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Francesca Sammarruca

Publications and source records attributed to Francesca Sammarruca.

At least 37 records · Page 2Linked to original sources
arXiv2016

Impact of the neutron matter equation of state on neutron skin and neutron drip lines in chiral effective field theory

We present predictions of the binding energy per nucleon and the neutron skin thickness in highly neutron-rich isotopes of Oxygen, Magnesium, and Aluminum. The calculations are carried out at and below the neutron drip line as predicted by our model. The nuclear properties are obtained via an energy functional whose input is the equation of state of isospin-asymmetric infinite matter. The latter is based on a microscopic derivation of the energy per particle in neutron matter applying chiral few-nucleon forces together with a phenomenological model for the equation of state of symmetric nuclear matter. We highlight the impact of the neutron matter equation of state at different orders of chiral effective field theory on neutron skins and the binding energy per particle and quantify the uncertainty carried by our predictions.

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arXiv2015

Short-range correlations in the deuteron: chiral effective field theory, meson-exchange, and phenomenology

We study high-momentum distributions and short-range correlation probabilities in the deuteron with a variety of modern potentials based on chiral effective field theory up to fifth order in the chiral expansion. We also consider some conventional (meson-exchange and phenomenological) interactions. We examine our predictions in the context of short-range correlation probabilities as extracted from analyses of inclusive electron scattering data and discuss whether modern interac- tions can be reconciled with the latter.

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arXiv2014

Short-range correlations in isospin symmetric and asymmetric nuclear matter: a microscopic perspective

Short-range correlations in nuclear and neutron matter are examined through the properties of the correlated wave function obtained by solving the Bethe-Goldstone equation. Tensor correlations are explored through the dominant tensor-driven transition and central correlations through the singlet and triplet S waves. Predictions from a popular meson-theoretic nucleon-nucleon potential employed in the Dirac-Brueckner-Hartree-Fock approach are compared with those from two- and three-body high-quality chiral interactions in Brueckner G-matrix calculations. Short-range correlations in symmetric matter are remarkably stronger than in neutron matter. It is found that short-range correlations are very model dependent and have a large impact on the symmetry energy above normal density.

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arXiv2013

Microscopic approach to the nucleon-nucleon effective interaction and nucleon-nucleon scattering in symmetric and isospin-asymmetric nuclear matter

After reviewing our microscopic approach to nuclear and neutron-rich matter, we focus on how nucleon-nucleon scattering is impacted by the presence of a dense hadronic medium, with special emphasis on the case where neutron and proton densities are different. We discuss in detail medium and isospin asymmetry effects on the total elastic cross section and the mean free path of a neutron or a proton in isospin-asymmetric nuclear matter. We point out that in-medium cross sections play an important role in heavy-ion simulations aimed at extracting constraints on the symmetry potential. We argue that medium and isospin dependence of microscopic cross sections are the results of a complex balance among various effects, and cannot be simulated with a simple phenomenological model.

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arXiv2011

Contribution of isovector mesons to the symmetry energy in a microscopic model

We examine the potential energy contribution to the symmetry energy (in the parabolic approximation) arising from the isovector mesons, π, ρ, and δ. The significance of a microscopic model which incorporates all important mesons is revealed. In particular, we demonstrate the importance of the pion for a realistic investigation of isospin-sensitive systems.

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arXiv2011

Probing the sensitivity of the total nucleus-nucleus reaction cross section at intermediate energies to medium effects and isospin asymmetries

This paper presents reaction cross section predictions. These predictions are the result of a continuous pipeline which originates from a microscopic nuclear interaction. Density parameters and effective nucleon-nucleon cross sections (both involved in the reaction calculations) are by-products of the same equation of state. First, we perform tests of sensitivity to medium effects using reactions involving 208-Pb, a stable but weakly isospin-asymmetric nucleus. We also show predictions for collisions of some neutron-rich isotopes of Calcium and Argon. We observe significant sensitivity of the reaction cross section to medium effects but very weak sensitivity to inclusion of isospin asymmetry in the effective nucleon-nucleon cross sections.

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arXiv2011

Spin- and isospin-polarized states of nuclear matter in the Dirac-Brueckner-Hartree-Fock model

Spin-polarized isospin asymmetric nuclear matter is studied within the Dirac-Brueckner-Hartree-Fock approach. After a brief review of the formalism, we present and discuss the self-consistent single-particle potentials at various levels of spin and isospin asymmetry. We then move to predictions of the energy per particle, also under different conditions of isospin and spin polarization. Comparison with the energy per particle in isospin symmetric or asymmetric unpolarized nuclear matter shows no evidence for a phase transition to a spin ordered state, neither ferromagnetic nor antiferromagnetic.

