Nuclear-structure aspects of nonanalog pion double charge exchange

The sensitivity of pion double charge exchange to nuclear structure in the shell model is examined. We consider the nonanalog ground-state to ground-state (T=0 to T=2) transitions on a variety of nuclear targets. The reaction model, which assumes that double charge exchange is driven by a π+ρ-meson–mediated, ${\Delta }_{33}$-nucleon interaction, reproduces the energy dependence and shape of the empirical cross section for all the (${\pi }^{+}$,${\pi }^{\mathrm{-}}$) transitions examined. The magnitude of the cross section is particularly sensitive to collectivity in the nuclear wave functions. All parameters of the model, with the exception of the range of the meson-${\Delta }_{33}$ form factor, are fixed by theoretical arguments. The form factor is then determined by normalizing to the ${}_{}{}^{16}{}_{}{}^{}$O(${\pi }^{+}$,${\pi }^{\mathrm{-}}$)${}^{16}$ Ne cross section. Predictions are made for a variety of other low-lying $0^{+}$ transitions.