Forging the Link between Nuclear Reactions and Nuclear Structure

Abstract

A comprehensive description of all single-particle properties associated with the nucleus 40 Ca is generated by employing a nonlocal dispersive optical potential capable of simultaneously reproducing all relevant data above and below the Fermi energy. The introduction of nonlocality in the absorptive potentials yields equivalent elastic differential cross sections as compared to local versions but changes the absorption profile as a function of angular momentum suggesting important consequences for the analysis of nuclear reactions. Below the Fermi energy, nonlocality is essential to allow for an accurate representation of particle number and the nuclear charge density. Spectral properties implied by (e, e ′ p) and (p, 2p) reactions are correctly incorporated, including the energy distribution of about 10% high-momentum nucleons, as experimentally determined by data from Jefferson Lab. These high-momentum nucleons provide a substantial contribution to the energy of the ground state, indicating a residual attractive contribution from higher-body interactions for 40 Ca of about 0.64 MeV/A.PACS numbers: 21.10. Pc,24.10.Ht,11.55.Fv The properties of a nucleon that is strongly influenced by the presence of other nucleons have traditionally been studied in separate energy domains. Positive energy nucleons are described by fitted optical potentials mostly in local form [1,2]. Bound nucleons have been analyzed in static potentials that lead to an independent-particle model modified by the interaction between valence nucleons as in traditional shell-model calculations [3,4]. The link between nuclear reactions and nuclear structure is provided by considering these potentials as representing different energy domains of one underlying nucleon self-energy. This idea was implemented in the dispersive optical model (DOM) by Mahaux and Sartor [5]. By employing dispersion relations, the method provides a critical link between the physics above and below the Fermi energy with both sides being influenced by the absorptive potentials on the other side.The DOM provides an ideal strategy to predict properties for exotic nuclei by utilizing extrapolations of these potentials towards the respective drip lines [6,7]. The main stumbling block so far has been the need to utilize the approximate expressions for the properties of nucleons below the Fermi energy that were developed by Mahaux and Sartor [5] to correct for the normalizationdistorting energy dependence of the Hartree-Fock (HF) potential. By restoring the proper treatment of nonlocality in the HF contribution, it was possible to overcome this problem [8] although the local treatment of the absorptive potentials yielded a poor description of the nuclear charge density and particle number.In the present work we have for the first time treated the nonlocality of these potentials for the nucleus 40 Ca with the aim to include all available data below the Fermi energy that can be linked to the nucleon single-particle propagator [9] while maintaining a correct description of the el...

Phonon coupling effects in proton scattering fromCa40

“…The present approach is complementary to the highly developed folding model, e.g., [12][13][14][15], incorporating a local density, LD, model. As remarked by Köhler [30] in the context of core polarization in shell model calculations, particle-hole excitations are allowed in finite systems.…”

“…Fitting data like that mentioned above evidently requires physics beyond the highly developed [12][13][14][15] local density model. Such models would not seem to have any place for angular momentum dependence, for example.…”

Effects of nonlocal potentials on(p,d)transfer reactions

“…In this work, we revisit the study in [16], but now using the DOM non-local interaction of [25] for the reactions 40 Ca(p, d) 39 Ca at E p =20, 35 and 50 MeV. For comparison, we also repeat the calculations with the Perey-Buck interaction for these reactions.…”

“…Thus, the first step in our work was to fit in detail the elastic-scattering predictions obtained with both the DOM [25] and the Perey-Buck [15] nonlocal interactions, with a local form. So far, the non-local DOM has only been developed for 40 Ca, so we concentrate our investigation to proton scattering on 40 Ca at E p =20, 35 and 50 MeV.…”

“…By analyzing theoretically calculated self-energies for Ca isotopes which include long-range [23] and short-range correlations [24], it was possible to clarify the importance of representing the imaginary part of the optical potential also in terms of non-local ingredients. These insights have recently led to an extension of the dispersive optical model formalism to explicitly include non-locality [25,26] in the real and imaginary part of the self-energy specifically for the 40 Ca nucleus. In order to fit a large range of bound-state and scattering data, the non-locality was required to be different above and below the Fermi energy for the imaginary components.…”