Aman D. Sood

Isospin effects on the energy of vanishing flow in heavy-ion collisions

Using the isospin-dependent quantum molecular dynamics model we study the isospin effects on the disappearance of flow for the reactions of 58Ni + 58Ni and 58Fe + 58Fe as a function of the impact parameter. We found good agreement between our calculations and experimentally measured energy of vanishing flow at all colliding geometries. Our calculations reproduce the experimental data within 5% (10%) at central (peripheral) geometries.

Sensitivity of the transverse flow to the symmetry energy

We study the sensitivity of transverse flow to symmetry energy in the Fermi energy region as well as at high energies. We find that transverse flow is sensitive to symmetry energy and its density dependence in the Fermi energy region. We also show that the transverse flow can address the symmetry energy at densities about twice the saturation density; however, it shows insensitivity to the symmetry energy at densities {rho}/{rho}{sub 0}>2. The mechanism for the sensitivity of transverse flow to symmetry energy and its density dependence is also discussed.

Isospin effects in the disappearance of flow as a function of colliding geometry

We study the effect of isospin degree of freedom on the balance energy (E{sub bal}) as well as its mass dependence throughout the mass range 48-270 for two sets of isobaric systems with N/Z=1 and 1.4 at different colliding geometries ranging from central to peripheral ones. Our findings reveal the dominance of Coulomb repulsion in isospin effects on E{sub bal} as well as its mass dependence throughout the range of the colliding geometry. Our results also indicate that the effect of symmetry energy and nucleon-nucleon cross section on E{sub bal} is uniform throughout the mass range and throughout the colliding geometry. We also present the counterbalancing of nucleon-nucleon collisions and mean field by reducing the Coulomb and the counterbalancing of Coulomb and mean field by removing the nucleon-nucleon collisions.

Isospin effects on the mass dependence of the balance energy

We study the effect of isospin degree of freedom on balance energy throughout the mass range between 50 and 350 for two sets of isotopic systems with N/A= 0.54 and 0.57 as well as isobaric systems with N/A= 0.5 and 0.58. Our findings indicate that different values of balance energy for two isobaric systems may be mainly due to the Coulomb repulsion. We also demonstrate clearly the dominance of Coulomb repulsion over symmetry energy.

Geometry of vanishing flow: A new probe to determine the in-medium nucleon–nucleon cross-section

Abstract.We studied the transverse flow throughout the mass range from 20Ne + 20Ne to 131Xe + 131Xe as a function of the impact parameter. We found that at smaller impact parameters the flow is negative while going through the impact parameter, transverse flow vanishes at a particular colliding geometry named GVF. We found that the mass dependence of GVF is insensitive to the equation of state and momentum-dependent interactions whereas it is quite sensitive to the cross-section. So it can act as a useful tool to pin down the nucleon–nucleon cross-section.

Model ingredients and peak mass production in heavy-ion collisions

We simulate the central reactions of {sup 20}Ne+{sup 20}Ne, {sup 40}Ar+{sup 45}Sc, {sup 58}Ni+{sup 58}Ni, {sup 86}Kr+{sup 93}Nb, {sup 129}Xe+{sup 118}Sn, {sup 86}Kr+{sup 197}Au, and {sup 197}Au+{sup 197}Au at different incident energies for different equations of state, different binary cross sections, and different widths of Gaussians. A rise-and-fall behavior of the multiplicity of intermediate mass fragments (IMFs) is observed. The system size dependence of peak center-of-mass energy E{sub c.m.}{sup max} and peak IMF multiplicity {sup max} is also studied, where it is observed that E{sub c.m.}{sup max} follows a linear behavior and {sup max} shows a power-law dependence. A comparison between two clusterization methods, the minimum spanning tree and the minimum spanning tree method with binding energy check (MSTB), is also made. We find that the MSTB method reduces the {sup max}, especially in heavy systems. The power-law dependence is also observed for fragments of different sizes at E{sub c.m.}{sup max} and the power-law parameter {tau} is found to be close to unity in all cases except A{sup max}.

N/Z and N/A dependence of the balance energy as a probe of the symmetry energy in heavy-ion collisions

We study the N/Z and N/A dependence of balance energy (E{sub bal}) for isotopic series of Ca having N/Z (N/A) varying from 1.0 to 2.0 (0.5 to 0.67). We show that the N/Z (N/A) dependence of E{sub bal} is sensitive to symmetry energy and its density dependence at densities higher than saturation density and is insensitive toward the isospin dependence of nucleon-nucleon (nn) cross section and Coulomb repulsion. We also study the effect of momentum-dependent interactions (MDI) on the N/Z (N/A) dependence of E{sub bal}. We find that although MDI influences the E{sub bal} drastically, the N/Z (N/A) dependence of E{sub bal} remains unchanged on inclusion of MDI.

Stability of the fragments and thermalization at the peak centre-of-mass energy

We simulated the central reactions of nearly symmetric and asymmetric systems, for energies at which maximum production of intermediate mass fragments (IMFs) occurred (

Impact parameter dependence of isospin effects on the mass dependence of balance energy

E_{\rm c.m.}^{\rm peak}

K+ and K- potentials in hadronic matter are observable quantities

). This study was carried out using hard EOS along with Cugnon cross-section employing MSTB method for clusterization. We studied the various properties of fragments. The stability of fragments was checked through persistence coefficient and gain term. The information about the thermalization and stopping in heavy-ion collisions was obtained via relative momentum, anisotropy ratio and rapidity distribution. We found that for a complete stopping of incoming nuclei very heavy systems are required. The mass dependence of various quantities (such as average and maximum central density, collision dynamics as well as the time zone for hot and dense nuclear matter) was also presented. In all cases (i.e., average and maximum central density, collision dynamics as well as the time zone for hot and dense nuclear matter) a power-law dependence was obtained.