Systematic Study of Bremsstrahlung Amplitude and a New Model for Bremsstrahlung Calculation.
Abstract
A general parametrization which enables us to construct all possible approximations to the bremsstrahlung amplitude is applied to explore generalizations of existing softphoton approximations. We establish the existence of theoretical ambiguity in defining the softphoton approximations and we show how the bremsstrahlung cross section calculated from a softphoton amplitude depends on the parameters. We also show that if bremsstrahlung spectrum exhibits resonant structure, then the position of this structure K(,(gamma)) and its width (GAMMA)(,(gamma)) can be predicted by either performing the detailed bremsstrahlung calculation or using two simple formulas which relate K(,(gamma)) and (GAMMA)(,(gamma)) directly to the resonant energy E(,R) and the width (GAMMA)(,el) of the resonant structure observed in the elastic scattering cross sections. All approximations have been divided into classes and the following approximations have been systematically studied: (i) The oneenergy oneangle approximation (OEOA), which is the generalized Low's approximation, (ii) the oneenergy twoangle approximation (OETA), which is another version of the generalized Low's approximation, (iii) the twoenergy oneangle approximation (TEOA), which is the generalized FeshbachYennie approximation, and (iv) the twoenergy twoangle approximation (TETA), which is essentially a new approximation for bremsstrahlung calculations. We find that all softphoton amplitudes in the OEOA or OETA fail to adequately describe the protoncarbon bremsstrahlung (p('12)C(gamma)) data near the 1.7MeV or 0.5MeV resonance. These amplitudes predict the values of K(,(gamma)) and (GAMMA)(,(gamma)) which do not agree with the experimental ones. Our study also shows that the limited existing data (which is available only in the soft photon region, K < 200 keV) can be described by many (infinite) softphoton amplitudes in the TEOA. Since these amplitudes in the TEOA can be differentiated at higher photon energies (200 keV < K < 600 keV), a new p('12) C(gamma) experiment is suggested to test these amplitudes so that the best one can be selected. Finally, we develop and test a new twoenergy twoangle 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(,(mu)) = 0. This approximation provides an excellent description of all the available (pi)('(+OR))p(gamma) and the p('12)C(gamma) data by means of a single softphoton approximation. (Abstract shortened with permission of author.).
 Publication:

Ph.D. Thesis
 Pub Date:
 December 1987
 Bibcode:
 1987PhDT........48D
 Keywords:

 Physics: Nuclear