NRQCD factorization for twist-2 light-cone wave-functions of charmonia

We show that the twist-2 light-cone wave-functions of eta(c) and J/psi can be factorized with nonrelativistic QCD (NRQCD) at the one-loop level, where the nonperturbative effects are represented by NRQCD matrix elements. In quarkonium at rest the c- or (c) over bar -quark moves with a small velocity v. The factorization is achieved by expanding the small velocity v. To the leading order of v, the twist-2 light-cone wave-functions of eta(c) and J/psi can be factorized as the product of a perturbative function and an NRQCD matrix element. The perturbative function is calculated at the one-loop level and is free from any soft divergences. Our results can be used for exclusive productions of quarkonia, which are studied in an experiment with two B-factories. (c) 2007 Elsevier B.V. All rights reserved.