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.

We present calculations of nucleon-deuteron scattering as well as ground and low-lying excited states of light nuclei in the mass range A=3-16 up through next-to-next-to-leading order in chiral effective field theory using semilocal coordinate-space regularized two-and three-nucleon forces. It is shown that both of the low-energy constants entering the three-nucleon force at this order can be determined from the triton binding energy and the differential cross section minimum in elastic nucleon-deuteron scattering. From all considered nucleon-deuteron scattering observables, the strongest constraint on these low-energy constants emerges from the precisely measured cross section minimum at EN = 70 MeV. The inclusion of the three-nucleon force is found to improve the agreement with the data for most of the considered observables.

We present a novel framework to decompose three-nucleon forces in a momentum space partialwave basis. The new approach is computationally much more efficient than previous methods and opens the way to ab initio studies of few-nucleon scattering processes, nuclei and nuclear matter based on higher-order chiral 3N forces. We use the new framework to calculate matrix elements of chiral three-nucleon forces at N 2 LO and N 3 LO in large basis spaces and carry out benchmark calculations for neutron matter and symmetric nuclear matter. We also study the size of the individual three-nucleon force contributions for 3 H. For nonlocal regulators, we find that the sub-leading terms, which have been neglected in most calculations so far, provide important contributions. All matrix elements are calculated and stored in a user-friendly way, such that values of low-energy constants as well as the form of regulator functions can be chosen freely.

We solve the Faddeev equation in an exactly Poincaré invariant formulation of the three-nucleon problem.The dynamical input is a relativistic nucleon-nucleon (NN) interaction that is exactly on-shell equivalent to the high precision CD Bonn NN interaction. S-matrix cluster properties dictate how the two-body dynamics is embedded in the three-nucleon mass operator (rest Hamiltonian). We find that for neutron laboratory energies above ≈ 20 MeV relativistic effects on A y are negligible. For energies below ≈ 20 MeV dynamical effects lower the nucleon analyzing power maximum slightly by ≈ 2% and Wigner rotations lower it further up to ≈ 10% increasing thus disagreement between data and theory. This indicates that three-nucleon forces (3NF) must provide an even larger increase of the A y maximum than expected up to now.

The three-nucleon (3N) photodisintegration of 3 He has been calculated in the whole phase space using consistent Faddeev equations for the three-nucleon bound and scattering states. Modern nucleon-nucleon and 3N forces have been applied, in addition to different approaches to nuclear currents. Phase space regions are localized where 3N force effects are especially large. In addition, semi-exclusive cross sections for 3 He (␥,N), which carry interesting peak structures, have been predicted. Finally, some data for the exclusive 3N breakup process of 3 He and its total breakup cross section have been compared to theory.

A series of measurements have been performed at KVI to obtain the vector analyzing power A(y) of the (2)H(p-->,pd) reaction as a function of incident beam energy at energies of 120, 135, 150, and 170 MeV. For all these measurements, a range of theta(c.m.) from 30 degrees to 170 degrees has been covered. The purpose of these investigations is to observe possible spin-dependent effects beyond two-nucleon forces. When compared to the predictions of Faddeev calculations, based on two-nucleon forces only, significant deviations are observed at all energies and at center-of-mass angles between 70 degrees and 130 degrees. The addition of present-day three-nucleon forces does not improve the description of the data, demonstrating the still insufficient understanding of the properties of three-nucleon systems.

The charge form factor of the neutron has been determined from asymmetries measured in quasi-elastic 3 − → He( e, e ′ n) at a momentum transfer of 0.67 (GeV/c) 2 . In addition, the target analyzing power, A o y , has been measured to study effects of final state interactions and meson exchange currents.