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  1. JUN



    Nuclear Physics Seminar

    "Measurements of charm, bottom, and Drell-Yan via dimuons in p+p and p+Au collisions at sNN=200 GeV with PHENIX at RHIC"

    Presented by Yue Hang Leung, Stonybrook University

    11 am, Small Seminar Room, Bldg. 510

    Tuesday, June 19, 2018, 11:00 am

    Hosted by: Jin Huang

    Dilepton spectra are a classic probe to study ultra-relativistic heavy ion collisions. At RHIC energies, the dimuon continuum is dominated by correlated pairs from charm and bottom semi-leptonic decays and the Drell-Yan process. In this talk, we present measurements of µµ pairs from charm, bottom, and Drell-Yan in p+p and p+Au collisions at sNN = 200 GeV. Differential yields from charm and bottom in p+p collisions will be presented and implications for the relative contributions from different heavy flavor production mechanisms will be discussed. We will also present results of bottom yields in p+Au collisions and discuss the implications on cold nuclear matter effects. This study also enables first measurements of the Drell-Yan cross-section at s_{NN} = 200 GeV. Studying Drell-Yan production in p+Au collisions is a clean probe for modifications of the initial state. The Drell-Yan differential cross-sections in p+p collisions and progress on p+Au collisions will be presented.

  2. JUN



    Physics Colloquium

    "Subatomic Swirls and Massive Magnetic Fields - Lambda Polarization in Heavy Ion Collisions at RHIC"

    Presented by Michael Lisa, Ohio State University

    3:30 pm, Large Seminar Room, Bldg. 510

    Tuesday, June 19, 2018, 3:30 pm

    Hosted by: Peter Petreczky

    Last year, the STAR Collaboration at RHIC published the first observation of global hyperon polarization in heavy ion collisions. This polarization may be used to extract rotational substructure of the flow field. The result represented a striking validation of the near-equilibrium hydrodynamic paradigm and established the quark-gluon plasma at RHIC as by far the most vortical fluid in nature. More recent studies quantify the vortical structure systematics to challenge hydro models in detail. In addition to the rotational fluid substructure, hyperon polarization should probe the strong magnetic fields expected in heavy ion collisions. Measuring these fields is crucial for establishing and quantifying the so-called Chiral Magnetic Effect at RHIC. Experimental uncertainties are currently too large to conclusively measure the magnetic field, but detector upgrades at STAR and dedicated running at RHIC may allow a breakthrough in this year's (2018) run.

  3. JUL



    Joint Nuclear Physics and High Energy Physics Seminar

    "Parity-Violating and Parity-Conserving Asymmetries in ep and eN Scattering in the Qweak Experiment"

    Presented by Wouter Deconinck, College of William & Mary

    11 am, Small Seminar Room, Bldg. 510

    Tuesday, July 10, 2018, 11:00 am

    Hosted by: Jin Huang

    The Standard Model provides the current best description of fundamental particles and forces, but among other limitations it fails to account for dark matter which could manifest itself as more massive particles. Precision measurements of well predicted observables in the Standard Model allow for highly targeted tests for physics beyond the Standard Model. The Qweak experiment at Jefferson Lab has made the first precise determination of the weak charge of the proton in elastic scattering of longitudinally polarized electrons from unpolarized protons. To achieve the required precision to measure the small parity-violating asymmetry of -226.5 ± 9.3 parts per billion, we directed a high current polarized electron beam on a liquid hydrogen target and integrated scattered events in eight azimuthally symmetric fused silica Cerenkov detectors. We find a value for the weak charge of proton of 0.0719 ± 0.0045, in agreement with predictions of the Standard Model. This result rules out leptoquark masses below 2.3 TeV and excludes generic new semi-leptonic parity-violation physics beyond the Standard Model below 3.5 TeV. To correct for the contributions from background processes, we conducted several additional parity-violating and parity-conserving asymmetry measurements with different kinematics (elastic and through the production of a Delta resonance), polarization (longitudinal and transverse), and targets (protons, electrons, aluminum, and carbon). I will discuss the results of the main experiment and highlight several ancillary results of interest to experiments at future facilities.

