Gauge invariance of DVCS off an arbitrary spin hadron: the deuteron   target case
  Using twist 3 contributions and the relations, which emanate from the QCD equations of motion, we derive the gauge invariant amplitude for the deeply virtual Compton scattering (DVCS) off hadron with an arbitrary spin. We emphasize that our derivation is not based on a certain parametrization of the relevant hadron matrix elements of the quark(gluon) operators. As an application, we present the gauge invariant amplitude for the DVCS off spin-one hadron. Using the derived gauge invariant amplitude, the single spin asymmetry is discussed. 
I. V. Anikin, R. S. Pasechnik, B. Pire, O. V. Teryaev
hep-ph