Evolution of the statistical disintegration of finite nuclei toward high energy

We develop a statistical approach for the description of complex nuclei formation from dynamically produced baryons in high energy heavy-ion reactions. We consider a finite highly excited expanding nuclear system formed after central nucleus-nucleus collisions. This system is subdivided into primary equilibrated nucleon clusters. The final nuclei are produced after the decay of these excited clusters. By the successful comparison with the FOPI experimental data we prove the possibility of such a local equilibrium in nuclear matter with the temperature corresponding to the phase coexistence region. The regularities obtained in this new nuclei production mechanism are shown.

Figure 1

Energy spectra for initial nucleons of the hot expanding nuclear system according to the microcanonical phase space distribution—PSG (a) and according to the hydrodynamical-like explosion—HYG (b). The assumed total kinetic energies are 25, 50, and 100 MeV per nucleon. The nucleon source size and composition are shown in the top panel.

Figure 2

Yield of coalescent-like clusters versus their mass number $A$ after the CB calculations at the source energy of 10, 25, and 100 MeV per nucleon. Composition and sizes of sources, nucleon generator (PSG), as well as coalescence parameters ($v_c$) are indicated in the panels.

Figure 3

Average internal energy of coalescent clusters versus their mass number $A$ produced as a result of the coalescence (CB) in the sources with $A_0=116$ and $Z_0=56$ after PSG (a) and HYG (b). The source energy and coalescence parameters are shown in the panels.

Figure 4

Yield of final nuclei versus their mass number $A$ after the de-excitation of primary clusters shown in Fig. 2. The notations are as in Fig. 2.

Figure 5

Yield of final nuclei versus their mass number $A$ after the de-excitation of primary clusters, by using the HYG initial nucleon distributions. Other notations are as in Fig. 4.

Figure 6

Average kinetic energies (per nucleon) of final nuclei versus their charges $Z$. The calculations are performed for the initial source with $A_0=116$ and $Z_0=56$ at the initial excitation energies of 10, 25, 50, and 100 MeV per nucleon. Notations with the parameters are in the figure. (a) is for the PSG initial nucleon generation, and (b) is for the HYG one.

Figure 7

Comparison of our calculations with the FOPI experimental data on the nuclei production in central $\mathrm{Ni}+\mathrm{Ni}$ collisions at $150A$ MeV (a) and $250A$ MeV (b). The parameters of the initial source are given in the figure. The nucleon distributions are after PSG, and parameters $v_c=0.18c$, $0.24c$, and $0.28c$ are used in the calculations.

Figure 8

Comparison of our calculations with the FOPI experimental data on the nuclei production in central $\mathrm{Au}+\mathrm{Au}$ collisions at $90A$ MeV (a) and $120A$ MeV (b). The parameters of the initial source are given in the figure. The nucleon distributions are after PSG, and parameters $v_c=0.18c$, $0.22c$, and $0.28c$ are used in the calculations.

Figure 9

The same as in Fig. 8, but for central $\mathrm{Au}+\mathrm{Au}$ collisions at $150A$ MeV (a) and $250A$ MeV (b). The parameters $v_c=0.18c$, $0.24c$, and $0.28c$ are used in the calculations.

Figure 10

Average excitation energy per nucleon ($E^{*}/A$) of local clusters of nuclear matter versus their mass number $A$ corresponding to the $v_c$ parameters which lead to the best description of the FOPI experimental data. The lines correspond to different reactions of central collisions, they are noted in the figure.

Figure 11

Comparison of average kinetic energies per nucleon of produced nuclei versus their charges $Z$ with the FOPI experimental data in $\mathrm{Au}+\mathrm{Au}$ central collisions. (a) is for $90A$ MeV collisions, and (b) is for $120A$ MeV. The parameters of the initial source are $A_0=394$, $Z_0=158$, and the energy $E_0$ is given in the figure. The nucleon distributions are after PSG. The parameters $v_c=0.18c$, $0.22c$, and $0.28c$ are used in the calculations.

Figure 12

The same as in Fig. 11, but for central $\mathrm{Au}+\mathrm{Au}$ collisions at $150A$ MeV (a) and $250A$ MeV (b). The parameters $v_c=0.18c$, $0.24c$, and $0.28c$ are used in the calculations.