Dileptons, Charm and Charmonium at Finite Temperature and Chemical Potential

Abstract

We discuss how dileptons, open charm and charmonia may be utilized in heavy-ion collisions to extract information specific to hot and dense matter at finite quark chemical potential, $\mu_q$. For each observable we briefly discuss underlying theoretical frameworks and the current status in interpreting available heavy-ion data at SPS and RHIC energies. Low-mass dileptons are particularly sensitive to baryonic medium effects in spectral modifications of the $\rho$ meson, and may serve as an accurate measure of the fireball lifetime. In the open-charm sector, observable signals may be generated by a ``critical'' enhancement of scattering rates via $t$-channel exchange of a soft $\sigma$ mode. For charmonia, finite-$T$ potential models could be used to extrapolate color-screening effects to finite $\mu_q$ to facilitate a quantitative evaluation of dissociation rates in the medium.