Two-particle azimuthal correlations in photonuclear ultraperipheral Pb+Pb collisions at 5.02 TeV with ATLAS

ATLAS Publications, T.M. Carter, A. Hasib, M.P. Heath, S. Palazzo, A. Søgaard, E.P. Takeva, N. Themistokleous, E.M. Villhauer

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Two-particle long-range azimuthal correlations are measured in photonuclear collisions using 1.7 nb−1−1 of 5.02 TeV Pb+Pb collision data collected by the ATLAS experiment at the LHC. Candidate events are selected using a dedicated high-multiplicity photonuclear event trigger, a combination of information from the zero-degree calorimeters and forward calorimeters, and from pseudorapidity gaps constructed using calorimeter energy clusters and charged-particle tracks. Distributions of event properties are compared between data and Monte Carlo simulations of photonuclear processes. Two-particle correlation functions are formed using charged-particle tracks in the selected events, and a template-fitting method is employed to subtract the non-flow contribution to the correlation. Significant nonzero values of the second- and third-order flow coefficients are observed and presented as a function of charged-particle multiplicity and transverse momentum. The results are compared with flow coefficients obtained in proton-proton and proton-lead collisions in similar multiplicity ranges, and with theoretical expectations. The unique initial conditions present in this measurement provide a new way to probe the origin of the collective signatures previously observed only in hadronic collisions.
Original languageEnglish
Article number014903
Pages (from-to)1-31
Number of pages31
JournalPhysical Review C
Volume104
Issue number1
DOIs
Publication statusPublished - 12 Jul 2021

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