Study of the$J/\Psi \to p\bar p\gamma$ and$\Upsilon /(1S) \to p\bar p\gamma$ decays as possible tests of the proton wave function

Abstract

Considering the proton either as a three-quark state with its wave function fulfilling QCD sum rules or as a quark-diquark state with wave function parametrizations that are shown to fitG _M ^P, we study the possibility of discriminating between these two competing pictures by comparing their respective predictions for$J/\Psi \to p\bar p\gamma$ and$\Upsilon (1S) \to p\bar p\gamma$ decays. ForJ/Ψ decay, thep $\bar p$ invariantmass distributions derived from either model are found to be of about the same magnitude, but neither of them is able by itself to reproduce present-day data. Differences between the two pictures may eventually show up in the case of Υ(1S) decay, but the predicted counting rates are small. We also consider some other possible production mechanisms for$p\bar p\gamma$ final states.