The E0 transition in pion photoproduction and radiative pion capture on 13C

Abstract

The E0 contribution of the reactions 13C( γ, π −) 13N g.s. as well as 13C( π +, γ) 13N g.s. has been calculated in an extended shell-model space using a nonlocal DWIA framework. A realistic shell-model wave function that includes configurations from the (2s, 1d) as well as the (2p, 1f) shells has been employed for the A = 13 system and leads to a significant suppression of the E0 transition. The large suppression can be understood in terms of the E0 radial integrals over the relevant single-particle densities. A variety of angular distributions demonstrates the good overall agreement with experimental data.