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Nuclear fragmentation in a d (4.4 GeV) + Au collision was studied with a 4π setup FASA on the external beam of the Dubna Nuclotron. The IMF-IMF relative angle correlation function was analyzed using the statistical model of multifragmentation (SMM) with the main goal of estimating the total time scale of the process. It was found that the fragmentation of the hot nucleus was ~100 fm/c delayed in respect to the collision moment. [ABSTRACT FROM AUTHOR]

The relative velocity correlation function of pairs of intermediate mass fragments has been studied for d+Au collisions at 4.4 GeV. Experimental correlation functions are compared to that obtained by multibody Coulomb trajectory calculations under the assumption of various decay times of the fragmenting system. The combined approach with the empirically modified intranuclear cascade code followed by the statistical multifragmentation model was used to generate the starting conditions for these calculations. The fragment emission time is found to be less than 40 fm/c. [ABSTRACT FROM AUTHOR]

Multiple emission of intermediate-mass fragments (IMF) in the collisions of protons (up to 8.1 GEV), [sup 4]He (4 and 14.6 GEV), and [sup 12]C (22.4 GeV) on Au has been studied with the 4π setup FASA. In all the cases, thermal multifragmentation of the hot and diluted target spectator takes place. The fragment multiplicity and charge distributions are well described by the combined model including the modified intranuclear cascade followed by the statistical multibody decay of the hot system. IMFIMF-correlation study supports this picture, giving a very short time scale of the process (≤70 fm/c). This decay process can be interpreted as the first-order nuclear "liquid-fog" phase transition inside the spinodal region. The evolution of the mechanism of thermal multifragmentation with increasing projectile mass was investigated. The onset of the radial collective flow was observed for heavier projectiles. The analysis reveals information on the fragment space distribution inside the breakup volume: heavier IMFs are formed predominantly in the interior of the fragmenting nucleus possibly due to the density gradient. [ABSTRACT FROM AUTHOR]

Multiple emission of intermediate-mass fragments has been studied for the collisions of p, 4He and 12C on Au with the 4π setup FASA. The mean IMF multiplicities (for the events with at least one IMF) are saturating at the value of 2.2±0.2 for the incident energies above 6 GeV. The observed IMF multiplicities cannot be described in a two-stage scenario, a fast cascade followed by a statistical multifragmentation. Agreement with the measured IMF multiplicities is obtained by introducing an intermediate phase and modifying empirically the excitation energies and masses of the remnants. The angular distributions and energy spectra from the p-induced collisions are in agreement with the scenario of “thermal” multifragmentation of a hot and diluted target spectator. In the case of 12C + Au(22.4 GeV) and 4He(14.6 GeV) + Au collisions, deviations from a pure thermal break-up are seen in the energy spectra of the emitted fragments, which are harder than those both from model calculations and from the measured ones for p-induced collisions. This difference is attributed to a collective flow. [Copyright &y& Elsevier]

The relative angle correlation of intermediate mass fragments has been studied for p+Au collisions at 8.1 GeV. Strong suppression at the small angles is observed caused by IMF–IMF Coulomb repulsion. Experimental correlation function is compared to that obtained by the multibody Coulomb trajectory calculations with the various decay times τ of fragmenting system. The combined model, including the empirically modified intranuclear cascade followed by statistical multifragmentation, was used to generate starting conditions for these calculations. The model dependence of the results obtained has been carefully checked. The mean decay time of fragmenting system is found to be τ⩽70 fm/c. [Copyright &y& Elsevier]

The multiple emission of intermediate-mass fragments (IMF) is studied for collisions of p, [sup 4]He, and [sup 12]C on Au with the 4π FASA setup. The mean multiplicities of IMF saturate at a value of around 2 for incident energies above 6 GeV. An attempt at describing the observed IMF multiplicities in the two-stage scenario, a fast cascade followed by a statistical multifragmentation, fails. Agreement with the measured IMF multiplicities is obtained by introducing an intermediate expansion phase and modifying empirically the excitation energies and masses of remnants. The angular distributions and energy spectra from p-induced collisions are in agreement with the scenario of "thermal" multifragmentation of a hot and expanded target spectator. In the case of [sup 12]C + Au (22.4 GeV) and [sup 4]He (14.6 GeV) + Au collisions, deviations from a pure thermal breakup are seen in the fragment energy spectra, which are harder than those both from model calculations and from the measured ones for p-induced collisions. This difference is attributed to a collective flow with the expansion velocity at the surface of about 0.1c (for [sup 12]C + Au collisions). [ABSTRACT FROM AUTHOR]

Critical temperature T c for the nuclear liquid-gas phase transition is estimated from both the multifragmentation and fission data. In the first case, the critical temperature is obtained by analysis of the intermediate-mass-fragment yields in p(8.1 GeV) + Au collisions within the statistical model of multifragmentation. In the second case, the experimental fission probability for excited 188Os is compared with the calculated one with T c as a free parameter. It is concluded for both cases that the critical temperature is higher than 15 MeV. [ABSTRACT FROM AUTHOR]

Thermal multifragmentation of hot nuclei is interpreted as the nuclear liquid-fog phase transition inside the spinodal region. The exclusive data for p(8.1 GeV) + Au collisions are analyzed within the framework of the statistical model SMM. It is found that the partition of hot nuclei is specified after expansion to a volume equal to V t = (2.6 ± 0.3) V 0. The freeze-out volume is found to be twice as large: V f = (5 ± 1) V 0. The similarity between multifragmentation and ordinary fission is discussed. [ABSTRACT FROM AUTHOR]