New statistical and nonstatistical effects in deep inelastic heavy-ion collisions

Abstract

The physics of deep inelastic heavy-ion collisions is briefly reviewed in the light of the experimental capabilities offered by large tandem accelerators. Three aspects are selected for illustration. The first is the problem posed by the angular distributions. The role of quantal fluctuations (diffraction) and of dynamical fluctuations is discussed. The possibility of extracting angular-momentum fluctuations from the angular-distribution width is pointed out, as well as the way to compare such results with those obtained from gamma-ray multiplicities or angular distributions. The likely sources of angular-momentum fluctuations are discussed. The second problem is that of energy dissipation and partition. The experimental evidence for thermal equilibrium is reviewed and experiments to test thermal equilibrium through the measurement of the variance in the energy distribution are suggested. The correlation between energy loss and the mass variance is reviewed in terms of the mass transfer mechanism. Possible ways to determine the mass of the transferred particle are illustrated. The third problem considered is the experimental lack of mass drift in the mass distributionsvs.Q-value when it is expected on the basis of potential-energy considerations. This problem is associated with the fast-fragment thermalization and explained in terms of a feedback effect associated with the temperature gradient that develops between two colliding nuclei of different mass.