Alternative interpretation of structure function

An alternative approach to QCD analysis of the photon structure function is presented. It differs from the conventional one by the presence of terms which in the conventional approach appear in higher orders. We show, that this difference concerns also the photonic parton distribution functions. In the alternative approach, the complete LO analysis of can be performed as all required quantities are known. At the NLO, however, one of the coefficient functions is so far not available and thus only the photonic parton distribution function can be computed and compared to that of the standard approach. We discuss the numerical difference in both approaches in the LO and the NLO approximation and show, that this difference in the case of is non-negligible and may play an important role in the analysis on photon data of future experiments.