Role of different parts of the nucleon-nucleon potential on fragment production in asymmetric collisions and their rapidity dependence

The role of different parts of the nucleon-nucleon (NN) interaction potential on the production of light- and intermediate-mass fragments in different mass asymmetric reactions ${}^{120}\mathrm{Sn}+{}^{120}\mathrm{Sn}$ ($\eta =0$), ${}^{82}\mathrm{Kr}+{}^{158}\mathrm{Gd}$ ($\eta =0.3$), ${}^{56}\mathrm{Fe}+{}^{184}\mathrm{W}$ ($\eta =0.5$), and ${}^{35}\mathrm{Cl}+{}^{205}\mathrm{Tl}$ ($\eta =0.7$) (with $A_{\text{total}}=240$ units) within different rapidity domains has been investigated using the isospin-dependent quantum molecular-dynamics model. The results indicate that the multiplicity of different fragments changes with the gradual addition of different parts of the NN interaction potential. The comparison between calculations and experimental data for the ${}^{120}\mathrm{Sn}+{}^{120}\mathrm{Sn}$ reaction reveals that both momentum dependent interactions (MDIs) and symmetry potential are indispensable to explain the charge distribution. The MDI plays a dominant role while the symmetry potential has minor influence on the fragment production, but both together lead to an increase in the multiplicity of light- and intermediate-mass fragments and hence show their significance in the fragment production at intermediate energies.

Figure 1

Phase space of nucleons for ${}^{120}\mathrm{Sn}+{}^{120}\mathrm{Sn}$ ($\eta =0$) [upper panel, (a)–(c)] and ${}^{35}\mathrm{Cl}+{}^{205}\mathrm{Tl}$ ($\eta =0.7$) [lower panel, (d)–(f)] reactions, at $E=50$ MeV/nucleon and $t=200$ fm/c for the SYC, SYCM, and SYCMS sets of potentials (shown from left to right).

Figure 2

Time evolution of mean density for the ${}^{120}\mathrm{Sn}+{}^{120}\mathrm{Sn}$ reaction at $E=50$ MeV/nucleon for different sets of potentials.

Figure 3

Charge distribution of fragments for the central collision of the reactions (a) ${}^{120}\mathrm{Sn}+{}^{120}\mathrm{Sn}$ ($\eta =0$), (b) ${}^{82}\mathrm{Kr}+{}^{158}\mathrm{Gd}$ ($\eta =0.3$), (c) ${}^{56}\mathrm{Fe}+{}^{184}\mathrm{W}$ ($\eta =0.5$), and (d) ${}^{35}\mathrm{Cl}+{}^{205}\mathrm{Tl}$ ($\eta =0.7$) at $E=50$ MeV/nucleon for different sets of potentials and comparison with experimental data [50] for the $\eta =0$ reaction.

Figure 4

Variation of the multiplicity of light charged particles in the participant region (left panel) and quasiparticipant region (right panel) with energies for different $\eta$.

Figure 5

Variation of the multiplicity of intermediate-mass fragments in the participant region (left panel) and quasiparticipant region (right panel) with energies for different $\eta$.

Figure 6

Variation of (a) LCP and (b) IMF multiplicity in the quasiparticipant region with $\eta$ at $E=110$ MeV/nucleon.