Near threshold enhancement of the pp̅ mass spectrum in J/Ψ decay

Abstract

We investigate the nature of the near-threshold enhancement in the pp̅ invariant-mass spectrum of the reaction J/Ψ→γpp̅ reported recently by the BES Collaboration. Using the Jülich NN̅ model we show that the mass dependence of the pp̅ spectrum close to the threshold can be reproduced by the S-wave pp̅ final state interaction in the isospin I=1 state within the Watson-Migdal approach. However, because of our poor knowledge of the NN̅ interaction near-threshold and of the J/Ψ→γpp̅ reaction mechanism and in view of the controversal situation in the decay J/Ψ→π0pp̅ , where no obvious signs of a pp̅ final state interaction are seen, explanations other than final state interactions cannot be ruled out at the present stage.