Isoscaling in dilute warm nuclear systems

Heavy-ion collisions are a good tool to explore hot nuclear matter below saturation density, ρ ₀. It has been established that if a nuclear system reaches the thermal and chemical equilibrium, this leads to scaling properties in the isotope production when comparing two systems which differ in proton fraction. This article presents a study of the isoscaling properties of an expanding gas source exploring different thermodynamic states (density, temperature, proton fraction). This experimental work highlights the existence of an isoscaling relationship for hydrogen and ³He, ⁴He helium isotopes which agrees with the hypothesis of thermal and chemical equilibrium. Moreover, this work reveals the limitations of isoscaling when the two systems differ slightly in total mass and temperature. Also, a discrepancy has been observed for the ⁶He isotope, which could be explained by finite size effects or by the specific halo nature of this cluster.