Symmetry energy effect on emissions of light particles in coincidence with fast fission

Abstract

The emission of light particles in coincidence with fast fission in near peripheral reactions of 40Ar+197Au at 30 MeV/u beam energy has been studied by using the Improved Quantum Molecular Dynamics Model (ImQMD). It is demonstrated that in the symmetrical fast fission of the heavy target-like fragment (TLF), the emission of the coalescence-invariant neutrons (CIN) is enhanced particularly at large angles in comparison to that in the events without fission. Due to the enhanced CIN emission and the accumulation of the isospin effect in the long-time process, the yield ratio of the CIN to the coalescence-invariant protons (CIP) in the fission events exhibits significant dependence on the symmetry energy Esym(ρ) varying with density. Considering that the large angle neutrons are experimentally advantageous to measure for the lower flying velocity and lower multiplicity, we emphasize that the yield ratio RCINP at large angles in the fast fission events can be used as a novel probe of the nuclear symmetry energy at sub-saturation densities.