Existence of two higher L=0 bound states of the dipositroniums

Symmetry has imposed very strong constraints on the internal structure of q uantum mechanical system. In particular, whether a state can access a given outgoing channel is constrained by symmetry. For the dipositroniums, the m ost important channel is the Ps-Ps channel. However, based on symmetry cons ideration it was found that only a few excited states are allowed to access the Ps-Ps channel, thereby at least the existence of two higher L = 0 boun d states (higher than the Ps-Ps threshold) has been affirmed.