Different formulations of <Superscript>3</Superscript>He and <Superscript>3</Superscript>H photodisintegration

Different momentum space Faddeev-like equations and their solutions for the radiative pd-capture and the three-nucleon photodisintegration of ³He are presented. Applications are based on the AV18 nucleon-nucleon and the Urbana IX three-nucleon forces. Meson exchange currents are included using the Siegert theorem. A very good agreement has been found in all cases indicating the reliability of the used numerical methods. Predictions for cross-sections and polarization observables in the pd-capture and the complete three-nucleon breakup of ³He at different incoming-deuteron/photon energies are presented.     

A charge-dependent three-nucleon potential

Using the p-wave part of the charge asymmetric three-nucleon potential we calculate the charge asymmetric binding energy in ³He³H nuclei. The total contribution which arise from the electromagnetic corrections to the three-nucleon potential turns out to be negligble.     

Incorporation of Three-Nucleon Force in the Effective-Interaction Hyperspherical-Harmonic Approach

It is shown how a bare three-nucleon force is incorporated into the formalism of the effective interaction approach for hyperspherical harmonics. As a practical example we calculate the ground-state properties of ³H and ³He using the Argonne V18 nucleon-nucleon potential and the Urbana IX three-nucleon force. A very good convergence of binding energies and matter radii is obtained. We also find a very good agreement of our results compared to other high-precision calculations.     

Ab-Initio Calculations of Four-Nucleon Elastic Scattering

We present microscopic calculations of low-energy scattering observables in all possible four-nucleon systems: n-³H, p-³He, and p-³H. Results were obtained by solving Faddeev-Yakubovski equations in configuration space, appropriately modified to include Coulomb and three-nucleon forces.     

Three-body structure of 6He=4He+n+n using realistic n-n potentials

With the use of realistic nucleon-nucleon forces (Paris, Bonn and Argonne potenfials) between the valence neutrons, the three-body structure of ⁶He=⁴He+n+n is investigated with emphasis on the short-range correlations between the halo neutrons and on dependence on the realistic forces. To solve the three-body problem regorously, use is made of the coupled-rearrangement-channel variational method with the Gaussian basis functions. The basis are represented by newly developed Gaussian lobe functions with infinitesimal shift parameters. Accuracy and usefulness of this basis functions are examined in the calculation of three-nucleon bound state with those realistic forces.     

Three-nucleon bound states: Detailed calculations of3H and3He

The works of the Sendai group on investigations of the properties of the trinucleon bound states³H and³He are reviewed in detail. For these mirror nuclei, results are summarized that have been obtained from rigorous solutions of the (Coulomb-modified) Faddeev equations for various realistic nucleon-nucleon potentials with inclusion of three-nucleon forces as well as chargeindependence-and charge-symmetry-breaking forces. It becomes evident that for most trinucleon bound-state observables quite reasonable results have been achieved.     

Interplay between two- and three-body interaction in light nuclei and nuclear matter

A recent study of different models of three-nucleon interaction (TNI) in ³He, ³H, ⁴He and nuclear matter is extended to study the influence of different choices of the accompanying two-body interaction. A new two-body potential, Argonne υ₁₄, is coupled with both the Tucson and isobar intermediate-state models of two-pion-exchange TNI, with a phenomenological intermediate-range repulsive TNI added to the latter. Variational calculations are carried out for these systems, and compared to the earlier work. We find that a stronger tensor component in the two-body potential, as typified by a larger deuteron D-state percentage, gives more attraction for the TNI, counteracting the saturation effect obtained when only two-body forces are considered.     

Selected Topics in Correlated Hyperspherical Harmonics

Correlated hyperspherical-harmonic basis functions are used to expand the three- and four-nucleon wave functions. Bound and scattering states are considered. Results for the binding energies of ³H, ³He, and ⁴He calculated using modern two- and three-nucleon forces are given and discussed. For scattering states, results for N-d differential cross section and vector analyzing powers are shown. The importance of the Coulomb and magnetic moment effects are discussed.     

Proton-deuteron radiative capture cross-sections at intermediate energies

Differential cross-sections of the reaction p(d, ³He)γ have been measured at deuteron laboratory energies of 110, 133 and 180 MeV. The data were obtained with a coincidence setup measuring both the outgoing ³He and the photon. The data are compared with modern calculations including all possible meson-exchange currents and two- and three-nucleon forces in the potential. The data clearly show a preference for one of the models, although the shape of the angular distribution cannot be reproduced by any of the presented models.     

