Probing the density dependence of the symmetry energy via multifragmentation at subsaturation densities

Abstract

Symmetry energy for asymmetric nuclear matter at subsaturation densities was investigated in the framework of an isospin-dependent quantum molecular dynamics model. A single ratio of neutrons and protons is compared with the experimental data of Famiano et al. [Phys. Rev. Lett. 97, 052701 (2006)] We have also performed a comparison for the double ratio with experimental as well as different theoretical results of Boltzmann-Uehling-Uhlenbeck in 1997, Isospin-dependent Boltzmann-Uehling-Uhlenbeck in 2004, Boltzmann-Nordeim-Vlasov, and Improved Quantum Molecular Dynamics models. It is found that the double ratio predicts the softness of symmetry energy, which is a little underestimated in the single ratio. Furthermore, the study of the single ratio is extended for different kinds of fragments, while the double ratio is extended for different neutron-rich isotopes of Sn.

Examining the effect of a binding-energy-dependent clusterization algorithm on isospin-sensitive observables in heavy-ion collisions

“…The MST method has been quite successful in explaining certain fragmentation observables such as charge distribution of emitted fragments [22,26], single and double yield ratio of neutrons to protons [6,7], while fails to describe some important detail in the production of free nucleons, light and heavy charged particles [22,[26][27][28]. The failure results are summarized as follow: (1) Yield of Z = 1 is overestimated, while Z = 2 is underestimated.…”

“…The most commonly and widely used algorithm depends on the spatial and momentum coordinates of the nucleons, is known as minimum spanning tree (MST) algorithm [7,13,22]. According to this method, two nucleons will undergo the cluster formation if the relative distance (|R i − R j |) and relative momentum (|P i − P j |) between the nucleons is less than 3.5-4 fm and 250-268 MeV/c, respectively.…”

“…The isospin physics, which is new and exciting field in the present era, has been widely explored by using the simple MST method till 2013 [3,7,8,13,21]. Meanwhile, in 2012, the attempts were done by incorporating modifications in MST in term of spatial distance between the nucleons on the basis of type of particles [25].…”

“…In the present work, IQMD model is used for generating the phase space of nucleons [7,13,21]. The model is modified by the authors for the density dependence of the symmetry energy, having form:…”

Effect of Coulomb energy on the symmetry energy coefficients of finite nuclei

“…The symmetry energy coefficient plays a key role, not only in nuclear physics, such as the dynamics of heavy-ion collisions induced by radioactive beams and the structure of exotic nuclei near the nuclear drip lines [1][2][3][4][5][6], but also a number of important issues in astrophysics, such as the dynamical evolution of the core collapse of a massive star and the associated explosive nucleosynthesis [7][8][9][10][11][12][13]. In the global fitting of the nuclear masses in the framework of the liquid-drop mass formula, the symmetry coefficient a sym of finite nuclei enters as a mass-dependent phenomenological parameter [14][15][16][17][18].…”