arXiv subjects

X. Roca-Maza

Publications and source records attributed to X. Roca-Maza.

58 records · Page 4Linked to original sources

arXiv2009

The Smoothness of Physical Observables

The Garvey-Kelson (GK) relations are powerful algebraic expressions connecting the masses of neighboring atomic nuclei and derived under reasonable physical assumptions. In this contribution we show that these relations are even more general than originally assumed as their validity is conditioned by the smoothness of the underlying nuclear mass function and nothing else. Based on the assumed smoothness of the underlying physical function, the main conclusions from this study are: (1) the GK relations are model independent; (2) any slowly-varying physical observable satisfies the GK relations; and (3) the accuracy of the GK relations may be systematically improved. Examples from nuclear physics (charge radii) and from particle physics (baryon masses) are used to illustrate the flexibility of the approach.

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arXiv2009

Nuclear symmetry energy probed by neutron skin thickness of nuclei

We describe a relation between the symmetry energy coefficients c_sym(rho) of nuclear matter and a_sym(A) of finite nuclei that accommodates other correlations of nuclear properties with the low-density behavior of c_sym(rho). Here we take advantage of this relation to explore the prospects for constraining c_sym(rho) of systematic measurements of neutron skin sizes across the mass table, using as example present data from antiprotonic atoms. The found constraints from neutron skins are in harmony with the recent determinations from reactions and giant resonances.

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arXiv2008

Theoretical study of elastic electron scattering off stable and exotic nuclei

Results for elastic electron scattering by nuclei, calculated with charge densities of Skyrme forces and covariant effective Lagrangians that accurately describe nuclear ground states, are compared against experiment in stable isotopes. Dirac partial-wave calculations are performed with an adapted version of the ELSEPA package. Motivated by the fact that studies of electron scattering off exotic nuclei are intended in future facilities in the commissioned GSI and RIKEN upgrades, we survey the theoretical predictions from neutron-deficient to neutron-rich isotopes in the tin and calcium isotopic chains. The charge densities of a covariant interaction that describes the low-energy electromagnetic structure of the nucleon within the Lagrangian of the theory are used to this end. The study is restricted to medium and heavy mass nuclei because the charge densities are computed in mean field approach. Since the experimental analysis of scattering data commonly involves parameterized charge densities, as a surrogate exercise for the yet unexplored exotic nuclei, we fit our calculated mean field densities with Helm model distributions. This procedure turns out to be helpful to study the neutron-number variation of the scattering observables and allows us to identify correlations of potential interest among some of these observables within the isotopic chains.

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arXiv2008

Impact of the symmetry energy on the outer crust of non-accreting neutron stars

The composition and equation of state of the outer crust of non-accreting neutron stars is computed using accurate nuclear mass tables. The main goal of the present study is to understand the impact of the symmetry energy on the structure of the outer crust. First, a simple "toy model" is developed to illustrate the competition between the electronic density and the symmetry energy. Then, realistic mass tables are used to show that models with a stiff symmetry energy - those that generate large neutron skins for heavy nuclei - predict a sequence of nuclei that are more neutron-rich than their softer counterparts. This result may be phrased in the form of a correlation: the larger the neutron skin of 208Pb, the more exotic the composition of the outer crust.

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