Regionwise absorption, interaction time, and annihilation cross-section in antiproton-nucleus collision

Summary

The relative importance of different regions of antiproton-nucleus optical potential in generating the total reaction cross-section σ_γ is examined using the method of regionwise absorption as formulated in heavy-ion scattering. We find that the maximum absorption takes place around 1.485×A ^1/3 fm for¹²C and 1.348×A ^1/3fm for⁴⁰Ca atE _lab=46.8 MeV and the absorption peak has a width of about 2.4fm in the case of¹²C and 2.3fm in the case of⁴⁰Ca. Using this method together with the estimate of antiproton mean free path inside the nucleus and the critical distance for$\overline {\text{p}} {\text{ - p}}$ annihilation, it is found that annihilation cross-section contribution to reaction cross-section is expected to be about 50% or more. The time scale involved in$\overline {\text{p}} {\text{ - A}}$ collision is calculated using classical Coulomb-nuclear trajectory and its correlation with the reaction cross-section is examined.