Heavy Quark Primer
The use of charm quarks produced in ultra-relativistic heavy-ion collisions as QGP probes has a rich tradition, starting with the seminal paper by Matsui and Satz, predicting the suppression of J/Psi production in a QGP:
J/psi Suppression by Quark-Gluon Plasma Formation
This paper was followed up by a calculation of color screening, which set the stage for Lattice Gauge Theory calculations to be used for calculating charmonium dissociation temperatures:
Color Screening and Deconfinement for Bound States of Heavy Quarks
With the release of the NA50 data on J/Psi production in Pb+Pb collisions at the CERN SPS, a vast number of phenomenology papers were written either claiming the data to be evidence for deconfinement or attempting to explain them in a purely hadronic scenario. Here is a small selection of the more impactful of these papers:
- A Quantitative analysis of charmonium suppression in nuclear collisions
- Charmonium suppression by Comover scattering in Pb + Pb collisions
- Modeling J/Psi production and absorption in a microscopic nonequilibrium approach
- Production and absorption of c anti-c pairs in nuclear collisions at SPS energies
A review of the experimental situation until the late 1990s can be found in
Charmonium suppression in heavy ion collisions
An overview of theoretical attempts to understand the observed suppression can be found in
Charmonium production in nucleus-nucleus collisions
More recent Lattice calculations have cast doubt on the original color screening idea of J/Psi dissociation at the critical temperature. These calculations have shown charmonium states to survive up to at least 1.5 Tc:
- J / psi and eta(c) in the deconfined plasma from lattice QCD
- Behavior of charmonium systems after deconfinement
Recently, open heavy flavor production has partially superseded quarkonia production as focus of interest: First data at RHIC show indications of strong interactions (i.e. elliptic flow and a suppression of the nuclear modification factor) between charm quarks and the deconfined medium indicating possible thermalization of heavy quarks. This unexpected discovery has not only opened the door to utilizing charm quarks as effective probes of the medium:
- Quark coalescence and elliptic flow of charm hadrons
- How much do heavy quarks thermalize in a heavy ion collision?
- Thermalization of heavy quarks in the quark-gluon plasma
- Heavy quark diffusion in perturbative QCD at next-to-leading order
but also lent credence to early suggestions that J/Psi production in heavy ion collisions could be dominated by c-cbar recombination from a deconfined phase, rather than direct production by hard QCD processes: