The $\jpsi$ $\pt$ spectrum and nuclear modification factor ($\raa$) are reported for $\pt < 5 \ \gevc$ and $|y|<1$ from 0\% to 60\% central Au+Au and Cu+Cu collisions at $\snn = 200 \ \gev$ at STAR. A significant suppression of $\pt$-integrated $\jpsi$ production is observed in central Au+Au events. The Cu+Cu data are consistent with no suppression, although the precision is limited by the available statistics. $\raa$ in Au+Au collisions exhibits a strong suppression at low transverse momentum and gradually increases with $\pt$. The data are compared to high-$\pt$ STAR results and previously published BNL Relativistic Heavy Ion Collider results. Comparing with model calculations, it is found that the invariant yields at low $\pt$ are significantly above hydrodynamic flow predictions but are consistent with models that include color screening and regeneration.
The invariant yield versus transverse momentum for |y| < 1 in 0-20% centrality in Au+Au collisions (solid circles). The results are compared to high-$p_T$ (3 < $p_T$ < 10 GeV/c) results from STAR [9] (solid squares) and PHENIX data [8] (open squares).
The invariant yield versus transverse momentum for |y| < 1 in 20-40% centrality in Au+Au collisions (solid circles). The results are compared to high-$p_T$ (3 < $p_T$ < 10 GeV/c) results from STAR [9] (solid squares) and PHENIX data [8] (open squares).
The invariant yield versus transverse momentum for |y| < 1 in 40-60% centrality in Au+Au collisions (solid circles). The results are compared to high-$p_T$ (3 < $p_T$ < 10 GeV/c) results from STAR [9] (solid squares) and PHENIX data [8] (open squares).
The analyzing power Ay for p+p elastic scattering at θlab=8.64°±0.07° (θcms=18.1°) and at a bombarding energy of 183.1±0.4 MeV has been determined to be Ay=0.2122±0.0017. The error includes statistics, systematic uncertainties, and the uncertainty in bombarding energy and angle. This measurement represents a calibration standard for polarized beams in this energy range. The absolute scale for the measurement has been obtained by comparison with p+C elastic scattering at the same energy at an angle where Ay is very nearly unity.
Axis error includes +- 0.0/0.0 contribution (?////).
Measurements of the eta meson production with a polarised proton beam in the reaction p(pol) p --> p p eta have been carried out at an excess energy of Q = 40 MeV. The dependence of the analysing power A_y on the polar angle theta^*_q of the eta meson in the center of mass system (CMS) has been studied. The data indicate the possibility of an influence of p- and d-waves to the close to threshold eta production.
Averaged value of the analyzing power and cross section as a function of the emmission angle of the ETA meson is the CM system.
The analyzing power A N of proton-proton, proton-hydrocarbon, and antiproton-hydrocarbon, scattering in the Coulomb-nuclear interference region has been measured using thhe 185 GeV/ c Fermilab polarized-proton and -antiproton beams. The results are found to be consistent with theoretical predictions within statistical uncertainties.
No description provided.
Data from hydrocarbon target.
Data from hydrocarbon target.
Measurements at 19 beam kinetic energies between 1795 and 2235 MeV are reported for the pp elastic scattering spin correlation parameter A00nn=ANN=CNN. The c.m. angular range is typically 60–100°. The measurements were performed at Saturne II with a vertically polarized beam and target (transverse to the beam direction and scattering plane), a magnetic spectrometer and a recoil detector, both instrumented with multiwire proportional chambers, and beam polarimeters. These results are compared to previous data from Saturne II and elsewhere.
Measured values of CNN at EKIN 1795 Mev.. Fractional systematic uncertainty in the absolute beam and target polarization is +-0.110.
Measured values of CNN at EKIN 1845 Mev.. Fractional systematic uncertainty in the absolute beam and target polarization is +-0.073.
Measured values of CNN at EKIN 1935 Mev.. Fractional systematic uncertainty in the absolute beam and target polarization is +-0.095.
The reaction pp -> pp pi0 was studied with the WASA detector at the CELSIUS storage ring. The center of mass angular distribution of the pi0 was obtained by detection of the gamma decay products together with the two outgoing protons, and found to be anisotropic with a negative second derivative slope, in agreement with the theoretical predictions from a microscopic calculation.
Acceptance corrected centre of mass PI0 angular distribution, normalized to 92.3 +- 7.2 MUB (Bilger et al.).
