Speaker
Description
Quarkonium states, and in particular charmonium, have been recognized
as sensitive probes of the properties of hot and dense strongly
interacting matter created in relativistic heavy-ion collisions. Since
the pioneering work of Matsui and Satz, who proposed that the
suppression of the $J/\psi$ meson could signal the onset of quark–gluon
plasma (QGP) formation, numerous theoretical and experimental efforts
have been devoted to understanding the mechanisms governing charmonium
production, dissociation, and regeneration in such environments.
At finite baryon chemical potential ($\mu_B$), lattice QCD predicts a
smooth crossover transition between hadronic and partonic matter,
whereas at larger $\mu_B$, beyond the conjectured critical end point,
the transition possibly becomes first order. Studying charmonium
behavior in baryon-rich systems—such as those accessible at SPS and the
upcoming GSI/FAIR facilities—therefore provides a unique opportunity to
explore the QCD phase diagram in regions of high net baryon density.
In this work, we employ the Parton–Hadron–String Dynamics (PHSD)
transport approach to investigate the influence of baryon-rich matter on
charmonium production and dissociation. The Remler coalescence formalism
is implemented to dynamically model charmonium formation from
charm–anticharm pairs. As a validation step, the formalism is first
benchmarked against experimental data from elementary p+p collisions and
then extended to p+A systems to extract the effective nuclear absorption
cross section of charmonium. This extracted cross section is
subsequently applied in A+A collisions to quantify medium-induced effects.
Our results demonstrate that the Remler formalism provides a
quantitatively consistent description of charmonium production at SPS
energies when the charmonium interaction rate in the QGP phase is
comparable to that of open-charm pairs. The approach is then
extrapolated to GSI/FAIR energies, where predictions for charmonium
yields and survival probabilities are presented. These findings
highlight the relevance of the Remler formalism as a dynamical framework
for studying heavy-quark bound-state formation in strongly interacting
baryon-rich matter and offer theoretical guidance for future
experimental programs at FAIR and NICA aimed at mapping the QCD phase
structure.
