title: Generalized counting rule for hard exclusive processes.
abstract: 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 l(z). We show that the wave-function amplitude psi(n)(x(i),k(i perpendicular ),l(zi)) has a leading behavior 1/(k(2)( perpendicular ))[n(+|l(z)|+min(n(')+|l(')(z)|)]/2-1) when all parton transverse momenta are uniformly large, where n(') and l(')(z) 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.
authors.affiliation: Department of Physics, University of Maryland, College Park, Maryland 20742, USA.
authors.forename: Xiangdong
authors.initials: X
authors.lastname: Ji
authors.forename: Jian-Ping
authors.initials: JP
authors.lastname: Ma
authors.forename: Feng
authors.initials: F
authors.lastname: Yuan