Mechanism of pion double charge exchange atTπ=292 MeV

At 5° and 292 MeV, the A dependence of pion-induced double-charge-exchange cross sections on T=1 targets differs significantly from the $A^{\mathrm{-}10/3}$ behavior expected theoretically. The addition of a second process, whose cross section varies as $A^{\mathrm{-}4/3}$, provides a good fit to the data. The resulting two-amplitude model predicts cross sections for heavier (T>1) nuclei that are in agreement with experiment.