Application of the approximate four body equations to description of the elastic scattering and charge exchange of pions by 3He nucleus

In the framework of the approximate four body equations the elastic scattering and charge-exchange of pions on 3He nucleus in the 68-208 MeV pion energy range is investigated. These equations differ from the description within the optical model with the first-order optical potential in two aspects. The equations are derived without the impulse approximation. The rescattering of pions on nucleus is taken into account in all orders. Basic equations are derived. The strong dependence of the obtained cross sections of elastic scattering on the form of parametrization of the elementary πN interaction indicates the necessity of a more thorough study of π-nuclear cross sections as functions of the off-mass-shell behaviour of elementary πN amplitudes. The energy dependence of the charge-exchange cross section at the fixed scattering angle 115 deg displays a more sharp decrease with increasing energy than that observed experimentally