Analysis of threshold (p,π0) reactions

A procedure is derived for analyzing ( p,π0) reactions near threshold where pions are present in only s- and p-wave states. The pions, which decay into two gammas, have an angular distribution in the center of mass which can be correlated to the angular distribution of its decay gammas in the laboratory. Functions are calculated which give the laboratory distribution of both gammas in terms of parameters describing the angular distribution of pions in the center of mass. By fitting these functions to the observed gamma distribution, the pion differential cross section is determined