The hadronic and point-like contributions to the F2 photon structure function in perturbative QCD

A detailed discussion is given of the hadronic and point-like contributions to the F2 photon structure function (F2γ) in both the naive parton model and QCD. The non-singlet part of the leading order solution, first found by Witten, is re-derived using the QCD improved parton model, enabling the hadronic and point-like terms to be clearly identified and correlated with observed jet structure in the final state. When important non leading-log terms are included, the sensitivity of the solution to Λ is found to be weak for all Q2 values, and the all orders solution to be well approximated by the O(αs2) solution. The approximations made in deriving the leading order solution are critically examined, and an approach enabling more quantitative test of QCD to be made from measurements of the point-like (perturbative) component of F2γ is suggested. (orig.)