Intrinsic charm contribution to double quarkonium hadroproduction

Double Jψ production has been observed by the NA3 collaboration in πN and pN collisions with a cross section of the order of 20–30 pb. The ψψ pairs measured in π− nucleus interactions at 150 and 280 GeV/c are observed to carry an anomalously large fraction of the projectile momentum in the laboratory frame, xψψ >- 0.6 at 150 GeV/c and >- 0.4 at 280 GeV/c. We postulate that these forward ψψ pairs are created by the materialization of Fock states in the projectile containing two pairs of intrinsic cc quarks We calculate the overlap of the charmonium states with the |udcccc〉 Fock state as described by the intrinsic charm model and find that the π− N → ψψ longitudinal momentum and invariant mass distributions are both well reproduced. We also discuss double Jψ production in pN interactions and the implications for other heavy quarkonium production channels in QCD.