The study of nuclear equation of state using stopping and anisotropic flow

Abstract

The present study sheds light on the theoretical aspects of equation of state of nuclear matter by studying the influence of various components of interaction potential as well as nucleon-nucleon cross section on the critical observables of heavy-ion collisions such as collective flow, nuclear stopping and multifragmentation. The dynamic microscopic theory- Isospin-dependent Quantum Molecular Dynamics (IQMD) model is used to carry out the present study. Chapter 1 describes the general introduction of the nuclear physics. The importance of heavy-ion collisions at intermediate energy regime to understand the reaction dynamics under extreme conditions is discussed. The dynamics of mass symmetric and mass asymmetric heavy-ion collisions is described. It also outlines the various observables to study the equation of state in the aforesaid energy regime such as collective flow, nuclear stopping and multifragmentation followed by the theoretical and experimental review of these observables. Chapter 2 presents a brief survey of various primary models used in the literature to study the reaction dynamics. The Isospin-dependent Quantum Molecular Dynamics model (IQMD) model used to carry out the present study is explained in detail. The secondary models (used to analyze the phase space generated by the primary model) such as Minimum Spanning Tree (MST), its updated versions MSTP, isoMST and GEMINI model are also discussed. In Chapter 3 the importance of various components of nucleon-nucleon interaction potential towards the transverse directed flow ⟨Pdir x ⟩ and ⟨Px/A⟩ as well as their balance energies is discussed for the reactions 58 26Fe+58 26Fe, 58 28Ni+58 28Ni, 86 36Kr+93 41Nb and 197 79 Au+197 79 Au. The results of our calculations are also compared with the experimental measurements. Our calculations for the considered energy range clearly demonstrate the dominance of the Coulomb potential and momentum-dependent interactions over the other components of nuclear potential for the lighter colliding systems. The symmetry potential also contribute significantly in the collision of heavier nuclei. In addition, the directed transverse flow (v1) of light fragments is studied for the semi-central collisions of the reaction 197 79 Au+197 79 Au at incident energy ranging between 40 and 250 MeV/nucleon. The cluster recognition 2 method is optimized by applying different isospin-dependent spatial and momentum constraints. In Chapter 4 the effect of isospin content as well as the contributions of various components of nucleon-nucleon interaction potential on stopping ratio of protons and neutrons for the reaction 120 50 Sn+120 50 Sn is presented. It is observed that the momentum dependent interactions affect the nuclear stopping to a larger extent compared to the other components of the nucleon-nucleon interaction potential. The isospin-dependent nucleon-nucleon cross section is also found to affect the stopping in central heavy-ion collisions. The momentum distribution of particles participating in nuclear stopping to get a better insight into the stopping of various charged fragments is also investigated. 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. In Chapter 5 the importance of various components of nucleon-nucleon interaction potential in the fragment production within different rapidity domains for the central collisions of the reactions 120 50 Sn+120 50 Sn , 82 36Kr+158 64 Gd, 56 26Fe+184 74 W, 35 17Cl+205 81 Tl at incident energy ranging between 50 and 110 MeV/nucleon is investigated. Moreover, the role of different components of nucleon-nucleon interaction potential with increase in mass asymmetry is also explored by keeping the total mass of the system fixed. The charge distribution of fragments under the influence of various sets of components of interaction potential is also investigated and the results are compared with the experimental data for symmetric reactions. Chapter 6 describes the conclusions and significance of the work done in this thesis along with the prospect for the extension of present work.