Cross sections and polarization observables for the ⁴⁰Ca(p,n) reaction at 345 MeV and multistep contributions in the continuum

The double-differential cross sections and analyzing powers over an angular range of 30° ≤ θ_lab ≤ 75°, and the induced polarizations P and polarization transfer values D_NN at 30° and 40° for the ⁴⁰Ca(p,n) reaction are measured at a bombarding energy of 345 MeV. The data are compared with theoretical calculations in a semiclassical distorted wave (SCDW) model employing through three- and two-step contributions for cross sections and polarization observables, respectively. At forward angles, the SCDW calculations reproduce the observed cross sections fairly well around the quasielastic peak. The one-step contribution is dominant at θ_lab = 30°, while the two- and three-step contributions become more important with increasing reaction angle. At backward angles the calculations underestimate the cross sections in the whole region, which indicates the significance of higher-step contributions. The D_NN values, which are sensitive to the effective nucleon-nucleon interaction in the nuclear medium, are close to those calculated with the G-matrix interaction parametrized by the Melbourne group.