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Register a new userJ/psi production at high transverse momentum in p+p and Cu+Cu collisions at sNN=200GeV
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The STAR collaboration at RHIC presents measurements of Jpsi$to{e^+e^-}$ at mid-rapidity and high transverse momentum ($p_T>5$ GeV/$c$) in pp and central cucu collisions at sNN = 200 GeV. The inclusive Jpsi production cross section for cucu collisions is found to be consistent at high $p_T$ with the binary collision-scaled cross section for pp collisions, in contrast to previous measurements at lower $p_T$, where a suppression of Jpsi production is observed relative to the expectation from binary scaling. Azimuthal correlations of $J/psi$ with charged hadrons in pp collisions provide an estimate of the contribution of $B$-meson decays to Jpsi production of $13% pm 5%$.
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The preliminary results of J/psi spectra at high transverse momentum (5<p_T<14 GeV/c) in p+p and Cu+Cu collisions at s_NN = 200 GeV are reported. The nuclear modification factor is measured to be 0.9+/-0.2 at p_T>5 GeV/c. The correlations between J/psi and charged hadrons are also studied in p+p collisions to understand the J/psi production mechanism at high p_T.
We report on the measurement of $rm{J}/psi$ production in the dielectron channel at mid-rapidity (|y|<1) in p+p and d+Au collisions at $sqrt{s_{NN}}$ = 200 GeV from the STAR experiment at the Relativistic Heavy Ion Collider. The transverse momentum $p_{T}$ spectra in p+p for $p_{T}$ < 4 GeV/c and d+Au collisions for $p_{T}$ < 3 GeV/c are presented. These measurements extend the STAR coverage for $rm{J}/psi$ production in p+p collisions to low $p_{T}$. The $<p_{T}^{2}>$ from the measured $rm{J}/psi$ invariant cross section in p+p and d+Au collisions are evaluated and compared to similar measurements at other collision energies. The nuclear modification factor for $rm{J}/psi$ is extracted as a function of $p_{T}$ and collision centrality in d+Au and compared to model calculations using the modified nuclear Parton Distribution Function and a final-state $rm{J}/psi$ nuclear absorption cross section.
We report $J/psi$ spectra for transverse momenta $p_T$> 5 GeV/$c$ at mid-rapidity in p+p and Au+Au collisions at sqrt(s_{NN}) = 200 GeV.The inclusive $J/psi$ spectrum and the extracted $B$-hadron feed-down are compared to models incorporating different production mechanisms. We observe significant suppression of the $J/psi$ yields for $p_T$> 5 GeV/$c$ in 0-30% Au+Au collisions relative to the p+p yield scaled by the number of binary nucleon-nucleon collisions in Au+Au collisions. In 30-60% collisions, no such suppression is observed.The level of suppression is consistently less than that of high-$p_T$ $pi^{pm}$ and low-$p_T$ $J/psi$.
We study dilepton production in proton-proton, Cu+Cu as well as in Au+Au collisions at the center-of-mass energy 200 GeV per participating nucleon pair within an extended statistical hadronization model. In extension to earlier studies we incorporate transport calculations for an estimate of uncorrelated e+e- -pairs from semileptonic D meson decays. While the invariant mass spectrum of dielectrons is well understood in the p+p collisions, severe discrepancies among different model scenarios based on hadronic degrees of freedom and recent data from the PHENIX Collaboration are found in heavy-ion collisions in the low mass region from 0.15 to 0.6 GeV as well as in the intermediate mass regime from 1.1 to 3 GeV when employing the standard dilepton sources. We investigate, furthermore, the background from correlated dileptons that are not emitted as a pair from a parent hadron but emerge from semileptonic decays of two correlated daughter hadrons. Our calculations suggest a sizeable contribution of such sources in central heavy-ion collisions in the low mass region. However, even the upper limits of our calculations are found to be far below the dilepton mass spectra of the PHENIX Collaboration.
Yields for J/psi production in Cu+Cu collisions at sqrt (s_NN)= 200 GeV have been measured by the PHENIX experiment over the rapidity range |y| < 2.2 at transverse momenta from 0 to beyond 5 GeV/c. The invariant yield is obtained as a function of rapidity, transverse momentum and collision centrality, and compared with results in p+p and Au+Au collisions at the same energy. The Cu+Cu data provide greatly improved precision over existing Au+Au data for J/psi production in collisions with small to intermediate numbers of participants, providing a key constraint that is needed for disentangling cold and hot nuclear matter effects.
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