L. S. Ferreira

The role of the Δ in nuclear physics

Abstract We review the properties of Δ , and the role it plays in Nuclear Physics. We try to assess what has been ascertained up to now, and what remains to be clarified about this hadron, which represents the outstanding structure in the medium-energy pion–nucleon interaction. We consider the free Δ first, with particular emphasis on those aspects which may give information on the internal hadron structure, such as the isospin mass splittings in the Δ multiplet, and the electromagnetic fingerprints of deviation from spherical symmetry. We then discuss the N – Δ interaction, both under the point of view of meson-exchange models, and under a microscopic quark-model perspective. In so doing, we review the present status of the meson–nucleon and meson– Δ coupling constants and form factors, whose knowledge is a prerequisite for a description of nuclei in terms of effective hadronic degrees of freedom. We discuss also the coupled-channel approach to the NN – NΔ system, and how it compares with relativistic treatments grounded on Quantum Field Theory. We then consider light nuclei, where the percentage of Δ components in the nuclear wave function, and Δ contributions to meson-exchange currents can be studied in a quantitative way, with a minimum of uncertainties due to nuclear-structure effects. Finally, we discuss Δ propagation in finite nuclei and nuclear matter. To this end, we try to give an update presentation of classical subjects, such as the effective Δ interaction in the nuclear environment, medium effects and quenching phenomena, where Δ -hole excitations and nuclear-structure effects are strictly intertwined.

Limiting temperature of hot nuclei from microscopic equation of state

The limiting temperature

Structure of proton-radioactive nuclei

{T}_{\mathit{lim}}

Theoretical Description of Proton Radioactivity

of a series of nuclei is calculated employing a set of microscopic nuclear equations of state (EOSs). It is shown that the value of

Repulsive core of NN S-wave scattering in a quark model with a condensed vacuum

{T}_{\mathit{lim}}

Proton Emission from Odd-Even and Odd-Odd Deformed Drip-Line Nuclei

is sensitive to the nuclear matter equation of state used. Comparison with the values extracted in recent phenomenological analysis appears to favor a definite selection of EOSs. On the basis of this phenomenological analysis, it therefore seems possible to check the microscopic calculations of the nuclear EOS at finite temperature, which is hardly accessible through other experimental information.

Resonances in nuclear physics

The non-adiabatic quasi-particle approach for proton radioactivity from deformed drip-line nuclei is discussed. All experimental data available on decay from ground and isomeric states, and fine structure of odd–even and odd–odd nuclei, are consistently interpreted without free parameters, by this theoretical approach.

Microscopic theory of the nuclear equation of state

The theory for proton radioactivity from deformed drip-line nuclei is discussed. All experimental data available on decay from ground and isomeric states, and fine structure of odd-even and odd-odd nuclei, are consistently interpreted without free parameters, by this theoretical approach.

Deformed proton emitters, Coriolis interaction and pseudo-spin doublets

We work in a chiral invariant quark model, with a condensed vacuum, characterized by only one parameter. Bound state equations for the nucleon and {Delta} are solved in order to obtain an updated value of their radii and masses. Nucleon-nucleon S-wave scattering is studied in the resonating group method framework both for isospin T=1 and T=0. The phase shifts are calculated and an equivalent local potential, which is consistent with K-N scattering, is derived. The result is a reasonable microscopic short range repulsion in the nucleon-nucleon interaction. {copyright} {ital 1997} {ital The American Physical Society}

Asymptotic properties of bound states in coupled quantum wave guides

The theoretical description of proton radioactivity from deformed odd-even and odd-odd drip-line nuclei is discussed. The resonances in deformed drip-line nuclei, and their corresponding half-lives for decay are evaluatedexactly. It is shown that all experimental data, currently available for decay from ground and isomeric states and fine structure, can be consistently described within our model.