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The Coulomb interaction between the two protons is included in the calculation of proton-deuteron elastic scattering, radiative proton-deuteron capture and two-body electromagnetic disintegration of 3 He. The hadron dynamics is based on the purely nucleonic charge-dependent (CD) Bonn potential and its realistic extension CD Bonn + ∆ to a coupled-channel two-baryon potential, allowing for single virtual ∆-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 already at moderate screening radii. The reliability of the method is demonstrated. The Coulomb effect on observables is seen at low energies for the whole kinematic regime. In proton-deuteron elastic scattering at higher energies the Coulomb effect is confined to forward scattering angles; the ∆-isobar effect found previously remains unchanged by Coulomb. In electromagnetic reactions Coulomb competes with other effects in a complicated way.

The Coulomb interaction between the two protons is included in the calculation of proton-deuteron breakup and of three-body electromagnetic disintegration of 3 He. The hadron dynamics is based on the purely nucleonic charge-dependent (CD) Bonn potential and its realistic extension CD Bonn + ∆ to a coupled-channel two-baryon potential, allowing for single virtual ∆-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.

A two-baryon coupled-channel potential is developed. It couples two-nucleon states and states in which one nucleon is turned into a ⌬ isobar. It is developed as extension of the purely nucleonic charge-dependent ͑CD͒ 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 ⌬ 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 ⌬ isobar yields an effective three-nucleon force in the three-nucleon system, besides other effects. ⌬-isobar effects in threenucleon scattering are isolated and discussed.

Background: The core excitation, being an important reaction mechanism, so far is not properly included in most calculations of three-body nuclear reactions.Purpose: We aim to include the excitation of the core nucleus using an exact Faddeev-type framework for nuclear reactions in the three-body (core + neutron + proton) system. Methods:We employ Alt, Grassberger, and Sandhas (AGS) integral equations for the three-particle transition operators and solve them in the momentum-space framework. The Coulomb interaction is included via the method of screening and renormalization.Results: We calculate elastic, inelastic, and transfer reactions involving 10 Be and 24 Mg nuclear cores.Conclusions: Important effects of the core excitation are found, often improving the description of the experimental data. In the neutron transfer reactions the core excitation effect is by far not just a simple reduction of the cross section by the respective spectroscopic factor. This indicates that widely used extraction of the spectroscopic factors from the ratio of the experimental and theoretical transfer cross sections is unreliable approach.

Four-body equations in momentum space are solved for neutron-3 He, proton-3 H, and deuteron-deuteron scattering; all three reactions are coupled. The Coulomb interaction between the protons is included using the screening and renormalization approach as was recently done for proton-deuteron and proton-3 He scattering. Realistic potentials are used between nucleon pairs. For the first time fully converged results for the observables pertaining to the six different elastic and transfer reactions are obtained and compared with experimental data.

The four-body equations of Alt, Grassberger and Sandhas are solved, for the first time, for proton-3 He scattering including the Coulomb interaction between the three protons using the method of screening and renormalization as it was done recently for proton-deuteron scattering. Various realistic two-nucleon potentials are used. Large Coulomb effects are seen on all observables. Comparison with data at different energies shows large deviations in the proton analyzing power but quite reasonable agreement in other observables. The effect of nucleon-nucleon magnetic moment interaction and correlations between p-d and p-3 He analyzing powers are studied.PACS numbers: 21.30. -x, 21.45.+v, 24.70.+s, 25.10.+s Modern calculations of light nuclear systems A ≤ 12 are essential to our understanding of the force models that have been developed to describe how nucleons interact at low energies [1,2]. Of these nuclear systems, the four-nucleon (4N ) system is particularly important because it gives rise, experimentally, to the simplest set of nuclear reactions that shows the complexity of heavier systems and the Coulomb interaction manifest itself in new ways relative to what is observed in the threenucleon (3N ) system. Theoretically it is also important because with powerful numerical techniques and fast computers one can calculate not only bound state properties [3] but also scattering observables [4,5,6,7,8,9, 10] for a number of elastic, transfer and breakup reactions that place new challenges to our understanding of the underlying force models. The importance of scattering calculations also has to do with the possibility to probe states in the continuum associated with specific resonances, states of higher angular momentum than corresponding bound states, effects that depend on the spin orientation of the projectile and/or target, and threshold effects on the observables, among others.While the three-nucleon system has been extensively studied [11,12] through neutron-deuteron (nd) and proton-deuteron (pd) elastic scattering and breakup experiments, exact calculations using realistic force models as well as interactions derived from Effective Field Theory were restricted, for a long time, to the nd system due to limitations in including the Coulomb force in the description of pd scattering beyond low energy pd → pd and pd ↔ γ 3 He calculations [13,14] in the framework of the variational hyperspherical approach. The situation has now changed due to the work of Refs. [15,16] where calculations of pd → pd, pd → ppn, pd ↔ γ 3 He, γ 3 He → ppn, e 3 He → e ′ pd, and e 3 He → e ′ ppn were performed at energies ranging from 1 MeV in the center of mass (c.m.) system to the pion production threshold. The work is based on the solution of the momentum-space Alt, Grassberger and Sandhas (AGS) equations [17] together with the screening and renormalization approach [18,19,20] for the Coulomb interaction leading to the results of observables that are independent of the screening radius, provided it is sufficiently large.In the prese...

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