We report STAR results on the azimuthal anisotropy parameter v2 for strange particles K0S, L and Lbar at midrapidity in Au+Au collisions at sNN = 130 GeV at RHIC. The value of v2 as a function of transverse momentum of the produced particles pt and collision centrality is presented for both particles up to pt 3.0 GeV/c. A strong pt dependence in v2 is observed up to 2.0 GeV/c. The v2 measurement is compared with hydrodynamic model calculations. The physics implications of the pt integrated v2 magnitude as a function of particle mass are also discussed.
$v_2$ of $K_s^0$ as a function of $p_T$ for 0-11% centrality in Au+Au collisions at 130 GeV. Systematic errors of $\pm$0.005 for particle identification and background subtraction and $^{+0}_{-0.005}$ for nonflow effects.
$v_2$ of $K_s^0$ as a function of $p_T$ for 11-45% centrality in Au+Au collisions at 130 GeV. Systematic errors of $\pm$0.005 for particle identification and background subtraction and $^{+0}_{-0.005}$ for nonflow effects.
$v_2$ of $\Lambda+\bar{\Lambda}$ as a function of $p_T$ for 0-11% centrality in Au+Au collisions at 130 GeV. Systematic errors of $\pm$0.005 for particle identification and background subtraction and $^{+0}_{-0.005}$ for nonflow effects.
Pion-kaon correlation functions are constructed from central Au+Au data taken at $\sqrt{s_{NN}} = 130$ GeV. 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.
Pion-kaon correlation functions and ratios of correlation functions. Errors are statistical only.
Pion-kaon correlation functions and ratios of correlation functions. Errors are statistical only.
Pion-kaon correlation functions and ratios of correlation functions. Errors are statistical only.
We present the first large-acceptance measurement of event-wise mean transverse momentum mean p_t fluctuations for Au-Au collisions at nucleon-nucleon center-of-momentum collision energy sqrt{s_{NN}} = 130 GeV. The observed non-statistical mean p_t fluctuations substantially exceed in magnitude fluctuations expected from the finite number of particles produced in a typical collision. The r.m.s. fractional width excess of the event-wise mean p_t distribution is 13.7 +/- 0.1(stat) +/- 1.3(syst)% relative to a statistical reference, for the 15% most-central collisions and for charged hadrons within pseudorapidity range |eta|<1, 2pi azimuth and 0.15 < p_t < 2 GeV/c. The width excess varies smoothly but non-monotonically with collision centrality, and does not display rapid changes with centrality which might indicate the presence of critical fluctuations. The reported mean p_t fluctuation excess is qualitatively larger than those observed at lower energies and differs markedly from theoretical expectations. Contributions to mean p_t mean fluctuations from semi-hard parton scattering in the initial state and dissipation in the bulk colored medium are discussed.
Event frequency distribution on $\sqrt{n}(\langle p_t\rangle - \hat{p}_t)/\sigma\hat{p}_t$ for 80% of primary charged hadrons in $|\eta|$ < 1 for 183k central events
Difference in upper panel between data and gamma reference
Centrality dependences of the measured charge independent (CI) and charge dependent (CD) difference factors $\Delta\sigma_{p_t:n}$ plus the corresponding values extrapolated to 100% tracking efficiency. Statistical errors $\pm$ 0.5 MeV/c; systematic errors are $\pm$ 9%. Difference factors extrapolated to 100% tracking efficiency and no secondary particle contamination. Uncertainties are $\pm$ 12%.
Azimuthal correlations for large transverse momentum charged hadrons have been measured over a wide pseudo-rapidity range and full azimuth in Au+Au and p+p collisions at $\sqrt{s_{NN}}$ = 200 GeV. The small-angle correlations observed in p+p collisions and at all centralities of Au+Au collisions are characteristic of hard-scattering processes already observed in elementary collisions. A strong back-to-back correlation exists for p+p and peripheral Au + Au. In contrast, the back-to-back correlations are reduced considerably in the most central Au+Au collisions, indicating substantial interaction as the hard-scattered partons or their fragmentation products traverse the medium.
Azimuthal distributions of opposite-sign pairs in p+p collisions. All correlation functions require a trigger particle with $4<p_T^{\rm trig}<6$ GeV/$c$ and associated particles with $2<p_T<p_T^{\rm trig}$ GeV/$c$.
