Evidence for collectivity in pp collisions at the LHC
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Author(s)
Abercrombie, Daniel Robert
Allen, Brandon Leigh
Apyan, Aram
Barbieri, Richard Alexander
Baty, Austin Alan
Bi, Ran
Bierwagen, Katharina
Brandt, Stephanie Akemi
Cali, Ivan Amos
Busza, Wit
Date Issued
February 2017
Journal
Physics Letters B
Publisher
Elsevier BV
Citation
Khachatryan, V., et al. “Evidence for Collectivity in Pp Collisions at the LHC.” Physics Letters B, vol. 765, Feb. 2017, pp. 193–220. © 2016 The Authors
Version
Final published version
Abstract
Measurements of two- and multi-particle angular correlations in pp collisions at √s=5, 7, and 13 TeV are presented as a function of charged-particle multiplicity. The data, corresponding to integrated luminosities of 1.0pb[superscript −1] (5 TeV), 6.2pb[superscript −1] (7 TeV), and 0.7pb[superscript −1] (13 TeV), were collected using the CMS detector at the LHC. The second-order (v[subscript 2]) and third-order (v[subscript 3]) azimuthal anisotropy harmonics of unidentified charged particles, as well as v[subscript 2] of K[superscript 0][subscript s] and Λ/[bar over Λ] particles, are extracted from long-range two-particle correlations as functions of particle multiplicity and transverse momentum. For high-multiplicity pp events, a mass ordering is observed for the v[subscript 2] values of charged hadrons (mostly pions), K[superscript 0][subscript s], and Λ/[bar overΛ], with lighter particle species exhibiting a stronger azimuthal anisotropy signal below p[subscript T] ≈2 GeV/c. For 13 TeV data, the v[subscript 2] signals are also extracted from four- and six-particle correlations for the first time in pp collisions, with comparable magnitude to those from two-particle correlations. These observations are similar to those seen in pPb and PbPb collisions, and support the interpretation of a collective origin for the observed long-range correlations in high-multiplicity pp collisions. Keywords: CMS, Physics, Heavy ion, Ridge, Correlation, pp
MIT Department
Massachusetts Institute of Technology. Department of Physics
Massachusetts Institute of Technology. Laboratory for Nuclear Science
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Creative Commons Attribution 4.0 International License
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DOI of Published Version
https://doi.org/10.1016/J.PHYSLETB.2016.12.009
