Associated charmonium production in low energy p(p)over-bar annihilation

The QCD mechanisms underlying the exclusive strong decays and hadronic production amplitudes of charmonium remain poorly understood, despite decades of study and an increasingly detailed body of experimental information. One set of hadronic channels of special interest are those that include baryon-antibaryon states. These are being investigated experimentally at BES and CLEO-c in terms of their baryon resonance content, and are also of interest for the future PANDA experiment, in which charmonium and charmonium hybrids will be produced in p (p) over bar annihilation in association with light mesons. In this paper we develop a simple initial-state light meson emission model of the near-threshold associated charmonium production processes p (p) over bar ->pi(0)Psi, and evaluate the differential and total cross sections for these reactions in this model. (Here we consider the states Psi=eta(c), J/psi, psi('), chi(0) and chi(1).) The predicted near-threshold cross section for p (p) over bar ->pi(0)J/psi is found to be numerically similar to two previous theoretical estimates, and is roughly comparable to the (sparse) existing data for this process. The theoretical charmonium angular distributions predicted by this model are far from isotropic, which may be of interest for PANDA detector design studies.