Isospin effect in the statistical sequential decay

Isospin effect of the statistical emission fragments from the equilibrated source is investigated in the frame of statistical binary decay implemented into GEMINI code, isoscaling behavior is observed and the dependences of isoscaling parameters $\alpha$ and $\beta$ on emission fragment size, source size, source isospin asymmetry and excitation energies are studied. Results show that $\alpha$ and $\beta$ neither depends on light fragment size nor on source size. A good linear dependence of $\alpha$ and $\beta$ on the inverse of temperature $T$ is manifested and the relationship of $\alpha=4C_{sym}[(Z_{s}/A_{s})_{1}^{2}-(Z_{s}/A_{s})_{2}^{2}]/T$ and $\beta=4C_{sym}[(N_{s}/A_{s})_{1}^{2}-(N_{s}/A_{s})_{2}^{2}]/T$ from different isospin asymmetry sources are satisfied. The symmetry energy coefficient $C_{sym}$ extracted from simulation results is $\sim$ 23 MeV which includes both the volume and surface term contributions, of which the surface effect seems to play a significant role in the symmetry energy.Comment: 8 pages, 8 figures; A new substantially modified version which has been accepted by the Physical Review

Hard photon flow and photon-photon correlation in intermediate energy heavy-ion collisions

Hard photons emitted from energetic heavy ion collisions are very interesting since they do not experience nuclear interaction, and therefore they are useful to explore properties of nuclear matter. We investigated hard photon production and its properties in intermediate energy heavy-ion collisions with the help of the Blotzmann-Uehling-Ulenbeck model. Two components of hard photons are discussed: direct and thermal. The positive directed flow parameter and negative elliptic flow parameter of direct photons are demonstrated and they are anti-correlated to the flows of free protons. The dependencies of hard photon production and anisotropic parameters on impact parameter, beam energy, nuclear equation of state and symmetry energy are also discussed. Furthermore, we investigated the two-photon momentum correlation function from which the space-time structure information of the photon source could be extracted as well as the two-photon azimuthal correlation which could provide another good method to determine the elliptic flow parameter $v_{2}$ of direct hard photons.Comment: 13 pages, 18 figure

Isoscaling in the Lattice Gas Model

The isoscaling behavior is investigated using the isotopic/isobaric yields from the equilibrated thermal source which is prepared by the lattice gas model for lighter systems with A = 36. The isoscaling parameters $\alpha$ and -$\beta$ are observed to drop with temperature. The difference of neutron and proton chemical potential shows a turning point around 5 MeV where the liquid gas phase transition occurs in the model. The relative free neutron or proton density shows a nearly linear relation with the N/Z (neutron to proton ratio) of system and the isospin fractionation is observed.Comment: 5 figures, 5 pages; the final version to appear in Phys Rev

A proposed reaction channel for the synthesis of the superheavy nucleus Z = 109

We apply a statistical-evaporation model (HIVAP) to calculate the cross sections of superheavy elements, mainly about actinide targets and compare with some available experimental data. A reaction channel $^{30}$Si + $^{243}$Am is proposed for the synthesis of the element Z = 109 and the cross section is estimated.Comment: 4 pages, 2 figures, 2 tables; two typos are corrected in Ref. [12] and [19

Dynamical and sequential decay effects on isoscaling and density dependence of the symmetry energy

The isoscaling properties of the primary and final products are studied via isospin dependent quantum molecular dynamics (IQMD) model and the followed sequential decay model GEMINI, respectively. It is found that the isoscaling parameters $\alpha$ of both primary and final products keep no significant change for light fragments, but increases with the mass for intermediate and heavy products. The dynamical effects on isoscaling are exhibited by that $\alpha$ value decreases a little with the evolution time of the system, and opposite trend for the heavy products. The secondary decay effects on isoscaling are reflected in the increasing of the $\alpha$ value for the final products which experiences secondary decay process. Furthermore the density dependence of the symmetry energy has also been explored, it is observed that in the low densities the symmetry energy coefficient has the form of $C_{sym}(\rho)\sim C_{0}(\rho/\rho_{0})^{\gamma}$, where $\gamma = 0.7 \sim 1.3$ for both primary and final products, but $C_{0}$ have different values for primary and final products. It is also suggested that it might be more reasonable to describe the density dependence of the symmetry energy coefficient by the $C_{sym}(\rho/\rho_{0})\approx C_{1}(\rho/\rho_{0})^{\gamma_{soft}} + C_{2}(\rho/\rho_{0})^{\gamma_{stiff}}$ with $\gamma_{soft}\leq 1$, $\gamma_{stiff}\geq 1$ and $C_{1}, C_{2}$ constant parameters.Comment: 10 pages, 10 figure