Pion scattering on medium-weight nuclei and distortion effects in double charge exchange reactions

An eikonal version of the DWIA is used to compute absorption and dispersion effects on the cross section for double charge exchange to its double analogue. Lacking information on the π?⁵¹V optical potential, recent data on π?⁴⁰ Ca elastic scattering have been analyzed in the Glauber approximation and the extracted elastic phase function has been scaled up to correspond to ⁵¹V. The result is used in a computation of the DWIA amplitude. Large reduction factors are obtained in agreement with experimental upper bounds. Discrepancies with previous estimates are discussed.