Isoscaling in central Sn+Sn collisions at 270 MeV/u

TL;DR

This study investigates isoscaling behavior in Sn+Sn heavy-ion collisions at 270 MeV/u, revealing that thermal equilibrium assumptions fail for high-momentum particles, challenging existing models.

Contribution

It provides new experimental data and analysis showing the breakdown of isoscaling at high transverse momentum, highlighting limits of current statistical and molecular dynamics models.

Findings

Isoscaling holds for low-energy particles in both models.

Breakdown of isoscaling observed at high transverse momentum.

Antisymmetrized molecular dynamics model cannot explain high-momentum behavior.

Abstract

Experimental information on fragment emissions is important in understanding the dynamics of nuclear collisions and in the development of transport model simulating heavy-ion collisions. The composition of complex fragments emitted in the heavy-ion collisions can be explained by statistical models, which assume that thermal equilibrium is achieved at collision energies below 100 MeV/u. Our new experimental data together with theoretical analyses for light particles from Sn+Sn collisions at 270 MeV/u, suggest that the hypothesis of thermal equilibrium breaks down for particles emitted with high transfer momentum. To inspect the system's properties in such limit, the scaling features of the yield ratios of particles from two systems, a neutron-rich system of ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ and a nearly symmetric system of ${}^{108}\mathrm{Sn}+{}^{112}\mathrm{Sn}$, are examined in the framework of the statistical multifragmentation model and the antisymmetrized molecular dynamics model. The isoscaling from low energy particles agree with both models. However the observed breakdown of isoscaling for particles with high transverse momentum cannot be explained by the antisymmetrized molecular dynamics model.