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Title: Evidence for collectivity in pp collisions at the LHC

Measurements of two- and multi-particle angular correlations in pp collisions at √s = 5,7, and 13TeV are presented as a function of charged-particle multiplicity. The data, corresponding to integrated luminosities of 1.0pb–1 (5 TeV), 6.2pb–1 (7TeV), and 0.7pb–1 (13 TeV), were collected using the CMS detector at the LHC. The second-order (v2) and third-order (v3) azimuthal anisotropy harmonics of unidentified charged particles, as well as v2 of KS0 and Λ/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 v2 values of charged hadrons (mostly pions), KS0, and Λ/Λ¯, with lighter particle species exhibiting a stronger azimuthal anisotropy signal below pT ≈ 2GeV/c. For 13 TeV data, the v2 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. Finally, 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.
Authors:
 [1]
  1. Yerevan Physics Institute, Yerevan (Armenia). et al.
Publication Date:
OSTI Identifier:
1335706
Report Number(s):
FERMILAB-PUB-16-255-CMS; CMS-HIN-16-010; CERN-EP-2016-147; arXiv:1606.06198
Journal ID: ISSN 0370-2693; 1471287
Grant/Contract Number:
AC02-07CH11359
Type:
Published Article
Journal Name:
Physics Letters. Section B
Additional Journal Information:
Journal Volume: 765; Journal ID: ISSN 0370-2693
Publisher:
Elsevier
Research Org:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Orgs:
CMS Collaboration
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; CMS; Physics; Heavy ion; Ridge; Correlation; pp