  
|
     
|
The European Physical Journal C
ISSN: 1434-6044 (printed version)
ISSN: 1434-6052 (electronic version)
Abstract Volume 2 Issue 4 (1998) pp 705-719
DOI 10.1007/s100529800716
theoretical physics:
Higher Fock states and power counting in exclusive $P$-wave quarkonium decays
Jan Bolz (1) (a), Peter Kroll (1), Gerhard A. Schuler (2) (b)
(1) Fachbereich Physik, Universität Wuppertal, D-42097 Wuppertal, Germany (e-mail: kroll@theorie.physik.uni-wuppertal.de)
(2) Theory Division, CERN, CH-1211 Geneva 23, Switzerland (e-mail: Gerhard.Schuler@cern.ch)
Received: 25 April 1997 / Published online: 20 February 1998
Abstract. 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 $|{\rm Q}\bar{\rm Q}{\rm g}\rangle$ 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 $\chi_{{\rm c} J}$ decays into pairs of pions, kaons, and etas. We also comment on $J/\psi$ decays into two pions.
(a) Supported by Deutsche Forschungsgemeinschaft
(b) Heisenberg Fellow
Article in PDF-Format
Article in (gzipped) PS-Format
Online publication: May 25, 1998
LINK Helpdesk
© Springer-Verlag Berlin Heidelberg 1998