Multiple scattering, theory for pion-nucleus elastic scattering and the in-medium TiN amplitude

Elastic scattering of positive and/or negative pions (pi(+) and/or pi(-)) by nuclei has been studied by means of Glauber's multiple scattering theory (GMST). The differential, total and total elastic cross sections using both the full series expansion and the first order correction (called optical limit results, OLA) of the Glauber amplitude, have been calculated. The in-medium pi N amplitude (sigma(eff)., sigma(eff).) as well as the free pi N one (sigma(free), sigma(free).) are invoked into the full series calculations of the Glauber amplitude and our results were compared with the corresponding experimental data. These calculations are carried out for the elastic collisions, pi(-)- He-2(4) at incident energy 180 MeV, pi(+/-)- Li-3(6) at 240 MeV, pi(-)- C-6(12) at incident energies 180, 200 and 260 MeV, pi(+) - O-8(16) at 240 and 270 MeV and pi(+/-) - Ca-20(40) at energy 292.5 MeV. The comparisons reflect that, except around the minima, the full series calculations with the in-medium pi N amplitude are better in describing the scattering data than those using the free nN one and both are better than the optical limit results.