Theoretical Study of the 4He(γ, p)3H and 4He(γ, n)3He Reactions

Ab initio calculation of the total cross section for the reactions ⁴He(γ, p)³H and ⁴He(γ, n)³He is presented, using state-of-the-art nuclear forces. The Lorentz integral transform (LIT) method is applied, which allows exact treatment of the final state interaction (FSI). The dynamic equations are solved using the effective interaction hyperspherical harmonics method. In this calculation of the cross sections the three-nucleon force is fully taken into account, except in the source term of the LIT equation for the FSI transition matrix element.     

Effect of the three-body force on trinucleon bound systems consideringS andS′-state admixture

We report the calculation of binding energy, charge form factor and point-like proton density of both³H and³He by the hyperspherical harmonics method with the inclusion of two-pion exchange three-nucleon force (Fujita-Miyazawa type). For the two-body force theN-N Afnan-Tang S-3 potential is taken. Coulomb and three-body forces are treated nonperturbatively. In this calculation the mixed symmetryS′-state of the trinucleon ground state is considered along with the space totally symmetricS-state.     

Variational calculations of resonant states in 4He

We present a modified R-matrix method which allows microscopic calculations of nucleon-nucleus scattering at low energies. This method may be applied in conjunction with any of the commonly used methods for the ground states of few-body systems, i.e. the Green function Monte Carlo, Faddeev and variational techniques. We then report results of variational calculations of low-energy tp scattering in the region of 0⁺, 0^? and 2^? resonances in ⁴He. The energies and widths of these resonances are calculated using realistic two- and three-nucleon interactions; but, the Coulomb interaction is neglected. The three-nucleon interaction is found to have a much smaller effect on the energies of the resonances than on the ground-state energy.     

Electron scattering on <Superscript>3</Superscript>He --A playground to test nuclear dynamics

The electron-induced processes on ³He are analyzed using the Faddeev formalism with modern nucleon-nucleon and three-nucleon forces as well as exchange currents. The kinematical region is restricted to a mostly nonrelativistic one where the three-nucleon c.m. energy is below the pion production threshold and the three-momentum of the virtual photon is sufficiently below the nucleon mass. Comparisons with available data are shown and cases of agreement and disagreement are found. It is argued that new and precise data are needed to systematically check the present-day dynamical ingredients.Received: 6 February 2004, Published online: 17 August 2004PACS: 21.45. + v Few-body systems - 21.10.-k Properties of nuclei; nuclear energy levels - 25.10. + s Nuclear reactions involving few-nucleon systems - 25.20.-x Photonuclear reactions     

Momentum-space calculations for three-nucleon scattering including a three-nucleon force

The formalism to include a three-nucleon force into three-nucleon continuum calculations is presented. First numerical results, obtained in momentum space, are shown. The two- and three-nucleon forces have been restricted to act only in the¹ S ₀ and³ S ₁-³ D ₁ partial-wave states. As two-nucleon interaction the Bonn-B potential and as three-nucleon interaction the Tucson-Melbourne two-pion exchange model has been used.     

Three-nucleon interaction in 3-, 4- and ∞-body systems

We report results of variational calculations of ³H, ³He, ⁴He and nuclear matter with the Urbana v₁₄ two-nucleon interaction and realistic models of the three-nucleon interaction (TNI). These include the Tucson and isobar intermediate-state models of the two-pion exchange TNI. The latter is also studied with an intermediate-range three-nucleon repulsion. In general, realistic TNI helps to bring the theory closer to experiment by giving extra binding energy to the A = 3 and 4 nuclei and providing extra saturation to the nuclear matter binding energy. The Coulomb energy of ³He and the rms radii of A = 3, 4 nuclei are also well described. However, some problems remain unresolved. There is a slight overbinding of ⁴He, an underbinding of nuclear matter, and the charge form factors of ³He and ⁴He, calculated with impulse approximation, deviate from the experimental at q²>5 fm^?2.     

Double-charge-exchange and inelastic scattering in π−+3He

The reactions π^?+³He→⁺+3n and π^?+³He→^?+³He were studied to investigate the $\text{T=}\text{3}\text{2}$ three-nucleon system. The differential cross sections were measured at scattering angles from 20 to 40 degrees. The secondary pion was momentum analyzed in a magnetostrictive-readout wire-chamber spectrometer. The double-charge-exchange reaction yielded a secondary pion energy distribution, the features of which can be due to either a $\text{T=}\text{3}\text{2}$ three-nucleon resonance or a resonace of the nucleons in the ³He nucleus. The inelasticc scaterring reaction yielded a secondary pion energy distribution peaked near threshold, consistent with resonances in both the $\text{T=}\text{3}\text{2}$ and $\text{T=}\text{1}\text{2}$ three-nucleon systems.