Unifying aspects of polarization of vector mesons from hard production in DIS and at Tevatron

Abstract

Virtual photons have both the transverse and longitudinal polarization. In the inclusive DIS the impact of longitudinal photons, quantified by R=sigmaL/\igmaT sim 0.2, is marginal, but in diffractive DIS with excitation of small mass hadronic states or exclusive diffraction into vector mesons, QCD predicts R >> 1 in agreement with the experiment. After a brief review of the modern status of QCD theory of diffractive vector meson production I argue that longitudinally polarized gluons give rise to a large longitudinal polarization of the prompt JPsi and Psiprim observed at the Tevatron.