Physical Society Colloquium

Physics at RHIC

Joe Kapusta

School of Physics & Astromy
University of Minnesota

The Relativistic Heavy Ion Collider (RHIC) has provided a wealth of data, some of it quite amazing, with more to come. Among the most significant findings are exhibitions of collective flow, jet quenching, and thermal equilibrium of observed hadrons at a temperature of about 170 million electron-volts. I will outline a theoretical program that describes nuclear collisions from first impact until final hadronic free-streaming. Various pieces are already in place, including coarse graining of the initial gluon fields (Color Glass Condensate), parton production and minijets, relativistic fluid flow, and late stage hadron scattering. Our calculations give initial energy densities of order several hundred GeV per cubic fermi. By varying the temperature or energy density dependence of transport coefficients it ought to be possible to infer the critical behavior of the equation of state of QCD.