Values of the ratios in the mid-rapidity yields of anti-Lambda/Lambda = 0.71 +/- 0.01(stat.) +/- 0.04(sys.), anti-Xi+/Xi- = 0.83 +/- 0.04(stat.) +/- 0.05 (sys.), anti-Omega+/Omega- = 0.95 +/- 0.15(stat) +/- 0.05(sys.) and K+/K- 1.092 +/- 0.023(combined) were obtained in central sqrt(s_NN) = 130 GeV Au+Au collisions using the STAR detector. The ratios indicate that a fraction of the net-baryon number from the initial system is present in the excess of hyperons over anti-hyperons at mid-rapidity. The trend in the progression of the baryon ratios, with increasing strange quark content, is similar to that observed in heavy-ion collisions at lower energies. The value of these ratios may be related to the charged kaon ratio in the framework of simple quark-counting and thermal models.
Invariant mass distributions for $\Lambda$ and Anti-$\Lambda$
Invariant mass distributions for $\Xi$ and Anti-$\Xi$
Invariant mass distributions for $\Omega$ and Anti-$\Omega$
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.
Mid-rapidity transverse mass spectra and multiplicity densities of charged and neutral kaons are reported for Au+Au collisions at $\snn$=130 GeV at RHIC. The spectra are exponential in transverse mass, with an inverse slope of about 280 MeV in central collisions. The multiplicity densities for these particles scale with the negative hadron pseudo-rapidity density. The charged kaon to pion ratios are $K^+/\pi^- = 0.161 \pm 0.002 {\rm (stat)} \pm 0.024 {\rm (syst)}$ and $K^-/\pi^- = 0.146 \pm 0.002 {\rm (stat)} \pm 0.022 {\rm (syst)}$ for the most central collisions. The $K^+/\pi^-$ ratio is lower than the same ratio observed at the SPS while the $K^-/\pi^-$ is higher than the SPS result. Both ratios are enhanced by about 50% relative to p+p and $\bar{\rm p}$+p collision data at similar energies.
Transverse mass distributions for different centralities: dE/dx identified charged kaons. K+
Transverse mass distributions for different centralities: dE/dx identified charged kaons. K-
Transverse mass distributions for different centralities: Neutral Kaons.
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 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 $(n_{ch}/n_{max})$
Inclusive transverse momentum distributions of charged hadrons within 0.2<pT<6.0 GeV/c have been measured over a broad range of centrality for Au+Au collisions at sqrt(sNN)=130 GeV. Hadron yields are suppressed at high pT in central collisions relative to peripheral collisions and to a nucleon-nucleon reference scaled for collision geometry. Peripheral collisions are not suppressed relative to the nucleon-nucleon reference. The suppression varies continuously at intermediate centralities. The results indicate significant nuclear medium effects on high pT hadron production in heavy ion collisions at high energy.
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.
We report the first measurement of strange ($\Lambda$) and anti-strange ($\bar{\Lambda}$) baryon production from $\sqrt{s_{_{NN}}}=130$ GeV Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC). Rapidity density and transverse mass distributions at mid-rapidity are presented as a function of centrality. The yield of $\Lambda$ and $\bar{\Lambda}$ hyperons is found to be approximately proportional to the number of negative hadrons. The production of $\bar{\Lambda}$ hyperons relative to negative hadrons increases very rapidly with transverse momentum. The magnitude of the increase cannot be described by existing hadronic string fragmentation models.
Transverse mass distributions of $\Lambda$ at mid-rapidity ($|y|<0.5$) for selected centrality bins. Only statistical errors are listed. Combined systematic errors estimated to be $10\%$. The dashed lines are Boltzmann fits. Note that multiplicative factors have been applied to data from the two most central data sets for display.
Transverse mass distributions of $\bar\Lambda$ at mid-rapidity ($|y|<0.5$) for selected centrality bins. Only statistical errors are listed. Combined systematic errors estimated to be $10\%$. The dashed lines are Boltzmann fits. Note that multiplicative factors have been applied to data from the two most central data sets for display.
The mid-rapidity $\bar\Lambda$ ($|y|<0.5$) transverse momentum distribution from the top $5\%$ most central collisions. For comparison the distributions for negative hadrons ($d^{2}N/(2 \pi p_{T})dp_{T}d\eta$, $|\eta|<0.1$) and anti-protons ($|y|<0.1$) for the similar centrality bin are included. Only statistical errors are listed. Statistical errors are less than the size of the data points. Combined systematic errors on hyperons estimated to be $10\%$. Correlated systematic errors for negative hadrons estimated to be $6\%$. Systematic errors on antiprotons are $8\%$ point-to-point and $10\%$ in the overall normalization.
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.
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 $^{+5}_{-20}%$.
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).
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).
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.
Transverse mass spectrum of K*0 with YRAP = -0.5 to 0.5 for the 14 PCT most central interactions. Numerical values requested from the authors.
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.
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