Wandzura-Wilczek approximation for the twist-3 DVCS amplitude

We present a derivation of Wandzura-Wilczek (WW) like relations for skewed parton distributions. It is demonstrated for photon-pion scattering that th e skewed twist-3 parton distributions contributing to the DVCS amplitude ha ve discontinuities at the points x = +/-xi in the WW approximation. This ma y lead to a violation of factorisation for the twist-3 DVCS amplitude with transverse polarization of the virtual photon. We show, however, that the c ontribution of the divergencies to the scattering of a transversely polariz ed virtual photon affects DVCS observables only at order 1/Q(2) and can be neglected at twist-3 accuracy. For the scattering of a longitudinally polar ized photon the twist-3 amplitude is free of such divergencies. (C) 2001 Pu blished by Elsevier Science B.V.