Evidence for collectivity in pp collisions at the LHC
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, vol.765, pp.193-220, 2017 (SCI-Expanded, Scopus)
- Publication Type: Article / Article
- Volume: 765
- Publication Date: 2017
- Doi Number: 10.1016/j.physletb.2016.12.009
- Journal Name: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
- Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
- Page Numbers: pp.193-220
- Keywords: CMS, Correlation, Heavy ion, Physics, pp, Ridge
- Yıldız Technical University Affiliated: Yes
Abstract
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 (7 TeV), 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 KS 0 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), KS 0, 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. 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.