critRHIC: The RHIC Low Energy Program

Recent experimental and theoretical developments have motivated interest in a more detailed exploration of heavy ion collisions in the range √ s NN =5–15 GeV. In contrast to interactions at the full RHIC energy of √ s NN =200 GeV, such collisions result in systems characterized by much higher baryon chemical potential, μB. Extensions of lattice QCD calculations to non-zero values of μB suggest that a critical point may exist in this region of the QCD phase diagram. Discovery of the critical point or, equivalently, determining the location where the phase transition from partonic to hadronic matter switches from a smooth crossover to 1 order would establish a major landmark in the phase diagram. Initial studies of Pb+Pb collisions in this energy range have revealed several unexpected features in the data. In response to these results, it has been suggested that the existing RHIC accelerator and experiments can be used to further the investigation of this important physics topic. This proceeding briefly summarizes the theoretical and experimental situation with particular emphasis on the conclusions from a RIKEN BNL workshop held in March of 2006. PACS numbers: 25.75.-q, 25.75.Nq, 24.85.+p Submitted to: J. Phys. G: Nucl. Part. Phys.