Second-order QCD analysis of the photon structure function

The QCD predictions for the photon structure function are reexamined with particular emphasis on the small-x behavior. A simple parametrization of the real photon structure function, free of 1/x singularity, is derived. The structure function is found to be sensitive at small x to the non-perturbatively calculable constant term in the n = 2 moment, and we show that the problem of a negative structure function can be solved on the basis of the knowledge of this single non-perturbative parameter.