On the balance energy and nuclear dynamics in peripheral heavy-ion collisions

TL;DR

This study investigates how the energy at which nuclear collisions balance depends on system size and impact parameter, revealing different power-law behaviors and emphasizing the role of Coulomb interactions in peripheral heavy-ion collisions.

Contribution

It provides a detailed analysis of system size and impact parameter dependence of balance energy using quantum molecular dynamics, highlighting the significance of Coulomb interactions at peripheral geometries.

Findings

Balance energy follows a power law with system mass.

Power factor varies with collision centrality, close to -1/3 centrally.

At peripheral collisions, the power factor is about -2/3.

Abstract

We present here the system size dependence of balance energy for semi-central and peripheral collisions using quantum molecular dynamics model. For this study, the reactions of $Ne^{20}+Ne^{20}$, $Ca^{40}+Ca^{40}$, $Ni^{58}+Ni^{58}$, $Nb^{93}+Nb^{93}$, $Xe^{131}+Xe^{131}$ and $Au^{197}+Au^{197}$ are simulated at different incident energies and impact parameters. A hard equation of state along with nucleon-nucleon cross-sections between 40 - 55 mb explains the data nicely. Interestingly, balance energy follows a power law $\propto{A^{\tau}}$ for the mass dependence at all colliding geometries. The power factor $\tau$ is close to -1/3 in central collisions whereas it is -2/3 for peripheral collisions suggesting stronger system size dependence at peripheral geometries. This also suggests that in the absence of momentum dependent interactions, Coulomb's interaction plays an exceedingly significant role. These results are further analyzed for nuclear dynamics at the balance point.