Measurement of Long-Range Near-Side Two-Particle Angular Correlations in pp Collisions at √s=8TeV

Abstract

Results on two-particle angular correlations for charged particles produced in p p collisions at a center-of-mass energy of 13 TeV are presented. The data were taken with the CMS detector at the LHC and correspond to an integrated luminosity of about 270 nb − 1 . The correlations are studied over a broad range of pseudorapidity ( | η | < 2.4 ) and over the full azimuth ( ϕ ) as a function of charged particle multiplicity and transverse momentum ( p T ). In high-multiplicity events, a long-range ( | Δ η | > 2.0 ), near-side ( Δ ϕ ≈ 0 ) structure emerges in the two-particle Δ η – Δ ϕ correlation functions. The magnitude of the correlation exhibits a pronounced maximum in the range 1.0 < p T < 2.0 GeV / c and an approximately linear increase with the charged particle multiplicity, with an overall correlation strength similar to that found in earlier p p data at √ s = 7 TeV . The present measurement extends the study of near-side long-range correlations up to charged particle multiplicities N ch ∼ 180 , a region so far unexplored in p p collisions. The observed long-range correlations are compared to those seen in p p , p Pb , and PbPb collisions at lower collision energies.