Pion double charge exchange in the. Delta. sub 33 resonance region

We examine the model dependence and nuclear-structure sensitivity of several {Delta}{sub 33}-dominated processes contributing to pion double charge exchange on nuclei in the region of the {Delta}{sub 33} resonance. These processes include the {Delta}{sub 33}-nucleon interaction {ital V}{sub {ital N}{Delta}} and sequential scattering, in which the pion undergoes single charge exchange on two different nucleons. In all cases, the scattering takes place through the exchange of an intermediate {pi} and {rho} meson. Sequential-mediated double charge exchange is found to be only moderately sensitive to short-range correlations, meson-nucleon form factors, and the rho meson, whereas {ital V}{sub {ital N}{Delta}}-mediated double charge exchange is very sensitive to all these effects. Results are given for double charge exchange on {sup 18}O (double isobaric analog transitions) and {sup 16}O (nonanalog transitions). Sequential double charge exchange is shown to favor non-spin-flip matrix elements of the transition operator whereas {ital V}{sub {ital N}{Delta}}-mediated double charge exchange favors spin-flip matrix elements. The energy dependence of the zero-degree cross sections for {ital V}{sub {ital N}{Delta}} and sequential scattering are also different: Sequential tends to increase monotonically from 100 to 300 MeV, whereas {ital V}{sub {ital N}{Delta}} peaks at about 150 MeV. The delta-nucleon interaction is found likely tomore » dominate over sequential scattering in nonanalog double charge exchange. The {ital V}{sub {ital N}{Delta}} is also large in analog double charge exchange, but it does not enable us to explain the anomalous behavior of the {sup 18}O differential cross sections.« less