Effects of cluster correlations on fragment emission in ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ at 50 MeV/nucleon

The effects of cluster correlations have been studied in the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ reaction at 50 MeV/nucleon, using three antisymmetrized molecular dynamics (AMD) models, the AMD (AMD/D) without any additional cluster correlations, AMD/D-COALS with nucleon correlations based on a coalescence prescription for light cluster formations with $A\le 4$, and AMD-cluster with an extended cluster correlation in two-nucleon collision processes and a special treatment for intermediate fragment formation with $A\le 9$. The angular distributions and energy spectra of fragments have been simulated and compared with the available experimental data. It is found that the cluster correlations take a crucial role to describe the productions of light charged particles (LCPs) and intermediate mass fragments (IMFs), and the AMD-cluster studied here provides a consistent overall reproduction of the experimental data. It is also shown that the significant effects of the secondary decay processes are involved for the fragment production besides the dynamical productions in the AMD stage. Detailed LCP and IMF production mechanisms involved in the intermediate energy heavy ion collisions are discussed.

Figure 1

Comparisons of the angular distributions of the primary (upper row) and secondary (lower row) for $p, d, t, {}^3\mathrm{He}$, and ${}^4\mathrm{He}$ from left to right, respectively, with different AMD simulations. The experimental data, taken from Ref. [1], are shown by open circles. Green dashed, blue dotted, and red solid lines show the simulated results from AMD/D, AMD/D-COALS, and AMD-cluster, respectively.

Figure 2

Comparisons of energy spectra of the secondary for $p, d, t, {}^3\mathrm{He}$, and ${}^4\mathrm{He}$ at selected angles. See also the Fig. 1 caption for symbol and histograms.

Figure 3

Comparisons of angular distributions of the primary (upper row) and secondary (lower row) for lithium and beryllium isotopes. See also the Fig. 1 caption for symbol and histograms.

Figure 4

Comparisons of angular distributions of the primary (upper row) and secondary (lower row) for boron and carbon isotopes. See also the Fig. 1 caption for symbol and histograms. The large error bars in the original experimental data for ${}^8\mathrm{B}$ are not shown because they are dominated in the systematic errors of the detector calibration. See details in Ref. [15].

Figure 5

Comparisons of energy spectra of the secondary for Li and Be isotopes at selected angles. See also the Fig. 1 caption for symbols and curves.

Figure 6

Similar plots as Fig. 5, but for B and C isotopes. See also the Fig. 1 caption.

Figure 7

Excitation energy distributions of IMFs emitted at ${\theta }_{\mathrm{lab}}>{20}^{\circ }$ (left panel) and ${\theta }_{\mathrm{lab}}\le {20}^{\circ }$ (right panel) from AMD/D-COALS and AMD-cluster and with kinetic energies above experimental energy thresholds. Blue dot and red solid lines represent the excited primary fragment by the AMD/D-COALS and AMD-cluster simulated, respectively. The experimental particle decay thresholds are also shown on the x axis by black arrows.

Figure 8

Similar plots as Fig. 7, but for AMD-cluster with two different $NN$ cross sections. Blue dotted and red solid histograms represent LM and free $NN$ cross sections, respectively. See also Fig. 7 caption.