On the determination of the time-scale of three-fragment emission in the 12.7 GeV⁴He+²³⁸U reaction using the polycarbonate track detector Makrofol

Abstract

The timescale for emission of three fragments (Z 8) in the 12.7 GeV 4 He + 238 U reaction has been studied using a sandwich configuration of the Makrofol polycarbonate track detector. In events with varying multiplicity of heavy fragments (Z > 20), the differences of the correlation functions for relative angle and relative velocity between pairs of fragments have been studied in order to determine the fragment emission timescale. A sequential decay mechanism for the excited residual nuclei was found to be consistent with experimental data. It was determined that the fragment emission time decreased with decreasing multiplicity of heavy fragments from 1200 ± 80 fm c −1 for events with two heavy fragments to 400 ± 50 fm c −1 for events with one heavy fragment.