Two-particle Correlations in $pp$ Collisions at 13 TeV Measured with CMS

S.M Dogra

doi:10.5506/aphyspolbsupp.9.207

Abstract

Results on two-particle angular correlations for charged particles emitted in pp collisions at a centerof-mass energy of 13 TeV are presented as a function of charged-particle multiplicity and transverse momentum (pT ). In high−multiplicity events, a long-range (| η |> 2.0), near-side (∆φ = 0) structure emerges in the two-particle ∆η − ∆φ correlation functions. The overall correlation strength is similar to that found in earlier pp data at 7 TeV, but is measured up to much higher multiplicity values. A detailed study in pp collisions at 7 TeV of the second-order (v2) azimuthal anisotropy harmonics of charged particles, K S and Λ/Λ particles are extracted from long-range two-particle correlations as a function of particle multiplicity and transverse momentum and are also compared with values obtained in pPb and PbPb collisions at similar multiplicities. Presented at WPCF-2015 XI Workshop on Particle Correlations and Femtoscopy Two-Particle Correlations in pp Collisions at 13 TeV Measured with CMS ∗

Highlights

The discovery of long-range two-particle azimuthal correlations at large relative pseudorapidity in high- multiplicity proton-proton [1] and proton-lead [2] collisions at CMS has opened up new opportunities of studying novel dynamics of particle production in small but highdensity Quantum Chromodynamic (QCD) systems
A detailed study in pp collisions at 7 TeV of the second-order (v2) azimuthal anisotropy harmonics of charged particles, KS0 and Λ/Λparticles are extracted from long-range two-particle correlations as a function of particle multiplicity and transverse momentum and are compared with values obtained in pPb and PbPb collisions at similar multiplicities
The data presented in this paper provide important insights to understand the origin of long-range correlations in pp collision, and shed light on the subnucleonic structure of the proton

Summary

Introduction

The discovery of long-range two-particle azimuthal correlations at large relative pseudorapidity in high- multiplicity proton-proton [1] and proton-lead [2] collisions at CMS has opened up new opportunities of studying novel dynamics of particle production in small but highdensity Quantum Chromodynamic (QCD) systems. Similar long-range correlation structures at small relative azimuthal angle ∆φ ≈ 0 were first observed in relativistic nucleus-nucleus (AA) collisions. Such correlations have been extensively studied and it has been suggested that the hydrodynamic collective flow of a strongly interacting and expanding medium is responsible for these long-range correlations in large heavy-ion collision systems. The anisotropy harmonics v2 and v3 identified particles are extracted at 7 of KS0 and TeV from long-range (|∆η| > 2) two-particle correlations by associating either an unidentified charged particle, or an identified V0 particle (KS0, Λ/Λ) with another unidentified charged particle and are expressed as a function of particle pT and event multiplicity

The CMS experiment and two particle correlations

Results

Summary