Quarkonia and heavy-flavour production in CMS

摘要

The Compact Muon Solenoid (CMS) has measured numerous quarkonium states via their decays into ~(μ +μ -) pairs in pp and PbPb collisions at sNN=2.76TeV. 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. Non-prompt J/ψ from b-hadron decays show a strong suppression in the transverse momentum range (6.5 < _(p T) < 30 GeV/c) when compared to the yield in pp collisions scaled by the number of inelastic nucleon-nucleon collisions. This suppression is related to the in-medium b-quark energy loss. In the same kinematic region, for prompt J/ψ, a strong, centrality-dependent suppression is observed in PbPb collisions. Such strong suppression at high _(p T) has previously not been observed at RHIC. At midrapidity (|y| < 1.6) and the same _(p T) region, inclusive ψ(2S) are even stronger suppressed than J/ψ, whereas ψ(2S) at forward rapidity (1.6 < |y| < 2.4) and lower _(p T) (3 < _(p T) < 30 GeV/c) appear to be less suppressed than J/ψ, however, with large uncertainties that prevent a conclusion. Furthermore, low-_(p T) Υ{hooked}(2S) and Υ{hooked}(3S) mesons are strongly suppressed in PbPb collisions. The suppression of the Υ{hooked}(1S) state is smaller than the suppression of the excited states and consistent with the suppression of the feed-down contribution only.