Solidarity of signal of measures for the liquid-gas phase transition in the statistical multifragmentation model

Abstract

A systematic study of system size, $N/Z$ asymmetry, and fragmenting volume effects as well as the Coulomb effect on experimental measures for the nuclear liquid-gas phase transition and the mechanism of phase transition are carried out in the framework of the statistical multifragmentation model (SMM). The measures examined here are the caloric curve, the specific heat capacity (${C}_{v}$), the multiplicity derivative ($dM/dT$), the moment parameters (${M}_{2}$ and ${\ensuremath{\gamma}}_{2}$), the fluctuation of maximum fragment charge number (NVZ), the Fisher exponent ($\ensuremath{\tau}$), and the Zipf's law parameter ($\ensuremath{\xi}$). A signal for the first-order phase transition for all the measures is observed. A stronger signal is observed in the system with smaller sizes or with more neutron rich or in smaller fragmenting volumes for the caloric curve, ${C}_{v}$, and $dM/dT$. The phase-transition temperatures are independent of the system size, $N/Z$ asymmetry, fragmenting volume, and Coulomb force, which indicates these measures give a solid signal for the liquid-gas phase transition in SMM. On the other hand, the phase transition temperature and its behavior of the others slightly depend on the size, the $N/Z$ asymmetry and the volume of the system. A negative heat capacity is observed for systems with ${A}_{s}\ensuremath{\ge}$ 100 without the Coulomb force but disappears with the Coulomb. An instructive picture is given in the charge distributions for the observed first-order phase transition.