We report first results on elliptic flow of identified particles at mid-rapidity in Au+Au collisions at $\sqrt{s_{_{NN}}}=130$ GeV using the STAR TPC at RHIC. The elliptic flow as a function of transverse momentum and centrality differs significantly for particles of different masses. This dependence can be accounted for in hydrodynamic models, indicating that the system created shows a behavior consistent with collective hydrodynamical flow. The fit to the data with a simple model gives information on the temperature and flow velocities at freeze-out.
Differential elliptic flow for pions for minimum-bias events, the systematic uncertainty for minimum-bias data is 13%.
Differential elliptic flow for protons + antiprotons for minimum-bias events, the systematic uncertainty for minimum-bias data is 13%.
Differential elliptic flow for kaons for minimum-bias events, the systematic uncertainty for minimum-bias data is 13%.
The minimum bias multiplicity distribution and the transverse momentum and pseudorapidity distributions for central collisions have been measured for negative hadrons (h-) in Au+Au interactions at sqrt(s_nn) = 130 GeV. The multiplicity density at midrapidity for the 5% most central interactions is dNh-/deta|_{eta = 0} = 280 +- 1(stat)+- 20(syst), an increase per participant of 38% relative to ppbar collisions at the same energy. The mean transverse momentum is 0.508 +- 0.012 GeV/c and is larger than in central Pb+Pb collisions at lower energies. The scaling of the h- yield per participant is a strong function of pt. The pseudorapidity distribution is almost constant within |eta|<1.
Normalized multiplicity distribution of $h^{−}$ with $p_{T} > 100$ MeV/$c$ at $|\eta| < 0.5$ in Au+Au collisions at $\sqrt{s_{NN}} = 130$ GeV. Systematic error on the vertical scale is estimated to be $10\%$. The systematic error on the horizontal scale is $6\%$ for the entire range of multiplicity. The shaded area is $5\%$ most central collisions, selected by ZDC coincidence. The solid curve is the prediction from the HIJING model.
$h^{−}$ $p_{T}$-spectra for the $5\%$ most central Au+Au collisions at midrapidity ($|\eta| < 0.1$) for several systems. The correlated systematical error is estimated to be below $6\%$. The curves are power-law fits to the data.
ratio of STAR and scaled UA1 $p_{T}$-distributions. The errors given are the errors of the STAR data only and do not include the systematic errors from the scaling of the UA1 data to $130$ GeV (i.e., the shaded region in Fig.2 lower panel). The STAR data is for the $5\%$ most central collisions.
We report results on the ratio of mid-rapidity anti-proton to proton yields in Au+Au collisions at $\rts = 130$ GeV per nucleon pair as measured by the STAR experiment at RHIC. Within the rapidity and transverse momentum range of $|y|<0.5$ and 0.4 $<p_t<$ 1.0 GeV/$c$, the ratio is essentially independent of either transverse momentum or rapidity, with an average of $0.65\pm 0.01_{\rm (stat.)} \pm 0.07_{\rm (syst.)}$ for minimum bias collisions. Within errors, no strong centrality dependence is observed. The results indicate that at this RHIC energy, although the $p$-$\pb$ pair production becomes important at mid-rapidity, a significant excess of baryons over anti-baryons is still present.
pbar over p ratio vs. pt
pbar over p ratio vs. rapidity (y)
pbar over p ratio vs. centrality $(n_{ch}/n_{max})$
Two-pion correlation functions in Au+Au collisions at $\sqrt{s_{NN}} = 130$ GeV have been measured by the STAR (Solenoidal Tracker at RHIC) detector. The source size extracted by fitting the correlations grows with event multiplicity and decreases with transverse momentum. Anomalously large sizes or emission durations, which have been suggested as signals of quark-gluon plasma formation and rehadronization, are not observed. The HBT parameters display a weak energy dependence over a broad range in $\sqrt{s_{NN}}$.
Multiplicity dependence of HBT parameters for low-pT (0.125-0.225 GeV/c) pi- pi- channel. They are Coulomb corrected (5 fm Gaussian source assumed), corrected for merging effects ("bad systematic" for STAR-HBT insiders), and corrected for finite-momentum-resolution effects. Systematic errors are estimated by the size of the merging correction and the effect of varying source size used in the Coulomb correction by +/- 1 fm.
Multiplicity dependence of HBT parameters for low-pT (0.125-0.225 GeV/c) pi+ pi+ channel. They are Coulomb corrected (5 fm Gaussian source assumed), corrected for merging effects ("bad systematic" for STAR-HBT insiders), and corrected for finite-momentum-resolution effects. Systematic errors are estimated by the size of the merging correction and the effect of varying source size used in the Coulomb correction by +/- 1 fm.
mT dependence of HBT parameters for high multiplicity (0-12%) collisions in pi- pi- channel. They are Coulomb corrected (5 fm Gaussian source assumed), corrected for merging effects ("bad systematic" for STAR-HBT insiders), and corrected for finite-momentum-resolution effects. Systematic errors are estimated by the size of the merging correction and the effect of varying source size used in the Coulomb correction by +/- 1 fm.
Mid-rapidity open charm spectra from direct reconstruction of $D^{0}$($\bar{D^0}$)$\to K^{\mp}\pi^{\pm}$ in d+Au collisions and indirect electron/positron measurements via charm semileptonic decays in p+p and d+Au collisions at \srt = 200 GeV are reported. The $D^{0}$($\bar{D^0}$) spectrum covers a transverse momentum ($p_T$) range of 0.1 $<p_T<$ 3 \GeVc whereas the electron spectra cover a range of 1 $<p_T<$ 4 GeV/$c$. The electron spectra show approximate binary collision scaling between p+p and d+Au collisions. From these two independent analyses, the differential cross section per nucleon-nucleon binary interaction at mid-rapidity for open charm production from d+Au collisions at RHIC is $d\sigma^{NN}_{c\bar{c}}/dy$=0.30$\pm$0.04 (stat.)$\pm$0.09(syst.) mb. The results are compared to theoretical calculations. Implications for charmoniumm results in A+A collisions are discussed.
