Measurements of two-particle correlation functions and the first five azimuthal harmonics, v1 to v5, are presented, using 28 nb-1 of p+Pb collisions at a nucleon-nucleon center-of-mass energy of √sNN=5.02 TeV measured with the ATLAS detector at the LHC. Significant long-range "ridgelike" correlations are observed for pairs with small (|Δϕ|<π/3) and back-to-back pairs (|Δφ|>2π/3) over the transverse momentum range 0.4<p<inf>T</inf><12 GeV and in different intervals of event activity. The event activity is defined by either the number of reconstructed tracks or the total transverse energy on the Pb-fragmentation side. The azimuthal structure of such long-range correlations is Fourier decomposed to obtain the harmonics ν<inf>n</inf> as a function of pT and event activity. The extracted ν<inf>n</inf> values for n=2 to 5 decrease with n. The ν<inf>2</inf> and ν<inf>3</inf> values are found to be positive in the measured pT range. The ν<inf>1</inf> is also measured as a function of pT and is observed to change sign around pT≈1.5-2.0 GeV and then increase to about 0.1 for pT>4 GeV. The ν<inf>2</inf> (pT), ν<inf>3</inf> (pT), and ν<inf>4</inf> (pT) are compared to the ν<inf>n</inf> coefficients in Pb+Pb collisions at √sNN=2.76 TeV with similar event multiplicities. Reasonable agreement is observed after accounting for the difference in the average pT of particles produced in the two collision systems. © 2014 CERN, for the ATLAS Collaboration.
Measurement of long-range pseudorapidity correlations and azimuthal harmonics in √s<inf>NN</inf> =5.02 TeV proton-lead collisions with the ATLAS detector / Aad, G; Aloisio, Alberto; Alviggi, Mariagrazia; Canale, Vincenzo; Chiefari, Giovanni; DELLA VOLPE, Domenico; Merola, Leonardo; Conventi, Francesco; DELLA PIETRA, Massimo; Giordano, Raffaele; Rossi, Elvira; SANCHEZ PINEDA, ARTURO RODOLFO; Carlino, Gianpaolo; de Asmundis, Riccardo; Di Donato, Camilla; Doria, Alessandra; Iengo, Paolo; Izzo, Vincenzo; Sekhniaidze, Givi; Et, A. l.. - In: PHYSICAL REVIEW. C, NUCLEAR PHYSICS. - ISSN 0556-2813. - 90:4(2014). [10.1103/PhysRevC.90.044906]
Measurement of long-range pseudorapidity correlations and azimuthal harmonics in √sNN =5.02 TeV proton-lead collisions with the ATLAS detector
ALOISIO, ALBERTO;ALVIGGI, MARIAGRAZIA;CANALE, VINCENZO;CHIEFARI, GIOVANNI;DELLA VOLPE, DOMENICO;MEROLA, LEONARDO;DELLA PIETRA, MASSIMO;GIORDANO, RAFFAELE;Rossi, Elvira;SANCHEZ PINEDA, ARTURO RODOLFO;
2014
Abstract
Measurements of two-particle correlation functions and the first five azimuthal harmonics, v1 to v5, are presented, using 28 nb-1 of p+Pb collisions at a nucleon-nucleon center-of-mass energy of √sNN=5.02 TeV measured with the ATLAS detector at the LHC. Significant long-range "ridgelike" correlations are observed for pairs with small (|Δϕ|<π/3) and back-to-back pairs (|Δφ|>2π/3) over the transverse momentum range 0.4T<12 GeV and in different intervals of event activity. The event activity is defined by either the number of reconstructed tracks or the total transverse energy on the Pb-fragmentation side. The azimuthal structure of such long-range correlations is Fourier decomposed to obtain the harmonics ν
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