Refined analysis of photon leptoproduction off a spinless target

We calculate the differential cross section for real-photon electroproduction off a spinless hadron which serves as a main probe of the hadrons structure via the concept of generalized parton distributions. Compared to previously available computations performed with twist-three power accuracy, we exactly accounted for all kinematical effects in hadron mass and momentum transfer which arise from leptonic helicity amplitudes. We performed numerical studies of these kinematical effects and demonstrated that in the valence quark region and rather low virtualities of the hard photon which sets the factorization scale, the available approximate results significantly overestimate the cross section rates in comparison to exact formulas.