Evidence for transverse-momentum- and pseudorapidity-dependent event-plane fluctuations in PbPb and pPb collisions
Name
PhysRevC.92.034911.pdf
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959.2 KB
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Author(s)
Khachatryan, V.
Sirunyan, A. M.
Tumasyan, A.
Adam, W.
Asilar, E.
Bergauer, T.
Brandstetter, J.
Dragicevic, M.
Erö, J.
Flechl, M.
Date Issued
September 2015
Journal
Physical Review C
Publisher
American Physical Society
Citation
Khachatryan, V., et al. "Evidence for transverse-momentum- and pseudorapidity-dependent event-plane fluctuations in PbPb and pPb collisions." Phys. Rev. C 92, 034911 (September 2015). © 2015 CERN, for the CMS Collaboration
Version
Final published version
Abstract
A systematic study of the factorization of long-range azimuthal two-particle correlations into a product of single-particle anisotropies is presented as a function of p[subscript T] and η of both particles and as a function of the particle multiplicity in PbPb and pPb collisions. The data were taken with the CMS detector for PbPb collisions at √[s[subscript NN] = 2.76 TeV and pPb collisions at √s[subscript NN] = 5.02 TeV, covering a very wide range of multiplicity. Factorization is observed to be broken as a function of both particle p[subscript T] and η. When measured with particles of different p[subscript T], the magnitude of the factorization breakdown for the second Fourier harmonic reaches 20% for very central PbPb collisions but decreases rapidly as the multiplicity decreases. The data are consistent with viscous hydrodynamic predictions, which suggest that the effect of factorization breaking is mainly sensitive to the initial-state conditions rather than to the transport properties (e.g., shear viscosity) of the medium. The factorization breakdown is also computed with particles of different η. The effect is found to be weakest for mid-central PbPb events but becomes larger for more central or peripheral PbPb collisions, and also for very-high-multiplicity pPb collisions. The η-dependent factorization data provide new insights to the longitudinal evolution of the medium formed in heavy ion collisions.
MIT Department
Massachusetts Institute of Technology. Department of Physics
Massachusetts Institute of Technology. Laboratory for Nuclear Science
Massachusetts Institute of Technology. School of Science
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DOI of Published Version
http://dx.doi.org/10.1103/PhysRevC.92.034911