Azimuthal distributions of same-sign pairs in p+p collisions. All correlation functions require a trigger particle with $4<p_T^{\rm trig}<6$ GeV/$c$ and associated particles with $2<p_T<p_T^{\rm trig}$ GeV/$c$.
Azimuthal distributions of same-sign and opposite-sign pairs in minimum bias and background-subtracted 0-10% central Au+Au collisions. All correlation functions require a trigger particle with $4<p_T^{\rm trig}<6$ GeV/$c$ and associated particles with $2<p_T<p_T^{\rm trig}$ GeV/$c$.
We report on the rapidity and centrality dependence of proton and anti-proton transverse mass distributions from Au+Au collisions at sqrt(sNN) = 130GeV as measured by the STAR experiment at RHIC. Our results are from the rapidity and transverse momentum range of |y|<0.5 and 0.35 <p_t<1.00GeV/c. For both protons and anti-protons, transverse mass distributions become more convex from peripheral to central collisions demonstrating characteristics of collective expansion. The measured rapidity distributions and the mean transverse momenta versus rapidity are flat within |y|<0.5. Comparisons of our data with results from model calculations indicate that in order to obtain a consistent picture of the proton(anti-proton) yields and transverse mass distributions the possibility of pre-hadronic collective expansion may have to be taken into account.
$p$ differential yield. Systematic uncertainties are $\pm$10%.
$\bar{p}$ differential yield. Systematic uncertainties are $\pm$10%.
Rapidity distribution of $p$. Combined statitiscal uncertainty and systematic uncertainty from PID contramination. Systematic uncertainties from the track reconstruction efficiency are $\pm$25%.
The first measurements of light antinucleus production in Au+Au collisions at RHIC are reported. The observed production rates for antideuterons and antihelions are much larger than in lower energy nucleus-nucleus collisions. A coalescence model analysis of the yields indicates that there is little or no increase in the antinucleon freeze-out volume compared to collisions at SPS energy. These analyses also indicate that the antihelion freeze-out volume is smaller than the antideuteron freeze-out volume.
Coalescence parameters $B_2$ and $B_3$ in Au+Au collisions at 130 GeV.
Invariant yields of $\overline{d}$ and $\overline{p}$. Systematic errors are estimated to be 15%.
Invariant yields of $^3\overline{\mathrm{He}}$ and $\overline{p}$. Systematic errors are estimated to be 15%.
We present the first measurement of midrapidity vector meson φ production in Au+Au collisions at RHIC (sNN=130 GeV) from the STAR detector. For the 11% highest multiplicity collisions, the slope parameter from an exponential fit to the transverse mass distribution is T=379±50(stat)±45(syst) MeV, the yield dN/dy=5.73±0.37(stat)±0.69(syst) per event, and the ratio Nφ/Nh− is found to be 0.021±0.001(stat)±0.004(syst). The measured ratio Nφ/Nh− and T for the φ meson at midrapidity do not change for the selected multiplicity bins.
Transverse mass distriution of $\phi$ for 0-11% centrality in Au+Au collisions at 130 GeV.
Transverse mass distriution of $\phi$ for 11-26% centrality in Au+Au collisions at 130 GeV.
Transverse mass distriution of $\phi$ for 26-85% centrality in Au+Au collisions at 130 GeV.
The STAR collaboration reports the first observation of exclusive rho^0 photo-production, AuAu->AuAu rho^0, and rho^0 production accompanied by mutual nuclear Coulomb excitation, AuAu->Au*Au*rho^0, in ultra-peripheral heavy-ion collisions. The rho^0 have low transverse momenta, consistent with coherent coupling to both nuclei. The cross sections at sqrt(s_NN)=130GeV agree with theoretical predictions treating rho^0 production and Coulomb excitation as independent processes.
