In isospin-conserving theories, pion single and double charge exchange scattering to analog states can be calculated from elastic amplitudes with simple isospin identities. It is shown that elastic amplitudes found by neglecting couplings from the elastic channel and back again cannot be used in these identities without introducing large errors in the total cross sections at some energies. However, the angular shapes are dominated by geometric effects, and are correctly predicted.

NUCLEAR REACTIONS Pion single and double charge exchange scattering calculations. Limitations on use of approximate elastic amplitudes.

• Received 20 March 1980

DOI:https://doi.org/10.1103/PhysRevC.22.2497