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We consider the J/psi photo-production data collected at HERA in the light of next-to-leading order predictions for the color-singlet yield and polarization. We find that, while the shapes of inclusive distributions in the transverse momentum and inelasticity are well reproduced, the experimental rates are larger than those given by the color-singlet contribution alone. Furthermore, the next-to-leading order calculation predicts the J/psis to be mostly longitudinally polarized at high transverse momentum in contrast with the trend of the preliminary data from the ZEUS collaboration.
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We consider J/Psi meson production in $ep$ deep inelastic scattering in the colour singlet model using the k_T-factorization QCD approach. We investigate the z-, Q^2-, p_T^2-, y^*- and W-dependences of inelastic J/Psi production on different forms of the unintegrated gluon distribution. The p_T^2- and Q^2-dependences of the J/Psi spin aligment parameter alpha are presented also. We compare the theoretical results with recent experimental data taken by the H1 and ZEUS collaborations at HERA. It is shown that experimental study of the polarization J/Psi mesons at Q^2 < 1 {GeV}^2 is an additional test of BFKL gluon dynamics.
The associated production of J/psi + gamma at the LHC is studied within the NRQCD framework. The signal we focus on is the production of a J/psi and an isolated photon produced back-to-back, with their transverse momenta balanced. It is shown that even for very large values of transverse momentum (pT of the order of 50 GeV) the dominant contribution to this process is not fragmentation. This is because of the fact that fragmentation-type contributions to the cross-section come from only a q q(bar) initial state, which is suppressed at the LHC. We identify gg-initiated diagrams higher-order in alpha(s) which do have fragmentation-type vertices. We find, however, that the contribution of these diagrams is negligibly small.
We study inclusive $J/psi$ photoproduction at NLO at large $P_T$ at HERA and the EIC. Our computation includes NLO QCD leading-$P_T$ corrections, QED contributions via an off-shell photon as well as those from $J/psi$+charm channels. For the latter, we employ the variable-flavour-number scheme. Our results are found to agree with the latest HERA data by H1 and provide, for the first time, a reliable estimate of the EIC reach for such a measurement. Finally, we demonstrate the observability of $J/psi$+charm production and the sensitivy to probe the non-perturbative charm content of the proton at high $x$, also known as intrinsic charm, at the EIC.
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.
We quantify perturbative and non-perturbative QCD effects in the exclusive $J/psi$-photoproduction cross section, and in the shrinkage of the differential cross section with respect to momentum transfer, $t$. We predict that in the high energy THERA region there will always be a significant contribution to this process that rises quickly with energy. This implies that the taming of the rise of the cross section with energy, due to both the expansion of spatially-small fluctuations in the photon and to higher twist effects, is rather gradual.
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