Statistical analysis of a dynamical multifragmentation path

A microcanonical multifragmentation model (MMM) is used for investigating whether equilibration really occurs in the dynamical evolution of two heavy ion collisions simulated via a stochastic mean field approach. The standard deviation function between the dynamically obtained freeze-out fragment distributions corresponding to the reaction ${}^{129}\mathrm{Xe}+{}^{119}\mathrm{Sn}$ at 32 MeV/nucleon and the MMM ones corresponding to a wide range of mass, excitation energy, freeze-out volume, and nuclear level density cutoff parameter shows a unique minimum. A distinct statistically equilibrated stage is identified in the dynamical evolution of the system.

Figure 1

Contour plots of the error function $\mathcal{E}$ [see Eq. (1)]: in the $(V/V_0,E)$ plane corresponding to $A=210$ (upper panel); in the $(A,V/V_0)$ plane corresponding to $E=5.7$ MeV/nucleon (lower panel). Darker regions correspond to smaller $\mathcal{E}$; units are relative.

Figure 2

Dynamical charge (upper panel) and number of IMF distributions (lower panel) in comparison with the statistical ones. Statistical results are represented by open squares; histogram (upper panel) and stars (lower panel) correspond to the dynamical ones.

Figure 3

(Upper panel) Statistical (open squares) and dynamical (histogram) fragment average kinetic energy versus charge. (Lower panel) Statistical (solid lines) and dynamical (dashed lines) radial distribution of fragments with largest (peak 1), second largest (peak 2), and third largest (peak 3) charge in one fragmentation event. The plot corresponds to $\langle (\tilde{V}/V_0){}_{\mathrm{IMF}}\rangle =9.08$.

Figure 4

Dynamical results. (Upper panel) Evolution of IMF (circles) and prefragment (squares) multiplicities in time. (Lower panel) Collective velocity (full line), nuclear density (dashed line), and excitation energy per nucleon (circles), as a function of the distance from the center of mass of the system, corresponding to 140 fm/c. The excitation energy is evaluated in the region occupied by prefragments.