Relativistic effects in proton-proton bremsstrahlung

Abstract

The pp y reaction at intermediate energies is investigated using a modern relativistic meson-exchange potential model. Both the single-scattering and rescattering terms are treated including relativistic corrections. It is shown that for energetic photons in the region near the end-point energy the relativistic spin correction is very large and reduces the ppy cross section by a factor of -2. This large correction is dynamical in origin and can be traced in a very simple way to the strong energy dependence of the So state contribution. It is also shown that, under these kinematical conditions, the rescattering term reduces the cross section, which amplifies the relativistic effects on the ppy reaction. For the kinematical conditions of the recent TRIUMF experiment at Ti,b =280 MeV the rescattering contribution enhances the cross section and reduces the discrepancy between the data and the calculation. PACS number(s): 25.20. Lj, 25.10.+s

Nucleon-nucleon potentials and their test with bremsstrahlung

“…1 and 2 for the smallest proton angles available in the TRIUMF experiment [26]. Shown are the published TRIUMF and not the unrenorxnalized data as used by Herrxnann and Nakayama in [27]. These TRIUMF data agree well with the complete potential xnodel calculation where the t matrices are exactly treated with their onand half off-shell values as they are ixnplied by theory.…”

A relativistic meson-baryon description ofpp-Bremsstrahlung

“…The measured spin-observables are, of course, independent of phase space and the absolute scale of the cross section data, but they are not well predicted except at larger proton scattering angles, where the photon energy becomes smaller and the NN scattering kinematics approaches it's on-shell limit. In the only recently published calculation [6] which includes both relativistic spin corrections and rescatter terms, only minor differences to earlier results are observed, and the familiar and persistent discrepancies with experiment are seen to remain.…”

“…This may take the form [2, 41 of a Foldy Wouthuysen transformation to obtain a nonrelativistic current with 'relativistic' spin corrections, which are retained to some approximate order, according to where the infinite p/m-expansion is truncated. In a more approximate scheme, it may take the form [6] of a direct Pauli reduction. These two approaches lead to differences of order 7% in the (p, pT) cross section at 280 MeV [10], and differ from the results that are obtained with a completely non-relativistic current density [3,5] by as much as 15% [-2, 6].…”

“…The essential advantage of this approach is that the NN Tmatrix is defined to all orders in the strong-interaction coupling constant. All recent (p, p 7) calculations use this two-potential formalism, and obtain the NN T-matrices from the Lippmann-Schwinger [24] or BlankenbeclerSugar [5,6] equations for a non-relativistic boson-exchange potential such as Bonn [7] or Paris [8], or from inverse-scattering methods [9], and therefore include only the positive frequency components of the two-nucleon wavefunctions. Under this restriction, only the positive frequency processes that are shown in Fig.…”

Combined analysis ofη′production reactions:γN→η′N,

“…We also follow Ref. [39] to convert the Paris NN interaction, which obeys the nonrelativistic Lippman-Schwinger equation, to the one obeying the threedimensionally reduced version (a la Blankenbecler-Sugar) of the relativistic Bethe-Salpeter equation in order to be consistent with the relativistic covariant approach used in the present work. We also use the Blankenbecler-Sugar propagator for the two-nucleon propagator G f in Eq.…”