Paper detail

Direct vs. resolved photon: an exercise in factorization

Direct and resolved photon interactions are shown to be intimately related through the factorization mechanism. It is argued that in theoretically consistent analysis of jet production in $γ$p and ep collisions the LO resolved $γ$ contribution must be considered together with the NLO direct $γ$ component. Recent data from HERA therefore do not provide a direct evidence for the former component, but should rather be interpreted as a manifestation of the $O(αα_s^2)$ term in $γ$p and, via the Weizsäcker-Williams approximation, in ep interactions.