Study of quarkonium production in heavy ions collisions with ALICE.

par Dr Antoine Lardeux (IRFU/SPhN, Saclay)

vendredi 5 févr. 2016, 14:30 → 16:00 Europe/Paris

Amphi Recherche

Heavy quarkonium states are expected to provide essential information on the properties of the deconfined state of nuclear matter, the Quark-Gluon Plasma (QGP), formed in the early stages of ultra-relativistic heavy ion collisions. In particular, the sequential suppression of the quarkonium states by color screening mechanism can be seen as a direct effect of deconfinement and a thermometer of the QGP. Results on charmonium suppression in Pb-Pb collisions at the LHC seem to indicate that additional mechanisms as J/ψ production via recombination of charm and anti-charm quarks also play a role. This so-called regeneration mechanism is expected to be small for bottomonia due to the smaller number of initial b-bbar pairs produced compared to c-cbar pairs. After a brief description of the apparatus, I will first report on the ALICE results from LHC run 1 on the quarkonium (J/ψ and Υ) production in Pb-Pb collisions at 2.76 TeV down to zero transverse momentum via the dimuon decay channel in the Forward Muon Spectrometer (2.5 < y < 4). These results will be compared to those obtained by other experiments and to theoretical predictions. Then, the observation of a J/ψ yield excess at very low pT (< 300 MeV/c) and forward rapidity (2.5 < y < 4) compared to expectations from hadronic production will be discussed as well as its implications on the J/ψ nuclear modification factor. Finally, the outlook for the coming years on quarkonium studies with ALICE will be presented.

pictures ALICE_PbPb_5TeV-1.png