The role of the relativistic amplitudes for a number of O(k) processes usually neglected in potential model calculations of NN bremsstrahlung is investigated.In particular, we consider the A excitation pole contributions related to the one-pion and one-rho exchange and in addition include the exchange contributions induced by the radiative u, p~7 rp decays. The contributions are calculated from relativistic Born amplitudes 6tted to A production and absorption data in the energy range up to 1 GeV and then used to supplement potential model and soft photon calculations for nucleon-nucleon bremsstrahlung.The eKects on NNp observables, although moderate in general, are found to be important in some kinematic domains.PACS number(s): 13.75.Cs, 25.20.x, 25.40.h
The decay η → π 0 γγ is discussed in the framework of SU(3) chiral perturbation theory. The process is dominated by the O(p 6 ) in the momentum expansion where tree-level amplitudes from the effective Lagrangian L 6 enter together with one-loop contributions from L 4 and two-loop contributions from L 2 . We estimate the 6 independent L 6 coupling constants by resonance saturation consistent with the pion production process γγ → π 0 π 0 and calculate the pion-loop part of the one-and two-loop amplitude. Predictions for the total rate and spectrum of η → π 0 γγ are given together with a discussion of the uncertainties involved.
A complete potential model for nucleon-nucleon bremsstrahlung is used to test t matrices of recent NN potentials. pygmy and nary cross sections and spin observables are calculated using the Paris, Bonn-B, and inversion potentials to the most recent phase shift analyses and Bonn-B phase shifts. We confront our results with older noncoplanar pyric data from Harvard and most recent but inclusive data from Saclay and the Indiana University Cyclotron Facility. We obtain a good agreement between experiment and theory for all potentials.Nonlocality effects of potentials, supposedly discerned by bremsstrahlung, are small in comparison to data errors and differences between the potentials themselves.PACS number(s): 13.75.Cs, 25.20.Dc
Due to the phenomenological character of the basic relativistic Hartree-Fock theory one has to adjust the effective Lagrangian to (basic) nuclear properties, which are not accurately known. The flexibility and capability of different Lagrangians in reproducing the bandwidth of nuclear parameters is investigated and discussed.
Two nucleon t-matrices, on-and half off-shell, of experiment and theory are used to put expectations into new Bremsstrahlung experiments on a realistic basis. A report is given about comprehensive studies of pp Bremsstrahlung which includes a reanalysis of TRIUMF data and other data of non coplanar geometry experiments. The Bremsstrahlung amplitudes associated with external, rescattering and exchange currents, by exact treatment of the Coulomb potential in on-and half-off-shell t-matrices, and the relativistic spin corrections were all computed and for both coplanar and non coplanar geometries.
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