Radiative capture of protons by deuterons

Abstract

The differential cross section for radiative capture of protons by deuterons is calculated using different realistic NN interactions. We compare our results with the available experimental data below Ex = 20 MeV. Excellent agreement is found when taking into account meson exchange currents, dipole and quadrupole contributions, and the full initial state interaction. There is only a small difference between the magnitudes of the cross sections for the different potentials considered. The angular distributions, however, are practically potential independent. PACS numbers(s): 21.45.+v, 25.40.Lw, 27.10.+h The radiative capture of protons by deuterons and the inverse reaction, the photodisintegration of 3 He, have been investigated experimentally and theoretically over the last decades with quite some interest. Despite the various corresponding investigations, the theory is only in rough agreement with experiment, and there are inconsistencies between the data up to 30% in the magnitudes of the cross sections From the theoretical side several attempts have been made to describe the cross sections in this energy region. In the early calculations by Barbour et al. [6] phenomenological interactions were used. It was shown that the final state interaction is quite important, and that the E2 contributions in the electromagnetic interaction are needed in the differential cross section. In the calculations by Gibson and Lehman [7] a more realistic Yamaguchi interaction, but only the E1 components were employed. King et al. [2] performed an effective two-body, direct capture calculation with the initial state being treated as a plane wave, or as a scattering state generated from an optical potential. Fonseca and Lehman [8] calculated the polarization observables A yy and T 20 at the excitation energy E x = 14.75 MeV including only the E1 interaction. A calculation at E x = 15 MeV based on realistic interactions and both, the E1 and E2 contributions has been done by Ishikawa and Sasakawa [9]. Another calculation of A yy in this energy region is by Jourdan et al. [10]. It was found in all these investigations that T 20 is independent of the deuteron and the helium D-state probability, whereas A yy shows a weak dependence on these quantities.Very-low-energy radiative capture processes are of considerable astrophysical relevance. The p-d radiative capture, which at such energies is almost entirely a magnetic dipole (M1) transition, was studied in plane wave (Born) approximation by Friar et al. [11]. In these investigations the authors employed their configuration-space Faddeev calculations of the helium wave function, with inclusion of three-body forces and pion exchange currents. Various trends, e.g., the correlation between cross sections and helium binding energies, and their potential dependence were pointed out. More recently a rather detailed investigation of such processes has been performed by Viviani et al. [12]. Their calculations employed the quite accurate three-nucleon bound-and continuum states obtained in the ...

Photonuclear reactions of three-nucleon systems

“…Moreover, in many cases the measured differential cross sections for p-d capture (aside from a normalization factor) can be explained theoretically over a large energy range. In [44] it was already shown that a similar normalization problem exists for the data below E x = 20 MeV. There, it was also shown that the angular distribution is insensitive to the underlying two-body interaction, whereas there is a strong correlation between the three-body binding energy and the normalization constant A 0 [42,43].…”

“…In Refs. [42][43][44], we have treated the 3 He and 3 H photodisintegration and the inverse processes, i.e., the radiative capture of protons or neutrons by deuterons, within the integral equation approach discussed below. These calculations were based on the Bonn A, Bonn B and Paris potentials in Ernst-Shakin-Thaler (EST) expansion: Bonn A (EST), Bonn B (EST), and Paris (EST) [45,46].…”

Isoscalar off-shell effects in threshold pion production frompdcollisions

“…The only difference is that the driving term of the n-d scattering equation ( i.e., the particle-exchange diagram, the so-called "Z" diagram) is replaced by the off-shell extension of the plane-wave pion-absorption amplitude. More details can be found in [15,31] and references therein.…”

Comparison of Triton Bound-State Properties Using Different Separable Representations of Realistic Nucleon-Nucleon Potentials

“…For further applications of separable approximations or expansions, e.g., in processes as the photodisintegration of three-nucleon systems [15,16], the corresponding radiative capture [17], or the pion absorption on such systems [18], additional tests of accuracy of the threebody wave functions involved appear desirable. In case of a 5 channel calculation and the EST method such a test has been made already in Ref.…”