Deeply virtual Compton scattering beyond next-to-leading order: The flavor singlet case

We study radiative corrections to deeply virtual Compton scattering in the kinematics of HERA collider experiments to next-to-leading and next-to-next-to-leading order. In the latter case the radiative corrections are evaluated in a special scheme that allows us to employ the predictive power of conformal symmetry. As observed before, the size of next-to-leading order corrections strongly depends on the gluonic input, as gluons start to contribute at this order. Beyond next-to-leading order we find, in contrast, that the corrections for an input scale of few GeV2 are small enough to justify the uses of perturbation theory. For ξ≳5×10−3 the modification of the scale dependence is also small. However, with decreasing ξ it becomes moderate or even large.