Statistical multifragmentation in central Au + Au collisions at 35 MeV/u

Abstract

Multifragment disintegrations, measured for central Au + Au collisions at E/A = 35M eV , are analyzed with the Statistical Multifragmentation Model. Charge distributions, mean fragment energies, and two-fragment correlation functions are well reproduced by the statistical breakup of a large, diluted and thermalized system slightly above the multifragmentation threshold.

Liquid-Gas Phase Transition in Nuclear Multifragmentation

“…Above 55 MeV per nucleon, multifragmentation seems to occur in a time scale that saturates at ≈125 fm/c. The result is consistent with breakup of a fragmenting source at low density including those driven by Coulomb instabilities as in the Au+Au reaction at E/A=35 MeV [42]. In the latter experiment, the source size was obtained by comparing various experimental observables to the prediction of the statistical multifragmentation model.…”

“…To fit the energy spectra, large radial expansion velocities are required in addition to the three sources [38,39]. Similarly, the mean kinetic and transverse energy of emitted fragments also provide measure of the radial collective velocities when compared to the predictions of thermal models [40][41][42]. Fig.5 shows a nearly linear relationship between the radial velocities with the incident energy [40].…”

“…The inconsistencies of the measurements, regarding the different radius values obtained from different particle correlations, illustrate the present experimental difficulties in extracting the precise values of the freeze-out densities since the analysis is highly model dependent. Other methods, such as comparing IMF multiplicities or mean kinetic energies with statistical models have been employed to determine the source sizes [42]. Independent of different analysis methods, densities lower than 1/3 of the normal nuclear matter density provide the best agreement with the data.…”

“…Experimentally, production of particles in multifragmentation appears to be dominated by their phase space [42,54,99]. Thus, one should be able to measure temperature and densities, basic quantities in statistical physics.…”

Comparison of statistical multifragmentation model simulations with canonical thermodynamic model results: A few representative cases

“…For example, one can choose the freeze-out volume to be dependent on the multiplicity of a channel. For reactions where equilibrated sources are formed, the SMM gives very good description of experimental data [1,2,3,4]. The canonical thermodynamic model (CTM) characterises the disintegrating system by a temperature T , the mass number A 0 , charge number Z 0 and a fixed freeze-out volume.…”