Anomalous magnetic moment contributions to NN bremsstrahlung in the soft-photon approximation

The soft photon approximation (SPA), which is relativistic and based upon a fundamental theorem for photon emission, is applied to explore two separate nucleon-nucleon bremsstrahlung (NNγ) processes: ppγ and npγ. They are examined together in an effort to understand the mechanism which governs photon emission from these basic two-nucleon systems. In this investigation we focus upon the effect of the anomalous magnetic moments of the proton (κp) and the neutron (κn). In our SPA calculation we use the standard Low amplitude MμLow as derived by Nyman plus the more recently developed amplitude MμTuTts, referred to as the two-u-two-t special (TuTts) amplitude. The amplitude MμTuTts is identical to the amplitude MμLow through order K0 in the soft-photon expansion. However, MμTuTts includes an additional term Mμ(3)(K1; κ) (plus higher order terms). The term Mμ(3)(K1; κ) is of order K1 in the soft-photon expansion and it is a function of κp and κn. Using the amplitudes MμTuTts and MμLow, we have calculated ppγ and npγ cross sections as a function of photon angle ψγ with and without contributions from κp and κn. Comparison with available ppγ data has been made; in particular, the contribution from Mμ(3)(K1; κ) has been investigated. Results will be presented and discussed which relate to the following: (i) The anomalous magnetic moment effect is significant in ppγ; however, it is small in npγ. That is, the two amplitudes MμTuTts and MμLow yield very similar npγ cross sections, but they predict very different ppγ cross sections. (ii) MμTuTts appears to provide a better SPA than MμLow in the case of ppγ. Because κp terms dominate the ppγ cross section, the contribution from Mμ(3)(K1; κ) is important. Clearly, Mμ(3)(K1; κ) makes a significant difference. (iii) The reason why MμTuTts and MμLow predict similar npγ cross sections will be analyzed and discussed