Observation of the Double Isobaric Analog TransitionO18(π+, π−)Ne18at 50 MeV

The angular distribution of the differential cross sections for the transition to the double-isobaric analog state in the reaction ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}({\pi }^{+}, {\pi }^{-}){}_{}{}^{18}{}_{}{}^{}\mathrm{Ne}$ was measured at six angles from 20° to 120°. Extra-polation of the differential cross section results in 5.3±0.5 μb/sr at 0° and an angle-integrated cross section of 16.7±1.2 μb. The forward peaking and magnitude of the cross sections differ from those predicted by simple sequential models and the trends of data at higher energies. The results are compared to recent data for the same transition on ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ at 50 MeV and to a calculation in the six-quark bag model.