Next-to-leading order mass effects in QCD Compton process of polarized DIS

A lot of articles dedicated to NLO QCD corrections to polarized DIS have been published. Calculations in most of them are performed in an assumption that the quark mass is equal to zero (see [1, 2, 3, 4, 5, 6, 7] and review [8]). However there are some works when authors estimate a finite quark mass effect for both unpolarized [9] and polarized structure functions [10, 11, 12, 13, 14, 15, 16]. The main difference of these two approaches is the method of tending the quark mass to zero and the procedure of integration of the squared matrix element over the phase space of emitted gluon. In the massless approsch a fermion mass is equal to zero before the integration while in the massive one this quantity goes to zero after the integration and survives only in LO terms. Notice that QCD and QED radiative corrections (RC) having different origins possess some common features on the one-loop level. If our consideration is restricted to so-called QCD Compton process then both corrections should be described by the identical sets of Feynman graphs. The transition from the strong radiative effects to the electromagnetic ones could be performed by the following replacement: 4 3 αs → e2qαQED. (1)