Nuclear Physics Seminar

"Measurements of long-range correlations in photonuclear collisions and prospects for small-system longitudinal decorrelation"

Presented by Blair Seidlitz, University of Colorado Boulder

Thursday, May 27, 2021, 1:00 pm — Videoconference / Virtual Event (see link below)

Abstract: The ultra-peripheral collisions of relativistic heavy-ion beams lead to a preva-
lent and diverse set of photon-nucleus interactions. Measurements of particles
produced in photonuclear collisions and their interactions can shed light on
the QCD dynamics of EM-induced, extremely asymmetric colliding systems,
with energies between those available at RHIC and the LHC. In addition, un-
derstanding the hadronic
uctuation spectrum of the photon in this fashion is
critical for maximizing the precision of measurements at the future Electron Ion
Collider facility. This talk presents a measurement of two-particle long-range
azimuthal correlations in photonuclear collisions using 5.02 TeV Pb+Pb col-
lision data. Candidate photonuclear events are selected using a combination
of single-sided zero-degree calorimeter activity and reconstructed pseudorapid-
ity gaps. Correlation functions are constructed and non-collective contributions
are removed. The resulting elliptic and triangular
ow coecients are presented
where signi cant non-zero values are observed and compared to proton{proton
and proton{lead collisions in similar multiplicity ranges.
The results in this highly-asymmetric system could be sensitive the longi-
tudinal structure of the initial state (i.e. event-plane twist) of which little has
been explored in small systems. This talk will also present the prospect for
understanding the relevant sub-nucleonic structure leading to small-system lon-
gitudinal decorrelation and how it relates to previous studies in large systems.

Hosted by: Takao Sakaguchi

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