Quarkonium and Quark Gluon Plasma: from SPS to LHC energies

Abstract
Quarkonium production is considered one of the main probes for the formation of a plasma of quarks and gluons in heavy-ion collisions. The binding of the c and cbar (or b and bbar) pair is, in fact, expected to be screened in a very hot environement, leading to the melting of the various quarkonium states (J/Psi, Psi(2S), Y(1S), Y(2S), Y(3S)...). Since these states are characterized by very different binding energies, their existence or suppression, at a given collision energy, should provide an estimate of the temperature reached in nucleus-nucleus interactions. This suppression picture is, however, complicated by several other hot or cold matter effects which might influence the quarkonium yields. Increasing the collision energy, the large charm quark density might lead to an additional quarkonium production mechanisms through quarks recombination, which can counterbalance the resonance suppression. Furthermore, mechanisms related to the underlying presence of cold nuclear matter effects (as nuclear shadowing, energy loss or nuclear absorption), investigated in proton-nucleus interactions, are also influencing the quarkonium yields. In the last thirty years quarkonium production has been extensively investigated both in nucleus-nucleus and in proton-nucleus collisions. A review of the results from SPS, RHIC and LHC experiments, covering more than two orders of magnitude in collision energy, will be presented. The role played by the aforementioned hot and cold matter effects, at the various collision energies, will be addressed and the findings obtained up to now will be highlighted, together with the prospects for the incoming LHC Run-II.

Pre-colloquium for students at 15:30