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Register a new userPossible solution of the J/psi production puzzle
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We argue that the s-channel cut contribution to J/psi hadroproduction can be significantly larger than the usual cut contribution of the color-singlet mechanism, which is known to underestimate the experimental measurements. A scenario accounting for intermediate $cbar(c)$ interactions is proposed that reproduces the data at low- and mid-range transverse momenta P_T from the Fermilab Tevatron and BNL Relativistiv Heavy Ion Collider. The J/psi produced in this manner are polarized predominantly longitudinally.
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We propose to use transverse momentum $p_T$ distribution of $J/psi$ production at the future Electron Ion Collider (EIC) to explore the production mechanism of heavy quarkonia in high energy collisions. We apply QCD and QED collinear factorization to the production of a $cbar{c}$ pair at high $p_T$, and non-relativistic QCD factorization to the hadronization of the pair to a $J/psi$. We evaluate $J/psi$ $p_T$-distribution at both leading and next-to-leading order in strong coupling, and show that production rates for various color-spin channels of a $cbar{c}$ pair in electron-hadron collisions are very different from that in hadron-hadron collisions, which provides a strong discriminative power to determine various transition rates for the pair to become a $J/psi$. We predict that the $J/psi$ produced in electron-hadron collisions is likely unpolarized, and the production is an ideal probe for gluon distribution of colliding hadron (or nucleus). We find that the $J/psi$ production is dominated by the color-octet channel, providing an excellent probe to explore the gluon medium in large nuclei at the EIC.
We study sub-threshold heavy quarkonium ($J/psi$ and $Upsilon$) photo-productions in $gamma A$ collisions as an independent test of the universality of the nucleon-nucleon short range correlation (SRC) in nuclear scattering processes. Just below the $gamma p$ threshold, the cross section is dominated by the mean field contribution of nucleons inside the nucleus. The SRC contributions start to dominate at lower photon energies, depending on the fraction of the SRC pairs in the target nucleus. We give an estimate of the cross sections in the sub-threshold region both for $J/psi$ and $Upsilon$. This may be helpful for future measurements at JLab as well as at the Electron-Ion Collider in the U.S., and especially in China.
The gluon distributions of the pion obtained from various global fits exhibit large variations among them. Within the framework of the color evaporation model, we show that the existing pion-induced $J/psi$ production data, usually not included in the global fits, can impose useful additional constraints on the pion parton distribution functions (PDFs). In particular, these data can probe the pions gluon densities at large $x$. Existing pion-induced $J/psi$ data covering a broad range of beam momenta are compared with next-to-leading-order QCD calculations using various sets of pion PDFs. It is found that $J/psi$ data measured at forward rapidity and at sufficiently high beam momentum are sensitive to the large-$x$ gluon distribution of pions. The current $J/psi$ data favor the Sutton-Martin-Roberts-Stirling and Gluck-Reya-Vogt pion PDFs, containing significant gluon content at large $x$.
A resonance-like structure, the P_c(4450), has recently been observed in the J/psi p spectrum by the LHCb collaboration. We discuss the feasibility of detecting this structure in J/psi photoproduction in the CLAS12 experiment at JLab. We present a first estimate of the upper limit for the branching ratio of the P_c(4450) to J/psi p. Our estimates, which take into account the experimental resolution effects, predict that it will be possible to observe a sizable cross section close to the J/psi production threshold and shed light on the P_c(4450) resonance in the future photoproduction measurements.
In a recent measurement LHCb reported pronounced structures in the $J/psi J/psi$ spectrum. One of the various possible explanations of those is that they emerge from non-perturbative interactions of vector charmonia. It is thus important to understand whether it is possible to form a bound state of two charmonia interacting through the exchange of gluons, which hadronise into two pions at the longest distance. In this paper, we demonstrate that, given our current understanding of hadron-hadron interactions, the exchange of correlated light mesons (pions and kaons) is able to provide sizeable attraction to the di-$J/psi$ system, and it is possible for two $J/psi$ mesons to form a bound state. As a side result we find from an analysis of the data for the $psi(2S)to J/psi pipi$ transition including both $pipi$ and $Kbar K$ final state interactions an improved value for the $psi(2S)to J/psi$ transition chromo-electric polarisability: $|alpha_{psi(2S)J/psi}|= (1.8pm 0.1)~mbox{GeV}^{-3}$, where the uncertainty also includes the one induced by the final state interactions.
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