  Observations by the PHENIX and STAR collaborations suggest that a strongly
coupled quark-gluon plasma is produced in heavy-ion collisions at the
Relativistic Heavy Ion Collider (RHIC). After a brief introduction to heavy-ion
physics, measurements of heavy-quark production in heavy-ion collisions and the
modification of heavy-quark spectra by the QGP are presented. Measurements of
the total charm cross-section in several different collision systems confirm
that charm quark-antiquark pairs are produced through parton hard-scattering in
the initial stages of the collisions. Non-photonic electrons (proxies for heavy
quarks) are suppressed by about a factor of 5 in central Au + Au collisions
relative to p + p collisions. This is larger than most current theoretical
predictions and has lead to a re-examination of heavy-quark energy loss in the
medium. The relative contributions of c and b decays to the non-photonic
electron spectrum have been predicted by perturbative QCD calculations; STAR
measurements of azimuthal correlation functions of non-photonic electrons and
hadrons agree with these predictions.
