Transition from Thermal to Rapid Expansion in Multifragmentation of Gold Induced by Light Relativistic Projectiles

摘要

Multiple emission of intermediate-mass fragments has been studied for thecollisions of p, $^4$He and $^{12}$C on Au with the $4\pi$ setup FASA. In thecase of $^{12}$C(22.4 GeV)+Au and $^4$He(14.6 GeV)+Au collisions, thedeviations from a pure thermal break-up are seen in the energy spectra of theemitted fragments: the spectra are harder than calculated and than measured inp-induced collisions. This difference is attributed to a collective flow withthe expansion velocity on the surface about 0.1 $c$ (for $^{12}$C+Aucollisions).