Higher Fock states and power counting in exclusive P-wave quarkonium decays
Jan Bolz1 - Peter Kroll1 - Gerhard A. Schuler2
1 Fachbereich Physik, Universität Wuppertal,
D-42097 Wuppertal, Germany (e-mail:
2 Theory Division, CERN, CH-1211 Geneva 23, Switzerland (e-mail: Gerhard.Schuler@cern.ch)
Received: 25 April 1997 / Published online: 20 February 1998
Exclusive processes at large momentum transfer Q factor into perturbatively calculable short-distance parts and long-distance hadronic wave functions. Usually, only contributions from the leading Fock states have to be included to leading order in 1/Q. We show that for exclusive decays of P-wave quarkonia the contribution from the next-higher Fock state contributes at the same order in 1/Q. We investigate how the constituent gluon attaches to the hard process in order to form colour-singlet final-state hadrons and argue that a single additional long-distance factor is sufficient to parametrize the size of its contribution. Incorporating transverse degrees of freedom and Sudakov factors, our results are perturbatively stable in the sense that soft phase-space contributions are largely suppressed. Explicit calculations yield good agreement with data on decays into pairs of pions, kaons, and etas. We also comment on decays into two pions.