Pion double charge exchange on O 16 at T π =300–500 MeV

Measurements of small-angle cross sections for the pion double-charge-exchange (DCX) reaction $^{16}\mathrm{O}$(${\mathrm{\ensuremath{\pi}}}^{+}$,${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$${)}^{16}$Ne (g.s.) at incident energies of 300\char21{}500 MeV are reported. These are the first measurements of DCX cross sections on a T=0 nucleus in this energy region. The behavior of the cross sections is similar to that of analog transitions, but they are smaller by more than an order of magnitude. This suggests sequential charge-exchange scattering as the dominant process, but suppressed by a mechanism not yet identified.