Flow in the RHIC Beam Energy Scan from STAR

Abstract

The first phase of the beam energy scan (BES) program at RHIC was successfully taken in the years 2010 and 2011. Data, were collected at =7.7, 11.5, 19.6, 27, 39 and 62.4 GeV, covering a wide range of baryon chemical potentials from μB 420 to 40 MeV. The main goals are the search for the QCD critical point and to find signatures for a phase transition between the hadron gas and the QGP. Directed (v1), elliptic (v2) and triangular (v3) flow are important observables to study the early evolution of the created matter in relativistic heavy-ion collision experiments. In particular, it is expected that flow is sensitive to the phase transition from a quark gluon plasma to a hadron gas.We will present measurements of identified hadrons for v1 (π±, p, p̄), v2 (π±, K±, K0s, p, p̄, for all BES energies, and v3 (π±K±, p, p̄) for = 39 GeV. We will discuss the beam-energy dependent difference of v2 between particles and anti-particles. Furthermore, we will address mass ordering at low pT and number-of-constituent-quark scaling at intermediate pT of v2 and v3 for identified hadrons.