Probing the symmetry energy at low density using observable from neck fragmentation

E De Filippo,P Guazzoni,M Trimarchi,V Baran,F Amorini,L Francalanza,A Grzeszczuk,R Płaneta,L Acosta,E Geraci,E Piasecki,C Maiolino,G Politi,P Russotto,G Cardella,F Rizzo,G Lanzalone,A Pagano,E La Guidara,L Zetta,F Porto,C Agodi,S Pirrone,T Cap,I Berceanu,L Quattrocchi,A Trifirò,I Skwira‐Chalot ,E V Pagano ,T Minniti,R Gianì ,Jifeng Han ,M Papa,I Lombardo,M Colonna,K Siwek‐Wilczyńska ,J Wilczyńskí ,G Verde,L Auditore,L Grassi,A Pop,E Rosato,M Vigilante

doi:10.1051/epjconf/20146603032

Abstract

Semi-peripheral collisions of 64 Ni + 124 Sn in direct and inverse kinematics, at 35 A MeV incident energy, are studied to characterize the dynamical origin and align- ments properties of fragments emission at midrapidity. This emission is partly due to the fragmentation of a transient neck joining the projectile and target in the early stages of the reaction. Recently we exploited observable from neck fragmentation to constraint the density dependence of the symmetry energy. In this contribution we focus on the den- sity evolution of the mid-rapidity source. An experimental survey is suggested to check if data are consistent with the formation of neck fragments in a dilute density region in contact with the projectile-like and target-like spectators at normal saturation density.

Highlights

We selected ternary events in the final state, where a PLF and TLF residue and one Intermediate mass fragments (IMF)
PLF−I MF − VT LF ) and the break-up axis defined as the relative velocity between the PLF and Intermediate mass fragments (IMF) oriented from the light to heavy fragment
The distribution of the ratio between E1−23 and the kinetic energy relative to the Coulomb repulsion Ecoul is shown in Fig. 2c) for Z=4 statistically emitted particles, and, as expected, is well centered around one and is used as validation of the method

Summary

Introduction

We selected ternary events in the final state, where a PLF and TLF residue and one IMF A way to study the dynamical origin and alignment of mid-rapidity fragments is to consider the angle θPROX between the TLF and IMF-PLF center of mass direction (n s = Vc.m. PLF−I MF − VT LF ) and the break-up axis defined as the relative velocity between the PLF and IMF oriented from the light to heavy fragment.

Results

Conclusion