Pion structure functions at 2 loops: final state interaction with spectator

Abstract

Pion structure functions are considered in the framework of QCD sum rules at the next to leading order. The 2-loop diargam, representing the gluon exchange between the struck quark and spectator, is calculated for space-like pion momentum p^2<0. After Borel transformation we obtain a leading twist correction to the pion structure function, which does not violate Bjorken scaling. Partial results can be used in the calculation of complete set of alpha_s corrections to the pion structure functions, which may serve as an intitial condition in the evolution equation. Probabilistic interpretation of the structure functions is discussed.