A big spectrum of processes induced by real and virtual photons on the 3 He and 3 H nuclei is theoretically investigated through many examples based on nonrelativistic Faddeev calculations for bound and continuum states. The modern nucleon-nucleon potential AV18 together with the threenucleon force UrbanaIX is used. The single nucleon current is augmented by explicit π-and ρ-like two-body currents which fulfill the current continuity equation together with the corresponding parts of the AV18 potential. We also employ the Siegert theorem, which induces many-body contributions to the current operator. The interplay of these different dynamical ingredients in the various electromagnetic processes is studied and the theory is compared to the experimental data.Overall we find fair to good agreement but also cases of strong disagreement between theory and experiment, which calls for improved dynamics. In several cases we refer the reader to the work of other groups and compare their results with ours. In addition we list a number of predictions for observables in different processes which would challenge this dynamical scenario even more stringently and systematically.
Faddeev equations for elastic Nd scattering have been solved using modern NN forces combined with the Tucson-Melbourne two-pion exchange threenucleon force, with a modification thereof closer to chiral symmetry and the Urbana IX three-nucleon force. Theoretical predictions for the differential cross section and several spin observables using NN forces only and NN forces combined with three-nucleon force models are compared to each other and to the existing data. A wide range of energies from 3 to 200 MeV is covered. Especially at the higher energies striking three-nucleon force effects are found, some of which are supported by the still rare set of data, some are in conflict with data and thus very likely point to defects in those three-nucleon force models.
Neutron-deuteron elastic scattering cross sections are calculated at different energies using modern nucleon-nucleon interactions and the TucsonMelbourne three-nucleon force adjusted to the triton binding energy. Predictions based on NN forces only underestimate nucleon-deuteron data in the minima at higher energies starting around 60 MeV. Adding the three-nucleon forces fills up those minima and reduces the discrepancies significantly.
The π-mesonic decay of the hypertriton is calculated based on a hypertriton wavefunction and 3N scattering states, which are rigorous solutions of 3-body Faddeev equations using realistic NN and hyperon-nucleon interactions. The total π-mesonic decay rate is found to be 92% of the free Λ decay rate, which is close to the experimental data. Together with the nonmesonic decay the total life time of 3 Λ H is predicted to be 2.78 × 10 −10 sec which is 6 % larger than for the free Λ particle. The differential decay rate is evaluated as a function of the pion momentum. The decay into the N + d + π channel is stronger than in the 3N + π channel in contrast to the situation for the nonmesonic decay. The ratio for the decay rate into 3 He + π − to the decay rate into all channels including π − is found to be 0.40, which is close to the experimental value. We visualise the decay into the dominant channel p + d + π − in a Dalitz plot. Finally we compare the polarisation of the outgoing proton in free unpolarised Λ-decay to the polarisation of 3 He in unpolarised 3 Λ H-decay and we compare the closely related asymmetry of π − emitted parallel and antiparallel with respect to the spin-direction for a polarised Λ to the corresponding asymmetry for a polarised 3 Λ H. 21.80.+a, 21.45.+v, 23.40.-s Typeset using REVT E X * present address:
We solved the three-nucleon (3N) Faddeev equation including relativistic features at incoming neutron lab energies E lab n = 28, 65, 135 and 250 MeV. Those features are relativistic kinematics, boost effects and Wigner spin rotations. As dynamical input a relativistic nucleon-nucleon (NN) interaction exactly on-shell equivalent to the AV18 NN potential has been used. The effects of Wigner rotations for elastic scattering observables were found to be small. The boost effects are significant at higher energies. They diminish the transition matrix elements at higher energies and lead in spite of the increased relativistic phase-space factor as compared to the nonrelativistic one to rather small effects in the cross section, which are mostly restricted to the backward angles.
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