1P1 charmonium state decay into p bar p in QCD models including constituent quark mass corrections

Stimulated by the experimental observation, made by the E760 Collaboration at Fermilab, of the 1P1 state of charmonium resonantly formed in p bar p annihilation, we perform a calculation of the decay width for the 1P1→p bar p process. To this end, we employ a phenomenological model which adds constituent quark mass corrections to the usual massless QCD models for exclusive processes. For massless models, in fact, the process under consideration is forbidden by the so-called helicity selection rules, while it is allowed in our extended model. We find Γ(1P1→p bar p) to be in the range 1 endash 10 eV. We also compare our results with previous, indirect estimates, based on QCD multipole expansion models. copyright 1996 The American Physical Society