Annihilation mechanism in low-energy antideuteron induced nuclear reactions

The annihilation mechanism of the partial, two-step, and one-step simultaneous processes is taken into account in collisions of $\overline{d}$ on target nuclei. The dependence of pion yields on target mass number and incident energy is systematically analyzed.

It is found that the pion momentum spectra from partial and two-step annihilation exhibit a strong dependence on the target nuclei, whereas those from one-step simultaneous annihilation show a relatively weak dependence. With increasing the mass number, the two-step annihilation gradually becomes dominant, accompanied by an increase in pion multiplicity. The pion momentum spectra from the different annihilation mechanism broaden and shift towards to the higher momenta with increasing the incident energy in the reaction of $\overline{d} + ^{12}\text{C}$.