Evidence for transverse-momentum- and pseudorapidity-dependent event-plane fluctuations in PbPb and p Pb collisions

CMS Collaboration

Research output: Contribution to journalArticle

91 Citations (Scopus)

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 pT 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 sNN=2.76 TeV and pPb collisions at sNN=5.02 TeV, covering a very wide range of multiplicity. Factorization is observed to be broken as a function of both particle pT and η. When measured with particles of different pT, 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.

Original languageEnglish
Article number034911
JournalPhysical Review C - Nuclear Physics
Volume92
Issue number3
DOIs
Publication statusPublished - 2015 Sep 22

Fingerprint

transverse momentum
factorization
collisions
breakdown
ionic collisions
coverings
transport properties
hydrodynamics
viscosity
shear
harmonics
anisotropy
detectors
products
predictions

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics

Cite this

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title = "Evidence for transverse-momentum- and pseudorapidity-dependent event-plane fluctuations in PbPb and p Pb collisions",
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 pT 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 sNN=2.76 TeV and pPb collisions at sNN=5.02 TeV, covering a very wide range of multiplicity. Factorization is observed to be broken as a function of both particle pT and η. When measured with particles of different pT, 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.",
author = "{CMS Collaboration} and V. Khachatryan and Sirunyan, {A. M.} and A. Tumasyan and W. Adam and E. Asilar and T. Bergauer and J. Brandstetter and M. Dragicevic and J. Er{\"o} and M. Flechl and M. Friedl and R. Fr{\"u}hwirth and Ghete, {V. M.} and C. Hartl and N. H{\"o}rmann and J. Hrubec and M. Jeitler and W. Kiesenhofer and V. Kn{\"u}nz and A. K{\"o}nig and M. Krammer and I. Kr{\"a}tschmer and D. Liko and I. Mikulec and D. Rabady and B. Rahbaran and H. Rohringer and J. Schieck and R. Sch{\"o}fbeck and J. Strauss and W. Treberer-Treberspurg and W. Waltenberger and Wulz, {C. E.} and V. Mossolov and N. Shumeiko and {Suarez Gonzalez}, J. and S. Alderweireldt and S. Bansal and T. Cornelis and {De Wolf}, {E. A.} and X. Janssen and A. Knutsson and J. Lauwers and S. Luyckx and S. Ochesanu and R. Rougny and {Van De Klundert}, M. and {Van Haevermaet}, H. and {Van Mechelen}, P. and Yoo, {H. D.}",
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doi = "10.1103/PhysRevC.92.034911",
language = "English",
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Evidence for transverse-momentum- and pseudorapidity-dependent event-plane fluctuations in PbPb and p Pb collisions. / CMS Collaboration.

In: Physical Review C - Nuclear Physics, Vol. 92, No. 3, 034911, 22.09.2015.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Evidence for transverse-momentum- and pseudorapidity-dependent event-plane fluctuations in PbPb and p Pb collisions

AU - CMS Collaboration

AU - Khachatryan, V.

AU - Sirunyan, A. M.

AU - Tumasyan, A.

AU - Adam, W.

AU - Asilar, E.

AU - Bergauer, T.

AU - Brandstetter, J.

AU - Dragicevic, M.

AU - Erö, J.

AU - Flechl, M.

AU - Friedl, M.

AU - Frühwirth, R.

AU - Ghete, V. M.

AU - Hartl, C.

AU - Hörmann, N.

AU - Hrubec, J.

AU - Jeitler, M.

AU - Kiesenhofer, W.

AU - Knünz, V.

AU - König, A.

AU - Krammer, M.

AU - Krätschmer, I.

AU - Liko, D.

AU - Mikulec, I.

AU - Rabady, D.

AU - Rahbaran, B.

AU - Rohringer, H.

AU - Schieck, J.

AU - Schöfbeck, R.

AU - Strauss, J.

AU - Treberer-Treberspurg, W.

AU - Waltenberger, W.

AU - Wulz, C. E.

AU - Mossolov, V.

AU - Shumeiko, N.

AU - Suarez Gonzalez, J.

AU - Alderweireldt, S.

AU - Bansal, S.

AU - Cornelis, T.

AU - De Wolf, E. A.

AU - Janssen, X.

AU - Knutsson, A.

AU - Lauwers, J.

AU - Luyckx, S.

AU - Ochesanu, S.

AU - Rougny, R.

AU - Van De Klundert, M.

AU - Van Haevermaet, H.

AU - Van Mechelen, P.

AU - Yoo, H. D.

PY - 2015/9/22

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N2 - 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 pT 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 sNN=2.76 TeV and pPb collisions at sNN=5.02 TeV, covering a very wide range of multiplicity. Factorization is observed to be broken as a function of both particle pT and η. When measured with particles of different pT, 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.

AB - 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 pT 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 sNN=2.76 TeV and pPb collisions at sNN=5.02 TeV, covering a very wide range of multiplicity. Factorization is observed to be broken as a function of both particle pT and η. When measured with particles of different pT, 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.

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DO - 10.1103/PhysRevC.92.034911

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