Studies of charm and beauty hadron long-range correlations in pp and pPb collisions at LHC energies

Abstract

Measurements of the second Fourier harmonic coefficient ( v 2 ) of the azimuthal distributions of prompt and nonprompt D 0 mesons produced in p p and p Pb collisions are presented. Nonprompt D 0 mesons come from beauty hadron decays. The data samples are collected by the CMS experiment at nucleon-nucleon center-of-mass energies of 13 and 8.16 TeV, respectively. In high multiplicity p p collisions, v 2 signals for prompt charm hadrons are reported for the first time, and are found to be comparable to those for light-flavor hadron species over a transverse momentum ( p T ) range of 2–6 GeV. Compared at similar event multiplicities, the prompt D 0 meson v 2 values in p p and p Pb collisions are similar in magnitude. The v 2 values for open beauty hadrons are extracted for the first time via nonprompt D 0 mesons in p Pb collisions. For p T in the range of 2–5 GeV, the results suggest that v 2 for nonprompt D 0 mesons is smaller than that for prompt D 0 mesons. These new measurements indicate a positive charm hadron v 2 in p p collisions and suggest a mass dependence in v 2 between charm and beauty hadrons in the p Pb system. These results provide insights into the origin of heavy-flavor quark collectivity in small systems.