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 central inclusive jet cross section has been measured using a successive-combination algorithm for reconstruction of jets. The measurement uses 87.3 pb^{-1} of data collected with the D0 detector at the Fermilab Tevatron ppbar Collider during 1994-1995. The cross section, reported as a function of transverse momentum (pT>60 GeV) in the central region of pseudorapidity (|\eta|<0.5), exhibits reasonable agreement with next-to-leading order QCD predictions, except at low pT where the agreement is marginal.
The inclusive jet cross section as a function of PT.
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%.
The cross section of the process e+e- -> pi+pi- has been measured using about 114000 events collected by the CMD-2 detector at the VEPP-2M e+e- collider in the center-of-mass energy range from 0.61 to 0.96 GeV. Results of the pion form factor determination with a 0.6% systematic uncertainty are presented. Implications for the hadronic contribution to the muon anomalous magnetic moment are discussed.
Updated measured values of the pion form factor and 'bare' cross section.
The inclusive production of the omega(782) vector meson in hadronic Z decays is measured and compared to model predictions. The analysis is based on 4 million hadronic Z decays recorded by the ALEPH detector between 1991 and 1995. The production rate for x_p = p_meson/p_beam > 0.05 is measured in the omega -> pi^+ pi^- pi^0 decay mode and found to be 0.585 +- 0.019_stat +- 0.033_sys per event. Inclusive eta meson production is also measured in the same decay channel for x_p > 0.10, obtaining 0.355 +- 0.011_stat +- 0.024_sys per event. The branching ratio for omega -> mu^+ mu^- is investigated. A total of 18.1 +- 5.9 events are observed, from which the muonic branching ratio is measured for the first time to be BR(omega -> mu^+ mu^-) = (9.0 +- 2.9_stat +- 1.1_sys)*10^-5.
Extrapolation using JETSET 7.4 is used to correct down to X = 0.0. The second DSYS error, where relevant, shows the estimated uncertainty on the extrapolation.
Production rate and differential cross sections for the ETA.
Production rate and differential cross sections for the OMEGA.
The cross section of the process $e^+e^-\to \pi^+\pi^-\pi^0$ was measured in the Spherical Neutral Detector experiment at the VEPP-2M collider in the energy region $\sqrt[]{s} = 980 \div 1380$ MeV. The measured cross section, together with the $e^+e^-\to \pi^+\pi^-\pi^0$ and $\omega\pi^+\pi^-$ cross sections obtained in other experiments, was analyzed in the framework of the generalized vector meson dominance model. It was found that the experimental data can be described by a sum of $\omega$, $\phi$ mesons and two $\omega^\prime$ and $\omega^{\prime\prime}$ resonances contributions, with masses $m_{\omega^\prime}\sim 1490$,$m_{\omega^{\prime\prime}}\sim 1790$ MeV and widths $\Gamma_{\omega^\prime}\sim 1210$, $\Gamma_{\omega^{\prime\prime}}\sim 560$ MeV. The analysis of the $\pi^+\pi^-$ invariant mass spectra in the energy region $\sqrt[]{s}$ from 1100 to 1380 MeV has shown that for their descriptionone should take into account the $e^+e^-\to\omega\pi^0\to\pi^+\pi^-\pi^0$ mechanism also. The phase between the amplitudes corresponding to the $e^+e^-\to\omega\pi$ and $e^+e^-\to\rho\pi$ intermediate states was measured for the first time. The value of the phase is close to zero and depends on energy.
The measured E+ E- --> PI+ PI- PI0 cross section.
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.
Using the HERA-B detector, the b-bbar production cross section has been measured in 920 GeV proton collisions on carbon and titanium targets. The b-bbar production was tagged via inclusive bottom quark decays into J/psi, by exploiting the longitudinal separation of J/psi->ll decay vertices from the primary proton-nucleus interaction. Both $e^+e^-$ and $\mu^+\mu^-$ channels have been reconstructed and the combined analysis yields the cross section $\sigma(b \bar b) = 32 ^{+14}_{-12} (stat) ^{+6}_{-7} (sys) nb/nucleon$.
The measured cross section for the E+ E- and MU+ MU- channels separately.
The measured and extrapolated combined B-BBAR production cross section.
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.
Forum