N̄N annihilation at low energies in a quark rearrangement model and decay widths of N̄N bound states

Using N̄N annihilation data at rest, we make a quark rearrangement model for annihilation into three mesons. This model describes the decay branching ratios of the p̄p and p̄n annihilations at rest satisfactorily. With this model we find considerable dependence of the annihilation on the isospin and spin of the initial N̄N system. By calculating the energy dependence due to the phase space of three mesons, we extend the model in the energy range E_c.m.. = 1400 MeV-2300 MeV where E_c.m. is the total energy in the c.m.s. We find the strong energy dependence of the annihilation, with the annihilation probability below the N̄N threshold reduced drastically, compared to that at threshold. Based on the result for the quantum number and energy dependence, we discuss the possibility of the existence of N̄N bound states with narrow decay widths.