When semantics turns to substance: reformulating QCD analysis of F₂^γ(x,Q²)

QCD analysis of F₂^γ is revisited. It is emphasized that the presence of the inhomogeneous term in the evolution equations for quark distribution functions of the photon implies important difference in the way factorization mechanism works in photon-hadron and photon-photon collisions as compared to the hadronic ones. Moreover, a careful definitions of the very concepts of the ``leading'' and ``next-to-leading'' order QCD analysis of F₂^γ are needed in order to separate genuine QCD effects from those of pure QED origin. Starting from such definitions, I present an alternative approach towards the QCD analysis of F₂^γ that differs in some important aspects from the conventional one. In this approach the NLO QCD analysis ofF₂^γ requires the knowledge of two so far uncalculated quantities, and thus is currently impossible to perform. At the LO four known, but in the conventional approach unused quantities are needed. Phenomenological consequences of these differences are discussed.