Examining the fragmentation of 158 A GeV lead ions on copper target: Charge-changing cross sections

Abstract

A stack of plastic CR-39 Track Detectors were exposed to 158 A GeV 207Pb ions at the CERN-SPS beam facility. The exposure of stack was performed at normal incidence with a fluence of about 1500 ions / cm 2 . The total number of lead ions in each spill was about 7.8 × 10 4 with eight spills on each stack. For the stack with the Cu target, the lengths of etched cones on one face of the CR-39 detectors (before and after the target) were measured. Using these measurements and charge identification methodology in CR-39 track detectors, total and partial charge changing cross sections of 158 A GeV Pb 82 + ions on Cu and CR-39 targets are determined in the charge region 63 ⩽ Z ⩽ 82 . The possibilities of presence and absence of odd–even effect in measured partial charge changing cross sections of 158 A GeV Pb ions for Cu and CR-39 targets are described. The charge resolution ( σ Z ) achieved in the present experiment is ∼ 0.18 e –0.21e. The analysis of discrepancies between our experimental results and other published results for the identical reaction is also presented.