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 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 $\sqrt{s_{NN}}$=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.
Uncorrected charged particle multiplicity distributions measured in −3.8 < $\eta$ < −2.8 (Au-direction) for d+Au collisions. Points are for minimum bias (triangles) and peripheral (circles, ZDC-d single neutron) collisions. Both are normalized to the total number of d+Au collisions. Histograms are Glauber model calculations.
Inclusive $p_{T}$ distributions for minimum bias and central d+Au collisions, and non-singly diffractive p+p collisions. Hash marks at the top indicate bin boundaries for $p_{T}$ > 3.8 GeV/c.
$R_{AB}(p_{T})$ from Eq. 1 for minimum bias and central d+Au collisions, and central Au+Au collisions. The minimum bias d+Au data are displaced 100 MeV/c to the right for clarity. The error bars are the quadrature sum of the statistical and point-to-point systematic uncertainties. The bands show the normalization uncertainties, which are highly correlated point-to-point and between the two d+Au distributions.
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
$p$ 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%.
Transverse momentum spectra of charged hadrons with p_T < 8 GeV/c and neutral pions with p_T < 10 GeV/c have been measured at mid-rapidity by the PHENIX experiment at RHIC in d+Au collisions at sqrt(s_NN) = 200 GeV. The measured yields are compared to those in p+p collisions at the same sqrt(s_NN) scaled up by the number of underlying nucleon-nucleon collisions in d+Au. The yield ratio does not show the suppression observed in central Au+Au collisions at RHIC. Instead, there is a small enhancement in the yield of high momentum particles.
Midrapidity $p_T$ spectra for charged hadrons.
Midrapidity $p_T$ spectra for $\pi^0$.
Nuclear modification factor $R_{dA}$ for $\pi^0$ in the PbGl and PbSc calorimeters in minimum bias $d$+$Au$.
The first measurement of the p n -> d omega total cross section has been achieved at mean excess energies of Q = 28 and 57 MeV by using a deuterium cluster-jet target. The momentum of the fast deuteron was measured in the ANKE spectrometer at COSY-Juelich and that of the slow spectator proton p(sp) from the p d -> p(sp) d omega reaction in a silicon telescope placed close to the target. The cross sections lie above those measured for p p -> p p omega but seem to be below theoretical predictions.
Total cross sections after the P N --> DEUT OMEGA reaction just above threshold.
First results on charm quarkonia production in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The yield of J/Psi's measured in the PHENIX experiment via electron-positron decay pairs at mid-rapidity for Au-Au reactions at sqrt(s_NN) = 200 GeV are analyzed as a function of collision centrality. For this analysis we have studied 49.3 million minimum bias Au-Au reactions. We present the J/Psi invariant yield dN/dy for peripheral and mid-central reactions. For the most central collisions where we observe no signal above background, we quote 90% confidence level upper limits. We compare these results with our J/Psi measurement from proton-proton reactions at the same energy. We find that our measurements are not consistent with models that predict strong enhancement relative to binary collision scaling.
Measured invariant differential yield at mid-rapidity of J/PSI, as a function of centratility, times branching ratio Be+e-, for three bins of centrality : 0-20%, 20-40% and 40-90% of Au-Au cross-section. The 90% confidence level upper limit (CLUL) for the yield is also given.
Measured differential yield of J/PSI per binary collisions,at mid rapidity, as a function of the centrality, times branching ratio Be+e-.The 90% confidence level upper limit (CLUL) for J/PSI differential yield is also given. The values of the number of participants for each centrality bins are calculated for general information.
We report high statistics measurements of inclusive charged hadron production in Au+Au and p+p collisions at \sqrtsNN=200 GeV. A large, approximately constant hadron suppression is observed in central Au+Au collisions for $5\lt\pT\lt12$ GeV/c. The collision energy dependence of the yields and the centrality and \pT 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 \pT-dependent suppression, which may be expected from models incorporating jet attentuation in cold nuclear matter or scattering of fragmentation hadrons.
Inclusive invariant pT distributions of (h+ + h−)/2 for centrality-selected Au+Au and p+p NSD interactions. Hash marks at the top indicate bin boundaries for pT>4 GeV/c.The invariant cross section for p+p is indicated on the right vertical axis.
R200/130(pT ) vs. pT for (h+ + h−)/2 for four different centrality bins. The overall normalization uncertainty is +6−14% for the 40-60% bin and is negligible for the other panels. Calculations are described in the text.
RAA(pT) (Eq. 1) for (h+ + h−)/2 in |η|<0.5, for centrality-selected Au+Au spectra relative to the measured p+p spectrum. The p+p spectrum is common to all panels. Calculations are described in the text.
We report on the yield of protons and anti-protons, as a function of centrality and transverse momentum, in Au+Au collisions at sqrt(s_NN) = 200 GeV measured at mid-rapidity by the PHENIX experiment at RHIC. In central collisions at intermediate transverse momenta (1.5 < p_T < 4.5 GeV/c) a significant fraction of all produced particles are protons and anti-protons. They show a centrality-scaling behavior different from that of pions. The p-bar/pion and p/pion ratios are enhanced compared to peripheral Au+Au, p+p, and electron+positron collisions. This enhancement is limited to p_T < 5 GeV/c as deduced from the ratio of charged hadrons to pi^0 measured in the range 1.5 < p_T < 9 GeV/c.
$p$/$\pi^+$ and $p$/$\pi^-$ ratios for central (0-10%) mid-central (20-30%) and peripheral (60-92%) Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV.
$p$/$\pi^-$ and $p$/$\pi^0$ ratios for central (0-10%) mid-central (20-30%) and peripheral (60-92%) Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV.
$p$ and $\bar{p}$ invariant yields scaled by $N_{coll}$. Error bars are statistical. Systematic errors on $N_{coll}$ range from ~ 10% for central to ~ 28% for 60-92% centrality. Multiplicity dependent normalization errors are ~3%.
The anisotropy parameter v_2, the second harmonic of the azimuthal particles distribution, has been measured with the PHENIX detector in Au+Au collisions at sqrt(s_NN) = 200 GeV for identified and inclusive charged particles at central rapidities (|eta| < 0.35) with respect to the reaction plane defined at high rapidities (|eta| = 3-4). The v_2 for all particles reaches a maximum at mid-centrality, and increases with p_T up to 2 GeV/c and then saturates or decreases slightly. Our results depart from hydrodynamically predicted behavior above 2 GeV/c. A quark coalescence model is also investigated.
Correlation of reaction planes between two beam counters for the second moment is shown as a function of centrality.
The value of $v_2$ for charged particles is shown as a function of centrality (middle) and as a function of $p_T$ (right).
The value of $v_2$ for charged particles is shown as a function of transverse momentum, $p_T$.
The reaction pp->d K+ Kbar0 has been investigated at an excess energy of Q=46 MeV above the (K+ Kbar0) threshold with ANKE at COSY-Juelich. From the detected coincident dK+ pairs about 1000 events with a missing Kbar0 were identified, corresponding to a total cross section of sigma(pp->d K+ Kbar0)=(38 +/- 2(stat) +/- 14(syst)) nb. Invariant-mass and angular distributions have been jointly analyzed and reveal s-wave dominance between the two kaons, accompanied by a p-wave between the deuteron and the kaon system. This is interpreted in terms of a0+(980)-resonance production.
Total cross section for P P --> DEUT K+ KBAR0.
Centre of mass angular distribution of the deuteron with respect to the direction of the incoming proton.
Centre of mass angular distribution of the vector joining the K+ and KBAR0 with respect to the direction of the incoming proton.
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