarrow 0,{g^2\over\omega}$ fixed. I demonstrate that such limit describes the non-local light-ray operators and present the results of calculation of two- and three-point correlation functions of these operators in this limit. The calculation is performed in ${\cal N}$=4 SYM but the result is valid in other gauge theories such as QCD.

Hosted by: Chun Shen

The MHV action is the Yang-Mills action quantized on the light-front, where the two explicit physical gluonic degrees of freedom have been canonically transformed to a new set of fields. This transformation leads to the action with vertices being off-shell continuations of the MHV amplitudes. We show that the solution to the field transformation expressing one of the new fields in terms of the Yang-Mills field is a certain type of the Wilson line. More precisely, it is a straight infinite gauge link with a slope extending to the light-cone minus and the transverse direction. One of the consequences of that fact is that certain MHV vertices reduced partially on-shell are gauge invariant — a fact discovered before using conventional light-front perturbation theory. We also analyze the diagrammatic content of the field transformations leading to the MHV action. We found that the diagrams for the solution to the transformation (given by the Wilson line) and its inverse differ only by light-front energy denominators.

Hosted by: Chun Shen

It has long been known that sub-nucleonic fluctuations of the energy density in the initial stages of heavy ion collisions play an important role in generating the observed distributions of particles and their flow. These energy density fluctuations are dominated by the radiation of small-x gluons which are populated to classically large occupation numbers in the wave functions of ultra-relativistic heavy ions. While these soft gluons dominate the initial conditions for the energy density, it is quark production which determines the initial conditions of other conserved charges, like flavor and baryon number. With the recent development of state-of-the art hydrodynamics codes tailored to the Beam Energy Scan which can propagate these conserved charges into the final state, it is timely and important to calculate the initial conditions of these conserved charges from first principles in QCD. In this talk, I will present new results for the spatial correlations among quarks and antiquarks produced at mid-rapidity by pair production from small-x gluons. This single-pair production mechanism, which has been studied for some time in momentum space, is the leading contribution to these correlations in coordinate space for dilute-dense collisions. As one moves from the dilute-dense regime toward the dense-dense regime, correlations due to double pair production become more important, and these correlations persist over larger length scales than the single-pair production mechanism. Over nonperturbative length scales, only the correlations from the overlap geometry remain. I will present explicit results for quark-antiquark correlations due to single pair production, and I will outline some preliminary results for the various double-pair production mechanisms. The ultimate goal of this work will be to construct a code which can initialize these conserved charges over all length scales in heavy-ion collisions.

Hosted by: Eric Lancon

Particle physics has an ambitious and broad experimental program for the coming decades. This program requires large investments in detector hardware, either to build new facilities and experiments, or to upgrade existing ones. Similarly, it requires commensurate investment into R&D of software to acquire, manage, process, and analyses the shear amounts of data to be recorded. In planning for the High Luminosity LHC in particular, it is critical that all of the collaborating stakeholders agree on the software goals and priorities, and that their efforts complement each other. In this spirit, the High Energy Physics community has created a white paper (arXiv:1712.06982) to describe and define the R&D activities required in order to prepare for this software upgrade. This presentation describes the expected software and computing challenges, and the plans to address them that are laid out in the white paper.

Hosted by: Yuya Tanizaki

Hosted by: Yuya Tanizaki

Hosted by: Chun Shen

Studying confining gauge theories on a circle can provide answers to some of the deepest questions about QCD. In this talk, I start by summarizing the main characteristics shared by the compactified theories and their four dimensional cousins. Next, I show that the glueball spectrum of the compactified theories is much richer than what have been thought before. In particular, new nonperturbative scales and glueballs emerge in the deep IR regime of the theory. I discuss the spectrum in the context of super Yang-Mills and show that the lightest glueball states fill a chiral supermultiplet with doubly nonperturbative binding energy. I end with possible implications of these findings for the four dimensional gauge theories.

Hosted by: Yuya Tanizaki

Hosted by: Enrico Rinaldi

Recently, we find a new 't Hooft anomaly of massless 3-flavor QCD, and it turns out to be useful for constraining the possible chiral symmetry breaking at finite density and zero temperature. We briefly review the anomaly matching by a toy example, and show that massless 3-flavor QCD has an 't Hooft anomaly related to ''center'' and discrete axial symmetries. We also discuss its consequences on the expectation value of the special symmetry-twisting operator, which gives the phase diagram of so-called Z(3)-QCD.

We review the denition of semi-inclusive jet functions within Soft Collinear Eective Theory (SCET) and their application to inclusive jet cross sections. We consider the fully inclusive production cross section of jets as well as several jet substructure observables in proton-proton collisions relevant for the LHC and RHIC. The corresponding semi-inclusive jet functions satisfy renormalization group (RG) equations which take the form of standard timelike DGLAP evolution equations, analogous to collinear fragmentation functions. By solving these RG equations, the resummation of potentially large single logarithms n s lnn R can be achieved. We present numerical results at NLO+NLLR accuracy and compare to the available data.

Hosted by: Enrico Rinaldi

Experimental searches for messengers of CP- and P- odd phenomena at RHIC and LHC have attracted much interest and are a prime motivation for significant theoretical effort: Anomalous and topological effects receive important contributions from the pre-equilibrium phase of a collision and an interesting question of phenomenological relevance is how the chiral imbalance generated at early times persists through a fluctuating background of sphalerons in addition to other "non-anomalous" interactions with the QGP. To address this question, we construct a relativistic chiral kinetic theory using the world-line formulation of quantum field theory. We outline how Berry's phase arises in this framework, and how its effects can be clearly distinguished from those arising from the chiral anomaly. We further outline how this framework can be matched to classical statistical simulations at early times and to anomalous chiral hydrodynamics at late times.

Hosted by: Yuya Tanizaki

Three-dimensional gauge theories with massless fermions provide a simple yet non-perturbative setting to understand why QCD has a scale, and also provide effective descriptions of condensed matter systems. Along these lines, I will present results on infra-red scaling and scale-breaking in three-dimensional QED, QCD and large-Nc theories. I will also present some preliminary results on three-dimensional QED with one flavor of fermion regulated with and without parity anomaly.

We study the Hagedorn transition in the singlet sector of the simplest super-string bit model in the tensionless limit. The gauge group of our model is SU(N) and this transition takes place when N is infinite. We use orthogonality of group characters in order to calculate the partition function. At the Hagedorn temperature there is a change in the distribution of parameters that maximize this partition function. We conclude by devising a field-theoretic interpretation of the this phenomenon.

Hosted by: Andrey Tarasov

In this talk, I will present a recent global QCD analysis of spin-dependent PDFs and FFs using a MC methodology by the Jefferson Angular Momentum collaboration (JAM).

Hosted by: Enrico Rinaldi

For nearly a century, dissipative effects have been included in fluid dynamics using gradients of macroscopic quantities such as the temperature and fluid velocity. Recently, results from heavy ion collision experiments and explicit model calculations have pushed the boundaries of relativistic fluid dynamics towards the far-from-equilibrium regime. In this talk I will present calculations of the large order behavior of the gradient expansion, both in kinetic theory and in holography, which have demonstrated that this series has zero radius of convergence. I will discuss the role played by novel non-equilibrium attractor solutions in determining the emergence of fluid dynamic behavior in many-body systems under extreme conditions.

Hosted by: Chun Shen

A coupled linear Boltzmann transport and hydrodynamics model (CoLBT-hydro) is developed for concurrent simulation of jet propagation and hydrodynamic evolution in high-energy nuclear collisions. Diverse microscopic scattering processes (elastic and inelastic) are incorporated for parton showers, and both massive and massless partons are calculated on the same footing. Energy deposition from jets into nuclear matter is treated as source term of hydrodynamic evolution. Within this CoLBT-hydro model, nuclear modification of heavy and light flavor hadrons are simultaneously described. Evidence of jet-induced medium excitation is explored with photon-triggered jets, where significant enhancement of soft hadron production is found due to energy deposition from jets.

Hosted by: Chun Shen

The phenomenon of jet quenching in ultra-relativistic heavy ion collisions reveals to effect of substantial finial state interactions which cause QCD jets to lose energy to the quark-gluon plasma (QGP), mainly by induced gluon radiation. In standard analytic approaches to energy loss, jets are approximated by single partons and thus higher-order effects in the strong coupling constant are neglected. This may prove insufficient to reliably extract QGP properties at high pT, where a significant jet suppression was recently reported by the ATLAS collaboration in PbPb collisions at the LHC. In this work we explore higher-order corrections to the inclusive jet spectrum which may be sizable owing to the fact that the probability for a highly virtual parton to split in the medium increases with the jet pT. As the effective number of jet constituents increases, jets are expected to lose more energy than a single color charge. This translates into large logarithmic enhancements of higher-orders in the perturbative series, that need to be resummed. As a result we obtain a Sudakov-like suppression factor which we investigate in the leading logarithmic approximation. We note, however, that the phase space for higher-order corrections is mitigated by coherence effects that relate to the fact that, below a characteristic angular scale, the medium does not resolve the inner jet structure. In this case, the jet lose energy coherently as a single color charge, namely, the primary parton.

Hosted by: Hiromichi Nishimura

We present non-perturbative first-principle results for quark-, gluon- and meson 1PI correlation functions of two-flavour Landau-gauge QCD in the vacuum and Yang-Mills theory at finite temperature. They are obtained by solving their Functional Renormalisation Group equations in a systematic vertex expansion, aiming at apparent convergence within a self-consistent approximation scheme. These correlation functions carry the full information about the theory and their connection to physical observables is discussed. The presented calculations represent a crucial prerequisite for quantitative first-principle studies of QCD and its phase diagram within this framework. In particular, we have computed the ghost, quark and scalar-pseudoscalar meson propagators, as well as gluon, ghost-gluon, quark-gluon, quark, quark-meson, and meson interactions and the magnetic and electric components of the gluon propagator, and the three- and four-gluon vertices. Our results stress the crucial importance of the quantitatively correct running of different vertices in the semi-perturbative regime for describing the phenomena and scales of confinement and spontaneous chiral symmetry breaking without phenomenological input. We confront our results for the correlators with lattice simulations and compare our Debye mass to hard thermal loop perturbation theory. Finally, applications to "QCD-enhanced" low-energy effective models of QCD are discussed.

Hosted by: Chun Shen

Hosted by: Hiromichi Nishimura

Hosted by: Sally Dawson

Hosted by: Hiromichi Nishimura

Quarkonium can be used as a probe of quark-gluon plasma (QGP) in heavy ion collisions. The production process is complicated by several factors: plasma screening effect, in-medium dissociation and recombination, cold nuclear matter effect and feed-down contributions. In this talk, I will present a set of Boltzmann transport equations that govern the in-medium evolution of the heavy quark and quarkonium system. The dissociation and recombination rates are calculated from potential non-relativistic QCD at leading order. I will explain how the system reaches equilibrium in a QGP box and show how the system evolves under a boost invariant longitudinal expansion. I will argue that the angular distribution of quarkonium probes the stages at which recombination occurs. The presented framework will be extended in future work to include other factors influencing quarkonium production.

Hosted by: Chun Shen

In the so-called isobar parametrization the three-particle states are populated via an interacting two-particle system (resonant or non-resonant), and a spectator. Using this parametrization, we derive the isobar-spectator interaction such that the three-body Unitarity is ensured exactly. In the first part of my talk I will show the major steps of this derivation. (arXiv:1706.06118) The second part of the talk will be dedicated to the finite-volume implementation of the framework (arXiv:1709.08222). Imaginary parts in the infinite volume, dictated by Unitarity, determine the dominant power-law finite volume effects to ensure the correct 3-body quantization condition. Furthermore, various building blocks of the 3->3 amplitude in the finite volume can become singular. However, when all contributions are summed-up, only genuine 3-body singularities remain. I will demonstrate the corresponding cancellation mechanisms explicitly for the simplified case of only one S-wave isobar.

Hosted by: Enrico Rinaldi

The nucleon axial form factor is a dominant contribution to systematic uncertainties in neutrino oscillation studies. The most commonly used model parametrization of the axial form factor has uncontrolled and underestimated systematic errors. First-principles computations from lattice QCD have the potential to control theory errors by disentangling the effects of nuclear corrections from the nucleon amplitudes. In this talk, I discuss fits to the axial form factor with deuterium bubble chamber data using the model-independent $z$ expansion parameterization. I then present preliminary results for a blinded lattice QCD calculation of the nucleon axial charge $g_A$ with physical light quark masses. This calculation is being done with the Highly Improved Staggered Quark (HISQ) action and 2+1+1 flavors of sea quarks.

Hosted by: Chun Shen

The Quark Gluon Plasma (QGP), nature's first and most perfect liquid, has been successfully reproduced in heavy-ion collisions at RHIC and the LHC. The dynamics of the QGP can be well described by relativistic viscous hydrodynamics, allowing for precise comparisons to experimental data in order to extract the properties of the QGP. While a small shear viscosity is well-established, questions still remain regarding the precise initial state, the temperature dependence of viscosity, the smallest system that displays QGP-like properties, and the equation of state at large densities. In this talk, the various flow harmonic observables are analyzed to help answer these remaining questions.

Hosted by: Heikki Mantysaari

Recent developments have shown that QCD-like theories can be engineered to remain in a confined phase when compactified on an arbitrarily small circle, where their features may be studied quantitatively in a controlled fashion. I'll explain how a non-perturbative mass gap and chiral symmetry breaking, which are both historically viewed as prototypical strong coupling effects, appear from systematic weak-coupling calculations. Then I'll describe the rich spectrum of hadronic states, including glueball, meson, and baryon resonances in the calculable small-circle context.

