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Register a new userStudy of $J/psi$ production in jets
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The production of $J/psi$ mesons in jets is studied in the forward region of proton-proton collisions using data collected with the LHCb detector at a center-of-mass energy of 13 TeV. The fraction of the jet transverse momentum carried by the $J/psi$ meson, $z equiv p_{rm T}(J/psi)/p_{rm T}({rm jet})$, is measured using jets with $p_{rm T}({rm jet}) > 20$ GeV in the pseudorapidity range $2.5 < eta({rm jet}) < 4.0$. The observed $z$ distribution for $J/psi$ mesons produced in $b$-hadron decays is consistent with expectations. However, the results for prompt $J/psi$ production do not agree with predictions based on fixed-order non-relativistic QCD. This is the first measurement of the $p_{rm T}$ fraction carried by prompt $J/psi$ mesons in jets at any experiment.
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Data are presented on the reaction J/psi--> p pbar eta using 7.8 million J/psi triggers collected by the BEjing Spectrometer (BES). A partial wave analysis is performed. A clear enhancement near the p eta(pbar eta) threshold is observed. It is fitted with a JP=1/2- resonance with mass $M= 1530pm 10$ MeV and width $Gamma = 95pm 25$ MeV. In addition, there is a peak around 1650 MeV with JP=1/2- preferred also, fitted with $M =1647pm 20$ MeV and $Gamma = 145^{+80}_{-45}$ MeV. These two N* resonances are believed to be the two well established states, S11(1535) and S11(1650), respectively. It is the first partial wave study of the production of these resonances from J/psi decays.
We present Monte Carlo preliminary results about the feasibility to detect the Chic family in p-p collisions at 14 TeV in the ALICE Central Barrel at CERN LHC. The Chic1 and Chic2 were forced to decay in the channel J/Psi + gamma -> e+ e- + gamma and were merged with a proton-proton non-biased collision. After MonteCarlo transport and simulation of the detector response, the e+, e- and converted gamma were reconstructed and identified in the ALICE ITS, TPC and TRD detectors. Separate signals corresponding to gamma from Chic1 and from Chic2 were observed. The position and relative weight of the fit to gaussians agreed with the input values within the statistical limits. Similar studies will be done for Pb-Pb collisions.
We report results on J/psi-hadron azimuthal angular correlations in 200 GeV p+p collision in the STAR experiment at RHIC. The extracted B-hadron feed-down contribution to inclusive J/psi yield is found to be 10-25% in 4<p_T<12 GeV/c and has no significant center-of-mass energy dependence from RHIC to LHC. The p_T spectrum of charged hadron associated with high-p_T J/psi triggers on the away side is found to be consistent with that from di-hadron correlations. J/psi signal from partially produced Au+Au 39 GeV data will also be presented to demonstrate STARs J/psi capability at RHIC low energy run.
The J/psi is considered to be among the most important probes for the deconfined quark gluon plasma (QGP) created by relativistic heavy ion collisions. While the J/psi is thought to dissociate in the QGP by Debye color screening, there are competing effects from cold nuclear matter (CNM), feed-downs from excited charmonia (chi_c and psi) and bottom quarks, and regeneration from uncorrelated charm quarks. Measurements that can provide information to disentangle these effects are presented in this paper.
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