Results from the STAR Beam Energy Scan Program

Abstract

The main aim of the beam energy scan (BES) program at the Relativistic Heavy-Ion Collider (RHIC) is to explore the quantum chromodynamics (QCD) phase diagram. The specific physics goal is to search for the phase boundary and the QCD critical point. We present results from Au+Au collisions at various energies collected in the BES program by the Solenoidal Tracker At RHIC (STAR) experiment. First results on transverse momentum ( p T ) spectra, d N / d y , and average transverse mass ( 〈 m T 〉 ) for identified hadrons produced at mid-rapidity for s N N = 7.7 GeV are presented. Centrality dependence of d N / d y and 〈 p T 〉 are also discussed and compared to corresponding data from other energies. In addition, first results on charged hadron directed ( v 1 ) and elliptic flow ( v 2 ) for s N N = 7.7 , 11.5 and 39 GeV are presented. New results on event-by-event fluctuations (particle ratio, net-proton and net-charge higher moments) are presented for s N N = 39 GeV .