Abstract
Measurements of two- and multi-particle angular correlations in pp collisions at s=5, 7, and 13 TeV are presented. The data, corresponding to integrated luminosities of 1.0 pb−1 (5 TeV), 6.2 pb−1 (7 TeV), and 0.7 pb−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‾ at pT≲2 GeV/c. The v2 signals are also extracted from four- and six-particle correlations for 13 TeV pp collisions, with comparable magnitude to those from two-particle correlations. These observations strongly support the interpretation of a collective origin for the observed long-range correlations in high-multiplicity pp collisions.
Highlights
Evidence for collective phenomena in pp collisionsMeasurements of two- and multi-particle angular correlations in pp collisions at s = 5, 7, and 13 TeV are presented
The v2 signals are extracted from four- and six-particle correlations for 13 TeV pp collisions, with comparable magnitude to those from two-particle correlations. These observations strongly support the interpretation of a collective origin for the observed long-range correlations in high-multiplicity pp collisions
Observation of long-range two-particle azimuthal correlations at large relative pseudorapidity in highmultiplicity proton-proton [1, 2] and proton-lead [3] collisions at CMS [4] has opened up new opportunities for studying novel dynamics of particle production in small, high-density quantum chromodynamic (QCD) systems
Summary
Measurements of two- and multi-particle angular correlations in pp collisions at s = 5, 7, and 13 TeV are presented. 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 twoparticle correlations as functions of particle multiplicity and transverse momentum. The v2 signals are extracted from four- and six-particle correlations for 13 TeV pp collisions, with comparable magnitude to those from two-particle correlations. These observations strongly support the interpretation of a collective origin for the observed long-range correlations in high-multiplicity pp collisions
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