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 $1500\mathrm{ions}/{\mathrm{cm}}^2$. The total number of lead ions in each spill was about $7.8\times {10}^4$ 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 ${\mathrm{Pb}}^{82+}$ 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 $({\sigma }_Z)$ achieved in the present experiment is $\sim 0.18\mathrm{e}$–0.21e. The analysis of discrepancies between our experimental results and other published results for the identical reaction is also presented.