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.
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.
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.
We report the first measurement of inclusive antiproton production at mid-rapidity in Au+Au collisions at 130 GeV by the STAR experiment at RHIC. The antiproton transverse mass distributions in the measured transverse momentum range of 0.25 < pT < 0.95 GeV/c are found to fall less steeply for more central collisions. The extrapolated antiproton rapidity density is found to scale approximately with the negative hadron multiplicity density.
Tranverse mass distributions for different centralities
Antiproton fit parameters and yields. Systematic errors are 10%.
Antiproton fit parameters and yields. Systematic errors are 10%.
Measurements at 18 beam kinetic energies between 1975 and 2795 MeV and at 795 MeV are reported for the pp elastic scattering spin correlation parameter A00nn=(N,N;0,0)=CNN=ANN. The c.m. angular range is typically 60°-100°. These results are compared to previous data from Saturne II and other accelerators. A search for energy-dependent structure at fixed c.m. angles is performed. Comparisons are made to phase shift analysis and theoretical model predictions of this spin observable.
Measured values of CNN at EKIN 795 Mev.. Fractional systematic uncertainty in the absolute beam and target polarization is +-0.032.
Measured values of CNN at EKIN 1975 Mev.. Fractional systematic uncertainty in the absolute beam and target polarization is +-0.052.
Measured values of CNN at EKIN 2035 Mev (from run period III).. Fractional systematic uncertainty in the absolute beam and target polarization is +-0.051.
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%.
The PS185 experiment at LEAR/CERN has investigated strangeness production in antiproton-proton collisions with final states such as $\overline{\Lambda} \Lambda$, $\overline{\Sigma}^0 \Lambda + c.c$, $\overline{\Sigma^+} \Sigma^+$, $\overline{\Sigma^-} \Sigma^-$ and $K_S K_S$. Results are presented from a study of about 32,000 {$K_S K_S X$} events obtained at several antiproton momenta in the regions of 1.45 and 1.7 GeV/c. The $\overline{p} p \to K_S K_S \eta$ cross sections extracted at these momenta constitute the first measurement of this reaction in flight and are broadly consistent with expectations of a phase-space extrapolation of branching ratios from annihilation at rest.
No description provided.
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%.
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.
The production of $J/\psi$ mesons in continuum $e^+e^-$ annihilations has been studied with the BABAR detector at energies near the $\Upsilon(4S)$ resonance, approximately 10.6 GeV. The mesons are distinguished from $J/\psi$ production in B decays through their center-of-mass momentum and energy. We measure the cross section $e^+e^-\to J/\psi X$ to be $2.52\pm 0.21\pm 0.21$ pb: for momentum above 2 GeV/c, it is $1.87\pm 0.10\pm 0.15$ pb. We set a 90% confidence level upper limit on the branching fraction for direct $\Upsilon(4S)$\to J/\psi X$ decays at $4.7\times 10^{-4}$.
Cross section measurement.
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