Abstract:
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.
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