Hard diffractive electroproduction of heavy flavor vector mesons in QCD

We outline QCD predictions for the diffractive electroproduction of heavy flavor vector mesons and compare them with available data. ∗On leave of absence from the St.Petersburg Nuclear Physics Institute, Russia. Supported by BSF Grant No. 9200126 1 Diffractive electroproduction of heavy flavor vector mesons in QCD It has been understood recently that at sufficiently large Q diffractive electroproduction of vector mesons is calculable in QCD [1]. The necessary conditions are: i) 1 2mNx should be much larger than the radius of the target so that the photon transforms predominantly into a quark component well before the target; ii) high Q is a necessary but not sufficient condition to guarantee small interquark distances in the quark component of the wave function of the projectile photon, and thus enables the applicability of the assumption of asymptotic freedom; iii) the initial photon should be longitudinally polarized to ensure the smallness of the produced quark configuration when it arrives at the target. Another potentially fruitful handle to guarantee the smallness of the interquark distances in the wave function of the photon is the large mass of the heavy quark (mq → ∞). M.Ryskin [2] suggested that the large mass of the c quark is a sufficient condition for the applicability of pQCD for the production of c quarks in the with a proton target and to ensure the applicability of the charmonium model to describe the light–cone wave function of the produced J/ψ meson. When the momentum transferred to the targett tends to zero, the cross section for the hard diffractive electroproduction of J/Ψ through the interaction of a longitudinally polarized photon with a target proton at sufficiently large Q has the form in QCD [1]: dσ p→V p L dt ∣