Pion Double Charge Exchange Formalism

We have investigated the behavior of an operator responsible for sequential pion double charge exchange (DCX) on nuclei in the plane wave limit for studying the spatial short-range correlation. The DCX cross sections were calculated for Ca isotopes and ^{14}C up to 300 MeV of energy using shell and seniority models. The operator is then modified. The effects of these modifications to the operator have been investigated at low energy where a resonance like structure in the energy dependence has been observed. These modifications include the pion true absorption to the pion optical potential. The other effect is the removal of the delta function from the DCX amplitude in its pp part which originated from the idea of point -like pion-nucleon coupling. These corrections have been studied in the plane wave limit and distorted wave run in the plane wave mode. These results agree with each other. The calculated DCX cross sections for Ca isotopes and ^{14}C using two single charge exchange (SCX) scatterings steps of the valence nucleons with different values of pion nucleon range (alpha) have been compared with observed data.