Hosted by: Hiromichi Nishimura

An infinite dimensional symmetry group which governs the infrared sectors of gauge and gravity theories has been recently discovered. This symmetry can be established both from an asymptotic symmetry analysis as well as from the corresponding Ward identities which are quantum field theoretic soft theorems. Moreover, the spontaneous breaking of these symmetries induces vacuum transitions which are detectable by charged particles through the so-called memory effect. In this seminar, I will explain the precise equivalence between asymptotic symmetries, soft theorems and memory effects in the context of tree level Yang-Mills. In particular, in this context the soft gluon theorem is Ward identity of a large gauge symmetry, whose action on the vacuum can be measured from the relative color charge of colored detectors.

Hosted by: Heikki Mantysaari

Starting from the Color Glass Condensate (CGC) cross section for dijet production in proton-nucleus collisions we derive a transverse-momentum-dependent (TMD) factorization formula for small transverse-momentum imbalance of the jets and for finite number of colors. For the eight TMD distributions appearing in the cross section we determine their operator definitions at small-x as CGC correlators of Wilson lines and we study their JIMWLK evolution. We find that at large transverse momentum the universality of TMDs gets restored. We also discuss an extension of the approach to generalized TMDs (GTMDs) that can give an insight into the angular correlations between impact parameter and dipole size in the CGC framework.

Hosted by: Hiromichi Nishimura

Multi-particle correlations measured in heavy-ion collision experiments carry info on fluctuations present in the entire evolutionary history of the system. Initial states include geometric and quantum fluctuations and are important contributors. The thermal fluctuations during the course of QGP evolution is another conceptually important source of these fluctuations and should be studied in detail. We begin by treating thermal fluctuations as a linearized perturbation on hydrodynamic background. We present a full calculation of hadronic and photonic observables including these fluctuations. Recently we have included fluctuations in our simulations in a non-perturbative manner. Progress based on this approach will be discussed.

Hosted by: Heikki Mantysaari

We discuss various cross sections and spin observables in high-pT hadron production in lepton proton collisions, with special focus on the role of perturbative QCD corrections. We present phenomenological studies relevant for present fixed-target experiments and for a future EIC.

Hosted by: Heikki Mantysaari

Factorization and phenomenology for Transverse Momentum Dependent distributions Abstract: The factorization of the hadronic part of the cross sections plays a central role in our comprehension of collider physics. I will review some aspects of the factorization, like the appearence of rapidity divergences and the related subtractions and log resummation (up to higher orders in QCD perturbative expansion) in transverse momentum dependent cross sections. As an application I will describe the inclusion of the TMD formalism in an analysis of vector boson production data.

Hosted by: Hiromichi Nishimura

In high energy heavy-ion collisions, the soft degrees of freedom at the very initial stage after the collision can be effectively represented by strong classical gluonic fields within the Color Glass Condensate framework. Understanding the space-time evolution of the system is equivalent to solving the classical Yang-Mills equations for the gluonic fields. There have been many efforts in the past two decades in numerically solving these equations. In this talk, on the contrary, I will use a semi-analytic approach that assumes the solution has the form of a power series expansion in the proper time. I will discuss the energy-momentum tensor and the gluon spectrum obtained from this approach and make comparisons with the numerical results in the literature.

Hosted by: Heikki Mantysaari

The large angle emission of soft gluons from QCD jets gives rise to the so-called nonglobal logarithms. In this talk I discuss the resummation of nonglobal logarithms at finite Nc with particular emphasis on its deep connection to the small-x logarithms in high energy scattering.

Hosted by: Heikki Mantysaari

I talk about general formulae to compute Wilson line correlators with the Color Glass Condensate approximated by the McLerran-Venugopalan model. Specifically, as an application, I explain about a perturbative expansion of the dipole correlators in terms of 1/N_c to derive fully analytical expressions. I finally discuss the validity of the large-N_c expansion by calculating the higher-order harmonics of the flow observables in the dipole model.

Hosted by: Heikki Mantysaari

I will discuss the general nature of the holographic Pomeron as a quantum QCD string exchange in both flat and curved AdS space for both pp and ep collisions at either large energies or small x. This description leads naturally to the concept of wee-strings and their distribution both in rapidity and transverse space. The holographic Pomeron carries intrinsic temperature and entropy, with the latter being identical to the recently reported entanglement entropy. I will show that this non-perturbative description of the Pomeron cross over to the the perturbative one, with a phase boundary dominated by string balls, i.e. long and massive strings near their intrinsic Hagedorn temperature. These string balls lead to a distribution of large multiplicity pp events that is in agreement with the one reported for pp collisions at the LHC. I will show that at low-x, the quantum string is so entangled that very weak string self-interactions can cause it to turn to a black hole. I will suggest that low-x saturation occurs when the density of wee-strings reaches the Bekenstein bound, with a proton size that freezes with increasing rapidity.

Hosted by: Heikki Mantysaari

In this talk, we will discuss the dijet azimuthal de-correlation in relativistic heavy ion collisions as an important probe of the transverse momentum broadening effects in heavy ion collisions. We take into account both the soft gluon radiation in vacuum associated with the Sudakov logarithms and the jet PT-broadening effects in the QCD medium. We find that the Sudakov effects are dominant at the LHC, while the medium effects can play an important role at RHIC energies. This explains why the LHC experiments have not yet observed sizable PT-broadening effects in the measurement of dijet azimuthal correlations in heavy ion collisions. Future investigations at RHIC will provide a unique opportunity to study the PT-broadening effects and help to pin down the underlying mechanism for jet energy loss in a hot and dense medium.

Hosted by: Heikki Mantysaari

One of the puzzles we have faced at the LHC is why the thermal models apparently cannot properly fit the yield of protons. I will explore how the fit improves if we assume that nucleon-antinucleon annihilations freeze-out way later than all other number changing processes or if strange particles freeze-out before non-strange particles, and how this affects the final particle distributions in hydrodynamical calculations.

Hosted by: Heikki Mantysaari

The past years have seen tremendous progress in the description of Quantum Chromodynamics at vanishing and finite temperature and density with functional approaches, such as the functional renormalisation group or Dyson-Schwinger equations. Within these approaches QCD correlation functions of quarks, gluon and hadrons are computed non-perturbatively from first principles. In the talk I will discuss results for the phase structure of QCD at finite temperature and density, as well as for thermodynamical obserables such as the pressure and the trace anomaly. The approach is also applied to baryon number fluctuations. By now functional approaches also allow for a direct computation of transport coefficients in QCD. First results concern the temperature dependence of the shear viscosity over entropy ratio in Yang-Mills theory and QCD. The talk concludes with a discussion of the further prospects for our understanding of the phase structure and dynamics of QCD.

Hosted by: Pier Paolo Giardino

Hosted by: Heikki Mantysaari

I will present the results of recent lattice QCD studies of the gluon generalised form factors of both hadrons and light nuclei. The generalised transversity gluon distributions are of particular interest since they are purely gluonic; they do not mix with quark distributions at leading twist. In light nuclei they moreover provide a clean signature of non-nucleonic degrees of freedom. The goal of these studies is to provide QCD predictions to be tested at an electron-ion collider (EIC) designed to access gluon structure quantities including transverse-momentum dependent distributions (TMDs) and gluon generalised parton distributions (GPDs).

Hosted by: Hiromichi Nishimura

Hosted by: Heikki Mantysaari

We develop a set of kinetic equations for hydrodynamic fluctuations which are equivalent to nonlinear hydrodynamics with noise. The hydrokinetic equations can be coupled to existing second-order hydrodynamic codes to incorporate the physics of these fluctuations. We use the hydrokinetic equations to analyze thermal fluctuations for a Bjorken expansion, evaluating the contribution of thermal noise from the earliest moments and at late times. In the Bjorken case, the solution to the kinetic equations determines the coefficient of the first fractional power of the gradient expansion $ \sim 1/(\tau T)^{3/2}$ for the expanding system. Numerically, we find that the contribution to the longitudinal pressure from hydrodynamic fluctuations is larger than second-order hydrodynamics for typical medium parameters used to simulate heavy ion collisions. Subsequently we analyze the behaviour of hydrodynamic fluctuations of near the QCD critical point, and dilineate the relevance Kiblle-Zurek scaling relative to other physics. If time permits we will also describe how thermal fluctuations place a lower bound on the bulk viscosity of QCD. References: Y.~Akamatsu, A.~Mazeliauskas and D.~Teaney, ``A kinetic regime of hydrodynamic fluctuations and long time tails for a Bjorken expansion,'' [arXiv:1606.07742 [nucl-th]]. Y.~Akamatsu, D. Teaney, F. Yan, Y. Yin, ``Transitting the critical point,'' in progress.

Hosted by: Hiromichi Nishimura

Symmetry and topology are powerful tools to study strongly interacting dynamics. In this talk, we will see that mixed 't Hooft anomaly and global consistency strongly constrains the possible low-energy dynamics in a simple quantum mechanical example. I will briefly explain the same idea is useful to study the phase diagram of bifundamental gauge theories at finite theta angles.

Hosted by: Hiromichi Nishimura

Hosted by: Pier Paolo Giardino

Hosted by: Hiromichi Nishimura

Hosted by: Heikki Mantysaari

Multi-particle correlations observed in small collision systems at top LHC energies exhibit signatures which are similar to those observed in large collision systems and generally attributed to the formation of a deconfined quark-gluon plasma (QGP). This suggests that even proton-proton and proton-lead collisions may produce small droplets of QGP which translate spatial inhomogeneities into final-state momentum anisotropies. A primary challenge in testing hydrodynamic descriptions of small collision systems is in modeling the initial stages of the collision. In this talk, I discuss recent efforts to apply Bayesian methodology to parametric descriptions of initial state physics. I show that such methods can be extended to smaller length scales which include partonic degrees of freedom and glean information regarding the fluctuating nature of the proton.

Hosted by: Enrico Rinaldi

"There is long-standing theoretical interest in the behavior of a strongly-coupled gauge theory in the presence of multiple fermions charged under different representations of the gauge group. In addition to the question of whether generation of dynamically separated scales will occur, such theories appear commonly in UV realizations of composite Higgs models with partially composite top quarks. I will present a first lattice study of SU(4) gauge theory with fermions in each of the two lowest-lying representations, discussing the finite-temperature phase structure and low-lying spectrum. Connections to BSM physics through a particular composite Higgs model will also be made."

Hosted by: Heikki Mantysaari

The conformal bootstrap aims to calculate scaling dimensions and correlation functions in various theories, starting from general principles such as unitarity and crossing symmetry. I will explain that local operators are not independent of each other but organize into analytic functions of spin, and I will present a formula, extending a classic one due to Froissart and Gribov in the early days of Regge theory, which quantifies the consequences of this fact. Applications will include a new way to solve crossing symmetry at large spin, as well as new bounds encoding bulk locality in theories with a gravity dual. Based on 1703.00278.

Hosted by: Heikki Mantysaari

Single inclusive particle production cross sections in high energy hadron collisions at forward rapidity are an important benchmark process for the CGC picture of small x QCD. The process can be calculated in the "hybrid formalism", where a collinear large-x quark or gluon scatters off the dense color field of the target. Recent calculations at next-to-leading order in perturbation theory have not led to a stable physical result for the single inclusive cross section at high transverse momenta. The problem with these NLO calculations lies in the subtraction procedure for the soft "rapidity" divergence which must be absorbed into BK renormalization group evolution of the target. This talk discusses recent work to understand and resolve the problems with the subtraction procedure. In particular, we have recently implemented numerically the quark channel production cross section using a new rapidity factorization procedure proposed by Iancu et al. For a fixed coupling one does indeed obtain a physically meaningful cross section which is positive and reduces in a controlled way to previous leading order calculations. However, it is not yet clear how to generalize this to running coupling in a way that is fully consistent with previous leading order calculations in coordinate space.

Hosted by: Heikki Mantysaari

Very strong magnetic fields can arise in non-central heavy-ion collisions at ultrarelativistic energies, which may not decay quickly in a conducting plasma. We carry out magnetohydrodynamics simulations to study the effects of this magnetic field on the evolution of the plasma and on resulting flow fluctuations. Our results show that magnetic field leads to enhancement in elliptic flow, while flow fluctuations lead to reorganization of magnetic flux resulting in a transient increase in the local magnetic field. We also show generation of vorticity arising from nontrivial dependence of magnetosonic waves on pressure gradients and magnetic field direction. Magnetic field from collision of deformed nuclei shows very nontrivial features and can lead to qualitatively new effects on plasma evolutions. We discuss possibility of dynamo effect in the presence of vortices if any exotic high baryon density QCD phases are achieved in heavy-ion collisions.

Hosted by: Heikki Mantysaari

In collisions of heavy ions at ultrarelativistic energies, a system of hot and dense strongly interacting matter is created. This matter exhibits a surprisingly strong degree of collectivity, implying a short mean free path of its constituents and, consequently, a small shear viscosity-to-entropy density ratio. This allows to describe the evolution of the system using relativistic dissipative fluid dynamics. Dissipative fluid dynamics can be understood as an expansion around local thermodynamical equilibrium, corresponding to the ideal-fluid limit where dissipative corrections are absent. A short mean free path means that this expansion is well defined and converges sufficiently rapidly. Nevertheless, in the initial stage of a heavy-ion collision, space-time gradients of the fluid-dynamical fields (energy-momentum and net-charge densities) are so large that dissipative corrections to the ideal-fluid limit can become sizable. In this situation, novel approaches to relativistic dissipative fluid dynamics are called for. One such approach is anisotropic dissipative fluid dynamics, which is based on an expansion around an anisotropic non-equilibrium state (instead of local thermodynamical equilibrium, as in conventional dissipative fluid dynamics). In this talk, I present a derivation of the equations of motion of anisotropic dissipative fluid dynamics from the Boltzmann equation, using the method of moments. I also discuss how to resolve an ambiguity to close the system of equations of motion in the case when there are no corrections to the anisotropic state which constitutes the basis of the moment expansion.

