Charmonium suppression at RHIC and SPS: A hadronic baseline

Abstract

A kinetic equation approach is applied to model anomalous J/ψ suppression at RHIC and SPS by absorption in a hadron resonance gas which successfully describes statistical hadron production in both experiments. The puzzling rapidity dependence of the PHENIX data is reproduced as a geometric effect due to a longer absorption path for J/ψ production at forward rapidity.Keywords: J/ψ suppression, heavy-ion collisions, hadron gas PACS: 14.40.Gx, 24.10.Pa, 25.75.-q IntroductionThe effect of J/ψ suppression [1] is one of the diagnostic tools to prove quark-gluon plasma (QGP) formation in heavy-ion collisions. After a rich phenomenology provided by the CERN-SPS experiments NA3, NA38, NA50 and NA60, which nevertheless could not unambiguously prove QGP formation, the situation became even more complex due to first results from RHIC experiments PHENIX and STAR. New experiments are planned at CERN-LHC and FAIR-CBM, for a recent review, see [2]. In order to make progress in the interpretation of experimental findings it is important to define benchmarks, such as a baseline from a statistical kinetic model provided in this communication, which is based on a purely hadronic description.Measurements of J/ψ suppression in Au-Au and Cu-Cu collisions by STAR and PHENIX experiments [3,4,5] brought up two unexpected re-

Quantum mechanical model for J/ψ suppression in the LHC era

“…While (i) is caused mainly by antishadowing and to some extent by geometry [70], the second finding is still not understood. For the puzzling In-In dip a suggestion has been made in [14] where this feature could be reproduced within the generalized Matsui approach by a subtle interplay of screening and absorption in the parametrization of the temperature dependence of the oscillator frequency.…”

Quarkonia and QGP studies

“…This effect, first observed at CERN SPS for Pb-Pb collisions at √ s = 17 GeV, has been qualitatively confirmed by RHIC experiments with Au-Au interactions at √ s = 200 GeV whereby surprising new findings were revealed: (i) the suppression is stronger at forward and backward rapidities rather than at midrapidity where the particle densities are highest, (ii) the onset of anomalous suppression and its dependence on centrality scales with the charged particle density at midrapidity rather than with energy density. While (i) is caused mainly by antishadowing and to some extent by geometry [37], the second finding is still not understood. A third puzzling issue raised by Carlos Lourenc ¸o in discussions at this meeting is (iii) the dip in the centrality dependence of the J/ψ suppression ratio which is seen in the rather precise data of the NA60 collaboration for In-In collisions and so far widely ignored by theorists.…”

Charmonium suppression at RHIC and SPS: a unified approach

“…where the initial time t 0 = 1 fm/c denotes the moment of the thermalization of the created hadronic matter and the beginning of the hydrodynamical expansion. The rapidity-momentum J /ψ distribution results from the kinematical change of variables d 3 p → d 2 p T dy and is given by F( r, y, p T , t) = M T cosh(y) × f ( r, p, t), where f ( r, p, t) is the formal solution of a kinetic equation (for details see [16,18,24]).…”

“…Both PHENIX results, concerning rapidity and N part dependencies of J /ψ suppression in Au-Au and Cu-Cu collisions, are simultaneously reproduced. More details are given in [18].…”

“…The evolution is decomposed into a longitudinal expansion inside a slice bordered by the front Left: an example of t final in a function of rapidity for p T = 2 GeV and the 0-20% centrality bin for Au-Au (solid) and Cu-Cu (dashed) collisions. More details are given in [18]. Right: J/ψ (dashed and dot-dashed lines) inside hadronic gas absorption region and the time evolution of the rarefaction front radius s at different z (continuous lines with labels denoting z in fm).…”