Diffractive Heavy Quarkonium Photo- and Electroproduction in Qcd

Hard diffractive photoand electroproduction of heavy vector mesons (J/ψ and Υ) is evaluated within the leading αs ln Q2 ΛQCD approximation of QCD. In difference On leave of absence from the St.Petersburg Nuclear Physics Institute, Russia. Now at NeuralWare, a subsidiary of Aspen Technology Inc. Also at St.Petersburg Nuclear Physics Institute, Russia. 1 from our earlier work on that subject, also the production of transversely polarized vector mesons is calculated. Special emphasis is placed on the role of the vector meson’s qq̄ light-cone wave function. In that context, conventional non-relativistic quarkonium models and a light-front QCD bound state calculation are critically examined and confronted with QCD expectations. Our numerical analysis finds a significant high momentum tail in the latter wave functions and a deviation from the expected asymptotic behavior of φV (z, b = 0) ∝ z(1 − z). We then design an interpolation to match the quarkonium models at large inter-quark separations with QCD expectations at small distances. We use these results to compare our predictions for the forward differential cross section of J/ψ photoand electroproduction with recent experimental results from HERA. In addition, our earlier discussion of ρo electroproduction is updated in light of recent experimental and theoretical enhancements.