A theoretical and experimental look to quarkonium production in heavy-ion collisions

by Elena Gonzalez Ferreiro (U Santiago de Compostela (Spain), Institute de Physique Nucleaire, Orsay (France)), Roberta Arnaldi (INFN Torino)

Thursday 5 Feb 2015, 15:30 → 16:30 Europe/Berlin

seminar room, basement (Excellence Cluster Universe)

For thirty years, quarkonia have been considered one of the main probes to investigate the formation of a plasma of quarks and gluons in heavy-ion collisions. In a hot and deconfined medium, in fact, quarkonium production is expected to be significantly suppressed because of the color screening of the force that binds the Q-Qbar pair. Since the various quarkonium states (J/psi, psi(2S), Y(1S), Y(2S), Y(3S)...) 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 collision, so that quarkonia have earned the name of "thermometer" of the created medium. However, this picture is complicated by several other mechanisms, such as the quarkonium production through quark recombination in a hot environment playing an impotant role, in particular at the highest collision energies. Furthermore, other mechanisms related to the underlying presence of cold nuclear matter effects are also going to influence the quarkonium yields and their precise estimate is crucial to quantify the pure hot matter effects. A review of the main quarkonium results, obtained in experiments covering more than two orders of magnitude in collision energy, will be presented. In particular, being at the eve of LHC Run II, we will focus on the most recent achievements from the LHC experiments. In parallel, the state of the art theory models will be introduced and compared to the experimental results to highlight the findings obtained up to now in this field. (Double feature talk given by two Cluster guests)