20-27 July 2011
Alpes Congrès - Alpexpo
Europe/Paris timezone

Quarkonia measurements by the CMS experiment in PbPb collisions

21 Jul 2011, 18:00
15m
Lesdiguières (Alpes Congrès - Alpexpo)

Lesdiguières

Alpes Congrès - Alpexpo

Parallel session talk Ultrarelativistic Heavy Ions

Speaker

Mrs Catherine Silvestre (LPSC, UIC, LANL (now LPSC, work done with UIC and LANL))

Description

CMS is fully equipped to measure hard probes in the di-muon decay channel in the high multiplicity environment of nucleus-nucleus collisions. Such probes are especially relevant for studying the quark gluon plasma since they are produced at early times and propagate through the medium, mapping its evolution. Quarkonia and bottomonia are sensitive to the evolution of the medium. In particular, the $J\psi$ production in heavy ion collisions has been studied at different energies and with different collision systems without yet giving a global picture that is fully understood. Measuring the charmonium production at the LHC energies in PbPb collisions will help constraining predictions, in particular those expecting high recombination of prompt J$/\jpsi$s or suppression in hot medium. We will review CMS J/\psi measurements in pp collisions at $\sqrt{s_{NN}}=7$~TeV, which allow precision studies of quarkonia production and serve as a reference for the observation of hot nuclear effects. CMS is able to distinguish non-prompt J$/\psi$ from prompt J/$\psi$ in PbPb collisions, and will present the prompt J/$\psi$ production cross-section in PbPb inclusively and as a function of transverse momentum, rapidity and number of nucleons participating in the collision. Finally, we compare the B fraction measured in PbPb collisions with that measured in pp at various energies. The LHC centre-of-mass energy allows copious $\Upsilon$ production in PbPb collisions. Detailed measurements of bottomonium will help characterize the dense matter produced in heavy-ion collisions beyond what was accessible at RHIC (mostly) with charmonia. The full spectroscopy of quarkonium states has been suggested as a possible thermometer for the QGP. With its excellent dimuon mass resolution, CMS has measured the three $\Upsilon$ states in pp collisions. With the 2010 PbPb data sample, CMS has observed the $\Upsilon$(1S) as well as excited states. The $\Upsilon(1S)$ cross-section is presented as a function of transverse momentum, rapidity and centrality, and excited state. Suppression of the excited state in PbPb will be discussed.

Primary authors

Mrs Catherine Silvestre (LPSC, UIC, LANL (now LPSC, work done with UIC and LANL)) Dr Manfred Krammer (HEPHY, Vienna)

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