Two-particle differential transverse momentum and number density correlations in p- Pb collisions at 5.02 TeV and Pb-Pb collisions at 2.76 TeV at the CERN Large Hadron Collider

Abstract

We present measurements of two-particle differential number correlation functions ${R}_{2}$ and transverse momentum correlation functions ${P}_{2}$, obtained from $p$-Pb collisions at 5.02 TeV and Pb-Pb collisions at 2.76 TeV. The results are obtained by using charged particles in the pseudorapidity range $|\ensuremath{\eta}|<1.0$ and transverse momentum range $0.2<{p}_{\mathrm{T}}<2.0$ GeV/$c$ as a function of pair separation in pseudorapidity, $|\mathrm{\ensuremath{\Delta}}\ensuremath{\eta}|$, azimuthal angle $\mathrm{\ensuremath{\Delta}}\ensuremath{\varphi}$, and for several charged-particle multiplicity classes. Measurements are carried out for like-sign and unlike-sign charged-particle pairs separately and combined to obtain charge-independent and charge-dependent correlation functions. We study the evolution of the width of the near-side peak of these correlation functions with collision centrality. Additionally, we study Fourier decompositions of the correlators in $\mathrm{\ensuremath{\Delta}}\ensuremath{\varphi}$ as a function of pair separation $|\mathrm{\ensuremath{\Delta}}\ensuremath{\eta}|$. Significant differences in the dependence of their harmonic coefficients on multiplicity classes are found. These differences can be exploited, in theoretical models, to obtain further insight into charged-particle production and transport in heavy-ion collisions. Moreover, an upper limit of nonflow contributions to flow coefficients ${v}_{n}$ measured in Pb-Pb collisions based on the relative strength of Fourier coefficients measured in $p$-Pb interactions is estimated.