Novel determination of density, temperature, and symmetry energy for nuclear multifragmentation through primary fragment-yield reconstruction

Abstract

For thefirst time primary hot isotope distributions are experimentally reconstructed in intermediate heavyion collisions and used with antisymmetrized molecular dynamics (AMD) calculations to determine density, temperature, and symmetry energy coefficient in a self-consistent manner. A kinematical focusing method is employed to reconstruct the primary hot fragment-yield distributions for multifragmentation events observed in the reaction system 64 Zn + 112 Sn at 40 MeV/nucleon. The reconstructed yield distributions are in good agreement with the primary isotope distributions of AMD simulations. The experimentally extracted values of the symmetry energy coefficient relative to the temperature, a sym /T , are compared with those of the AMD simulations with different density dependence of the symmetry energy term. The calculated a sym /T values change according to the different interactions. By comparison of the experimental values of a sym /T with those of calculations, the density of the source at fragment formation was determined to be ρ/ρ 0 = (0.63 ± 0.03). Using this density, the symmetry energy coefficient and the temperature are determined in a self-consistent manner as a sym = (24.7 ± 1.9) MeV and T = (4.9 ± 0.2) MeV. PACS number(s): 25.70.PqConstraining the density dependence of the symmetry energy is one of the key objectives of contemporary nuclear physics. It plays a key role for various phenomena in nuclear astrophysics, nuclear structure, and nuclear reactions [1,2]. Heavy-ion collisions provide a unique opportunity to study the nuclear symmetry energy and its density dependence at and around normal nuclear matter density. However, reliable extraction is difficult because of the complexity of the reaction dynamics.In violent heavy-ion collisions in the intermediate energy regime (20 E inc a few hundred MeV/nucleon), intermediate mass fragments (IMFs) are copiously produced through a multifragmentation process. Nuclear multifragmentation was predicted a long time ago [3] and has been studied extensively following the advent of 4π detectors. Studies of nuclear multifragmentation provide important information on the properties of the hot nuclear matter equation of state. The recent status of the experimental and theoretical work is reviewed in Refs. [4][5][6].In general, the nuclear multifragmentation process, can be divided into three stages, i.e., dynamical compression and * wada@comp.tamu.edu heating, expansion and freeze-out of primary fragments, and finally the separation and cooling of the primary fragments by evaporation.Different models have been developed to model the multifragmentation process. These include dynamical transport models such as fermionic molecular dynamics (FMD) [7], antisymmetrized molecular dynamics (AMD) [8][9][10] constrained molecular dynamics (CoMD) [11], improved quantum molecular dynamics model (ImQMD) [12], quantum molecular dynamics model (QMD) [13], Vlasov-Uehling-Uhlenbeck theory (VUU) [14], the stochastic mean field (SMF) [15], Boltzmann-Uehling-Uhlenbeck (BUU) [16] a...

Isoscaling and nuclear reaction dynamics

“…In principle, information on the asymmetry energy could be constrained if temperature and density are properly evaluated. For example, in references [34,35], the authors describe their method of evaluating T, ρ, and therefore C asym in the context of antisymmetrized molecular dynamics simulations. This method can be applied to the Zn + Zn systems studied in the present work, which could then yield a constraint on the asymmetry energy.…”

Isoscaling constraining sources' sizes

“…One alternative to overcome this shortcoming is the reconstruction of the freeze-out configuration, as has been done in some experiments [14][15][16]. An other option is the construction of observables which are weakly affected by the fragment deexcitation process.…”

Post breakup dynamical evolution of fragments produced in nuclear multifragmentation

“…Despite such difficulties, experimental studies have provided much important information, which has helped establish more accurate representations for the actual scenario of the multifragmentation process [1][2][3]. Furthermore, a few groups have recently developed techniques to reconstruct information corresponding to the freeze-out configuration from the final yields [32][33][34][35][36][37].…”