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

Measurements of the second Fourier harmonic coefficient (${v}_{2}$) of the azimuthal distributions of prompt and nonprompt D$^{0}$ mesons produced in $pp$ and $p\text{Pb}$ 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 $pp$ 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 $pp$ and $p\text{Pb}$ 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 $p\text{Pb}$ 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 $pp$ collisions and suggest a mass dependence in ${v}_{2}$ between charm and beauty hadrons in the $p\text{Pb}$ system. These results provide insights into the origin of heavy-flavor quark collectivity in small systems.