Measurement of long-range near-side two-particle angular correlations in pp collisions at sqrt(s) = 13 TeV

TL;DR

This paper reports on the observation of long-range near-side two-particle angular correlations in proton-proton collisions at 13 TeV, revealing a multiplicity-dependent structure similar to that seen in larger collision systems.

Contribution

It extends the study of long-range correlations in pp collisions to higher multiplicities and compares these findings with other collision systems and energies.

Findings

Long-range correlations emerge in high-multiplicity events.

Correlation strength peaks at 1.0 < pt < 2.0 GeV/c.

Correlation increases linearly with charged particle multiplicity.

Abstract

Results on two-particle angular correlations for charged particles produced in pp 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 inverse nanobarns. The correlations are studied over a broad range of pseudorapidity (abs(eta) < 2.4) and over the full azimuth (phi) as a function of charged particle multiplicity and transverse momentum (pt). In high-multiplicity events, a long-range (abs(Delta eta) > 2.0), near-side (Delta phi approximately 0) structure emerges in the two-particle Delta eta-Delta phi correlation functions. The magnitude of the correlation exhibits a pronounced maximum in the range 1.0 < pt < 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 pp data at sqrt(s) = 7 TeV. The present measurement extends the study of near-side long-range correlations up to charged particle multiplicities of N[ch] approximately 180, a region so far unexplored in pp collisions. The observed long-range correlations are compared to those seen in pp, pPb, and PbPb collisions at lower collision energies.