Low energy n+t scattering and the NN forces

Abstract

The Faddeev-Yakubovsky equations have been solved in configuration space for the four nucleon system. The n+t elastic cross section has been calculated using several realistic interactions and a phenomenological three-nucleon force. Special attention is devoted to the description of the observed resonant structure at T lab ≈ 4 MeV. In the present state of the calculations, the realistic NN interactions are unable to describe the energy region considered, i.e. n+t S-and P-waves. Whereas the inclusion of a three-nucleon force improves the zero energy region, the disagreement in the resonant peak remains. This failure contrasts with the results of a pure phenomenological model. The origin of this disagreement as well as the possible issues are discussed.

Proton-He3elastic scattering at low energies

“…The σ T calculations by Fonseca [7] and Pfitzinger, Hofmann, and Hale [12] are in good agreement with the experimental data, while the calculations by the Grenoble [8,14,20] and Pisa groups [14] are well below the data. The origin of this disagreement is still not clear.…”

Ab-Initio Calculations of Four-Nucleon Elastic Scattering

“…Nevertheless this system contains two, spin degenerated, narrow resonances at low energy (E cm ≈ 3 MeV). Ability of nuclear interaction models to describe scattering cross sections in this resonance region is still an open question [6,8].…”

“…Situation is less obvious for realistic potentials, which require much larger partial wave basis (PWB) to obtain converged results. Recently we have managed to considerably enlarge our PWB compared to [8]. Despite of having some effect on the negative parity phase shifts, the total cross section near the resonance peak (E cm = 3 M eV ) has not been improved (see Fig.…”

Benchmark calculations and new advances in four-nucleon systems

“…The underprediction at the peak was already found some time ago [26] and it is confirmed now after more advanced numerical computations [30]. In this region, the cross section is dominated by the NN interaction in P-waves [27].…”

“…Up to now, only the FY [6,26,27], the Alt-Grassberger-Sandhas (AGS) [10,28,29], the resonating group model (RGM) [8], and the HH techniques have been employed to solve this problem with realistic Hamiltonians. A detailed comparison between the phase-shifts obtained by the FY calculation of the Grenoble group [6,27,30], the RGM calculation of the Erlangen group [8] and our calculation using the HH technique [30] is reported in Table 2.…”