• Suneel Kumar

Articles written in Pramana – Journal of Physics

• The simulations of Ca-Ca collisions: Binary break-up, onset of multifragmentation and vaporization

The incomplete fusion, onset of multifragmentation and vaporization is studied in Ca-Ca collisions at bombarding energies between 20–1000 A MeV and at impact parameters between b=0 to bmax using quantum molecular dynamics model. We find incomplete fusion events at E/A=20 MeV. The light mass fragment production at a given incident energy does not show any rise and fall with a change in the impact parameter. Whereas, the IMF production at higher energies (≥ 150 A MeV) has a clear rise and fall.

• Fragment production in 16O+80Br reaction within dynamical microscopic theory

We analyze the formation of fragments in O—Br reaction at different incident energies between E/A=50 MeV and 200 MeV. This study is carried out within the quantum molecular dynamics (QMD) model coupled with recently advanced simulated annealing clusterization algorithm (SACA). For comparison, we also use the conventional minimum spanning tree (MST) method. Our detailed study shows that the SACA can detect the final stable fragment configuration as early as 60 fin/c which is marked by a dip in the heaviest fragment. On the other hand, the MST method needs several hundred fm/c to identify the final stable distribution. A comparison of the charge distribution with experimental data shows that the SACA is able to reproduce the data very nicely whereas (as reported earlier) the MST method fails to break the spectator matter into intermediate mass fragments. Furthermore, our results with SACA method indicate the onset of multi-fragmentation around 75 MeV/A which is again in good agreement with experimental findings.

• A comparative study of model ingredients: Fragmentation in heavy-ion collisions using quantum molecular dynamics model

We aim to understand the role of NN cross-sections, equation of state as well as different model ingredients such as width of Gaussian, clusterization range and different clusterization algorithms in multifragmentation using quantum molecular dynamics model. We notice that all model ingredients have sizable effect on the fragment pattern.

• On the elliptic ﬂow for nearly symmetric collisions and nuclear equation of state

We present the results of elliptic ﬂow for the collision of nearly symmetric nuclei (10Ne20+13Al27, 18Ar40+21Sc45, 30Zn64+28Ni58, 36Kr86+41Nb93) using the quantum molecular dynamics (QMD) model. General features of elliptic ﬂow are investigated with the help of theoretical simulations. The simulations are performed at beam energies between 45 and 105 MeV/nucleon. A signiﬁcant change can be seen from in-plane to out-of-plane elliptic ﬂow of different fragments with incident energy. A comparison with experimental data is also made. Further, we show that elliptic ﬂow for different fragments follows power-law dependence as given by the function $C(A_{\text{tot}})^{\tau}$.

• Energy of vanishing ﬂow in heavy-ion collisions: Role of mass asymmetry of a reaction

We aim to understand the role of Coulomb interactions as well as different equations of state on the disappearance of transverse ﬂow for various asymmetric reactions leading to the same total mass. For the present study, the total mass of the system is kept constant (A_{\text{TOT}} = 152) and mass asymmetry of the reaction is varied between 0.2 and 0.7. The Coulomb interactions as well as different equations of state are found to affect the balance energy signiﬁcantly for larger asymmetric reactions.

• Effect of isospin-dependent cross-section on fragment production in the collision of charge asymmetric nuclei

To understand the role of isospin effects on fragmentation due to the collisions of charge asymmetric nuclei, we have performed a complete systematical study using isospin-dependent quantum molecular dynamics model. Here simulations have been carried out for ${}^{124}X_n + {}^{124}X_n$ ,where 𝑛 varies from 47 to 59 and for 40Y$_m$ + 40Y$_m$ , where 𝑚 varies from 14 to 23. Our study shows that isospin-dependent cross-section shows its inﬂuence on fragmentation in the collision of neutron-rich nuclei.

• Impact of density-dependent symmetry energy and Coulomb interactions on the evolution of intermediate mass fragments

Within the framework of isospin-dependent quantum molecular dynamics (IQMD) model, we demonstrate the evolution of intermediate mass fragments in heavy-ion collisions. In this paper, we study the time evolution, impact parameter, and excitation energy dependence of IMF production for the different forms of density-dependent symmetry energy. The IMF production and charge distribution show a minor but considerable sensitivity towards various forms of densitydependent symmetry energy. The Coulomb interactions affect the IMF production significantly at peripheral collisions. The IMF production increases with the stiffness of symmetry energy.

• On the momentum distribution of particles participating in nuclear stopping

Nuclear stopping is studied as a function of incident energy and charge of the fragment produced in central heavy-ion collisions (HIC) of $^{197}_{79}$Au+$^{197}_{79}$Au and $^{58}_{28}$Ni+$^{58}_{28}$Ni using stopping parameter VARXZ. Various momentum constraints were imposed to get better insight into the stopping. The comparison of measured and calculated values of stopping for protons reveals the significance of these constraints. Maximum stopping is obtained for the particles lying in the lowest range of the momentum distribution at all incident energies.

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019
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