Antisymmetry in Strangeness -1 and -2 Three-Baryon Systems

Using the generalized Pauli principle by adding particle labels to the usual space and spin labels a symmetric Hamiltonian and a corresponding antisymmetric wavefunction is constructed for systems of three baryons in the strangeness sectors $S=-1$ and -2. Applications are the $\Xi NN-\Lambda\Lambda N$ and $NN\Lambda -NN\Sigma$ systems. Minimal sets of generalized coupled Faddeev equations for breakup and rearrangement operators as well as (possible) bound states are derived which have the ordinary Pauli principle among identical particles built in. The equations found confirm our previous sets of coupled Faddeev equations for those systems whose derivation was carried through for distinguishable particles and not using the generalized Pauli principle.Comment: 28 pages and 2 figure

The nn quasi-free nd breakup cross section: discrepancies to theory and implications on the 1S0 nn force

Large discrepancies between quasi-free neutron-neutron (nn) cross section data from neutron-deuteron (nd) breakup and theoretical predictions based on standard nucleon-nucleon (NN) and three-nucleon (3N) forces are pointed out. The nn 1S0 interaction is shown to be dominant in that configuration and has to be increase to bring theory and data into agreement. Using the next-to-leading order (NLO) 1S0 interaction of chiral perturbation theory (chiPT) we demonstrate that the nn QFS cross section only slightly depends on changes of the nn scattering length but is very sensitive to variations of the effective range parameter. In order to account for the reported discrepancies one must decrease the nn effective range parameter by about 12 % from its value implied by 19charge symmetry and charge independence of nuclear forces.Comment: 19 pages, 11 figure

Three-Body Scattering Below Breakup Threshold: An Approach without using Partial Waves

The Faddeev equation for three-body scattering below the three-body breakup threshold is directly solved without employing a partial wave decomposition. In the simplest form it is a three-dimensional integral equation in four variables. From its solution the scattering amplitude is obtained as function of vector Jacobi momenta. Based on Malfliet-Tjon type potentials differential and total cross sections are calculated. The numerical stability of the algorithm is demonstrated and the properties of the scattering amplitude discussed.Comment: 21 pages, 7 figures included, uses psfig, revised versio

Model Study of Three-Body Forces in the Three-Body Bound State

The Faddeev equations for the three-body bound state with two- and three-body forces are solved directly as three-dimensional integral equation. The numerical feasibility and stability of the algorithm, which does not employ partial wave decomposition is demonstrated. The three-body binding energy and the full wave function are calculated with Malfliet-Tjon-type two-body potentials and scalar Fujita-Miyazawa type three-body forces. The influence of the strength and range of the three-body force on the wave function, single particle momentum distributions and the two-body correlation functions are studied in detail. The extreme case of pure three-body forces is investigated as well.Comment: 25 pages, 15 postscript figure

Solution of the Faddeev-Yakubovsky equations using realistic NN and 3N interaction

We solve the Faddeev-Yakubovsky equations for 3N and 4N bound states based on the most modern realistic nucleon-nucleon interactions. We include different realistic 3N forces. It is shown that all 3N force models can remove the underbinding of the triton and alpha-particle which one obtains with existing NN interactions. The agreement of theoretical predictions and the experimental binding energy is quite good and there is little room left for the action of four-nucleon forces in the alpha-particle. The effect of 3N forces on the wave function is investigated.Comment: 4 pages, to appear in the proceedings of the "European Few-Body Conference", Evora 200