arXiv subjects

R. A. Ramon

Publications and source records attributed to R. A. Ramon.

3 recordsLinked to original sources

arXiv2026

Extension of the dispersive optical model to improve the description of high-momentum components

An improved treatment of high-momentum components in nuclei is introduced in the framework of the dispersive optical model (DOM). The well-established feature that the peak of the spectral function appears at higher excitation energy in the $A$-1 system with increasing momentum has so far not been successfully accounted for in the DOM. To achieve this feature, it is necessary to abandon the factorization of energy dependence and geometry of the DOM self-energy. The volume absorption below the Fermi energy has thus been represented by a decreasing radius at larger missing energy implying that a numerical treatment of the dispersion relations is necessitated. Earlier DOM results for ${}^{48}$Ca are also improved with this approach, demonstrating that a small neutron skin can still be accompanied by protons having a larger high-momentum tail than neutrons.

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arXiv2026

Single-particle structure of the semi-magic nucleus ${}^{90}$Zr from a nonlocal dispersive optical model

A nonlocal dispersive-optical-model (DOM) analysis has been carried out for neutrons and protons in the semi-magic nucleus $^{90}$Zr. Elastic-scattering angular distributions, total and reaction cross sections, single-particle energies, the neutron and proton numbers, the charge distribution, and the binding energy have been fitted to extract the neutron and proton self-energies both above and below the Fermi energy. The resulting spectroscopic factors and other DOM ingredients yield a good description of the $(e,e'p)$ cross sections when the open-shell proton system is described with an extension of the DOM that treats pairing. The distinct difference between the open-shell proton system and a closed one is illustrated by the smooth transition from mostly full to mostly empty orbits.

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arXiv2026

Dispersive-optical-model analysis of the asymmetry dependence of neutron skins

New dispersive optical model analyses of ${}^{54}$Fe and ${}^{90}$Zr together with updated results for ${}^{40}$Ca, ${}^{48}$Ca, and the earlier result for ${}^{208}$Pb shed light on the behavior of neutron skins in nuclei. Starting with a negative skin for ${}^{40}$Ca, a trend increasing somewhat stronger than linear emerges when the neutron skin of these nuclei is considered as a function of asymmetry, $(N-Z)/A$, and linked to the Green's function Monte Carlo results for asymmetric He nuclei. This general trend is consistent with the expectation that nuclei near the neutron drip line are expected to have very large neutron skins. The present analysis therefore motivates the question of which nuclei provide the most relevant link to neutron star physics.

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