The polarized photon structure function $g_1^{\gamma }(x,Q^2)$ in massive parton model in NLO

Abstract

We investigate the one-gluon-exchange ($\alpha {\alpha }_s$) corrections to the polarized real photon structure function $g_1^{\gamma }(x,Q^2)$ in the massive parton model. We employ a technique based on the Cutkosky rules and the reduction of Feynman integrals to master integrals. The NLO contribution is noticeable at large $x$ and does not vanish at the threshold of the massive quark pair production due to the Coulomb singularity. It is found that the first moment sum rule of $g_1^{\gamma }$ is satisfied up to the NLO.

Comments: 11 pages, 4 figures; An overall sign of the NLO contribution has been changed. Fig.3 and 4 were replaced by the new ones. As a result, the first sentence in the paragraph just below Eq.(14) was corrected. The minus sign was inserted into the r.h.s of the equation for delta just below Eq.(15). The conclusions are unchanged