Observation of the B${}_{\mathrm{c}}^{+}$ meson in PbPb and pp collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV and measurement of its nuclear modification factor

Abstract

The B${}_{\mathrm{c}}^{+}$ meson is observed for the first time in heavy ion collisions. Data from the CMS detector are used to study the production of the B${}_{\mathrm{c}}^{+}$ meson in lead-lead (PbPb) and proton-proton (pp) collisions at a center-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV, via the B${}_{\mathrm{c}}^{+}$ $\to$ (J/$\psi$ $\to$ ${\mu }^{+}{\mu }^{-}$)${\mu }^{+}{\nu }_{\mu }$ decay. The B${}_{\mathrm{c}}^{+}$ nuclear modification factor, derived from the PbPb-to-pp ratio of production cross sections, is measured in two bins of the trimuon transverse momentum and of the PbPb collision centrality. The B${}_{\mathrm{c}}^{+}$ meson is shown to be less suppressed than quarkonia and most of the open heavy-flavor mesons, suggesting that effects of the hot and dense nuclear matter created in heavy ion collisions contribute to its production. This measurement sets forth a promising new probe of the interplay of suppression and enhancement mechanisms in the production of heavy-flavor mesons in the quark-gluon plasma.

arXiv commentReplaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/HIN-20-004 (CMS Public Pages)

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