Paris N N ¯ potential constrained by recent antiprotonic-atom data and n ¯ p total cross sections

We report on an updated Paris NN optical potential. The long- and intermediate-range real parts are obtained by G-parity transformation of the Paris NN potential based on a theoretical dispersion-relation treatment of the correlated and uncorrelated two-pion exchange. The short-range imaginary potential parametrization results from the calculation of the NN annihilation box diagram into two mesons with a nucleon-antinucleon intermediate state in the crossed channel. The parametrized real and imaginary short range parts are determined by fitting not only the existing experimental data included in the 1999 version of the Paris NN potential, but also the recent antiprotonic-hydrogen data and np total cross sections. The description of these new observables is improved. Only this readjusted potential generates an isospin zero {sup 1}S{sub 0}, 52 MeV broad quasibound state at 4.8 MeV below the threshold. Recent BES data on J/{psi} decays could support the existence of such a state.