The strong, electromagnetic and mixed strong-electromagnetic amplitudes of the $psi(2S)$ decays into baryon-anti-baryon pairs have been obtained by exploiting all available data sets in the framework of an effective Lagrangian model. We observed that at the $psi(2S)$ mass the QCD regime is not completely perturbative, as can be inferred by the relative strength of the strong and the mixed strong-electromagnetic amplitudes. Recently a similar conclusion has been reached also for the $J/psi$ decays. The relative phase between the strong and the electromagnetic amplitudes is $varphi = (58pm 8)^circ$, to be compared with $varphi = (73pm 8)^circ$ obtained for the $J/psi$. On the other hand, in the case of the $psi(2S)$ meson, different values of the ratio between strong and mixed strong-electromagnetic amplitudes are phenomenologically required, while for the $J/psi$ meson only one ratio was enough to describe the data. Finally, we also observed a peculiar behavior of the mixed strong-electromagnetic amplitudes of the decays $psi(2S)toSigma^+ overline Sigma{}^-$ and $psi(2S)toSigma^- overline Sigma{}^+$.
تحميل البحث