Open and closed heavy-flavour suppression in heavy-ion collisions with CMS

摘要

The Compact Muon Solenoid (CMS) is fully equipped to measure quarkonia in the dimuon decay channel in the high multiplicity environment of nucleus-nucleus collisions. Quarkonia are especially relevant for studying the quark-gluon plasma since they are produced at early times and propagate through the medium, mapping its evolution. CMS has measured the nuclear modification factors of non-prompt J= (from b-hadron decays), prompt J/ψ, inclusive ψ(2S), and the first three γ states in PbPb collisions at √s_(NN) = 2.76 TeV. A suppression of non-prompt J/ψ, which is sensitive to the in-medium b-quark energy loss, has been measured at relatively high pT (6:5 < pT < 30 GeV/c) in PbPb collisions, compared to the yield in pp collisions scaled by the number of inelastic nucleon-nucleon collisions. For prompt J/ψ in the same kinematic range, a strong, centrality-dependent suppression is observed. Such strong suppression at high pT has previously not been observed at RHIC. At mid-rapidity and high pT, ψ(2S) show an even stronger suppression than J/ψ. Furthermore, CMS has measured the suppression of the three γ states, separately, down to pT = 0 GeV/c. A clear ordering of the suppression with binding energy is observed, as expected from sequential melting of quarkonium states.