Giuseppina Orlandini

State dependent effective interaction for the hyperspherical formalism

The effective interaction method, traditionally used in the framework of a harmonic oscillator basis, is applied to the hyperspherical formalism of few-body nuclei

State-dependent effective interaction for the hyperspherical formalism with noncentral forces

(A=3\ensuremath{-}6)

Modern ab initio approaches and applications in few-nucleon physics with A≥4

. The separation of the hyperradial part leads to a state dependent effective potential. Undesirable features of the harmonic oscillator approach associated with the introduction of a spurious confining potential are avoided. It is shown that with the present method one obtains an enormous improvement of the convergence of the hyperspherical harmonics series in calculating ground state properties, excitation energies, and transitions to continuum states.

Benchmark calculation of the three nucleon photodisintegration

Abstract The recently developed effective interaction method for the hyperspherical harmonic formalism is extended to noncentral forces. Binding energies and radii of three- and four-body nuclei are calculated with AV6 and AV14 NN potentials. Excellent results for the convergence of the expansion are found, particularly for the three-nucleon system. Due to the higher density the convergence rate is a bit slower for the alpha particle. In comparison to central potential models there is only a very slight deterioration of the convergence due the tensor force, while other potential terms have no visible effect on the convergence. The obtained values for binding energy and radii also agree well with the results in the literature obtained with other few-body techniques.

Accurate Four-Body Response Function with Full Final State Interaction: Application to Electron Scattering off4He

Abstract We present an overview of the evolution of ab initio methods for few-nucleon systems with A ≥ 4 , tracing the progress made that today allows precision calculations for these systems. First a succinct description of the diverse approaches is given. In order to identify analogies and differences the methods are grouped according to different formulations of the quantum mechanical many-body problem. Various significant applications from the past and present are described. We discuss the results with emphasis on the developments following the original implementations of the approaches. In particular we highlight benchmark results which represent important milestones towards setting an ever growing standard for theoretical calculations. This is relevant for meaningful comparisons with experimental data. Such comparisons may reveal whether a specific force model is appropriate for the description of nuclear dynamics.

Nucleon momentum distributions in doubly closed shell nuclei

Abstract A benchmark is set on the three-nucleon photodisintegration calculating the total cross section with modern realistic two- and three-nucleon forces using both the Faddeev equations and the Lorentz integral transform method. This test shows that the precision of three-body calculations involving continuum states is considerably higher than experimental uncertainties. Effects due to retardations, higher multipoles, meson exchange currents and Coulomb force are studied.

Is There a Pronounced Giant Dipole Resonance in {sup 4}He?

The longitudinal (e,e{sup {prime}}) response function of {sup 4}He is calculated precisely with full final state interaction. The explicit calculation of the four-body continuum states is avoided by the method of integral transforms. Precision tests of the response show the high level of accuracy. Nonrelativistic nuclear dynamics are used. The agreement with experimental data is very good over a large energy range for all considered momentum transfers (q=300, 400, 500MeV/c). Only at higher q the theoretical response overestimates the experimental one beyond the quasielastic peak. {copyright} {ital 1997} {ital The American Physical Society}

Total photoabsorption cross-sections of A = 6 nuclei with complete final state interaction

The momentum distributions in nuclei like4He,16O and40Ca are explicitly calculated within a phenomenological model which includes dynamical short range and tensor correlation effects. The common behaviour of such distributions in the high momentum region, already established in light nuclei, is extended to the medium weight region. Comparison with existing calculations is discussed and, for completeness, also form factors are evaluated within the same framework.

Dynamical correlations in finite nuclei: A simple method to study tensor effects

A four-nucleon calculation of the total {sup 4}He photodisintegration cross section is performed. The full final-state interaction is taken into account for the first time. This is achieved via the method of the Lorentz integral transform. Semirealistic NN interactions are employed. Different from the known partial two-body {sup 4}He( {gamma},n){sup 3} He and {sup 4}He( {gamma},p){sup 3} H cross sections our total cross section exhibits a pronounced giant resonance. Thus, in contrast to older ({gamma},np) data, we predict quite a strong contribution of the ({gamma},np) channel at the giant resonance peak energy. {copyright} {ital 1997} {ital The American Physical Society}

Ground state wave functions in the hyperspherical formalism for nuclei with A>4

The total photoabsorption cross sections of 6He and 6Li are calculated microscopically with full inclusion of the six-nucleon final state interaction using semirealistic nucleon-nucleon potentials. The Lorentz Integral Transform (LIT) method and the effective interaction approach for the hyperspherical formalism are employed. While 6Li has a single broad giant resonance peak, there are two well separated peaks for 6He corresponding to the breakup of the neutron halo and the α core, respectively. The comparison with the few available experimental data is discussed. PACS numbers: 21.45.+v, 24.30.Cz, 25.20.Dc, 31.15.Ja