Speaker
Ermias T. Atomssa
(LLR, Ecole Polytechnique)
Description
Heavy ion collisions provide a unique experimental way to create and characterize the
hot and dense matter that lattice QCD predicts to be produced at high energy density
and temperature. Products of hard processes, which take place in the early stage of
the collision, are highly sensitive probes to the evolution of the created system.
Suppression of the quarkonium J/\psi, which constitutes such a probe, has been
measured by the PHENIX experiment at RHIC in AuAu, CuCu, dAu and pp interactions, as
a function of impact parameter, rapidity and transverse momentum.
The strong suppression factors observed in central collisions in heavy ion systems
suggest that cold nuclear matter effects such as shadowing and nuclear absorption are
not the only mechanisms involved. On the other hand, suppression due to color
screening effects alone seems to overestimate the suppression measured both at
forward rapidity and at mid rapidity. PHENIX also measures a stronger suppression at
forward rapidity compared to the one measured at mid rapidity. Regeneration has been
suggested as a possible explanation for these observations. Here, models that combine
in different ways a regeneration scenario with color screening and cold nuclear
effects will be compared to the data. Higher luminosities are expected to bring more
information in the future by allowing to perform differential measurements in other
variables.
Author
Ermias T. Atomssa
(LLR, Ecole Polytechnique)
