Systematics of continuum pion double charge exchange on T=0 nuclei

Pion double-charge-exchange cross sections have been measured at forward angles for targets of C12, Mg24, Si28, S32, and Ca40 at incident pion energies of 120210 MeV. Angular distributions were obtained at 164 MeV for the lightest (12C) and heaviest (40Ca) targets. Pions corresponding to excitation energies up to 25 MeV in the final nuclei have been detected. Double differential cross sections d2/d dE are presented and the dependence on target mass, incident pion energy, excitation energy, and scattering angle has been investigated. The summed cross sections show a much smoother energy dependence than the ground state transition and mass dependence as Ap, with p varying with excitation energy rougly from -2 to -1. The excitation functions for the discrete nonanalog transitions to the first 2+ state in 12O and 40Ti have been measured.