N ¯N S-Wave Elastic Cross Section and Possible Bound States in a Constituent Quark Model

In the framework of a chiral constituent quark model, considering the contributions of π annihilation and one-gluon annihilation, the proton--antiproton s-wave elastic scattering cross section experimental data can be
reproduced by adjusting properly one-gluon annihilation coupling constant. After fixing the model parameters, we perform a dynamical calculation for all possible s-wave nucleon--antinucleon states. The results show that there is no s-wave bound state as indicated by a strong enhancement at threshold of p¯p in J/Ψ and B decay.