We report the beam energy ( √ sNN = 7.7 -200 GeV) and collision centrality dependence of the mean (M ), standard deviation (σ), skewness (S), and kurtosis (κ) 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.

Vector mesons may be photoproduced in relativistic heavy-ion collisions when a virtual photon emitted by one nucleus scatters from the other nucleus, emerging as a vector meson. The STAR Collaboration has previously presented measurements of coherent ρ 0 photoproduction at center of mass energies of 130 GeV and 200 GeV in AuAu collisions. Here, we present a measurement of the cross section at 62.4 GeV; we find that the cross section for coherent ρ 0 photoproduction with nuclear breakup is 10.5 ± 1.5 ± 1.6 mb at 62.4 GeV. The cross-section ratio between 200 GeV and 62.4 GeV is 4.4 ± 0.6, less than is predicted by most theoretical models. It is, however, proportionally much larger than the previously observed 15% ± 55% increase between 130 GeV and 200 GeV.

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We report measurements of charmed-hadron (D 0 , D * ) production cross sections at mid-rapidity in p + p collisions at a center-of-mass energy of 200 GeV by the STAR experiment. Charmed hadrons were reconstructed via the hadronic decaysand their charge conjugates, covering the pT range of 0.6−2.0 GeV/c and 2.0−6.0 GeV/c for D 0 and D * + , respectively. From this analysis, the charm-pair production cross section at mid-rapidity is dσ/dy| cc y=0 = 170 ± 45 (stat.) +38 −59 (sys.) µb. The extracted charm-pair cross section is compared to perturbative QCD calculations. The transverse momentum dierential cross section is found to be consistent with the upper bound of a Fixed-Order Next-to-Leading Logarithm calculation.