Excitation-energy-gated two-fragment correlation functions have been studied between E(*)/A = (2-9)A MeV for equilibriumlike sources formed in 8-10 GeV/c pi(-) and p+197Au reactions. Comparison with an N-body Coulomb-trajectory code shows an order of magnitude decrease in the fragment emission time in the interval E(*)/A = (2-5)A MeV, followed by a nearly constant breakup time at higher excitation energy. The decrease in emission time is strongly correlated with the onset of multifragmentation and thermally induced radial expansion, consistent with a transition from surface-dominated to bulk emission expected for spinodal decomposition.

An extensive study of GeV light-ion-induced multifragmentation and its possible interpretation in terms of a nuclear liquid-gas phase transition has been performed with the Indiana Silicon Sphere (ISiS) 4π detector array. Measurements were performed with 5-15 GeV/c p, p, and π − beams incident on 197 Au and 2-5 GeV 3 He incident on nat Ag and 197 Au targets. Both the reaction dynamics and the subsequent decay of the heavy residues have been explored. The data provide evidence Preprint submitted to Elsevier Science 10 March 2018for a dramatic change in the reaction observables near an excitation energy of E*/A = 4-5 MeV per residue nucleon. In this region, fragment multiplicities and energy spectra indicate emission from an expanded/dilute source on a very short time scale (20-50 fm/c). These properties, along with caloric curve and scaling-law behavior, yield a pattern that is consistent with a nuclear liquid-gas phase transition.

Excitation-energy distributions have been derived from measurements of 5.0-14.6 GeV/c antiproton, proton and pion reactions with 197 Au target nuclei, using the ISiS 4π detector array. The maximum probability for producing high excitationenergy events is found for the 8 GeV/c antiproton beam relative to other hadrons, 3 He andp beams from LEAR. For protons and pions, the excitation-energy distributions are nearly independent of hadron type and beam momentum above about 8 GeV/c. The excitation energy enhancement forp beams and the saturation effect are qualitatively consistent with intranuclear cascade code predictions. For all systems studied, maximum cluster sizes are observed for residues with E*/A ∼ 6 MeV.

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