Nuclear annihilation by antinucleons

We examine the momentum dependence of $\bar p$$p$ and $\bar n$$p$ annihilation cross sections by considering the transmission through a nuclear potential and the $\bar p p$ Coulomb interaction. Compared to the $\bar n p$ annihilation cross section, the $\bar p p$ annihilation cross section is significantly enhanced by the Coulomb interaction for projectile momenta below $p_{\rm lab} <$ 500 MeV/$c$, and the two annihilation cross sections approach the Pomeranchuk's equality limit [JETP Lett. {\bb 30}, 423 (1956)] at $p_{\rm lab}\sim 500$ MeV/$c$. Using these elementary cross sections as the basic input data, the extended Glauber model is employed to evaluate the annihilation cross sections for $\bar n$ and $\bar p$ interaction with nuclei and the results compare well with experimental data.