Systematic study of bremsstrahlung amplitude and a new model for bremsstrahlung calculation

A general parameterization which enables them to construct all possible approximations to the bremsstrahlung amplitude is applied to explore generalizations of existing soft-photon approximations. They establish the existence of theoretical ambiguity in defining the soft-photon approximations and they show how the bremsstrahlung cross section calculated from a soft-photon amplitude depends on the parameters. They also show that if bremsstrahlung spectrum exhibits resonant structure, then the position of this structure K/sub γ/ and its width Gamma/sub γ/ can be predicted by either performing the detailed bremsstrahlung calculation or using two simple formulas which relate K/sub γ/ and Gamma/sub γ/ directly to the resonant energy E/sub R/ and the width Gamma/sub el/ of the resonant structure observed in the elastic scattering cross sections. They develop and test a new two-energy two-angle approximation for describing bremsstrahlung processes. The natural choice of kinematic variables leads to the situation in which the second term of the amplitude vanishes, B/sub μ/ = 0. This approximation provides an excellent description of all the available π/sup +/-/ pγ and the p12Cγ data by means of a single soft-photon approximation