QCD analysis of pbar N →γ∗ π in the scaling limit

We study the scaling regime of nucleon-antinucleon annihilation into a deeply virtual photon and a meson, pbar N →γ^∗ π, in the forward kinematics, where | t | ≪Q² ∼ 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 Q² 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 πN →N^‧γ^∗ and γ^∗ N →N^‧ π which may be experimentally studied at intense meson beams facilities and at JLab or Hermes, respectively.