Inclusive electrons yield versus transverse momentum in D+AU collisions Data points at PT = 2.2, 2.7 and 3.5 GeV/c was obtained using only the TPC (Time Projection Chamber) and cover a pseudo-rapidity range of -1<eta<1, while other points were obtained using both a prototypeTime-of-Flight System and the TPC and cover a pseudo-rapidity range of -1<eta<0.
Inclusive electrons yield versus transverse momentum in P+P collisions.
D0 yield versus transverse momentum in D+AU collisions.
We report the first observation of $K^{\star}(892)^{0}\to\pi K$ in relativistic heavy ion collisions. The transverse momentum spectrum of $(K^{\star0}+\bar{K}^{\star0})/2$ from central Au+Au collisions at $\sqrt{s_{_{NN}}}=130$ GeV is presented. The ratios of the $K^{\star0}$ yield derived from these data to the yields of negative hadrons, charged kaons, and $\phi$ mesons have been measured in central and minimum bias collisions and compared with model predictions and comparable $e^{+}e^{-}$, $pp$, and $\bar{p}p$ results. The data indicate no dramatic reduction of $K^{\star0}$ production in relativistic heavy ion collisions despite expected losses due to rescattering effects.
K*0 to negative hadron ratio using hadron data from Adler et al PRL 87,112303(2001).
K*0 to kaon ratio using STAR kaon data.
PHI to K*0 ratio measured in this study.
The STAR collaboration at RHIC reports measurements of the inclusive yield of non-photonic electrons, which arise dominantly from semi-leptonic decays of heavy flavor mesons, over a broad range of transverse momenta ($1.2 < \pt < 10$ \gevc) in \pp, \dAu, and \AuAu collisions at \sqrtsNN = 200 GeV. The non-photonic electron yield exhibits unexpectedly large suppression in central \AuAu collisions at high \pt, suggesting substantial heavy quark energy loss at RHIC. The centrality and \pt dependences of the suppression provide constraints on theoretical models of suppression.
Non photonic electron yield in P+P collisions versus $p_{T}$. To obtain a differential cross-section in mb/(GeV$^2$), multiply listed data by 30.
Non photonic electron yield in P+P collisions versus PT To obtain a differential cross-section in mb/(GeV2), multiply listed data by 30 Note that, in addition to the statistical and systematical errors, there is a normalization error on the value, given in the second column.
Non photonic electron yield in minimum bias D+AU collisions versus $p_{T}$.
We present STAR measurements of the azimuthal anisotropy parameter $v_2$ and the binary-collision scaled centrality ratio $R_{CP}$ for kaons and lambdas ($\Lambda+\bar{\Lambda}$) at mid-rapidity in Au+Au collisions at $\sqrt{s_{_{NN}}}=200$ 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 $p_T \approx 5$ GeV/c as the value where the centrality dependent baryon enhancement ends. The $K_S^0$ and $\Lambda+\bar{\Lambda}$ $v_2$ values are consistent with expectations of constituent-quark-number scaling from models of hadron fromation by parton coalescence or recombination.
The minimum bias (0-80% of the collision cross-section) v2(pT) of K0s. Errors listed include statistical and point-to-point systematic uncertainties from the background. Additional non-flow systematic uncertainties are approximately -20%.
The minimum bias (0-80% of the collision cross-section) v2(pT) of Lambda+Lambdabar. Errors listed include statistical and point-to-point systematic uncertainties from the background. Additional non-flow systematic uncertainties are approximately -20%.
The minimum bias (0-80% of the collision cross-section) v2(pT) of charged hadrons. Errors listed include statistical and point-to-point systematic uncertainties from the background. Additional non-flow systematic uncertainties are approximately -20%.
Charged hadrons in 0.15 < pt < 4 GeV/c associated with particles of pt^trig > 4 GeV/c are reconstructed in pp and Au+Au collisions at sqrt(s_NN)=200 GeV. The associated multiplicity and pt magnitude sum are found to increase from pp to central Au+Au collisions. The associated pt distributions, while similar in shape on the near side, are significantly softened on the away side in central Au+Au relative to pp and not much harder than that of inclusive hadrons. The results, consistent with jet quenching, suggest that the away-side fragments approach equilibration with the medium traversed.
Dphi correlation functions for 0.15 < pT < 4 GEV/c and 4 < p_T^trig < 6 GEV/c.
Dphi correlation functions for 0.15 < pT < 4 GEV/c and 4 < p_T^trig < 6 GEV/c.
Dphi correlation functions for 2 < pT < 4 GEV/c and 4 < p_T^trig < 6 GEV/c.
We present a systematic analysis of two-pion interferometry in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV using the STAR detector at RHIC. We extract the HBT radii and study their multiplicity, transverse momentum, and azimuthal angle dependence. The Gaussianess of the correlation function is studied. Estimates of the geometrical and dynamical structure of the freeze-out source are extracted by fits with blast wave parameterizations. The expansion of the source and its relation with the initial energy density distribution is studied.
1D correlation function for different values of SL (antisplitting cut).
1D correlation functions for differeny values of the maximum fraction of merged hits allowed.
Projections of the 3 dimensional correlation function and corresponding fits for negative pions from the 0-5% most central events and k_T = [150,250] MeV/c according to the standard and Bowler-Sinyukov procedures.
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