QCD factorizations in gamma*gamma*-rho(0)(L)rho(0)(L)

摘要

We calculate the lowest order QCD amplitude, i.e. the quark exchange contribution, to the forward production amplitude of a pair of longitudinally polarized rho mesons in the scattering of two virtual photons gamma(*)(Q(1))gamma(*)(Q(2)) -> rho(0)(L) rho(0)(L). We show that the scattering amplitude simultaneously factorizes in two quite different ways: the part with transverse photons is described by the QCD factorization formula involving the generalized distribution amplitude of two final rho mesons, whereas the part with longitudinally polarized photons takes the QCD factorized form with the gamma(*)(L) -> rho(0)(L) transition distribution amplitude. Perturbative expressions for these, in general, non-perturbative functions are obtained in terms of the rho-meson distribution amplitude. (c) 2006 Elsevier B.V. All rights reserved.