Abstract: | We report the beam energy (sqrt s_{NN} = 7.7 - 200 GeV) and collision
centrality dependence of the mean (M), standard deviation (sigma), skewness
(S), and kurtosis (kappa) of the net-proton multiplicity distributions in
Au+Au collisions. The measurements are carried out by the STAR experiment at
midrapidity (|y| < 0.5) and within the transverse momentum range 0.4 < pT < 0.8
GeV/c in the first phase of the Beam Energy Scan program at the Relativistic
Heavy Ion Collider. These measurements are important for understanding the
Quantum Chromodynamic (QCD) phase diagram. The products of the moments, Ssigma
and kappasigma^{2}, are sensitive to the correlation length of the hot and
dense medium created in the collisions and are related to the ratios of baryon
number susceptibilities of corresponding orders. The products of moments are
found to have values significantly below the Skellam expectation and close to
expectations based on independent proton and anti-proton production. The
measurements are compared to a transport model calculation to understand the
effect of acceptance and baryon number conservation, and also to a hadron
resonance gas model. |