Hosted by: Hiromichi Nishimura

At the core of nuclear physics is to understand complex phenomena occurring in the hottest and densest known environments in nature, and to unravel the mystery of the dark sector and other new physics possibilities. Nuclear physicists are expected to predict, with certainty, the reaction rates relevant to star evolutions and nuclear energy research, and to obtain the "standard" effects in nuclei to reveal information about the "non-standard" sector. To achieve such certainty, the field has gradually started to eliminate its reliance on the phenomenological models and has entered an era where the underlying interactions are "effectively" based on the Standard Model of particle physics, in particular Quantum Chromodynamics (QCD). The few-nucleon systems can now emerge directly from the constituent quark and gluon degrees of freedom and with only QCD interactions in play, using the numerical method of lattice QCD. Few-body observable, such as few-nucleon interactions and scattering amplitudes, as well transition amplitudes and reaction rates, have been the focus of this vastly growing field, as once obtained from QCD, and matched to effective field theories, can advance and improve the nuclear many-body calculations of exceedingly complex systems. This talk is a brief introduction to this program and its goals, with a great focus on the progress in few-body observables from QCD.

Hosted by: Enrico Rinaldi

The current measurement of muonic g-2 disagrees with the theoretical calculation by about 3 standard deviations. Hadronic vacuum polarization (HVP) and hadronic light by light (HLbL) are the two types of processes that contribute most to the theoretical uncertainty. The current value for HLbL is still given by models. We report our latest lattice calculation of hadronic light-by-light contribution to muon g-2 using our recent developed moment method. The connected diagrams and the leading disconnected diagrams are included. The calculation is performed on a 48^3 × 96 lattice with physical pion mass and 5.5 fm box size. We expect sizable finite volume and finite lattice spacing corrections to the results of these calculations which will be estimated in calculations to be carried out over the next 1-2 years.

Hosted by: Heikki Mantysaari

The Skyrme model is a low energy effective field theory of strong interactions where nuclei and baryons appear as collective excitations of pionic degrees of freedom. Proposed by Tony Skyrme in the sixties, his ideas received further support when it was discovered that in the limit of the large number of colours of QCD, an effective theory of mesons arises. In the last years, there has been a revival of Skyrme's ideas and new related models, some of them with BPS bounds (topological lower energy bounds), have been proposed. It is the aim of this talk to focus on the one known as BPS Skyrme model. After a brief introduction to this BPS limit we study its application to neutron stars where we will find that high maximal masses are supported. In addition, the BPS Skyrme model allow us to perform both mean-field and exact calculations and a comparison between both approaches will be presented.

Hosted by: Heikki Mantysaari

Fragmentation is the earliest and perhaps most interesting QCD jet observable, since it directly deals with the parton-hadron duality at the end of the QCD cascade. The most basic fragmentation observables all enjoy the property of being universal, in the sense that a sufficiently energetic parton that initiates the cascade factorizes from the rest of the event, so that the underlying soft structure of the event to a good approximation does not change the fragmentation spectrum. With the luminosities and resolution of modern detectors, we can begin to study the fragmentation process in three dimensions: both the energy spectrum and the transverse fluctuations to the collinear direction of initiating hard parton. However, when one wants to study the transverse fluctuations, one becomes very sensitive to the underlying jet definition, in particular, how the collinear direction is defined. Intuitive definitions of the jet direction, like the total momentum of the jet constituents, are inherently sensitive to soft processes, and can spoil the universality of the spectrum. I will discuss how a simple change in the jet definition removes this soft sensitivity, and allows one to study the intrinsic three dimensional structure of collinear splittings, which should be process independent.

Hosted by: Hiromichi Nishimura

Hosted by: Pier Paolo Giardino

Hosted by: Heikki Mantysaari

Since decades expressions for the thermodynamic potential were calculated perturbatively at finite temperature (and density) and pushed to higher orders. I review the current status of these efforts including resummation techniques and compare them to results of lattice Monte Carlo simulations and address unanswered questions. Finally, I present results for several thermodynamic quantities within the next-to-leading order calculation of the thermodynamic potential at finite T and \mu including non-vanishing quark masses.

Hosted by: Hiromichi Nishimura

Symmetry and its spontaneous breaking are of basic importance for understanding the low energy physics in many-body systems. When a continuum symmetry is spontaneously broken, there exist a zero mode called Nambu-Goldstone (NG) mode, which is well developed in Lorentz invariant systems. In contrast, in non-Lorentz invariant systems, the NG theorem has not been well developed. In this talk, we discuss the recent progress in generalization of NG theorem in non-relativistic systems, open systems, and systems with higher form symmetries.

Hosted by: Hiromichi Nishimura

The entanglement entropy is a candidate of an entropy in Non-equilibrium physics and recently, relaxation or thermalization is studied through the entanglement entropy with quamtum quenching, which is sudden change of parameter(s) in the Hamiltonian of the system. Global quantum quench with a finite rate which crosses critical points is known to lead to universal scaling of correlation functions as functions of the quench rate. We explore scaling properties of the entanglement entropy of a subsystem of a scaler field on the lattice, harmonic chain, during a mass quench which asymptotes to finite constant values at early and late times and for which the dynamics is exactly solvable. Both for fast and slow quenches we find that the entanglement entropy has a constant term plus a term proportional to the subsystem size. For slow quenches, the constant piece is consistent with Kibble- Zurek predictions. Furthermore, the quench rate dependence of the extensive piece enters solely through the instantaneous correlation length at the Kibble-Zurek time, suggesting a new scaling hypothesis similar to that for correlation functions. This talk is based on arXiv:1702.04359.

Hosted by: Hiromichi Nishimura

Relativistic hydrodynamics is formulated based on the assumption that systems are almost in local thermal equilibrium. However, a quantum field theoretical way to handle such a locally thermalized system has not been clearly clarified. In this study, we develop a complete path-integral formulation of relativistic quantum fields in local thermal equilibrium, which brings about the emergence of thermally induced curved spacetime. The obtained path-integral formula for local thermal equilibrium enables us to derive nondissipative part of hydrodynamic constitutive relations based on symmetry arguments. As one application, we discuss a field theoretical derivation of anomalous hydrodynamics which captures the chiral magnetic/vortical effects.

Hosted by: Mattia Bruno

Hosted by: Chun Shen

Hosted by: Heikki Mantysaari

In this talk, I plan to discuss the recent theoretical progress towards the exploration of the gluon saturation phenomenon in pA collisions and at the future EIC. Two important pillars of this exploration are the single inclusive forward hadron productions and forward dijet correlations, which have both been computed up to one-loop order within the small-x factorization formalism. Complementary measurements in pA collisions and at the EIC can help us measure small-x gluon distributions and test the generalized small-x factorization. In addition, DIS diffractive dijet process is another interesting process which is sensitive to the dipole Wigner gluon distributions. This process can provide us 3D tomographic images of low-x gluons inside high energy protons and nuclei.

Hosted by: Mattia Bruno

Hosted by: Heikki Mantysaari

Recent classical-statistical numerical simulations have established the "bottom-up" thermalization scenario of Baier et al. as the correct weak coupling effective theory for thermalization in ultrarelativistic heavy-ion collisions. I will talk on a parametric study of photon production in the various stages of this bottom-up framework to ascertain the relative contribution of the off-equilibrium "Glasma" relative to that of a thermalized Quark-Gluon Plasma. Taking into account the constraints imposed by the measured charged hadron multiplicities at RHIC and the LHC, we find that Glasma contributions are important especially for large values of the saturation scale at both energies. Furthermore, I will report on first kinetic simulations of photon production in the expanding Glasma that will quantify our estimates.

Hosted by: Hiromichi Nishimura

In recent years significant progress has been made in our understanding of the small-x physics beyond the eikonal approximation. Rigorous analysis of the dependence on the transverse momentum helps us better understand not only physics of the Regge limit, but to connect it to the kinematic limit of the moderate-x as well. I'll describe the technique we used in calculation of TMD evolution observed in the Drell-Yan process and present some recent results.

Hosted by: Hiromichi Nishimura

Vector mesons play a prominent role for the detection of chiral symmetry restoration in the quark-gluon plasma since their in-medium modifications are directly observable in dilepton spectra. However, a direct connection between their in-medium modifications and chiral symmetry restoration remains elusive. To shed some light on this, I will first address the question how chiral symmetry breaking and the light (vector) mesons emerge from the underlying quark-gluon dynamics. Then, I will present preliminary results on the in-medium spectral functions of the rho and a1 mesons obtained from analytic continuation of Euclidean two-point functions.

Hosted by: Heikki Mantysaari

We discuss a new approach to solve the sign problem arising in the Monte Carlo evaluation of path integrals. It is based on deforming the contour of integration into complex space. We will argue that for conceptual and numeric reasons it may be advantageous not to use the steepest descent manifolds (thimbles). We will discuss a variety of algorithms and their application to field theories with a fermionic sign problem and to quantum mechanical models, including real time dynamics.

Hosted by: Heikki Mantysaari

In this talk I discuss the determination of plasmon mass in classical real-time Yang-Mills theory on a lattice in 3 spatial dimensions. I compare 3 different methods to determine the plasmon mass : a hard thermal loop expression in terms of the particle distribution, an effective dispersion relation constructed from fields and their time derivatives, and by measuring oscillations between electric and magnetic field modes after artificially introducing a homogeneous color electric field. Due to plasma instabilities, small quantum fluctuations on top of the classical background may significantly affect the dynamics of the system. I argue for the need for a numerical calculation of a system of classical gauge fields and small linearized fluctuations in a way that keeps the separation between the two manifest. I derive and test an explicit algorithm to solve these equations on the lattice, maintaining gauge invariance and Gauss's law.

Hosted by: Heikki Mantysaari

The discoveries of the extraterrestrial neutrino flux by IceCube renewed interest in the precise evaluation of the background neutrinos which are produced in the atmosphere due the cosmic ray interactions. One of the most relevant processes at high energies is the charm and beauty production in proton-nucleus collisions which needs to be evaluated at very high energies where small x effects may become important. I will discuss a recent calculation of the forward charm production in pp and pA, and compare results from different models which include small x effects due to resummation and saturation. Comparison with the LHC data will be presented and nuclear effects on light nuclei will also be discussed. Finally, I will show the resulting prompt neutrino flux and its uncertainties and discuss the potential improvements.

Hosted by: Heikki Mantysaari

The effect of intrinsic fluctuations of the proton saturation momentum scale on event-by-event rapidity distributions in small systems is explored. Saturation scale fluctuations generate an asymmetry in the single particle rapidity distribution in each event resulting in genuine n-particle correlations. We introduce a color domain model that naturally explains the centrality dependence of the two-particle rapidity correlations recently measured by ATLAS, constraining the probability distribution of saturation scale fluctuations in the proton. Predictions for n=4, 6 and 8 particle rapidity correlations find that the four- and eight-particle cumulant change sign at intermediate multiplicities, a signature which could be tested experimentally.

Hosted by: Pier Paolo Giardino

Hosted by: Heikki Mantysaari

I will discuss recent developments at the interplay between hydrodynamic gradient expansion and transient modes in expanding plasma.

Hosted by: Heikki Mantysaari

I will start by reviewing some previous results for the McLerran-Venugopalan model for nuclear collisions solved analytically in space-time coordinates. I will then discuss some recent work on initial angular momentum in the resulting Yang-Mills system, which leads to an interesting picture of gluon flow in the event plane. I will also describe further evolution of these results in fluid dynamics. Time permitting I will touch on ongoing efforts to construct an event generator based on analytic solutions.

Hosted by: Heikki Mantysaari

Squeeze out happen when the expanding central fireball flows around a large surface flux tube in a central Au-Au collision at RHIC. We model such an effect in a flux tube model. Two particle correlations with respect to the $v_2$ axis formed by the soft fireball particles flowing around this large flux tube is a way of measuring the effect.

Hosted by: Heikki Mantysaari

The large scale structure of the universe forms a particular type of fluid which is governed by the properties of dark matter. I discuss how one can derive renormalization group equations for the effective action that describes the statistical properties of this fluid. Taking into account in particular effective viscosity and sound velocity terms leads to an improved framework to determine density and velocity power spectra.

Hosted by: Mattia Bruno

Lattice QCD calculations of electroweak decays with single, strong-interaction-stable hadrons in the initial and final state have recently reached a high level of precision. Many phenomenologically important decays, however, involve hadronic resonances, and their naive analysis on the lattice leads to uncontrolled systematic errors. Recent theoretical developments in the finite-volume treatment of $1 \to 2$ transition matrix elements now enable us to perform rigorous lattice calculations of electroweak decays to light resonances such as the $\rho$. After presenting the Briceno-Hansen-Walker-Loud formalism, I will discuss our numerical implementation for the $D\to\rho \ell \nu$ and $B\to\rho \ell \nu$ decays, where we aim to quantify the effect of the unstable nature of the $\rho$. Our calculations are performed on a gauge ensemble with 2+1 flavors of clover fermions with a pion mass of ~320 MeV and a lattice size of ~3.6 fm.

Hosted by: Heikki Mantysaari

In the first part of the talk I will discuss recent computations of the transport coefficients of dense QCD from the Kubo formalism on the basis of a two-flavor model of QCD. The second part of the talk will discuss the properties of compact stars featuring color superconducting phases of dense QCD. This will include modeling of massive compact stars, neutrino cooling of such stars, and possible signatures of a phase transition within the QCD phase diagram in the X-ray data from the young neutron star in Cassiopea A.

