Collective features of nuclear dynamics with exotic nuclei within microscopic transport models

Virgil Baran,Daniel Dumitru,Maria Colonna,Massimo Di Toro,Andreea Croitoru,S Lunardi,P Di Nezza,M Chiari,R Menegazzo,J.J Valiente-Dobon,C Signorini,C Bucci,P.G Bizzeti,A Nannini,A Dainese

doi:10.1051/epjconf/20146603004

Abstract

We employ a transport model based on Landau-Vlasov equation to explore the dipolar response of neutron rich systems and its dependence on the symmetry energy. We present evidences for collective features of the Pygmy Dipole Resonance (PDR) and study its dependence with the mass number. We extract a parametrization for the energy centroid position, 41A 1=3 , which agrees quite well with the data for Ni, Zr, Sn and Pb. A linear correlation between the Energy Weighted Sum Rule (EWSR) associated to PDR and the neutron skin thickness is evidenced. An increase of 15MeV fm 2 of EWSR to a change of 0:1fm of neutron skin size is obtained. We conclude that di erent nuclei having close neutron skin size will exhaust the same EWSR in the pygmy region. Consequently a precise experimental estimate of total EWSR exhausted by PDR allows the determination of the neutron skin size and to constrain the slope parameter of the symmetry energy.

Highlights

The fragmentation facilities at GANIL, GSI, MSU and RIKEN provide important results regarding the behavior of exotic nuclei and stimulated new studies of the nuclear properties over an extended range of the neutrons to protons ratio, N/Z
Within a relativistic random-phase approximation (RPA) he observed that for Sn isotopes the fraction of Energy Weighted Sum Rule (EWSR) acquired in the energy region between 5MeV and 10MeV manifests a linear dependence with the neutron skin size up to mass A=120 followed by a mild anti-correlation
Since we intend to investigate the possible correlations between the neutron skin and the properties of Pygmy Dipole Resonance (PDR) we explore first the prediction of the model for the mean-square radius of proton and neutron distributions

Summary

Introduction

The fragmentation facilities at GANIL, GSI, MSU and RIKEN provide important results regarding the behavior of exotic nuclei and stimulated new studies of the nuclear properties over an extended range of the neutrons to protons ratio, N/Z. Within a relativistic random-phase approximation (RPA) he observed that for Sn isotopes the fraction of EWSR acquired in the energy region between 5MeV and 10MeV manifests a linear dependence with the neutron skin size up to mass A=120 followed by a mild anti-correlation. Such a strong correlation was questioned by Reinhard and Nazarewicz [17].

The transport model

Results and discussion

68 N i αD it changes from