Two-nucleon mechanism for antiproton annihilation in nuclei

The annihilation probability of an antiproton inside a nucleus is evaluated via the anti pNN → Nnπ reaction. For that purpose the anti pN → (n+1)π reaction is started from and one of the pions is allowed to be virtual, carrying the appropriate energy and momentum to produce physical particle-hole excitations. The new mechanism proves to be very important: at nuclear densities around ρ = 0.2 ρ0 it has about the same strength as the one-nucleon annihilation mechanism, and becomes much more important as the nuclear density increases. The repercussion of the new channel in the anti p-nucleus annihilation cross section is studied and its relevance in anti p atoms and anti p-nucleus elastic scattering is commented on. (orig.)