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arXiv2010

The quark-hadron phase transition in weakly isospin-asymmetric nuclear matter

We consider the transition from quark to hadronic matter which may result during the cooling/expansion of the quark-gluon plasma formed in energetic collisions of weakly isospin-asymmetric ions. This transition involves the energy density of u and d quark matter and the one of nearly isospin-symmetric nuclear matter. Within bag models, the former entails knowledge of the bag pressure, a poorly constrained quantity. The bag pressure at high density can be fixed imposing equality of quark and nucleonic energy densities at the (assumed known) transition point. We find this value to be very model dependent.

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arXiv2010

Temperature-dependence of single-particle properties in isospin-symmetric and -asymmetric matter within the Dirac-Brueckner-Hartree-Fock model

The understanding of the interaction of nucleons in nuclear and neutron-rich matter at non-zero temperature is important for a variety of applications ranging from heavy-ion collisions to nuclear astrophysics. In this papre we apply the Dirac-Brueckner-Hartree-Fock method along with the Bonn B potential to predict single-particle properties in symmetric nuclear matter and neutron-rich matter at finite temperature. It is found that temperature effects are generally small but can be significant at low density and momentum.

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arXiv2010

The splitting of the one-body potential in spin-polarized isospin-symmetric nuclear matter

Spin-polarized symmetric nuclear matter is studied within the Dirac-Brueckner-Hartree-Fock approach. We pay particular attention to the difference between the one-body potentials of upward and downward polarized nucleons. This is formally analogous to the "Lane potential" for isospin-asymmetric nuclear matter. We point out the necessity for additional information on this fundamentally important quantity and suggest ways to constrain it.

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arXiv2010

The Microscopic Approach to Nuclear Matter and Neutron Star Matter

We review a variety of theoretical and experimental investigations aimed at improving our knowledge of the nuclear matter equation of state. Of particular interest are nuclear matter extreme states in terms of density and/or isospin asymmetry. The equation of state of matter with unequal concentrations of protons and neutrons has numerous applications. These include heavy-ion collisions, the physics of rare, short-lived nuclei and, on a dramatically different scale, the physics of neutron stars. The "common denominator" among these (seemingly) very different systems is the symmetry energy, which plays a crucial role in both the formation of the neutron skin in neutron-rich nuclei and the radius of a neutron star (a system 18 orders of magnitude larger and 55 orders of magnitude heavier). The details of the density dependence of the symmetry energy are not yet sufficiently constrained. Throughout this article, our emphasis will be on the importance of adopting a microscopic approach to the many-body problem, which we believe to be the one with true predictive power.

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arXiv2009

Temperature dependence of single-particle properties in nuclear and neutron matter in the Dirac-Brueckner-Hartree-Fock model

The understanding of the interaction of nucleons in nuclear and neutron-rich matter at non-zero temperature is important for a variety of applications ranging from heavy-ion collisions to nuclear astrophysics. In this paper we apply the Dirac-Brueckner-Hartree-Fock method along with the Bonn B nucleon-nucleon potential to predict single-particle properties in symmetric nuclear matter and pure neutron matter at finite temperature. It is found that temperature effects are generally small but can be significant at low density and momentum.

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arXiv2009

Effects of $Λ$ hyperons on the nuclear equation of state in a Dirac-Brueckner-Hartree-Fock model

We predict the energy per baryon in nuclear matter with non-zero fraction of $Λ$ hyperons. We include Dirac effects on the nucleons as well as the $Λ$ and describe how the latter is implemented. We use the nucleon-hyperon meson-exchange potentials from the Juelich group, the latest as well as an earlier version. The dependence of the results on the many-body framework and on the nucleon-hyperon interaction model is discussed.

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arXiv2009

The neutron skin of $^{208}$Pb and the density dependence of the symmetry energy

We explore neutron skin predictions for $^{208}$Pb in relation to the symmetry pressure in various microscopic models based on realistic nucleon-nucleon potentials and either the Dirac-Brueckner-Hartree-Fock approach or the conventional Brueckner-Hartree-Fock framework implemented with three-body forces. We also discuss the correlation between the neutron skin and the radius of a fixed-mass neutron star.

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