The Topology of Intermediate Mass Fragment Emission

Abstract

The study of the patterns in momentum and/or coordinate space, i.e., the topology, of fragment emission in central heavy-ion collisions allows one to distinguish between the sequential binary (SB) and multifragmentation (MF) disassembly modes. We present results on fragment azimuthal correlations using two different methods, and each implies beam energy dependent transitions between these two disassembly modes. An experimental data set consisting of 40 reactions in the entrance channels ¹²C + ¹²C, ²⁰Ne + ²⁷Al, ⁴⁰Ar + ⁴⁵Sc, ⁸⁴Kr + ⁹³Nb, and ¹²⁹Xe + ¹³⁹La was used for these analyses, as well as our previous studies of central event topology using the sphericity variable. The SB to MF transitional behavior extracted from all of these analyses will be compared to independently measured disassembly time scales. It will be shown that, for increasing energies, the SB to MF transitions that we observe occur at energies consistent with those leading to strong decreases in the disassembly time scales. This lends credence to the identification that the present SB to MF transitions are the physical manifestation of a nuclear liquid-gas phase transition.

For the MSU 4π Group: National Superconducting Cyclotron Laboratory, Michigan State University; T. W. Bonner Nuclear Laboratory, Rice University; Department of Chemistry, State University of New York — Stony Brook; Department of Physics, U. of Michigan — Dearborn; Cyclotron Institute, Texas A&M University; Department of Physics and Astronomy, U. of Iowa.