Acceptance corrected centre of mass PI0 angular distribution for relative proton momenta < 53 MeV, normalized to Bilger et al... Statistical errors only.
The Drell-Yan and J ψ cross-sections measured in PbPb collisions are compared with the values extrapolated from the results obtained in proton and light ion induced reactions. While the Drell-Yan production exhibits the normal expected behaviour, the yield of J ψ in PbPb interactions is abnormally low, as it lies 9 standard deviations below the expected value. Moreover, the departure from the expected behaviour increases significantly from peripheral to central collisions.
The results from other experiments are also presented.
Different data are rescaled at 200 GeV.
The PHENIX experiment has measured mid-rapidity transverse momentum spectra (0.4 < p_T < 4.0 GeV/c) of single electrons as a function of centrality in Au+Au collisions at sqrt(s_NN) = 200 GeV. Contributions to the raw spectra from photon conversions and Dalitz decays of light neutral mesons are measured by introducing a thin (1.7% X_0) converter into the PHENIX acceptance and are statistically removed. The subtracted ``non-photonic'' electron spectra are primarily due to the semi-leptonic decays of hadrons containing heavy quarks (charm and bottom). For all centralities, charm production is found to scale with the nuclear overlap function, T_AA. For minimum-bias collisions the charm cross section per binary collision is N_cc^bar/T_AA = 622 +/- 57 (stat.) +/- 160 (sys.) microbarns.
Value of the Alpha power as used in a fit of dN/dy versus Ncoll of the form A*Ncoll^Alpha, where N is the non photonic electron yield and Ncoll the number of p+p collisions This value only includes data from Au+Au collisions The value of Alpha = 1 is the expectation in the absence of medium effects.
Value of the Alpha power as used in a fit of dN/dy versus Ncoll, of the form A*Ncoll^Alpha, where N is the non photonic electron yield and Ncoll the number of p+p collisions This value is calculated including previous data of p+p collisions, measured by PHENIX, in addition of the Au+Au data The value of Alpha = 1 is the expectation in the absence of medium effects.
Spectrum in transverse momentum of electrons created in open heavy flavor decays, for minimum bias events.
This publication describes the methods used to measure the centrality of inelastic Pb-Pb collisions at a center-of-mass energy of 2.76 TeV per colliding nucleon pair with ALICE. The centrality is a key parameter in the study of the properties of QCD matter at extreme temperature and energy density, because it is directly related to the initial overlap region of the colliding nuclei. Geometrical properties of the collision, such as the number of participating nucleons and number of binary nucleon-nucleon collisions, are deduced from a Glauber model with a sharp impact parameter selection, and shown to be consistent with those extracted from the data. The centrality determination provides a tool to compare ALICE measurements with those of other experiments and with theoretical calculations.
$N_\mathrm{part}$ for Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV with the corresponding uncertainties derived from a Glauber calculation. The ${\langle N_\mathrm{part}^{\rm data} \rangle}$ are calculated from the NBD-Glauber fit to the VZERO amplitude, while the ${\langle N_\mathrm{part}^{\rm geo} \rangle}$ are obtained by slicing the impact parameter distribution. ${\langle N_\mathrm{part}^{\rm data} \rangle}$ is also calculated for two variations of the AP, i.e. moving it to 91 % (${\langle N_\mathrm{part}^{\rm data +} \rangle}$) and to 89 % (${\langle N_\mathrm{part}^{\rm data +} \rangle}$) respectively. The last three columns report the discrepancies between ${\langle N_\mathrm{part}^{\rm geo} \rangle}$ and ${\langle N_\mathrm{part}^{\rm data} \rangle}$ and ${\langle N_\mathrm{part}^{\rm data} \rangle}$ with the uncertainty of the AP.
Same as Table A.1 for $N_\mathrm{coll}$.
Same as Table A.1 for $T_\mathrm{AA}$.
Data on multiplicities of charged particles produced in proton-nucleus and nucleus-nucleus collisions at 200 GeV per nucleon are presented. It is shown that the mean multiplicity of negative particles is proportional to the mean number of nucleons participating in the collision both for nucleus-nucleus and proton-nucleus collisions. The apparent consistency of pion multiplicity data with the assumption of an incoherent superposition of nucleon-nucleon collisions is critically discussed.
No description provided.
No description provided.
No description provided.
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