Psi production through three-gluon fusion

We consider a mechanism for psi hadroproduction involving the fusion of a gluon from the beam hadron with two gluons from the target or vice versa. The matrix element is obtained by crossing from the charmonium decay amplitude. A model for the joint distribution function of two gluons in a hadron is constructed based on the counting-rule form for the single-gluon distribution function. Particularly strong effects are found in psi production from heavy nuclei, in agreement with recent experimental results