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Wandzura-Wilczek approximation for the twist-3 DVCS amplitude

N. Kivel·M. V. Polyakov·A. Schafer·O. V. Teryaev
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Abstract

We present a derivation of Wandzura-Wilczek (WW) like relations for skewed parton distributions. It is demonstrated for photon-pion scattering that the skewed twist-3 parton distributions contributing to the DVCS amplitude have discontinuities at the points $x=\pmξ$ in the WW approximation. This may lead to a violation of factorisation for the twist-3 DVCS amplitude with transverse polarization of the virtual photon. We show, however, that the contribution of the divergencies to the scattering of a transversely polarized 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 polarized photon the twist-3 amplitude is free of such divergencies.

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N. Kivel, M. V. Polyakov, A. Schafer, O. V. Teryaev. 2000-10-31. Wandzura-Wilczek approximation for the twist-3 DVCS amplitude. https://doi.org/10.1016/s0370-2693(00)01313-7

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