Hosted by: Heikki Mantysaari

The shear and the bulk relaxation times are important ingredients of the second order hydrodynamics whose success in heavy ion phenomenology is unquestioned. Unlike viscosites themselves, field theoretical calculations of the relaxation times are hard to come by in literature, especially for the bulk relaxation time. In this talk, we report two field-theoretical analyses involving the shear and the bulk relaxation time. First, by carefully examining the analytic structure of the stress-energy tensor response functions, we have been able to derive, for the first time, a Kubo formula involving both the shear and the bulk relaxation times. Second, by evaluating the Kubo formula within the massless scalar theory, we have so far been able to calculate the shear relaxation time in a simple form. We will then show how this calculation can be extended to calculate the bulk relaxation time as well.

Hosted by: Hiroshi Oki

Hosted by: Pier Paolo Giardino

Hosted by: Heikki Mantysaari

I will present the result of the glue spin in proton from the lattice QCD simulation, and also the renormalization and matching issues. The lattice calculation is carried out with valence overlap fermions on 2+1 flavor DWF gauge configurations on four lattice spacings and four volumes including an ensemble with physical values for the quark masses. The glue spin $S_G$ in the $\overline{\text{MS}}$ scheme is obtained with the 1-loop perturbative matching. I will also discuss the generic strategy and possible difficulties of calculating the glue helicity on the lattice, from the large momentum effective theory to the lattice simulations.

Hosted by: Hiromichi Nishimura

We study the quantum Yang-Mills theory in the presence of topologically nontrivial backgrounds. The topologically stable gauge fields are constrained by the form invariance condition and the topological properties. Obeying these constraints, the known classical solutions to the Yang-Mills equation in the 3- and 4-dimensional Euclidean spaces are recovered, and the other allowed configurations form the nontrivial topological fluctuations at quantum level. Together, they constitute the background configurations, upon which the quantum Yang-Mills theory can be constructed. We demonstrate that the theory mimics the Higgs mechanism in a certain limit and develops a mass gap at semi-classical level on a flat space with finite size or on a sphere.

Hosted by: Mattia Bruno

Hosted by: Heikki Mantysaari

Hosted by: Hiroshi Oki

Using a hybrid (viscous hydrodynamics + hadronic cascade) framework, we model the bulk dynamics of relativistic heavy-ion collisions at the RHIC BES collision energies, including the effects from non-zero net baryon current and its dissipative diffusion during the evolution. The framework is in full 3+1 dimension which allows us to study the non-trivial longitudinal structure and dynamics of the collision systems, for example, the baryon stopping/transport. The collision energy dependence of hadronic chemistry, identified particle spectra, anisotropic flows, and HBT radii is studied from 200 GeV to 19.6 GeV. Effects of breaking boost-invariance, net-baryon current, and its related diffusion on hadronic observables will be addressed. Finally, flow prediction for recent d+Au collisions at the BES energies will be presented within the same framework.

Hosted by: Pier Paolo Giardino

Hosted by: Chun Shen

Relativistic hydrodynamic simulations play a key role in exploring the QGP bulk property and the QCD phase transition from analyses of high-energy heavy-ion collisions at RHIC and LHC. From the intensive study based on relativistic viscous hydrodynamic models with event-by-event initial fluctuations, we can extract detailed information of the bulk feature of the QGP such as transport coefficients and the QCD equations of states. In the quantitative analyses of the QGP property, high-precision numerical treatment on the hydrodynamic calculation is important. Recently, we developed a new 3+1 dimensional relativistic viscous hydrodynamics code in Cartesian coordinates. In the algorithm, we use a Riemann solver based on the two-shock approximation which is stable under existence of large shock waves. We extend the algorithm in Cartesian coordinates to that in Milne coordinates so that we can efficiently apply it to the analyses of relativistic heavy-ion collisions. We check the correctness of the numerical algorithm by comparing numerical calculations and analytical solutions in various problems for ideal and viscous fluids. The new numerical scheme is stable even with small numerical viscosity, which is very important to discuss the physical viscosities at RHIC and LHC.

Hosted by: Hiroshi Oki

We present a first-principles study of anomaly induced transport phenomena by performing real-time lattice simulations with dynamical fermions coupled simultaneously to non-Abelian SU(Nc) and Abelian U(1) gauge fields. Investigating the behavior of vector and axial currents during a sphaleron transition in the presence of an external magnetic field, we demonstrate how the interplay of the chiral magnetic and chiral separation effect leads to the formation of a propagating wave. We further analyze the dependence of the magnitude of the induced vector current and the propagation of the wave on the amount of explicit chiral symmetry breaking due to finite quark masses. Further we perform simulations using overlap-fermions for the first time in real-time, showing that in the classical statistical regime they can be related to the Wilson formulation.

Hosted by: Hiroshi Oki

We exploit the universality between the QCD critical point and the three dimensional Ising model to derive closed form expressions for non-equilibrium critical cumulants on the crossover side of the critical point. Novel expressions are obtained for the non-Gaussian Skewness and Kurtosis cumulants; our results reveal that they can differ both in magnitude and sign from equilibrium expectations. We show further that key elements of the Kibble-Zurek framework of non-equilibrium phase transitions can be employed to describe the dynamics of these critical cumulants. As a consequence, observables sensitive to critical dynamics in heavy-ion collisions are expressible as universal scaling functions and thereby provide powerful model independent guidance in searches for the QCD critical point.

Hosted by: Pier Paolo Giardino

Hosted by: Hiroshi Oki

We consider the effective action of the Polyakov loop at finite temperature and density. Using simple models, we show two novel manifestations of the sign problem in QCD: the non-hermitian transfer matrix and the complex saddle point. As a result the mass matrix associated with the Polyakov loop becomes complex, and it gives rise to damped oscillatory behavior in Polyakov loop correlation functions, which reflects oscillatory behavior in the quark-number density reminiscent of density-density correlation functions in liquids. The complex spectrum should be observable in lattice simulations of QCD and may provide a test for finite-density algorithms.

Hosted by: Hiroshi Oki

Parton distribution functions in the small-x limit have long been known to be dominated by gluon bremsstrahlung produced in the BFKL and BK / JIMWLK evolution mechanisms. This small-x gluon cascade generates high color-charge densities, leading to the effective semi-classical theory known as the color-glass condensate (CGC). While this unpolarized small-x evolution has been thoroughly studied, the evolution of the polarized parton distributions is much less understood. Using modern CGC techniques, we calculate the small-x evolution equations for the helicity distribution of polarized quarks. This polarized small-x evolution is quite different from the unpolarized evolution, bringing in much more complicated dynamics which transfer spin to small x. Although the quark polarization at small x is initially suppressed, strong evolution corrections substantially enhance the amount of spin at small x. By solving our equations (numerically, in the large-Nc limit), we compute the asymptotic behavior of the quark helicity at small x, and we discuss the implications of this result for the outstanding Proton Spin Puzzle.

Hosted by: Pier Paolo Giardino

Hosted by: Hiroshi Oki

I will talk about inclusive prompt photon and photon-jet production in p+A collisions at RHIC and the LHC. In particular, I show that photon-jet correlations in the Color Glass Condensate (CGC) picture exhibit long-range azimuthal collimation at near-side for low transverse momenta of the produced photon and jet in high-multiplicity events. These ridge-like features are strikingly similar to the observed ridge effect for di-hadron correlations at RHIC and the LHC. I show that correlations in the relative rapidity and the relative azimuthal angle between pairs of prompt photon and jet strongly depend on the gluon saturation dynamics at small-x kinematics and such measurements can help to understand the true origin of the observed di-hadron ridge in p+A collisions, and address whether the ridge is a universal phenomenon for all two particle correlations at high energy and high multiplicity events.

Hosted by: Hiroshi Ohki

Anomalous chiral transport processes, with the notable examples of Chiral Magnetic Effect (CME) and Chiral Magnetic Wave (CMW), are remarkable phenomena that stem from highly nontrivial interplay of QCD chiral symmetry, axial anomaly, and gluonic topology. The heavy ion collisions, in which topological fluctuations generate chirality imbalance, and very strong magnetic fields $|\vec{\bf B}|\sim m_\pi^2$ are present during the early stage of such collisions, provide a unique environment to study these anomalous chiral transport processes. Significant experimental efforts have been made to look for signals of CME and various other signals of anomalous chiral transport effects in heavy ion collisions. Crucial for such efforts, is the theoretical development of quantitative simulations based on hydrodynamics that incorporates chiral anomaly, implements realistic initial conditions and properly accounts for possible backgrounds. We will introduce our recent progress to understand CME qualitatively, based on a 2+1D viscous hydrodynamics framework

Hosted by: Hiroshi Oki

In condensed matter physics, Kondo effect is known as an enhancement of electrical resistance of impure metals with decreasing temperature/energy. This phenomenon is the first known example of asymptotic freedom in physics, which is found well before the discovery of that of QCD. Kondo effect is caused by the combination of the following ingredients: In addition to the existence of a heavy impurity, (i) Fermi surface, (ii) quantum fluctuations (loop effects), (iii) non-Abelian nature of interaction (e.g. spin-flip interaction in the case of condensed matter physics). In this talk, I will discuss Kondo effect realized in QCD. We found the characteristic behavior of Kondo effect in quark matter with heavy quark impurity. There, the color exchange interaction mediated by gluons plays the role of the third condition (iii) for the appearance of Kondo effect. Furthermore, we found a novel type of Kondo effect induced by strong magnetic fields. In addition to the fact that the magnetic field dose not affect the color degrees of freedom, dimensional reduction to 1+1 dimensions and degenerate quarks in lowest Landau level play essential role for the magnetically induced QCD Kondo effect.

Hosted by: Soeren Schlichting

In this talk, I would like to start with a brief introduction to non-equilibrium quantum field theory in the Schwinger-Keldysh formalism. This formalism provides a systematic way to study isotropization and other time-dependent non-equilibrium (and equilibrium) phenomena in heavy-ion collisions. I shall first discuss the foundation of classical field approximations (CSA), which is an important tool to study the evolution at very early stages. It is, however, found to be non-renormalizable. This helps us understand better the applicability of such an approximation. it is now well-known that isotropization can not be established before the breakdown of the CSA. We then use another approximation, the quasi-particle approximation (the Boltzmann equation), to study the isotropization in a scalar field theory. Our result shows explicitly the importance of quantum effects. Motivated by these observations, we have been studying whether the isotropization can be reached before the dense system of gluons, produced in the collisions of two big nuclei, becomes too dilute to be studied perturbatively in the Schwinger-Keldysh formalism. Some preliminary results shall be reported.

Hosted by: Hiroshi Oki

Hosted by: Hiroshi Oki

Hosted by: Hiroshi Ohki

Recently, Picard-Lefschetz theory gets much attention in the context of the sign problem, because it enables us to study the system with the complex classical action nonperturbatively by employing the semiclassical analysis. In this seminar, after its brief introduction, I will apply it to the one-site Hubbard model. This model has a severe sign problem, which looks quite similar to that of the finite-density QCD at low temperatures. By solving this model using the Lefschetz-thimble path integral, we are trying to understand the structure of the sign problem of finite-density QCD. Especially, I give a qualitative picture (or speculation) about the early-onset problem of the baryon number density, called the baryon Silver Blaze problem. The complex Langevin method will also be discussed if time allows.

Hosted by: Soeren Schlichting

Based on prior work by the JET collaboration, the importance of the factorization and scale evolution of the jet quenching parameter q-hat will be outlined. This will turn out to be important for both phenomenological extractions of q-hat as well as for first principle determinations on the lattice. I will argue that for jets at RHIC and LHC, q-hat does not lie within the range of Bjoerken-x where small x effects would be considered to be dominant. Given this situation, q-hat will be found to be an integral over an operator product separated in both light-cone and transverse distance, but somewhat different from a ``traditional'' TMDPDF. This new distribution will be studied at Next-to-Leading Order and the fate of non-standard divergences discussed.

Hosted by: Daniel Pitonyak

In 2+1 dimensional system, the most important phase transition should be of the Kosterlitz-Thouless (KT) type. We determined the KT transition temperature T_KT as well as the mass melting temperature T^* as a function of the magnetic field. It is found that the pseudogap domain T_KT < T < T^* is enlarged with increasing strength of the magnetic field. The influence of a chiral imbalanceμ_5 was also studied. We found that even a constant axial chemical potential μ_5 can lead to inverse magnetic catalysis of the KT transition temperature in 2+1 dimensions. This is actually the de Haas—van Alphen oscillation. Furthermore, we studied the QCD vacuum structure under the influence of an electromagnetic field with a nonzero second Lorentz invariant I_2=E·B. We showed that the presence of I_2 can induce neutral pion (π_0) condensation in the QCD vacuum through the electromagnetic triangle anomaly. Within the frameworks of chiral perturbation theory at leading small-momenta expansion as well as the Nambu—Jona-Lasinio model at leading 1/Nc expansion, a universal dependence of the π_0 condensate on I_2 was found. The stability of the π_0-condensed vacuum is also discussed.

Hosted by: Pier Paolo Giardino

Higgs pair production is not only interesting as a probe of the trilinear Higgs self-coupling, but beyond the Standard Model physics can influence the Higgs pair production cross section in many different ways, for example by new couplings, new loop particles or new resonances. In this talk, I will address the question whether we could see for the first time deviations from the Standard Model in Higgs pair production assuming that no deviations were seen before. Furthermore, for certain models I will show how higher order corrections influence the cross section.

Hosted by: Soeren Schlichting

Energetic jets are particularly interesting probes of QGP created in heavy ion collisions. Recently a lot of progress was made in attempting to describe the jet evolution in holography. In this talk I'll present an application of a simple dual model to study the jet substructure starting with energy and angle distributions from pQCD. In particular I will show that there are two competing effects: (1) each individual jet widens as it propagates through plasma; (2) the final jet opening angle distribution becomes narrower since wider jets lose more energy and less likely to survive. So, the mean opening angle for jets with a given energy can easily shift toward smaller angles, even while every jet in the ensemble broadens.

