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

  • Author(s): Aad, G
  • Abbott, B
  • Abbott, DC
  • Abed Abud, A
  • Abeling, K
  • Abhayasinghe, DK
  • Abidi, SH
  • Abouzeid, OS
  • Abraham, NL
  • Abramowicz, H
  • Abreu, H
  • Abulaiti, Y
  • Abusleme Hoffman, AC
  • Acharya, BS
  • Achkar, B
  • Adam, L
  • Adam Bourdarios, C
  • Adamczyk, L
  • Adamek, L
  • Adelman, J
  • Adiguzel, A
  • Adorni, S
  • Adye, T
  • Affolder, AA
  • Afik, Y
  • Agapopoulou, C
  • Agaras, MN
  • Aggarwal, A
  • Agheorghiesei, C
  • Aguilar-Saavedra, JA
  • Ahmad, A
  • Ahmadov, F
  • Ahmed, WS
  • Ai, X
  • Aielli, G
  • Akatsuka, S
  • Akbiyik, M
  • Åkesson, TPA
  • Akilli, E
  • Akimov, AV
  • Al Khoury, K
  • Alberghi, GL
  • Albert, J
  • Alconada Verzini, MJ
  • Alderweireldt, S
  • Aleksa, M
  • Aleksandrov, IN
  • Alexa, C
  • Alexopoulos, T
  • Alfonsi, A
  • Alfonsi, F
  • Alhroob, M
  • Ali, B
  • Ali, S
  • Aliev, M
  • Alimonti, G
  • Allaire, C
  • Allbrooke, BMM
  • Allport, PP
  • Aloisio, A
  • Alonso, F
  • Alpigiani, C
  • Alunno Camelia, E
  • Alvarez Estevez, M
  • Alviggi, MG
  • Amaral Coutinho, Y
  • Ambler, A
  • Ambroz, L
  • Amelung, C
  • Amidei, D
  • Amor Dos Santos, SP
  • Amoroso, S
  • Amrouche, CS
  • Anastopoulos, C
  • Andari, N
  • Andeen, T
  • Anders, JK
  • Andrean, SY
  • Andreazza, A
  • Andrei, V
  • Anelli, CR
  • Angelidakis, S
  • Angerami, A
  • Anisenkov, AV
  • Annovi, A
  • Antel, C
  • Anthony, MT
  • Antipov, E
  • Antonelli, M
  • Antrim, DJA
  • Anulli, F
  • Aoki, M
  • Aparisi Pozo, JA
  • Aparo, MA
  • Aperio Bella, L
  • Aranzabal, N
  • Araujo Ferraz, V
  • Arcangeletti, C
  • Arce, ATH
  • Arguin, JF
  • et al.
Abstract

Two-particle long-range azimuthal correlations are measured in photonuclear collisions using 1.7nb-1 of 5.02 TeV Pb+Pb collision data collected by the ATLAS experiment at the CERN Large Hadron Collider. 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 nonflow 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.

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