CMS-PAS-HIN-19-009

CMS-PAS-HIN-19-009
Studies of charm and beauty long-range correlations in pp and pPb collisions
CMS Collaboration
November 2019

Abstract: 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.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, PLB 813 (2021) 136036. The superseded preliminary plots can be found here.

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