Hosted by: Daniel Pitonyak

This talk will start with a very general introduction to the Functional Renormalization Group method, a powerful non-perturbative tool which can be applied to various problems. The second part of the talk will demonstrate this by discussing the influence of an external magnetic field on the chiral phase transition in the theory of strong interaction. The Functional Renormalization Group analysis shows that, driven by gluon dynamics, the chiral critical temperature decreases for small values of the magnetic field. For large values of the external field, however, the phase transition temperature increases.

Hosted by: Tomomi Ishikawa

This talk will be centered around the calculation of the high temperature topological susceptibility in QCD. It will provide some background on our motivation from cosmology and particle physics, which is the dependence of axion physics on non-perturbative QCD. I will show our recent results on the quenched high temperature topological susceptibility and discuss difficulties with this conventional approach, which render dynamical studies unfeasible. I will also present our new approach based on formulating QCD on a non-orientable manifold, which is a promising candidate to solve issues related to topological freezing and the divergence of autocorrelations when approaching the continuum limit.

Hosted by: Soeren Schlichting

Local momentum anisotropies become large in the early stages of the quark-gluon plasma created in relativistic heavy-ion collisions, due to the extreme difference in the longitudinal and transverse expansion rates. In such situations, fluid dynamics derived from an expansion around an isotropic local equilibrium state is bound to break down. Instead, we subsume the slowest nonhydrodynamic degree of freedom (associated with the deviation from momentum isotropy) at leading order defining a local anisoptropic quasi-equilibrium state, thereby treating the longitudinal/transverse pressure anisotropy nonperturbatively. Perturbative transport equations are then derived to deal with the remaining residual momentum anisotropies creating a complete transient effective theory called viscous anisotropic hydrodynamics. This approach has been shown to dramatically outperform viscous hydrodynamics in several simplified situations for which exact solutions exits but which share with realistic expansion scenarios the problem of large dissipative currents. We will discuss the present status of applying viscous anisotropic hydrodynamics to the phenomenological description of the quark-gluon plasma in realistic expansion scenarios.

Hosted by: Daniel Pitonyak

Vorticity describes the local rotation of the fluid. I will talk about our recent study of the event-by-event generation of flow vorticity in heavy-ion collisions. Several special properties of the vorticity in heavy-ion collisions will be discussed, e.g., the impact parameter dependence, the collision energy dependence, the spatial distribution, the event-by-event fluctuation of the magnitude and azimuthal direction. Vorticity can drive vector and axial current in chiral quark-gluon plasma via the chiral vortical effect. I will discuss the collective gapless mode, the chiral vortical wave, emerging from CVE and its experimental implications in heavy-ion collisions. Finally, I will consider the rotating trapped cold atomic gases and show that when there is a Weyl spin-orbit coupling such cold atomic gases provide a desktop simulator of the chiral magnetic effect and chiral separation effect.

Hosted by: Tomomi Ishikawa

Hosted by: Soeren Schlichting

Monte Carlo method, a robust way of studying field theories and many body systems, suffers from the sign problem when the action is complex. This includes an important set of problems such as most field theories, including QCD, and strong correlated electronic systems at finite density, as well as computation of real time quantities like transport coefficients. I will show that lifting the path integration to a complex manifold provides a way to ameliorate the sign problem, and introduce a new algorithm for carrying on such a computation. I will give some quantum mechanical examples with severe sign problems, including finite density of fermions and real time observables where Monte Carlo simulations can be profitably performed by this method. Finally I will discuss the 3+1d Bose gas with nonzero chemical potential.

Hosted by: Daniel Pitonyak

We study a (1+1)-dimensional version of the famous Nambu-Jona-Lasinio model of Quantum Chromodynamics (QCD2) both at zero and finite chemical potential. We use non- perturbative techniques (non-Abelian bosonization and Truncated Conformal Space Approach). At zero chemical potential we describe a formation of fermion three-quark (nucleons and ?-baryons) and boson (two-quark mesons, six-quark deuterons) bound states and also a formation of a topo- logically nontrivial phase. When the chemical potential exceeds the critical value, the model has a rich phase diagram which includes phases with density wave and superfluid quasi-long-range (QLR) order and also a phase of a baryon Tomonaga-Luttinger liquid (strange metal). The QLR order results as a condensation of scalar mesons (the density wave) or six-quark bound states (deuterons).

Hosted by: Cen Zhang

We discuss overlooked resonance shapes of heavy Higgs bosons that arise from the resonance-continuum interference with a complex phase. They include pure resonance dips and nothingness. We derive conditions under which they are produced and we modify narrow width approximation suitable for them. We then discuss how MSSM heavy Higgs searches at the LHC can be challenged and changed.

Hosted by: Soeren Schlichting

Hosted by: Daniel Pitonyak

Compositeness of the bound states and the Lorentz slowing down of high energy interactions in QED and QCD lead to emergence of new coherent phenomena. We focus on the phenomena related to the fluctuations of the strength of interaction (color fluctuations phenomena). First we consider gross violations of the Glauber model for centrality dependence of production of the leading jets in pA scattering predicted earlier within QCD and recent evidence for this phenomenon from the studies of hard pA collisions at the LHC and dAu collisions at RHIC. Color fluctuations also explain a large suppression of the cross section of coherent vector meson photoproduction as compared to the Glauber model observed recently in the ultraperipheral collisions at LHC. We outline perspectives of future studies of the color fluctuation phenomenon in ultraperipheral heavy ion collisions at the LHC and electron - nucleus colliders.

Hosted by: Soeren Schlichting

The strongly coupled quark-gluon plasma created in high-energy heavy-ion collisions has rich vortical structures that are caused by global total orbital angular momentum and transverse evolution of longitudinal flow. Fermions (quarks in sQGP phase and baryons in the hadronic phase) in such a vorticular fluid are naturally polarized due to spin-orbital. I will discuss both local and global quark polarization and how one can use the lambda polarization in the final state to study the vortical structure and constrain the transport properties of sQGP.

Hosted by: Soeren Schlichting

Both chiral solitons and confined solitons are discussed at finite temperatures and densities in effective models. Based on the solitons the nucleon properties are studied in thermal medium. The nucleon mass in medium is carefully calculated. It is showed that the chiral solitons could even survive after the chiral phase transition, while confined solitons collapse after the system is deconfined.

Hosted by: Daniel Pitonyak

In this talk, I will present a first computation of sphalerons in the glasma; the highly occupied, weakly coupled gluon dominated pre-equilibrium matter created at early times after an ultra-relativistic heavy ion collisions. The sphaleron transition is a well known ingredient in the generation of anomalous vector current from a strong external magnetic field, the so-called Chiral Magnetic Effect. We perform classical-statistical real-time lattice simulations to study the dynamics of these topological transitions; simplifying our description by employing SU(2) gauge fields and neglecting the longitudinal expansion for this first study. I will show that the non-equilibrium sphaleron transition rate is time dependent and non-Markovian, in addition to being dominant in comparison to the thermal equilibrium sphaleron transition rate. In addition, we can measure the scaling and separation of physical scales in analogy to those from thermal equilibrium, in order to parameterize this rate and understand the approach to equilibrium. I will then demonstrate that it is the magnetic screening length, which we extract non-perturbatively, that controls this rate. Additionally, I will briefly mention studies of related anomalous transport effects that we plan on studying using this first principles classical-statistical real-time lattice technology.

Hosted by: Hiroshi Oki

We investigate the topological properties of Nf = 2 + 1 QCD with physical quark masses, both at zero and finite temperature. At zero temperature both finite size and finite cut-off effects have been studied by comparing the continuum extrapolated results for the topological susceptibility χ with the predictions from chiral perturbation theory. At finite temperature, we explore a region going from Tc up to around 4Tc, where continuum extrapolated results for the topological susceptibility and for the fourth moment of the topological charge distribution are obtained. While the fourth moment converges to the dilute instanton gas prediction the topological susceptibility differs strongly both in the size and in the temperature dependence. This results in a shift of the axion dark matter window of almost one order of magnitude with respect to the instanton computation.

Hosted by: Soeren Schlichting

Montonen and Olive found evidence that a duality could exist in Yang-Mills with adjoint scalars. In this scheme, the 't Hooft-Polyakov monopole forms a gauge triplet with the photon, leading to a theory equivalent to the Georgi-Glashow model but with magnetic charge replacing electric charge. The duality is believed to be realized in N=4 super-Yang-Mills. We are pursuing numerical, nonperturbative evidence for this S-duality using our lattice formulation. Two lines of approach are being taken, which I will discuss. First, we attempt to show that there is a value of the gauge coupling for which the W boson mass is equal to the monopole mass. Second, we are relating the 't Hooft loop to the Wilson loop at this self-dual coupling. On a somewhat unrelated topic, we also discuss the determination of anomalous dimensions on the lattice. In the dual gravitational picture these correspond to masses of fields in the bulk, so that some aspects of the gauge-gravity duality could be tested by such determinations. In particular in N=4 super-Yang-Mills there are predictions for the dimensions of non-protected operators at the self-dual point, based on the superconformal bootstrap.

Hosted by: Cen Zhang

Hosted by: Daniel Pitonyak

We investigate the impact of the Adler-Bell-Jackiw axial anomaly on the real-time dynamics of gauge theories in the strong field regime. By studying and comparing Abelian gauge theories, such as QED, with non-Abelian systems, we try to clarify the role of topological properties and initial conditions relevant far from equilibrium. We show that the Abelian version of the Chiral Magnetic Effect, which has been predicted in the context of ultra-relativistic heavy ion collisions, can result in non-trivial experimental signatures, which could possibly be observed in future high-intensity laser experiments. Further I will report on recent investigations of chiral production mechanisms in strong non-Abelian gauge fields and I will discuss the influence of topological objects such as sphalerons, far from equilibrium. Moreover I will show first results of the studies we have undertaken since my arrival here at BNL and discuss how the combination of these studies might be used to shed more light on the role played by anomalies in the early stages of a heavy ion collision.

Hosted by: Cen Zhang

Hosted by: Soeren Schlichting

I review the basic ideas of real time formulation of thermal field theory. Then I like to consider the following topics in this formulation: 1) thermal propagator for a scalar field 2) spectral representation of two-point functions for arbitrary fields 3) perturbation expansion 4) one-loop self -energy 5) dilepton production

Hosted by: Hiroshi Oki

Recently, a new approach to investigate hadron interactions in lattice QCD has been proposed[1] and developed extensively by the HAL QCD Collaboration[2]. This method can be easily applied to heavy baryon systems even though it is difficult to obtain experimental data of heavy baryons. We have investigated the interaction between Lambda_c and nucleon (N) from lattice QCD using the HAL QCD method. This is the first step to understand charmed-baryon interaction in lattice QCD. In this talk, we present the current status of our research project onLambda_c-N interactions as well as future prospects. This talk is based on PoS (LATTICE 2015) 090.

Hosted by: Soeren Schlichting

An ongoing program of evaluating transverse momentum dependent parton distributions (TMDs) within lattice QCD is reviewed, summarizing recent progress with respect to several challenges faced by such calculations. These lattice calculations are based on a definition of TMDs through hadronic matrix elements of quark bilocal operators containing staple-shaped gauge connections. A parametrization of the matrix elements in terms of invariant amplitudes serves to cast them in the Lorentz frame preferred for a lattice calculation. Results presented include data on the naively T-odd Sivers and Boer-Mulders effects, as well as the transversity and a worm-gear distribution. Correlating quark transverse momentum with impact parameter, one can extract quark orbital angular momentum directly,including both the Ji as well as the Jaffe-Manohar definitions.

Hosted by: Soeren Schlichting

Perturbative QCD based on the Parton Model of the nucleon is a very successful theoretical approach to describe high-energy processes at particle accelerators and colliders. In particular, parton distribution functions are key ingredients of this approach and give information on the partonic substructure of the nucleon. As such they deliver a one-dimensional picture of how the parton momenta are distributed in the nucleon. In this talk extensions of the parton model are presented which provide access to more detailed information on the dynamics of partons in the nucleon. In particular observables involving transversely polarized nucleons are discussed. They can be described in terms of dynamical quark-gluon correlations which in turn can be studied at an Electron-Ion Collider. Another extension of the parton model takes into account the intrinsic transverse motion of the partons. In this approach - called Transverse Momentum Dependent (TMD) factorization - one can study three-dimensional distributions of the parton momenta. In addition, implications of the transverse motion of gluons in the nucleon will be discussed for LHC physics.

Hosted by: Soeren Schlichting

Almost all of the visible matter in the universe is built from hadrons, which are composed of quarks and gluons. One of the main challenges in nuclear physics is to understand this complex internal structure. In this talk, I will discuss how hard-scattering processes that involve the spin of hadrons give us insight into aspects of their inner-workings that otherwise would be inaccessible. I will focus on phenomena that arise when hadrons carry spin transverse to their direction of motion, which allow us to examine them in 3D and analyze correlations between their quarks and gluons. I will also consider a new attempt to resolve the so-called "spin crisis" of how the proton gets its spin by looking at how much spin can be carried by small-x quarks and gluons.

Hosted by: Hiroshi Ohki

Hydrodynamics is an effective theory of systems close to equilibrium. It has been applied to description of fireballs created in the heavy-ion collisions. With growing interests in fluctuation of observables, theoretical identification of its origin is crucial. One of such origins is thermal fluctuation required by the fluctuation-dissipation theorem. In this talk, I will present a new insight into the thermal fluctuation of hydrodynamics by separating the hard and soft scales in a given background. As an illustration, we adopt the Bjorken expansion as a background. The kinetic description of hard modes allows us simple interpretation of renormalization, long-time tails, and fractional powers of derivative expansion.

