Critical-like behaviours in central and peripheral collisions: a comparative analysis

Quasi-projectile events from peripheral 35 A MeV Au+Au collisions are compared with 25 A MeV Au+C, 25 and 35 A MeV Au+Cu and 35 A MeV Au+Au central events. By fitting the measured charge yields with the Fisher droplet model technique, all the different data sets coherently point to a value E ∗ c≈4.5 A MeV as the excitation energy where size distribution are best fitted by a power law. The physical parameters extracted from the fit strongly depend on the detailed shape assumed for the scaling function with the exception of τ and σ which are consistent with the critical exponents of the liquid-gas phase transition. Possible implications concerning the observation of a phase transition in multifragmentation experiments are discussed.