Studies of charm and beauty long-range correlations in pp and pPb collisions

Studies of collective long-range (large $\eta$ gap) correlations involving open charm and beauty hadrons in pp and pPb collisions are presented, using data samples collected by the CMS experiment with center-of-mass energies of 13 and 8.16 TeV, respectively. The elliptic flow harmonics ($v_2$) of prompt and nonprompt $D^{0}$ mesons (from beauty hadron decays) are extracted from long-range two-particle azimuthal correlations, with respect to inclusive charged particles. In pp collisions, positive $v_2$ signals for prompt charm hadrons are reported for the first time over a transverse momentum ($p_{\mathrm{T}}$) range of 2-4 GeV. The signals are comparable to those for light-flavor hadron species. Compared at similar event multiplicities, the prompt $D^{0}$ meson $v_2$ values in pp and pPb are similar in magnitude. The $v_2$ signal for open beauty hadrons is extracted for the first time via nonprompt $D^{0}$ meson in pPb collisions, with a magnitude smaller than that for prompt $D^{0}$ meson at $p_{\mathrm{T}}$ between 2-5 GeV. The new measurements provide strong indications of a postive charm hadron $v_2$ in the smallest pp systems and a flavor hierarchy of $v_2$ between charm and beauty hadrons in the pPb systems, providing key insights to further understand the origin of heavy flavor quark collectivity in small-system collisions.