Hosted by: Soeren Schlichting

An essential feature of the parton shower that form a jet evolving in vacuum is color coherence that suppresses large angle soft gluon radiation and thus, ensuing the collimation of the jet. In the presence of dense QCD matter jet constituents suffer a rapid color randomization and thus an alteration of color coherence: as a result a medium-induced gluon cascade, that can be described by a classical Makovian process, develop at large angles with respect to the jet axis [3]. A remarkable phenomenon emerges from such a cascade: the energy spectrum (of jet constituents) exhibits a scaling behavior, akin to wave turbulence, characterized by a constant flow of energy from the forward energetic patrons towards low momentum gluons down to the temperature of the plasma where energy is dissipated [4]. This picture is in agreement with a recent CMS analysis of missing energy in asymmetric dijet events where the energy balance is recovered at large angles and very soft particles [5]. In the second part of the talk I will discuss radiative corrections to jet observables that were shown to exhibit large double logarithmic enhancements. Owing to a large separation of time scales we have shown that these large corrections can be reabsorbed in a renormalization of the jet-quenching parameter q^, preserving the probabilistic picture of the parton cascade [6]. This result leads us to question the standard viewpoints of the coupling of jets to the medium: the naive perturbative approach based on a leading order calculation and the AdS/CFT correspondence for strongly coupled plasmas. I will briefly invoke in the final part of my talk the various questions that remain to be addressed. Indeed, despite the recent progress much remains to be understood about jet fragmentation in a dense medium in order to construct a systematic and predictive approach to jet-quenching from first principles.

Hosted by: Daniel Pitonyak

I will present numerical results based on an interacting ensemble of instanton-dyons, that explains the connection between chiral symmetry breaking and confinement. The instanton-dyons have the nice properties to behave as monopoles at low temperatures, and as instantons at high temperatures. We will see how the scaling behavior of the instanton-dyons creates a Polyakov loop dependent potential, which forces the Polyakov loop to the confining value as the density of dyons increases at lower temperatures. For 2 flavors we find that the dominating configuration in the ensemble exhibit a chiral symmetry transition at the same temperature as the confinement transition, within accuracy. The important factor in explaining confinement and chiral symmetry breaking is the density of the Instanton-dyons.

Hosted by: Hiroshi Oki

Both Luscher's finite volume method and HAL QCD method are used to analyze the hadron-hadron interaction in lattice QCD. However, some systematic discrepancies are reported between them.For example, Luscher's method shows the bound states of both deuteron and di-neutron at the heavy pion mass,while these channels are scattering states from HAL QCD method. In this talk, to understand the deviations between them, we investigate the baryon interaction from both methods with the same lattice setups.From a systematic comparison of two methods, we clarify the problems in the previous studies. We also discuss the improvement of the analyses.

Hosted by: Soeren Schlichting

Recently we obtained an evolution equation for gluon TMDs, which addresses a problem of unification of different kinematic limits. It describes evolution in the whole range of Bjorken x and transverse momentum k⊥. I plan to discuss this evolution equation and show how in different kinematic regimes it yields several well-known and some previously unknown results.

Hosted by: Hiroshi Oki

As the precision frontier of particle physics continues to develop, the field of lattice QCD has risen to the challenge. Modern lattice simulations, have increasingly included light non-degenerate up and down quark masses and electromagnetism. Previously answered questions about the vacuum structure of QCD on the lattice must be reexamined when these isospin breaking effects are included. If not careful, lattice practitioners may simulate in non-physical phases which cannot be extrapolated to the continuum limit. Using chiral perturbation theory, I will discuss where these non-physical phases can arise for Wilson and twisted mass fermions. I will also explain some of the complications which arise when tuning the up and down twisted quark masses to their critical values in the presence of electromagnetism.

Hosted by: Sally Dawson

Hosted by: Soeren Schlichting

I will discuss the use of semi-classics and instanton calculus and argue that, contrary to common wisdom, complex solutions of the equations of motion are a necessary ingredient of any semi-classical expansion. In particular, I will show that without the complex solutions semi-classical expansion of supersymmetric theories cannot be reconciled with supersymmetry. This has a natural interpretation in the Picard-Lefschetz theory.

Hosted by: Amarjit Soni

Hosted by: Daniel Pitonyak

Sterile neutrinos are SU(2) singlets that mix with active neutrinos via a mass matrix, its diagonalization leads to mass eigenstates that couple via standard model vertices. We study the production of sterile neutrinos in the early universe from pion decays shortly after the QCD phase transition in the absence of a lepton asymmetry. We introduce the quantum kinetic equations that describe their production, freeze out and decay and discuss the various processes that lead to their production in a wide range of temperatures assessing their feasibility as dark matter candidates. We consider the production of heavy neutrinos in the mass range < 140MeV from pion decay shortly after the QCD crossover including finite temperature corrections to the pion form factors and mass. We consider the different decay channels that allow for the production of heavy neutrinos showing that their frozen distribution functions exhibit effects from "kinematic entanglement" and argue for their viability as mixed dark matter candidates. We discuss abundance, phase space density and stability constraints and argue that heavy neutrinos with lifetime >1/H0 freeze out of local thermal equilibrium.

Hosted by: Soeren Schlichting

We study the transverse momentum dependent (TMD) evolution of the Collins azimuthal asymmetries in e+eâˆ' annihilations and semi-inclusive hadron production in deep inelastic scattering (SIDIS) processes. All the relevant coefficients are calculated up to the next-to-leading logarithmic (NLL) order accuracy. By applying the TMD evolution at the approximate NLL order in the Collins-Soper-Sterman (CSS) formalism, we extract transversity distributions for u and d quarks and Collins fragmentation functions from current experimental data by a global analysis of the Collins asymmetries in back-to-back di-hadron productions in e+eâˆ' annihilations measured by BELLE and BABAR Collaborations and SIDIS data from HERMES, COMPASS, and JLab HALL A experiments. The impact of the evolution effects and the relevant theoretical uncertainties are discussed. We further discuss the TMD interpretation for our results, and illustrate the unpolarized quark distribution, transversity distribution, unpolarized quark fragmentation and Collins fragmentation functions depending on the transverse momentum and the hard momentum scale. We make detailed predictions for future experiments and discuss their impact.

Hosted by: Amarjit Soni

We study the collider signature of pseudo-Dirac heavy neutrinos in the inverse seesaw scenario, where the heavy neutrinos with mass at the electro-weak scale can have sizable mixings with the Standard Model neutrinos, while providing the tiny light neutrino masses by the inverse seesaw mechanism. Based on a simple, concrete model realizing the inverse seesaw scenario, we fix the model parameters so as to reproduce the neutrino oscillation data and to satisfy other experimental constraints, assuming two typical flavor structures of the model and the different types of hierarchical light neutrino mass spectra. For completeness, we also consider a general parametrization for the model parameters by introducing an arbitrary orthogonal matrix and the nonzero Dirac and Majorana phases. We perform a parameter scan to identify an allowed parameter region which satisfies all experimental constraints. With the fixed parameters, we analyze the heavy neutrino signal at the LHC through trilepton final states with large missing energy and at the ILC through a single lepton plus dijet with large missing energy.

Hosted by: Daniel Pitonyak

We compute the correction to the thermal photon emission rate in first order of shear components of fluid velocity gradients in near-equilibrium hydrodynamic plasma at strong coupling regime using the real-time Schwinger-Keldysh formalism in AdS/CFT correspondence. We find that the gradient correction to the thermal photon emission rate at strong coupling is about 0.3 - 0.4 times of the equilibrium rate.

Hosted by: Soeren Schlichting

Using fluid/gravity correspondence, we study all-order resummed hydrodynamics in a weakly curved spacetime. The underlying microscopic theory is a finite temperature \mathcal{N}=4 super-Yang-Mills theory at strong coupling. To linear order in the amplitude of hydrodynamic variables and metric perturbations, the fluid's stress-energy tensor is computed with derivatives of both the fluid velocity and background metric resummed to all orders. In addition to two viscosity functions, we find four curvature induced structures coupled to the fluid via new transport coefficient functions, which were referred to as gravitational susceptibilities of the fluid (GSF). We analytically compute these coefficients in the hydrodynamic limit, and then numerically up to large values of momenta. We extensively discuss the meaning of all order hydrodynamics by expressing it in terms of the memory function formalism, which is also suitable for practical simulations. We also consider Gauss-Bonnet correction in the dual gravity, which is equivalent to some 1/N corrections in the dual CFT. To leading order in the Gauss-Bonnet coupling, we find that the memory function is still vanishing.

Hosted by: Amarjit Soni

Hosted by: Tomomi Ishikawa

The gluon-fusion Higgs production cross section has been recently computed through the next-to-next-to-next to leading order (N^3LO) in QCD. This unprecedented level of accuracy is crucial to exploit fully the LHC data in the validation of the Standard Model and in the search for potential (small) deviations due to new physics. I will give an overview of the tools that we employed to achieve this result, from the framework of heavy-quark effective theories to the analytical and mathematical machinery that we developed. I will conclude with some results and future prospects.

Hosted by: Soeren Schlichting

Massless QED in three (two space and one Euclidean time) with even number of flavors does not break parity. There are analytical arguments for chiral symmetry to be spontaneously broken and some numerical evidence supporting these arguments. An interesting "open" question is the possibility of a critical number of flavors below which chiral symmetry is broken. Numerical results obtained using dynamical Wilson fermions will be presented with emphasis on the behavior of the low lying eigenvalues of the Wilson Dirac operator. Finite volume analysis will be used to obtain conclusions about the absence or presence of a chiral condensate.

Hosted by: Daniel Pitonyak

Hosted by: Soeren Schlichting

One of the major lessons from the field of heavy-ion physics in the past several years has been the significance of the role played by event-by-event fluctuations in the evolution of a heavy-ion collision. Their important effects on many momentum-space observables (particle yields and spectra, anisotropic flows, etc.) have already been studied systematically, and some of the properties of their event-by-event distributions, and their consequences for the extraction of medium properties such as the specific viscosity of the quark-gluon plasma (QGP), are already known. In this talk it is pointed out that similar event-by-event fluctuations of spatiotemporal observables provide complementary constraints on our understanding of the dynamical evolution of heavy-ion collisions. The relation of Hanbury Brown-Twiss (HBT) radii extracted from ensemble-averaged correlation function measurements to the mean of their event-by-event probability distribution is clarified, and a method to experimentally determine the mean and variance of this distribution is proposed and demonstrated using an ensemble of fluctuating events generated with the viscous hydrodynamic code VISH2+1. The sensitivity of the mean and variance of the HBT radii to the specific QGP shear viscosity η/s is studied using simulations with the same code. We report sensitivity of the mean pion HBT radii and their variances to the temperature dependence of η/s near the quark-hadron transition at a level similar (10-20%) to that which was previously observed for elliptic and quadrangular flow of charged hadrons.

Hosted by: Cen Zhang

Hosted by: Soeren Schlichting

Early fluid-dynamical calculations of direct photon spectra and momentum anisotropy were found to be systematically smaller than measurements from the RHIC and the LHC, an observation that became known as the "direct photon puzzle". I will show that the use of a modern hydrodynamical model of heavy ion collisions and of the latest photon emission rates greatly improves agreement with both ALICE and PHENIX data, supporting the idea that thermal photons are the dominant source of direct photon momentum anisotropy in heavy ion collisions. The event-by-event hydrodynamical model used includes, for the first time, both shear and bulk viscosities, along with second order couplings between the two viscosities. Calculations using different photon emission rates will be shown, including one that takes into account the effect of confinement on photon emission. The effect of both shear and bulk viscosities on the photon rates will be shown to have a measurable effect on the photon momentum anisotropy.

Hosted by: Amarjit Soni

Hosted by: Tomomi Ishikawa

We present our lattice results of SU(3) gauge theory with many flavors, in particular with Nf=8, as a model of a walking or conformal gauge theory. We study the scaling properties of various hadron spectra including the (pseudo)scalar, vector, and baryon channels. From the Nf dependence of the theory, possible signals of walking or conformal dynamics will be discussed.

Hosted by: Tomomi Ishikawa

The exclusive semileptonic $B$-meson decays $B\to K(\pi)\ell^+\ell^-$, $B \to K(\pi)\nu\bar\nu$, and $B\to\pi\tau\nu$ are used to extract the CKM elements and probe new physics beyond Standard Model. The errors of the form factors used to be an important source of the uncertainties in the theoretical predictions. Recent developments in lattice-QCD provide more accurate form factors and enable us to have better theoretical predictions. In this talk, I will present the latest lattice-QCD results of the form factors in the semileptonic $B$-meson decays processes. In addition, I will compare the theoretical predictions and recent experimental results. The tension between the Standard Model and semileptonic $B$-meson decay experimental data will be discussed.

Hosted by: Soeren Schlichting

Hosted by: Daniel Pitonyak

Results for several thermodynamic quantities within the next-to-leading order calculation of the thermodynamic potential in perturbative QCD at finite temperature and chemical potential including non-vanishing quark masses are presented. These results are compared to lattice data and to higher-order optimized perturbative calculations to investigate the trend brought about by mass corrections. Furthermore, the equation of state for nonvanishing isospin density was investigated within the introduced framework and the findings are also presented.

Hosted by: Cen Zhang

Hosted by: Soeren Schlichting

We discuss the recent improvement of the NLO calculation of single inclusive particle production in pA collisions within the CGC formalizm. The two points that have not been addressed previously, and are treated consistently in the current approach are the Ioffe time cutoff on the configurations that can participate in the scattering, and the careful treatment of the evolution interval.

