Exclusive quarkonium production or decay in soft gluon factorization.

In this paper, we study the application of the recently proposed soft gluon factorization (SGF) to exclusive quarkonium production or decay. We find that in the nonrelativistic QCD factorization framework there are too many nonperturbative parameters. Thanks to the factorization of kinematical physics from dynamical physics, the SGF significantly reduces the number of nonperturbative parameters. Therefore, the SGF can improve our predictive power of exclusive quarkonium production or decay. By applying to η_c + γ production at B-factories, our result is the closest one to data among all theoretical calculations. [ABSTRACT FROM AUTHOR]