Differential cross section $d\sigma(\gamma Au \rightarrow \rho Au)/dt$ of $\rho^0$ candidates
Differential cross section $d\sigma/dM_{\pi\pi}$ for two-track (xn,xn) events with pair $p_T<150$ MeV/$c$
Total background in the differential cross section $d\sigma/dM_{\pi\pi}$
Transverse mass and rapidity distributions for charged pions, charged kaons, protons and antiprotons are reported for sqrt{s_NN}=200 GeV pp and Au+Au collisions at RHIC. The transverse mass distributions are rapidity independent within |y|<0.5, consistent with a boost-invariant system in this rapidity interval. Spectral shapes and relative particle yields are similar in pp and peripheral Au+Au collisions and change smoothly to central Au+Au collisions. No centrality dependence was observed in the kaon and antiproton production rates relative to the pion production rate from medium-central to central collisions. Chemical and kinetic equilibrium model fits to our data reveal strong radial flow and relatively 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.
invariant yield as function of transverse mass for $\pi^{\pm},K^{\pm}$ and inclusive $p$ and $\bar{p}$ at mid-rapidity ($|y|<0.1$) for pp (bottom) and Au+Au events from $70-80\%$ (second bottom) to the $0-5\%$ centrality bin (top). Statistical and point-to-point systematic errors have been added in quadrature. Additional correlated systematic error due to uncertainty in the normalization is estimated to be $5\%$. Open circles are for positive particles (all proton spectra are scaled by 0.8), and closed triangles are for negative particles. The curves shown (Bose-Einstein fits for $\pi^-$ and blast-wave model fits for $K^-$ and $\bar{p}$) are explained in the text.
invariant yield as function of transverse mass for $\pi^{\pm},K^{\pm}$ and inclusive $p$ and $\bar{p}$ at mid-rapidity ($|y|<0.1$) for pp (bottom) and Au+Au events from $70-80\%$ (second bottom) to the $0-5\%$ centrality bin (top). Statistical and point-to-point systematic errors have been added in quadrature. Additional correlated systematic error due to uncertainty in the normalization is estimated to be $5\%$. Open circles are for positive particles (all proton spectra are scaled by 0.8), and closed triangles are for negative particles. The curves shown (Bose-Einstein fits for $\pi^-$ and blast-wave model fits for $K^-$ and $\bar{p}$) are explained in the text.
invariant yield as function of transverse mass for $\pi^{\pm},K^{\pm}$ and inclusive $p$ and $\bar{p}$ at mid-rapidity ($|y|<0.1$) for pp (bottom) and Au+Au events from $70-80\%$ (second bottom) to the $0-5\%$ centrality bin (top). Statistical and point-to-point systematic errors have been added in quadrature. Additional correlated systematic error due to uncertainty in the normalization is estimated to be $5\%$. Open circles are for positive particles (all proton spectra are scaled by 0.8), and closed triangles are for negative particles. The curves shown (Bose-Einstein fits for $\pi^-$ and blast-wave model fits for $K^-$ and $\bar{p}$) are explained in the text.
Elliptic flow holds much promise for studying the early-time thermalization attained in ultrarelativistic nuclear collisions. Flow measurements also provide a means of distinguishing between hydrodynamic models and calculations which approach the low density (dilute gas) limit. Among the effects that can complicate the interpretation of elliptic flow measurements are azimuthal correlations that are unrelated to the reaction plane (non-flow correlations). Using data for Au + Au collisions at sqrt{s_{NN}} = 130 GeV from the STAR TPC, it is found that four-particle correlation analyses can reliably separate flow and non-flow correlation signals. The latter account for on average about 15% of the observed second-harmonic azimuthal correlation, with the largest relative contribution for the most peripheral and the most central collisions. The results are also corrected for the effect of flow variations within centrality bins. This effect is negligible for all but the most central bin, where the correction to the elliptic flow is about a factor of two. A simple new method for two-particle flow analysis based on scalar products is described. An analysis based on the distribution of the magnitude of the flow vector is also described.
Correlation between the event plane angles determined from pairs of subevents partitioned randomly (circles), partitioned with opposite signs of pseudorapidity (squares) and partitioned with opposite signs of charge (crosses). The correlation is plotted as a function of centrality, namely, charged particle multiplicity $n_{ch}$ divided by the maximum observed charged multiplicity, $n_{max}$.
The event plane resolution for full events as a function of centrality, using randomly partitioned subevents with (circles) and without (triangles) $p_{t}$ weight.
Elliptic flow signal $v_{2}$ as a function of centrality, from study of the correlation between particle pairs consisting of randomly chosen particles (circles), particles with opposite signs of charge (crosses), particles with the same signs of charge (triangles), and particles with opposite signs of pseudorapidity (squares).
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