Hosted by: Soeren Schlichting

Hosted by: Soeren Schlichting

Asymptotic freedom of gluons is defined in terms of scale-dependent renormalized QCD Hamiltonian operators that act in the Fock space. These operators are calculable in a new way [1,2], by solving a double-commutator differential equation [3], where the derivative is with respect to a scale parameter defined within the renormalization group procedure for effective particles (RGPEP). The RGPEP equation and its solutions are invariant with respect to boosts and may serve as a tool in attempts to dynamically explain the parton and constituent models of hadrons in QCD. The third-order QCD solution of the RGPEP equation to be discussed [2], provides an explicit example of how asymptotic freedom of gluons is exhibited in the scale-dependence of Hamiltonians as operators in the Fock space. This example also prepares ground for the fourth-order calculations of effective strong interactions using the same RGPEP equation [3], to facilitate Hamiltonian studies of many strong-interaction processes, e.g., those that involve heavy quarkonia in relativistic motion. Applications to other sectors of the Standard Model than the strong interactions await development, while only preliminary results are currently available in the domain of precise calculations in QED[4]. [1] Dynamics of effective gluons, S. D. Glazek, Phys. Rev. D63, 116006, 29p (2001). [2] Asymptotic freedom in the front-form Hamiltonian for gluons, M. Gomez-Rocha, S. D. Glazek, arXiv:1505.06688 [hep-ph], to appear in Phys. Rev. D. [3] Perturbative formulae for relativistic interactions of effective particles, S. D. Glazek, Acta Phys. Pol. B43, 1843, 20p (2012). [4] Calculation of size for bound-state constituent

Hosted by: Daniel Pitonyak

A general method for exactly computing the nonlinear collision term of the Boltzmann equation for a massless relativistic gas in a homogeneous and isotropic spacetime is presented. This approach is used to find an exact analytical solution of the nonlinear relativistic Boltzmann equation in a Friedmann-Robertson-Walker spacetime. This solution can be used to investigate analytically the interplay between global expansion and local thermalization in rapidly evolving systems.

Hosted by: Chien-Yi Chen

Hosted by: Soeren Schlichting

Recent efforts to investigate the thermodynamics of lattice QCD with N_f=2+1+1 fermion degrees of freedom at realistic strange and charm quark masses and at various up and down quark mass values within the framework of Wilson twisted mass fermion discretization are discussed. Comparing with recently published results in the N_f=2 case we are going to present results for the pseudo-critical temperature and preliminary results on the way to the thermodynamic equation of state. Moreover, we would like to discuss various methods to determine the topological susceptibility as a function of the temperature.

Hosted by: Soeren Schlichting

I will discuss high energy collisions of dilute on dense systems (pA) and review some ideas about initial-state induced correlations.

Hosted by: Daniel Pitonyak

"Hypothesis testing is arguably the most common and elementary task in information processing (e.g., we constantly make decisions based on incomplete information). Its quantum version, quantum state discrimination, is likewise central in quantum information processing. The talk gives an introduction to the topic, focussing on discrimination of a large amount of identically prepared systems. In this limit, a powerful bound on the error rate can be derived. In classical statistics this is know as Chernoff bound. The quantum version of the Chernoff bound will be presented and discussed."

Hosted by: Sally Dawson

Hosted by: Soeren Schlichting

Hosted by: Chien-Yi Chen

Higgs coupling measurements can shed light on the nature of electroweak symmetry breaking. However it is not trivial to go beyond generic intuitions, such as the expectation that natural theories generate large deviations, and make precise statements. In this talk I will show in a model independent way that measuring deviations at the LHC implies the existence of new bosons between a few TeV and a few hundred TeV. This is true in general, including theories where new fermions produce the deviations.

Hosted by: Soeren Schlichting

I will discuss the recently proposed generalized Landau-level representation for charged fermions in an external magnetic field. After demonstrating its key advantages over the other existing representations, I will mention several of its applications. One of them is the quantum Hall effect in graphene, where the new representation is essential for a sufficiently detailed theoretical description, in which all the dynamical parameters are running functions of the Landau-level index. The other application is the chiral asymmetry induced in dense relativistic matter in an external magnetic field. The quantitative measure of such an asymmetry is the chiral shift parameter that measures a relative shift of the longitudinal momenta (along the direction of the magnetic field) in the dispersion relations of opposite chirality fermions. Using the language of solid state physics, the corresponding ground state of dense relativistic matter could be interpreted as a Weyl metal state. Incidentally, the exact same mechanism also works in real Dirac metals.

Hosted by: Daniel Pitonyak

The P-odd spectral density of current correlation functions appears in several physical observables which are related to chiral anomaly, and is a sensitive probe of microscopic dynamics which is less protected by symmetry alone. We discuss two examples of their appearance: photon emission and the second order transport coefficient from chiral anomaly. We describe leading order weak coupling computations for these examples.

Hosted by: Chien-Yi Chen

Hosted by: Speren Schlichting

The BK-JIMWLK equations describing the evolution of the Color Glass Condensate with increasing energy have recently been extended to next-to-leading order (NLO) accuracy. However, some of the NLO corrections turn out to be extremely large, since amplified by (double and single) `collinear' logarithms, i.e. logarithms of ratios of transverse momenta. This difficulty points towards the existence of large radiative corrections to all orders in $\alpha_s$, as generated by the transverse phase-space, which must be computed and resummed in order to restore the convergence of the perturbative expansion. In a couple of recent papers, we developed a resummation scheme in that sense, which achieves a complete resummation of the double-logarithmic corrections and a partial resummation of the single-logarithmic ones (including the running coupling effects). We have thus deduced a collinearly-improved version of the BK equation which includes the largest radiative corrections to all orders. To demonstrate the usefulness of this equation as a tool for phenomenology, for have used it for fits to the HERA data for electron-proton deep inelastic scattering at high energy. We have obtained excellent fits with a reduced number of free parameters and with initial conditions at low energy taken from perturbative QCD.

Hosted by: Soeren Schlichting

High-energy particles passing through matter lose energy by showering via hard bremsstrahlung and pair production. At very high energy, the quantum duration of each splitting process, known as the formation time, exceeds the mean free time for collisions with the medium, leading to a significant reduction in the splitting rate, known as the Landau-Pomeranchuk-Migdal (LPM) effect. A long-standing problem in field theory has been to understand how to implement this effect in cases where the formation times of two consecutive splittings overlap. I will review why this question is interesting and discuss recent progress in the context of jet energy loss in quark-gluon plasmas.

Hosted by: Tomomi Ishikawa

Hosted by: Soeren Schlichting

We introduce an event-by-event perturbative-QCD + saturation + hydro ("EKRT") framework for ultrarelativistic heavy-ion collisions, where we compute the produced fluctuating QCD-matter energy densities from next-to-leading order perturbative QCD using a saturation conjecture to control soft particle production, and describe the space-time evolution of the QCD matter with dissipative fluid dynamics, event by event. We perform a simultaneous comparison of the centrality dependence of hadronic multiplicities, transverse momentum spectra, and flow coefficients of the azimuth-angle asymmetries, against the LHC and RHIC measurements. We compare also the computed event-by-event probability distributions of relative fluctuations of elliptic flow, and event-plane angle correlations, with the experimental data from Pb+Pb collisions at the LHC. We show how such a systematic multi-energy and multi-observable analysis tests the initial state calculation and the applicability region of hydrodynamics, and in particular how it constrains the temperature dependence of the shear viscosity-to-entropy ratio of QCD matter in its different phases in a remarkably consistent manner.

Hosted by: Daniel Pitonyak

The chiral condensate of one-flavor QCD is continuous when the quark mass crosses zero. In the sector of fixed topological charge though, the chiral condensate becomes discontinuous at zero mass in the the thermodynamical limit. To reconcile these contradictory observations, we have evaluated the spectral density of the Dirac operator in the epsilon domain of one-flavor QCD. In this domain, we have obtained exact analytical expressions which show that the spectral density at $\theta = 0$ becomes a strongly oscillating function for negative quark mass with an amplitude that increases exponentially with the volume. As is the case for QCD at nonzero chemical potential, these strong oscillations invalidate the Banks-Casher formula and result in a chiral condensate that is continuous as a function of the quark mass. An additional subtlety is the effect of the topological zero modes which will be discussed as well.

Hosted by: Soeren Schlichting

The advent of the LHC opened up new perspectives for jet-quenching physics. For the first time, high enough energies are reached in heavy-ion experiments to produced jets in large numbers, and the unprecedented detector capabilities of ALICE, ATLAS and CMS, not only extend the kinematic range for the measurements previously performed at RHIC, but also allow to explore a variety of new jet-quenching observables. In this talk, I address the question of the angular broadening of jets in the presence of a dense QCD matter. I start by discussing the fundamental mechanisms underlying the formation of gluon cascades induced by multiple interactions of high energy jets with the quark-gluon plasma. Then, the rate equation that describes the evolution of the energy and angular distribution of the in-medium gluon shower is presented and solved. Two remarkable phenomena emerge. First and foremost the energy spectrum (of jet constituents) exhibits a scaling behavior characterized by a constant flow of energy towards low momenta akin to wave turbulence. As a result, energy is rapidly transported from the energy containing partons to low momentum gluons before it dissipates into the medium. Second, medium-induced gluon cascades develop and transport energy at parametrically large angles with respect to the jet axis. This picture is in semi-quantitive agreement with a recent CMS analysis of the missing energy in asymmetric dijet events where the energy balance is recovered at large angles and very soft particles.

Hosted by: Daniel Pitonyak

We show by solving Maxwell's equations in the presence of chiral magnetic current that the chiral anomaly would induce the inverse cascade of magnetic helicity. We found at late time, the evolution of magnetic helicity spectrum is self-similar and axial charge decays as a power law in time. We visualize how a linked magnetic configuration would evolve into a knotted configuration in real space during such evolution.

Hosted by: Amarjit Soni

Hosted by: Chien-Yi Chen

I will discuss interpretations of the recent updated angular analysis of the B->K*mu+mu- decay by the LHCb collaboration. A global fit to all relevant measurements probing the flavor changing neutral current b->s mu mu transition shows tensions with Standard Model expectations. Assuming hadronic uncertainties are estimated in a sufficiently conservative way, I will discuss the implications of the experimental results on new physics, both model independently as well as in the context of models with flavor changing Z' bosons.

Hosted by: Soeren Schlichting

Charmonium production in pA collisions is known to be suppressed by shadowing and absorption. There are however nuclear effects, which enhance charmonium yield. They steeply rise with energy and seem to show up in LHC data for J/psi production in pA collisions. In the case of heavy ion collisions produced charmonia are additionally suppressed by final state interaction in the created dense medium. On the contrary to current evaluations of the melting effects caused by Debye screening, a charmonium produced with a large pT easily survives even at high temperatures. Another source of charmonium suppression, missed in previous calculations, color-exchange interactions with the medium, leads to suppression of a comparable magnitude. A quantitative comparison is performed.

Hosted by: Tomomi Ishikawa

Hosted by: Chien-Yi Chen

Hosted by: Tomomi Ishikawa

I will present a study of the time evolution of Ginibre matrices whose elements undergo Brownian motion. The non-Hermitian character of the Ginibre ensemble binds the dynamics of eigenvalues to the evolution of eigenvectors in a non-trivial way, leading to a system of coupled nonlinear equations resembling those for turbulent systems. We will formulate a mathematical framework allowing simultaneous description of the flow of eigenvalues and eigenvectors, and unravel a hidden dynamics as a function of new complex variable, which in the standard description is treated as a regulator only. We shall solve the evolution equations for large matrices and demonstrate that the non-analytic behavior of the Green's functions is associated with a shock wave stemming from a Burgers-like equation describing correlations of eigenvectors. I will start by reviewing similar notions in a simpler, Hermitian setting. Joint work with Zdzislaw Burda, Jacek Grela, Maciej A. Nowak and Wojtek Tarnowski (Phys.Rev.Lett. 113 (2014) 104102).

Hosted by: Soeren Schlichting

Hosted by: Daniel Pitonyak

Geometrical is a consequence of a traveling wave solution of the non-linear QCD evolution equation, so called Balitski-Kovchegov equation. We shall demonstrate the existence of GS in various high energy reactions. Among different consequences of GS there is a linear rise of charged particle multiplicity (Nch) and mean transverse momentum (pT) with scattering energy. Furthermore, a correlation of meant pT and Nch is predicted to scale in a way that depends on the the way particles are produced from the volume excited in a hadron-hadron scattering. This is mostly visible in heavy ion collisions at different centralities.

Hosted by: CheinYi Chen

Hosted by: Soeren Schlichting

We present results from a numerical solution of the next-to-leading order (NLO) Balitsky-Kovchegov (BK) equation in coordinate space in the large Nc limit. We show that the solution is not stable for initial conditions that are close to those used in phenomenological applications of the leading order equation. We identify the problematic terms in the NLO kernel as being related to large logarithms of a small parent dipole size, and also show that rewriting the equation in terms of the "conformal dipole" does not remove the problem. Our results qualitatively agree with expectations based on the behavior of the linear BFKL equation.

Hosted by: Amarjit Soni

Hosted by: Daniel Pitonyak

Hosted by: Soeren Schlichting

Effective field theory (EFT) is a powerful framework based on exploiting symmetries and controlled expansions for problems with a natural separation of energy or distance scales. EFTs are particularly important in QCD and nuclear physics. An effective theory of QCD, ideally suited to jet applications, is Soft-Collinear Effective Theory (SCET). Recently, first steps were taken to extend SCET and describe jet evolution in strongly-interacting matter. In this talk I will demonstrate that the newly constructed theory, called SCETG, allows us to go beyond the traditional energy loss approximation in heavy ion collisions and unify the treatment of vacuum and medium-induced parton showers. It provides quantitative control over the uncertainties associated with the implementation of the in-medim modification of hadron production cross sections and allows us to accurately constrain the coupling between the jet and the medium. I will further show how SCET and SCETG can be implemented to evaluate reconstructed jet observables, such as jet shapes.

