• Energy Research

Using the no-core shell model approach, we report on the first results for 7Li based on the next-to-next-to-leading order chiral nuclear interaction. Both, two-nucleon and three-nucleon interactions are taken into account. We show that the p-shell nuclei are sensitive to the subleading parts of the chiral interactions including three-nucleon forces. Though chiral interactions are soft, we do not observe overbinding for this p-shell nucleus and find a realistic description for the binding energy, excitation spectrum and radius. 12 pages, 12 figures

A new single Faddeev equation for the inclusion of a three-nucleon force (3NF) into the three-nucleon (3N) continuum and a new partial wave decomposition of a 3NF is presented. This allows for the first time in momentum space calculations the inclusion of a 3NF in higher angular momenta. The authors present converged calculations including a 3NF up to j{sub max} = 6 for the three-nucleon bound state and j{sub max} = 3 in the 3N continuum, where j is the total nucleon-nucleon angular momentum. Several 3N Hamiltonians are generated based on modern nucleon-nucleon (NN) forces and properly adjusted 3NFs, which give the correct triton binding energy. They are used to analyze recent measurements of spin transfer coefficients in elastic nucleon-deuteron scattering. They show that scales with the triton binding energy, whereas K{sub y}{sup z{prime}z{prime}} does not.

Chiral two- and three-nucleon interactions are studied in a few-nucleon systems. We investigate the cut-off dependence and convergence with respect to the chiral expansion. It is pointed out that the spectra of light nuclei are sensitive to the three-nucleon force structure. As an example, we present calculations of the 1{sup +} and 3{sup +} states of {sup 6}Li using the no-core shell model approach. The results show contributions of the next-to-next-to-leading order terms to the spectra, which are not correlated to the three-nucleon binding energy prediction.

Properties of finite nuclei are evaluated with two-nucleon (NN) and three-nucleon (NNN) interactions derived within chiral effective field theory (EFT). The nuclear Hamiltonian is fixed by properties of the A=2 system, except for two low-energy constants (LECs) that parameterize the short range NNN interaction. We constrain those two LECs by a fit to the A=3 system binding energy and investigate sensitivity of 4He, 6Li, 10,11B and 12,13C properties to the variation of the constrained LECs. We identify a preferred choice that gives globally the best description. We demonstrate that the NNN interaction terms significantly improve the binding energies and spectra of mid-p-shell nuclei not just with the preferred choice of the LECs but even within a wide range of the constrained LECs. At the same time, we find that a very high quality description of these nuclei requires further improvements to the chiral Hamiltonian. 4 pages, 4 figures

Recently developed chiral nucleon-nucleon (NN) forces at next-to-leading order (NLO) that describe NN phase shifts up to about 100 MeV fairly well have been applied to 3N and 4N systems. Faddeev-Yakubovsky equations have been solved rigorously. The chiral NLO forces depend on a momentum cut-off ��lying between 540-600 MeV/c. The resulting 3N and 4N binding energies are in the same range as found using standard NN potentials. In additon, low-energy 3N scattering observables are very well reproduced like for standard NN forces. Surprisingly, the long standing A_y-puzzle is resolved at NLO. The cut-off dependence of the scattering observables is rather mild. 4 pp, revtex, 3 figures