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M. Chiapparini

Publications and source records attributed to M. Chiapparini.

25 records · Page 2Linked to original sources
arXiv2001

The Isospin Asymmetry in the Pseudo-spin Dynamical Symmetry

Pseudo-spin symmetry in nuclei is investigated considering the Dirac equation with a Lorentz structured Woods-Saxon potential. The isospin correlation of the energy splittings of pseudo-spin partners with the nuclear potential parameters is studied. We show that in an isotopic chain, the pseudo-spin symmetry is better realized for neutrons than for protons. This behavior comes from balance effects amongst the central nuclear potential parameters. In general, we found an isospin asymmetry of the nuclear pseudo-spin interaction, opposed to the nuclear spin-orbit interaction which is quasi isospin symmetric.

nucl-th↗
arXiv2000

Neutron stars in a class of non-linear relativistic models

We introduce in this work a class of relativistic models for nuclear matter and neutron stars which exhibits a parameterization, through mathematical constants, of the non-linear meson-baryon couplings. For appropriate choices of the parameters, it recovers current QHD models found in the literature: Walecka and the Zimanyi and Moszkowski models (ZM and ZM3). For other choices of the parameters, the new models give very interesting and new physical results.We have obtained numerical values for the maximum mass and radius of a neutron star sequence, red-shift, hyperon populations, radial distribution of particles, among other relevant static properties of these stellar objects. The phenomenology of neutron stars in ZM models is presented and compared to the phenomenology obtained in other versions of the Walecka model. We have found that the ZM3 model is too soft and predicts a very small maximum neutron star mass, $\sim0.72 M_\odot$. A strong similarity between the results of ZM-like models and those with exponential couplings is noted. Sensibility of the results to the specific choice of the values for the binding energy and saturation density is pointed out. Finally, we discuss the very intense scalar condensates found in the interior of neutron stars which may lead to negative effective masses.

nucl-th↗
arXiv2000

$D^*Dπ$ and $B^*Bπ$ form factors from QCD Sum Rules

The $H^*Hπ$ form factor for H = B and D mesons is evaluated in a QCD sum rule calculation. We study the Borel sum rule for the three point function of two pseudoscalar and one vector meson currents up to order four in the operator product expansion. The double Borel transform is performed with respect to the heavy meson momenta. We discuss the momentum dependence of the form factors and two different approaches to extract the $H^*Hπ$ coupling constant.

hep-ph↗
arXiv1998

Modified Zimanyi-Moszkowski Model for Finite Nuclei

By scaling the mesonic masses in the Walecka model, to the inverse of the hadronic effective mass in medium, we generate the Zimanyi-Moszkowski (ZM) models added to a surface term. For infinite nuclear matter, the surface term vanishes and this new model becomes equivalent to the usual ZM model. For finite nuclei calculations, the surface contribution changes the spin-orbit splitting in the right experimental direction. Calculations for some nuclei are presented.

nucl-th↗
arXiv1998

Alternative Linear Chiral Models for Nuclear Matter

The equation of state of a family of alternative linear chiral models in the mean field approximation is discussed. We investigate the analogy between some of these models with current models in the literature, and we show that it is possible to reproduce very well the saturation properties of nuclear matter.

nucl-th↗
arXiv1996

Finite Nuclei in a Relativistic Mean-Field Model with Derivative Couplings

We study finite nuclei, at the mean-field level, using the Zimanyi-Moskowski model and one of its variations (the ZM3 model). We calculate energy levels and ground-state properties in nuclei where the mean-field approach is reliable. The role played by the spin-orbit potential in sorting out mean-field model descriptions is emphasized.

nucl-th↗
arXiv1996

Derivative-Coupling Models and the Nuclear-Matter Equation of State

The equation of state of saturated nuclear matter is derived using two different derivative-coupling Lagrangians. We show that both descriptions are equivalent and can be obtained from the sigma-omega model through an appropriate rescaling of the coupling constants. We introduce generalized forms of this rescaling to study the correlations amongst observables in infinite nuclear matter, in particular, the compressibility and the effective nucleon mass.

nucl-th↗