QCD at High Temperature: the quark gluon plasma and relativistic heavy-ion collisions

The formation of the quark gluon plasma (QGP) in relativistic heavy-ion collisions was named one of the top 10 newsmakers of the last decade by the APS. So, what is the QGP? The QGP forms when matter governed by quantum chromodynamics undergoes a transition at high temperature or high density from hadronic bound states to deconfined quarks and gluons. The QGP is believed to be experimentalluy accessible in relativistic heavy-ion collisions, such as those at the Relativistic Heavy-Ion Collider (RHIC) at BNL and now also at the Large Hadron Collider (LHC) at CERN. I will present motivation for studying the QGP and discuss some of the interesting experimental and theoretical developments. I will emphasize the power of energetic partons produced in the early moments of a heavy-ion collision to help quantify the properties of the QGP, with an eye on future progress theory must make in order to keep up with experimental programs.