Charge-changing fragmentation of 10.6 GeV/nucleon 197Au nuclei.

Abstract

We have measured the charge-changing cross sections of 10.6 GeV/nucleon $^{197}\mathrm{Au}$ nuclei interacting in targets of ${\mathrm{CH}}_{2}$ (polyethylene), C, Al, Cu, Sn, and Pb. Cross sections for H are calculated from those measured in C and ${\mathrm{CH}}_{2}$. The total charge-changing cross sections are higher than those measured at energies of \ensuremath{\le}1 GeV/nucleon. The measured cross sections for the heavier targets are somewhat larger than those predicted by a model based on data taken at lower energies with lighter targets. Partial charge-changing cross sections for the production of fragments from the incident Au projectiles were measured for charge changes (\ensuremath{\Delta}Z) from \ensuremath{\Delta}Z=+1${,}_{80}$Hg, down to approximately \ensuremath{\Delta}Z=-29${,}_{50}$Sn. In comparison to lower energy measurements, these partial cross sections are found to be smaller for small \ensuremath{\Delta}Z and larger or the same for large \ensuremath{\Delta}Z. The H partial cross sections are found to follow a power law in \ensuremath{\Delta}Z similar to that for heavier targets, instead of the exponential form observed at lower energies. Factorization is found to hold for all partial cross sections with \ensuremath{\Delta}Z greater than two. In the heavier targets, the cross sections for one and two proton removal have significant contributions from electromagnetic dissociation. The electromagnetic dissociation contribution to the total cross section is derived and found to be relatively small, but with a strong dependence on the charge of the target nuclei of the form ${\mathit{Z}}_{\mathit{T}}^{1.75\ifmmode\pm\else\textpm\fi{}0.01}$.