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 $
pbar over p ratio vs. pt
pbar over p ratio vs. rapidity (y)
pbar over p ratio vs. centrality $(n_{ch}/n_{max})$
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.
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.
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 results from the STAR Collaboration on directed flow (v_1), elliptic flow (v_2), and the fourth harmonic (v_4) in the anisotropic azimuthal distribution of particles from Au+Au collisions at sqrtsNN = 200 GeV are summarized and compared with results from other experiments and theoretical models. Results for identified particles are presented and fit with a Blast Wave model. Different anisotropic flow analysis methods are compared and nonflow effects are extracted from the data. For v_2, scaling with the number of constituent quarks and parton coalescence is discussed. For v_4, scaling with v_2^2 and quark coalescence is discussed.
Directed flow of charged hadrons v1{3} as a function of pseudorapidity for 10–70% centrality.
Directed flow of charged hadrons v1 {EP1,EP2} as a function of pseudorapidity for 20–60% centrality.
Charged hadron v2 for the centrality bins 5 to 10% and in steps of 10% starting at 10, 20, 30, 40, 50, 60, and 70 up to 80% along with min. bias as a function of p_T.
Inclusive transverse momentum distributions of charged hadrons within 0.2
Inclusive $p_T$ distributions of ($h^+ + h^−)/2$. Non-central bins are scaled down by the indicated factors. The combined statistical and systematic errors are shown. Curves are fits to Eq. (2). Hash marks at the top indicate bin boundaries for $p_T>1.5$ GeV/c.
Ratio of charged hadron yields within $|\eta| < 0.5$ for central over peripheral collisions, normalized to $\langle Nbin\rangle$.
$R_{AA}$($p_T$) for various centrality bins, for Au+Au relative to an NN reference spectrum. Error bars are described in the text. Errors between different $p_T$ and centrality bins are highly correlated.
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.
Data from the first physics run at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory, Au+Au collisions at $\sqrt{s_{NN}}=130$ GeV, have been analyzed by the STAR Collaboration using three-pion correlations with charged pions to study whether pions are emitted independently at freezeout. We have made a high-statistics measurement of the three-pion correlation function and calculated the normalized three-particle correlator to obtain a quantitative measurement of the degree of chaoticity of the pion source. It is found that the degree of chaoticity seems to increase with increasing particle multiplicity.
Values for the three-pion correlation function using high multiplicity negative pions. Errors are statistical+systematic.
Three-pion correlator values (r3/2) for positive and negative pions in central and mid-central events. Errors are statistical+systematic.
Three-pion correlator intercept values (r3(0)/2) for positive and negative pions in central and mid-central events compared with other experiments. Errors are statistical+systematic.
We present the results of a systematic study of the shape of the pion distribution in coordinate space at freeze-out in Au+Au collisions at RHIC using two-pion Hanbury Brown-Twiss (HBT) interferometry. Oscillations of the extracted HBT radii vs. emission angle indicate sources elongated perpendicular to the reaction plane. The results indicate that the pressure and expansion time of the collision system are not sufficient to completely quench its initial shape.
Squared HBT radii relative to the reaction plane angle for three centrality classes.
Squared HBT radii relative to the reaction plane angle for four kT (GeV/c) bins, 20-30% centrality events.
Fourier coefficients of azimuthal oscillations of HBT radii vs number of participating nucleons, for three kT (GeV/c) bins. Larger participant numbers correspond to more central collisions.
Azimuthal anisotropy ($v_2$) and two-particle angular correlations of high $p_T$ charged hadrons have been measured in Au+Au collisions at $\sqrt{s_{NN}}$=130 GeV for transverse momenta up to 6 GeV/c, where hard processes are expected to contribute significantly. The two-particle angular correlations exhibit elliptic flow and a structure suggestive of fragmentation of high $p_T$ partons. The monotonic rise of $v_2(p_T)$ for $p_T<2$ GeV/c is consistent with collective hydrodynamical flow calculations. At $\pT>3$ GeV/c a saturation of $v_2$ is observed which persists up to $p_T=6$ GeV/c.
$v_{2}$($p_{T}$) for different collision centralities. The errors are statistical only. The systematic uncertainties, which are highly correlated point-to-point, are $^{+5}_{-20}%$.
$v_{2}$($p_{T}$) for minimum-bias events (circles). The error bars represent the statistical errors and the caps show the systematic uncertainty. The data are compared with hydro+pQCD calculations [9] assuming the initial gluon density $dN^{g}/dy$ = 1000 (dashed line), 500 (dotted line), and 200 (dashed-dotted line). Also shown are pure hydrodynamical calculations [16] (solid line).
High $p_{T}$ azimuthal correlation functions for central events. Upper panel: Correlation function for $|\Delta\eta|$ < 0.5 (solid circles) and scaled correlation function for 0.5 < $|\Delta\eta|$ < 1.4 (open squares). Lower panel: Difference of the two correlation functions. Also shown are the fits to the data (described in the text).
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