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

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 1500ions/cm2. The total number of lead ions in each spill was about 7.8x104 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 Pb82+ 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 (σZ) achieved in the present experiment is ∼0.18e-0.21e. The analysis of discrepancies between our experimental results and other published results for the identical reaction is also presented