Three-nucleon system: Irreducible and reducible contributions of the three-nucleon force

The three-nucleon bound and scattering equations are solved in momentum space for a coupled-channels Hamiltonian. The Hamiltonian couples the purely nucleonic sector of Hilbert space with a sector in which one nucleon is excited to a Δ isobar. The interaction consists of irreducible two-baryon and irreducible three-baryon potentials. The calculation keeps only the purely nucleonic one among the irreducible three-baryon potentials. The coupled-channels two-baryon potential yields additional reducible contributions to the three-nucleon force. The Coulomb interaction between the two protons is included using the method of screening and renormalization. Three-nucleon force effects on the bound-state energies and on observables of elastic nucleon-deuteron scattering and breakup are studied

Effect of the three-nucleon force on the three-nucleon ground state: Reducible and irreducible contributions

The Tucson-Melbourne two-pion exchange three-nucleon force is split into a reducible part mediated by Δ excitation and an irreducible part not mediated by Δ excitation. The triton binding energy is calculated. The irreducible part of the Tucson-Melbourne force is taken into account in the calculation. Its reducible part is discarded, but regenerated by the explicit treatment of the Δ isobar in a coupled-channel approach. The remaining irreducible part of the Tucson-Melbourne force makes a nonnegligible contribution to the triton binding energy. The strong dependence of the triton binding energy on the cutoff parameter for the πNN vertex in the Tucson-Melbourne force is considerably reduced

Inelastic electron scattering from the three-nucleon bound states with polarization

Spin-dependent inelastic electron scattering from polarized 3He is studied. The theoretical description uses the plane-wave impulse approximation. A spin-dependent spectral function, which summarizes all of the nuclear structure information on the process, is introduced. The formalism is developed for inclusive processes in all kinematic regimes of inelastic electron scattering. A comparison between theoretical predictions and experimental data is carried out in the region of quasifree scattering. The use of a polarized 3He target as a neutron spin target is discussed

Effect of the nucleon-delta interaction on properties of the three-nucleon ground state

Wave-function components containing a single Δ isobar are included in the calculation of the three-nucleon bound state. In extension to previous work, a nucleon-Δ potential based on meson exchange is incorporated in the interaction models. The interaction models are constructed phase equivalent with the purely nucleonic Paris and Bonn one boson exchange potential in q space (OBEPQ) potentials. The nucleon-Δ potential yields an additional contribution of the order of 0.1–0.2 MeV to the effective three-nucleon force. Its effect on the electromagnetic properties of the three-nucleon bound state is also considered and found to be small

Relativistic corrections of one-nucleon current in low-energy three-nucleon photonuclear reactions

Proton-deuteron radiative capture and two- and three-body photodisintegration of 3He at low energy are described using realistic hadronic dynamics and including the Coulomb force. The sensitivity of the observables to the relativistic corrections of the one-nucleon electromagnetic current operator is studied. Significant effects of the relativistic spin-orbit charge are found for the vector-analyzing powers in the proton-deuteron radiative capture and for the beam-target parallel-antiparallel spin asymmetry in the three-body photodisintegration of 3He

Momentum-space description of three-nucleon breakup reactions including the Coulomb interaction

The Coulomb interaction between two protons is included in the calculation of proton-deuteron breakup and of three-body electromagnetic disintegration of 3He. The hadron dynamics is based on the purely nucleonic charge-dependent (CD) Bonn potential and its realistic extension, CD Bonn + Δ, to a coupled-channel two-baryon potential, allowing for single virtual Δ-isobar excitation. Calculations are done using integral equations in momentum space. The screening and renormalization approach is employed for including the Coulomb interaction. Convergence of the procedure is found at moderate screening radii. The reliability of the method is demonstrated. The Coulomb effect on breakup observables is seen at all energies in particular kinematic regimes

Comment on "exact three-dimensional wave function and the on-shell t matrix for the sharply cut-off Coulomb potential: Failure of the standard renormalization factor"

The results by W. Glöckle et al. [Phys. Rev. C 79, 044003 (2009)] are shown to be consistent with the screening and renormalization theory, and they do not invalidate previous numerical calculations of physical observables

Realistic two-baryon potential coupling two-nucleon and nucleon-Δ-isobar states: Fit and applications to three-nucleon system

A two-baryon coupled-channel potential is developed. It couples two-nucleon states and states in which one nucleon is turned into a Δ isobar. It is developed as extension of the purely nucleonic charge-dependent (CD) Bonn potential. It is fitted to two-nucleon scattering data up to 350 MeV nucleon lab energy. Since scattering energies just touch the pion-production threshold, the Δ isobar is considered a stable baryon. The resulting fit of the coupled-channel potential is of the same quality as that for CD Bonn. The coupled-channel potential is as realistic as CD Bonn and as any other modern two-nucleon potential. It is charge-dependent as CD Bonn. It is employed for the description of elastic and inelastic three-nucleon scattering. The Δ isobar yields an effective three-nucleon force in the three-nucleon system, besides other effects. Δ-isobar effects in three-nucleon scattering are isolated and discussed

Nucleon-deuteron scattering with Δ-isobar excitation: Perturbation theory

A perturbative approach for the description of elastic and inelastic nucleon-deuteron scattering is developed. Its validity is discussed. The aim of the perturbative approach is the isolation of details of different reaction mechanisms. The dynamics is based on a two-baryon potential allowing for the excitation of a nucleon to a Δ isobar. The coupled-channel potential yields an effective three-nucleon force in three-nucleon scattering. The purely nucleonic reference potential is the charge-dependent CD-Bonn potential

Faddeev equations with three-nucleon force in momentum space

Modified Faddeev equations that allow the inclusion of irreducible three-body forces in addition to two-body interactions are formulated and the technical apparatus for their solution in momentum space is described. Results for the triton binding energy are obtained with realistic two-nucleon interactions and the Tucson-Melbourne two-pion exchange three-nucleon force and compared with previous calculations. Excellent agreement with the results of other groups is found confirming that the accuracy of present-day techniques for handling three-nucleon forces is very high indeed