This paper reports results for directed flow \(v_{1}\) and elliptic flow \(v_{2}\) of charged particles in Cu+Cu collisions at \(\sqrt{s_{NN}}=\) 22.4 GeV at the Relativistic Heavy Ion Collider. The ...measurements are for the 0-60% most central collisions, using charged particles observed in the STAR detector. Our measurements extend to 22.4 GeV Cu+Cu collisions the prior observation that \(v_1\) is independent of the system size at 62.4 and 200 GeV, and also extend the scaling of \(v_1\) with \(\eta/y_{\rm beam}\) to this system. The measured \(v_2(p_T)\) in Cu+Cu collisions is similar for \(\sqrt{s_{NN}} = 22.4-200\) GeV. We also report a comparison with results from transport model (UrQMD and AMPT) calculations. The model results do not agree quantitatively with the measured \(v_1(\eta), v_2(p_T)\) and \(v_2(\eta)\).
Phys.Rev.Lett.97:132301,2006 We report the measurements of $\Sigma (1385)$ and $\Lambda (1520)$ production
in $p+p$ and $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV from the STAR
collaboration. ...The yields and the $p_{T}$ spectra are presented and discussed
in terms of chemical and thermal freeze-out conditions and compared to model
predictions. Thermal and microscopic models do not adequately describe the
yields of all the resonances produced in central $Au+Au$ collisions. Our
results indicate that there may be a time-span between chemical and thermal
freeze-out during which elastic hadronic interactions occur.
We report the measurements of \(\Sigma (1385)\) and \(\Lambda (1520)\) production in \(p+p\) and \(Au+Au\) collisions at \(\sqrt{s_{NN}} = 200\) GeV from the STAR collaboration. The yields and the ...\(p_{T}\) spectra are presented and discussed in terms of chemical and thermal freeze-out conditions and compared to model predictions. Thermal and microscopic models do not adequately describe the yields of all the resonances produced in central \(Au+Au\) collisions. Our results indicate that there may be a time-span between chemical and thermal freeze-out during which elastic hadronic interactions occur.
We report results on rho(770)(0)-->pi(+)pi(-) production at midrapidity in p+p and peripheral Au+Au collisions at sqrts(NN)=200 GeV. This is the first direct measurement of rho(770)(0)-->pi(+)pi(-) ...in heavy-ion collisions. The measured rho(0) peak in the invariant mass distribution is shifted by approximately 40 MeV/c(2) in minimum bias p+p interactions and approximately 70 MeV/c(2) in peripheral Au+Au collisions. The rho(0) mass shift is dependent on transverse momentum and multiplicity. The modification of the rho(0) meson mass, width, and shape due to phase space and dynamical effects are discussed.
Transverse mass and rapidity distributions for charged pions, charged kaons, protons, and antiprotons are reported for square root of sNN=200 GeV pp and Au+Au collisions at Relativistic Heary Ion ...Collider (RHIC). Chemical and kinetic equilibrium model fits to our data reveal strong radial flow and long duration from chemical to kinetic freeze-out in central Au+Au collisions. The chemical freeze-out temperature appears to be independent of initial conditions at RHIC energies.
We present STAR measurements of the azimuthal anisotropy parameter v(2) and the binary-collision scaled centrality ratio R(CP) for kaons and lambdas (Lambda+Lambda) at midrapidity in Au+Au collisions ...at square root of s(NN)=200 GeV. In combination, the v(2) and R(CP) particle-type dependencies contradict expectations from partonic energy loss followed by standard fragmentation in vacuum. We establish p(T) approximately 5 GeV/c as the value where the centrality dependent baryon enhancement ends. The K(0)(S) and Lambda+Lambda v(2) values are consistent with expectations of constituent-quark-number scaling from models of hadron formation by parton coalescence or recombination.
Pion-kaon correlation functions are constructed from central Au+Au STAR data taken at sqrts(NN)=130 GeV by the STAR detector at the Relativistic Heavy Ion Collider (RHIC). The results suggest that ...pions and kaons are not emitted at the same average space-time point. Space-momentum correlations, i.e., transverse flow, lead to a space-time emission asymmetry of pions and kaons that is consistent with the data. This result provides new independent evidence that the system created at RHIC undergoes a collective transverse expansion.
We report high statistics measurements of inclusive charged hadron production in Au+Au and p+p collisions at sqrts(NN)=200 GeV. A large, approximately constant hadron suppression is observed in ...central Au+Au collisions for 5<p(T)<12 GeV/c. The collision energy dependence of the yields and the centrality and p(T) dependence of the suppression provide stringent constraints on theoretical models of suppression. Models incorporating initial-state gluon saturation or partonic energy loss in dense matter are largely consistent with observations. We observe no evidence of p(T)-dependent suppression, which may be expected from models incorporating jet attenuation in cold nuclear matter or scattering of fragmentation hadrons.
We report measurements of single-particle inclusive spectra and two-particle azimuthal distributions of charged hadrons at high transverse momentum (high p(T)) in minimum bias and central d+Au ...collisions at sqrts(NN)=200 GeV. The inclusive yield is enhanced in d+Au collisions relative to binary-scaled p+p collisions, while the two-particle azimuthal distributions are very similar to those observed in p+p collisions. These results demonstrate that the strong suppression of the inclusive yield and back-to-back correlations at high p(T) previously observed in central Au+Au collisions are due to final-state interactions with the dense medium generated in such collisions.
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