QCD analysis of (p)over-bar-N→γ*π in the scaling limit

We study the scaling regime of nucleon-antinucleon annihilation into a deeply virtual photon and a meson, (p) over barN -> gamma*pi, in the forward kinematics, where vertical bar t vertical bar << Q(2) similar to s. We obtain the leading twist amplitude in the kinematical region where it factorizes into an antiproton distribution amplitude, a short-distance matrix element related to nucleon form factor and the long-distance dominated transition distribution amplitudes which describe the nucleon to meson transition. We give the Q(2) evolution equation for these transition distribution amplitudes. The scaling of the cross section of this process may be tested at the proposed GSI intense antiproton beam facility FAIR with the PANDA or PAX detectors. We comment on related processes such as pi N -> N'gamma(*) and y(*)N -> N'pi which may be experimentally studied at intense meson beams facilities and at JLab or Hermes, respectively. (c) 2005 Elsevier B.V. All rights reserved.