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 | η | < 1.0 and transverse momentum range 0.2 < p T < 2.0 GeV/ c as a function of pair separation in pseudorapidity, | Δ η | , azimuthal angle Δ φ , 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 Δ φ as a function of pair separation | Δ η | . 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.