DVCS amplitude with kinematical twist-3 terms

Abstract

We compute the amplitude of deeply virtual Compton scattering (DVCS) using the calculus of QCD string operators in coordinate representation. To restore the electromagnetic gauge invariance (transversality) of the twist-2 amplitude we include the operators of twist-3 which appear as total derivatives of twist-2 operators. Our results are equivalent to a Wandzura-Wilczek approximation for twist-3 skewed parton distributions. We find that this approximation gives a finite result for the amplitude of a longitudinally polarized virtual photon, while the amplitude for transverse polarization is divergent, i.e., factorization breaks down in this term. However, the divergent part has zero projection onto the polarization vector of the final real photon.

8 pages, Latex; discussion of singularities corrected

References in corpus (2)

• On the Structure of the Virtual Compton Amplitude in the Generalized Bjorken Region: Integral Relations
• Twist decomposition of nonlocal light-cone operators II: General tensors of 2nd rank

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