  4. SEP



    Nuclear Physics Seminar

    "Neutron production and capture in stellar nucleosynthesis:^{22}Ne(\Alpha,n)^{25}Mg reaction and radiative neutron captures of radioactive nuclei"

    Presented by Shuya Ota, Texas A&M University

    11 am, Small Seminar Room, Bldg. 510

    Tuesday, September 4, 2018, 11:00 am

    Hosted by: Jin Huang

    Most of elements heavier than Fe in the Universe are produced by a series of neutron capture reaction and ??-decay in stars. The s-process, which occurs under moderate neutron environments (~107-10 neutrons/cm3) such as in He burning of massive stars, is responsible for producing almost half of the heavy elements. Neutrons for the s-process environment is believed to be supplied by two dominant reactions, one of which is 22Ne(?,n)25Mg reaction. This reaction in massive stars is dominated by a few resonance reactions. Nevertheless, there remain large uncertainties about contribution of the reaction to the s-process nucleosynthesis because the reaction cross sections are too small for direct measurements due to Coulomb barrier (E? = 400-900 keV in the lab system). In the first half of this seminar, I will present our experiment to determine these resonance strengths with a cyclotron accelerator at Texas A&M University. The experiment was performed by an indirect approach using 6Li(22Ne,25Mg+n)d ?-transfer reaction, in which resonance properties such as neutron decay branching ratios of produced 26Mg were studied by measuring deuterons, ?-ray, and 26Mg in coincidence using large arrays of Si and Ge, and a magnetic spectrometer. Our results showed neutron production from 22Ne(?,n)25Mg reaction can be about 10 times lower than past measurements. The effect of our measurements on the s-process nucleosynthesis will be discussed. In the second half of this seminar, I will present our experiments to determine neutron capture cross sections of radioactive nuclei using the Surrogate Reaction method [1]. Neutron capture reactions for the s-process involve relatively long-lived nuclei neighboring stability in the nuclear chart. Therefore, the Surrogate Reaction, which creates the same compound nuclei as the neutron capture reaction using a stable beam and target, can be a useful approach. On the other hand, the r- process, which produces the other half

  1. Nuclear Physics Seminar

    "High-pt Hadron Production in Au+Au and d+Au Collisions at sqrt (s) = 200 GeV"

    Presented by Sasha Milov, Stony Brook University

    Tuesday, July 1, 2003, 11 am
    Small Seminar Room, Bldg. 510

  2. Nuclear Physics Seminar

    "Production of Lambda (1520) at RHIC at sqrt (s) = 200 GeV"

    Presented by Ludovic Gaudichet, Subatech, France

    Tuesday, July 15, 2003, 11 am
    Small Seminar Room, Bldg. 510

  3. Nuclear Physics Seminar

    "Induced Criticality of Non-Order Parameter Fields"

    Presented by Agnes Mocsy, Niels Bohr Institute, Denmark

    Tuesday, July 22, 2003, 11 am
    Small Seminar Room, Bldg. 510

  4. Nuclear Physics Seminar

    "Strangeness Production in Au+Au Collisions at RHIC"

    Presented by Ben Norman, Kent State University

    Tuesday, July 29, 2003, 11 am
    Small Seminar Room, Bldg. 510

  5. Nuclear Physics & RIKEN Theory Seminar

    "Hydrodynamic Afterburner for Color Glass Condensate"

    Presented by Yasushi Nara, University of Arizona

    Friday, August 8, 2003, 2 pm
    Small Seminar Room, Bldg. 510

  6. High-Energy Physics & RIKEN Theory Seminar

    "Strong Interaction Effect on Muon g-2"

    Presented by Masashi Hayakawa, RIKEN/BNL Research Center

    Sunday, August 10, 2003, 1:30 pm
    Small Seminar Room, Bldg. 510

  7. High-Energy Physics & RIKEN Theory Seminar

    "Elitzurs Theorem and the Sign Problem"

    Presented by Kim Splittorff, Stony Brook University

    Wednesday, August 13, 2003, 1:30 pm
    Small Seminar Room, Bldg. 510

  8. Instrumentation Division Seminar

    "Development of Novel Silicon Stripixel Detectors for High energy and Nuclear Physics Experiments"

    Presented by Zheng Li, Instrumentation Division

    Wednesday, September 10, 2003, 2:30 pm
    Large Seminar Room, Bldg. 535

  9. Nuclear Physics Seminar

    "Discovery of Penta Quarks"

    Presented by Prof. Ken-chi Imai, Kyoto University, Japan

    Tuesday, October 14, 2003, 11 am
    Small Seminar Room, Bldg. 510

  10. RIKEN BNL Research Center Workshop

    "Collective Flow and QGP Properties"

    Monday, November 17, 2003, 9 am
    Large Seminar Room, Bldg. 510