Rescattering effects of baryon and antibaryon in heavy quarkonium decays

Rescattering effects of baryon and antibaryon in heavy quarkonium decays are investigated by studying their angular distributions. The rescattering amplitudes are phenomenologically evaluated by modeling the intermediate range interaction as a $\sigma$ or pion meson exchange between $\qqbar$ quarks. The results show that the rescattering effects play an important role in determination of the angular distribution in heavy quarkonium decays. Especially, for $J/psi$ and $\psi'$ decays into $\Lambda \bar \Lambda$, $\Sigma^0\bar \Sigma^0$ and $\Xi^-\bar \Xi^+$ the angular distribution parameters could turn to be negative values in the limit of helicity conservation. These results provide us a possible explanation for understanding the negative sign of the angular distribution parameter measured for $J/psi \to\Sigma^0\bar\Sigma^0$, namely, {\it it might come from the baryonic SU(3)$_F$ symmetry breaking by incorporating rescattering effects