Near threshold enhancement of thepp¯mass spectrum inJ/Ψdecay

Abstract

We investigate the nature of the near-threshold enhancement in the pp invariant-mass spectrum of the reaction J/{psi}{yields}{gamma}pp reported recently by the BES Collaboration. Using the Juelich NN model we show that the mass dependence of the pp spectrum close to the threshold can be reproduced by the S-wave pp final state interaction in the isospin I=1 state within the Watson-Migdal approach. However, because of our poor knowledge of the NN interaction near-threshold and of the J/{psi}{yields}{gamma}pp reaction mechanism and in view of the controversal situation in the decay J/{psi}{yields}{pi}{sup 0}pp, where no obvious signs of a pp final state interaction are seen, explanations other than final state interactions cannot be ruled out at the present stage.