Generalized Counting Rule for Hard Exclusive Processes

We derive a generalized counting rule for hard exclusive processes involving parton orbital angular momentum and hadron helicity flip. We start with a systematic way to enumerate the Fock components of a hadronic light-cone wave function with n partons and orbital angular momentum projection lz. We show that the wave-function amplitude ψₙ(xᵢ,k_i⊥,lzi) has a leading behavior 1/(k_⊥²)^[n+|lz|+min(n^'+|lz^'|)]/2-1 when all parton transverse momenta are uniformly large, where n^' and lz^' are the number of partons and orbital angular momentum projection, respectively, of an amplitude that mixes under renormalization. Besides the generalized counting rule, the result can be used as a constraint in modeling the hadronic light-cone wave functions.