Hosted by: Chien-Yi Chen

Hosted by: Soeren Schlichting

Hadrons under extreme conditions of density and temperature have captured the interest of particle and nuclear physicists as well as astrophysicists over the years in connection with an extensive variety of physical phenomena in the laboratory as well as in the interior of stellar objects, such as neutron stars. One of the physics goals is to understand the origin of hadron masses in the context of the spontaneous breaking of the chiral symmetry of Quantum Chromodynamics (QCD) at low energies in the non-perturbative regime and to analyze the change of the hadron masses due to partial restoration of this symmetry under extreme conditions. Lately other proper QCD symmetries have also become a matter of high interest, such as heavy-quark flavor and spin symmetries. These symmetries appear when the quark masses become larger than the typical confinement scale and they are crucial for characterizing hadrons with heavy degrees of freedom. In this talk I will address the properties of heavy hadrons under extreme conditions based on effective theories that incorporate the most appropriate scales and symmetries of QCD in each case. With the on-going and upcoming research facilities, the aim is to move from the light-quark to the heavy-quark sector and to face new challenges where heavy hadrons and new QCD symmetries will play a dominant role.

Hosted by: Soeren Schlichting

Abstract: We utilize a new framework, CUJET3.0, to deduce the energy and temperature dependence of jet transport parameter, q^(E>10GeV,T), from a combined analysis of available data on nuclear modification factor and azimuthal asymmetries from RHIC/BNL and LHC/CERN on high energy nuclear collisions. Extending a previous perturbative-QCD based jet energy loss model (known as CUJET2.0) with (2+1)D viscous hydrodynamic bulk evolution, this new framework includes three novel features of nonperturbative physics origin: (1) the Polyakov loop suppression of color-electric scattering (aka "semi-QGP" of Pisarski et al) and (2) the enhancement of jet scattering due to emergent magnetic monopoles near Tc (aka "magnetic scenario" of Liao and Shuryak) and (3) thermodynamic properties constrained by lattice QCD data. CUJET3.0 reduces to v2.0 at high temperatures T>400 MeV, but greatly enhances q^ near the QCD deconfinement transition temperature range. This enhancement accounts well for the observed elliptic harmonics of jets with pT>10 GeV. Extrapolating our data-constrained q^ down to thermal energy scales, E∼2 GeV, we find for the first time a remarkable consistency between high energy jet quenching and bulk perfect fluidity with η/s∼T3/q^∼0.1 near Tc.

Hosted by: Tomomi Ishikawa

Hosted by: Chris Kelly

Hosted by: Soeren Schlichting

Consistent formulations of relativistic viscous hydrodynamics involve short lived modes, leading to asymptotic rather than convergent gradient expansions. In this talk I will consider the Mueller-Israel-Stewart theory applied to a longitudinally expanding quark-gluon plasma system and identify hydrodynamics as a universal attractor without invoking the gradient expansion. I will give strong evidence for the existence of this attractor and then show that it can be recovered from the divergent gradient expansion by Borel summation. This requires careful accounting for the short-lived modes which leads to an intricate mathematical structure known from the theory of resurgence.

Hosted by: Chien-Yi Chen

Hosted by: Soeren Schlichting

A remarkable observation from RHIC and the LHC is that the quark-gluon plasma produced in heavy-ion collisions behaves as a strongly coupled and nearly ideal liquid. Data also suggests that the debris produced by proton-nucleus collisions can also behave as a liquid. Understanding the dynamics responsible for the rapid equilibration of such tiny droplets is an outstanding problem. In recent years holography has emerged as a powerful tool to study non-equilibrium phenomena, mapping challenging quantum dynamics onto the classical dynamics of gravitational fields in one higher dimension. In the dual gravitational description the process of quark-gluon plasma formation and equilibration maps onto the process of gravitational collapse and black hole formation. I will describe how one can apply techniques and lessons learned from numerical relativity to holography and present recent work on holographic models of high energy collisions and the applicability of hydrodynamics to tiny droplets of quark-gluon plasma.

Hosted by: Daniel Pitonyak

The next-generation Electron-Ion Collider (EIC) will make high precision measurements of spin-dependent observables at high energies on nuclear targets. This unique nuclear physics laboratory will bring together access to the multitude of spin-spin and spin-orbit structures which can exist in hadronic targets, and the high color-charge densities which generate the most intense gluon fields permitted by quantum mechanics. The interplay between those two features gives rise to new physical mechanisms which translate these spin-orbit structures into the observed cross-sections, and it makes these mechanisms amenable to first-principles calculation. In this talk, I will discuss the spin-orbit structure of quarks within an unpolarized heavy nucleus in the quasi-classical approximation. The possibility of polarized nucleons with orbital motion inside the unpolarized nucleus generates nontrivial mixing between the spin-orbit structures of the nucleons, and the corresponding structures in the nucleus. This generic feature of a dense quasi-classical system leads to direct predictions testable at an EIC, and in principle allows direct access to the orbital angular momentum in the nucleus.

Hosted by: Chien-Yi Chen

Hosted by: Chien-Yi Chen

All matter in the Standard Model appears in three generations, with an intricate flavor structure the origin of which is not well understood. This motivates the question whether distinct phenomenological features arise if dark matter (DM) also has a non-trivial flavor structure. In this talk I will review the experimental signatures of this scenario. In the case of lepton-flavored DM, I will argue that the generation of a lepton asymmetry at a high energy scale can also produce a DM asymmetry, which can strongly affect the sensitivity of direct detection experiments, and I will present novel signatures that can appear at colliders and in indirect detection experiments. I will also review the case of top quark-flavored DM with a distinct collider phenomenology including final states of top pairs and missing energy as well the possibility of displaced decays.

Hosted by: Soeren Schlichting

Collectivity in high multiplicity pp and p-Pb collisions is the most unexpected discovery at the LHC, its origin is still an open question. In heavy ion collisions, collectivity is attributed to final state effects due to the presence of a hot and dense QCD medium, and it is well described by viscous hydrodynamical calculations with fluctuating initial state geometries. Surprisingly, calculations which employ hydrodynamics reproduce qualitatively well the features of p-Pb data, but, the applicability of hydro in small systems faces conceptual problems. This is not the case of other approaches which do not require a medium to be formed and also are able to reproduce qualitatively well some features of data. In this talk it will be shown that multi-parton interactions and color reconnection (CR) produce flow-like effects in high multiplicity pp collisions. A study of the transverse momentum (pT) distribution of identified hadrons as a function of the event multiplicity will be presented. This comprises studies of the average pT vs hadron mass and number of constituent quarks, and a pT differential study using the Boltzmann-Gibbs Blast-Wave model. A comparison between hydro and color reconnection calculations will be presented. In this context, the results from the same study using LHC data (pp, p-Pb and Pb-Pb collisions) will be discussed.

Hosted by: Chien-Yi Chen

Hosted by: Samuel Aronson

Relativistic heavy ion collisions can reproduce the conditions necessary to form a hot and dense medium known as the Quark Gluon Plasma (QGP), the state of the universe immediately following the Big Bang, in which quarks and gluons are deconfined. Results from experiments at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), which study the properties of the QGP, will be presented. This seminar will focus on two particle correlations and jet physics results in Pb-Pb and Au-Au collisions at the LHC and RHIC respectively and the prospects for such measurements at the proposed sPHENIX detector. In addition, the implications of using p-p or p-A systems as a reference for these A-A measurements will be discussed. Jets are the result of a hard scattering, which occurs early in the collision process, and probe how partons interact and lose energy in the medium. Two particle correlations are used to study jet physics and energy loss, as well as the underlying event. The interplay between the two is important for understanding how high momentum particles lose energy and for finding where that lost energy goes. To quantify the influence of the QGP on these measurements, it is important to have a good baseline measurement. A-A measurements are typically compared to expectations based on p-p collisions. Recent results from p-A collisions are used to quantify cold nuclear matter effects not captured in p-p collisions. However, p-A measurements have proven to be interesting in their own unexpected way which has implications for physics measurements at the future Electron Ion Collider.

Hosted by: Sally Dawson

Hosted by: Sally Dawson

Hosted by: Tomomi Ishikawa

We discuss recent progress, using the kinetic theory framework, in understanding the non-equilibrium evolution of overpopulated systems that resemble the glasma during the early stage of heavy ion collisions. We analyze a number of important factors that influence the course of thermalization in such systems, and in particular their consequences for the nontrivial dynamics driving Bose-Einstein Condensation as well as the isotropization. We discuss recent progress, using the kinetic theory framework, in understanding the non-equilibrium evolution of overpopulated systems that resemble the glasma during the early stage of heavy ion collisions. We analyze a number of important factors that influence the course of thermalization in such systems, and in particular their consequences for the nontrivial dynamics driving Bose-Einstein Condensation as well as the isotropization.

Hosted by: Sally Dawson

In this talk I will discuss the role of electric dipole moments (EDMs) as probes of physics beyond the Standard Model (BSM). In the first part of the talk I will present an overview of the physics reach of various searches and I will discuss the complementarity of different EDM probes. In the second part of the talk I will discuss ongoing work towards the computation of the BSM-induced neutron and proton EDM using lattice Quantum ChromoDynamics.

Hosted by: Sally Dawson

Hosted by: Tomomi Ishikawa

Hosted by: Koji Kashiwa

Hosted by: Bjoern Schenke

Hosted by: Tomomi Ishikawa

Hosted by: Tomomi Ishikawa

Hosted by: Tomomi Ishikawa

The Higgs boson with the mass recently announced by the LHC experiments corresponds within current precision to the boundary value between the situations when the electroweak vacuum is stable and metastable. I will discuss the latest developments in the calculation of this boundary mass and importance of measurement of other SM parameters (top quark mass and the strong coupling constant). I will also discuss what is the meaning of this boundary value in various minimal modifications of the Standard Model.

Hosted by: Tomomi Ishikawa

Hosted by: Bjoern Schenke

In this talk, I will present our study on the azimuthal anisotropy of high p_t particles (from jets) in the relativistic heavy ion collisions, which encode the information about jet energy loss in the medium as well as the medium itself. We focus on three different models with distinctive path-length and matter-density dependence of the energy loss: L^{2}, L^{3}, and near-Tc-enhancement (NTcE). We will first show our simple estimate of jet response to the shape fluctuation of the medium (initial state fluctuation) in the central 200 AGeV Au-Au collision. Second, the MC Glauber model is applied to study different Fourier-harmonics (V_{1,2,3,,,6}) of the final high P_t hadron spectrum in the non-central collisions at both RHIC and LHC (Pb-Pb collision). We find both L^{3} and NTcE can explain V_2 at RHIC (L^{2} underestimates it by roughly 20%), while L^{2} and NTcE are successful at LHC@2.76 TeV (L^{3} overestimates it by roughly 20%). In addition, we see the consistency between our NTcE calculations for other higher harmonics and the LHC@2.76 TeV data. The predictions of these harmonics for LHC@5.5 TeV will also be presented.

Hosted by: Koji Kashiwa

Hosted by: Adam Bzdak

Using hydrodynamics we explore the effects of the initial state, baryon stopping and baryon number transport on various observables such as spectra, elliptic flow and particle yields for heavy ion collisions at beam energies from $\sqrt{s_{NN}}=7.7$ to $200$ GeV. In our setup the transition from the equilibrated hydrodynamical phase to the final transport phase occurs over a broad range of temperatures/densities. Even though particle yields, extracted at this transition, can be described well by a single temperature freeze out we observe a correlation of particle mass, average transition temperature and flow velocity which allows us to successfully describe the measured non-monotonic behavior of the effective slope parameter as a function of particle mass. Furthermore we show that observed phenomena such as the centrality dependent freeze out parameters as well the asymmetry in particle/antiparticle $v_2$ at large baryon densities can be explained by a collective hydrodynamic expansion, once baryon stopping and baryon number conservation are properly taken into account. We will further discuss how the various stages of the collision contribute to the $p_{\bot}$ spectra and the mass dependence of $T_{eff}$.

Hosted by: Bjoern Schenke

The effect of the complex phase of the fermion determinant is a key question related to the sign problem in finite-density QCD. Recently, based on a field-theoretic argument inspired by the string theory, it has been shown that ignoring the complex phase -- the phase quenching -- does not change the expectation values of a class of observables in a certain region of the phase diagram when a number of colors Nc is large. In this talk we briefly explain this equivalence and show that the same equivalence holds in effective models and holographic models. We show, in a unified manner, that the phase quenching gives exact results for a class of fermionic observables (e.g., chiral condensate) in the mean-field approximation and for gauge-invariant gluonic observables (e.g., Polyakov loop) up to one-meson-loop corrections beyond mean field. We also discuss implications for the lattice simulations and confirm good quantitative agreement between our prediction and existing lattice QCD results. Therefore the phase quenching provides rather accurate answer already at Nc=3 with small 1/Nc corrections which can be taken into account by the phase reweighting.

Hosted by: Tomomi Ishikawa

Thermalization of strongly coupled gauge theory can be described by a gravitational collapse process via gauge/gravity duality. We studied the evolution of unequal time correlator in a gravitational collapse background, which allowed us to probe different stages of thermalization process. We found that the singularities of the correlator are consistent with geometric optics picture in the gravitational collapse background. We found the thermalization is characterized by the disappearance of singularities on real time axis and possible emergence of singularities in complex time plane in the correlator.

Hosted by: Bjoern Schenke

Various observables of neutron stars depend on hydrodynamic properties of the matter inside the star. This matter is likely to be a superfluid, for instance in the color-flavor locked (CFL) phase of quark matter. I will discuss the nontrivial superfluid properties of CFL and, in particular, present a "translation" between microscopic, field-theoretical calculations and the two-fluid picture of a relativistic superfluid.