An Interesting Charmonium State Formation and Decay : $p\bar{p}{\to }^1{D}_2{\to }^1{P}_1\gamma$

Abstract

Massless perturbative QCD forbids, at leading order, the exclusive annihilation of proton-antiproton into some charmonium states, which, however, have been observed in the $p\bar{p}$ channel, indicating the significance of higher order and non perturbative effects in the few GeV energy region. The most well known cases are those of the ${}^1{S}_0$ (${\eta }_c$) and the ${}^1{P}_1$. The case of the ${}^1{D}_2$ is considered here and a way of detecting such a state through its typical angular distribution in the radiative decay ${}^1{D}_2\to$ ${}^1{P}_1\gamma$ is suggested. Estimates of the branching ratio $BR{(}^1{D}_2\to p\bar{p})$, as given by a quark-diquark model of the nucleon, mass corrections and an instanton induced process are presented.

Comments: 9 pages (no figures), Plain TeX, CBPF-NF-014/94, INFNCA-TH-94-5