A theory of low-energy pion double charge exchange

We propose a theory of sequential charge exchange that describes, for the first time, the general features of the excitation function and the angular distributions of charge exchange on a [sup 14]C target to the isobaric and double isobaric analog states for pion kinetic energies up to 80 MeV. Our theory consists of conventional coupled-channel scattering through important low-lying states. We conclude that exotic contributions to the double charge exchange process must make a relatively small contribution (less than a factor of 2), effectively ruling out a prominent role for dibaryon resonances recently suggested as an explanation for the data.