Charge-changing interactions of ultrarelativisticPbnuclei

Abstract

Experimental data and theoretical results on charge loss $\ensuremath{-}27\ensuremath{\leqslant}\ensuremath{\Delta}Z\ensuremath{\leqslant}\ensuremath{-}1$, charge pickup $\ensuremath{\Delta}Z=+1$, and total charge-changing cross sections for $158A\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}$ $_{82}^{208}\mathrm{Pb}$ ions on ${\mathrm{CH}}_{2}$, $\mathrm{C}$, $\mathrm{Al}$, $\mathrm{Cu}$, $\mathrm{Sn}$, and $\mathrm{Au}$ targets are presented. Calculations based on the revisited abrasion-ablation model for hadronic interaction and the relativistic electromagnetic dissociation (RELDIS) model for electromagnetic interaction describe the data. The decay of excited nuclear systems created in both types of interaction is described by the statistical multifragmentation model (SMM), which includes evaporation, fission, and multifragmentation channels. We show that at very high projectile energy the excitation energy of residual nuclei may be described on average as $\ensuremath{\sim}40\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ per removed nucleon, with some increase in this value compared to fragmentation of intermediate energy heavy ions at $\ensuremath{\sim}1A\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}$. The importance of the electromagnetic interaction in production of $_{80}\mathrm{Hg}$, $_{81}\mathrm{Tl}$, and $_{83}\mathrm{Bi}$ projectile fragments on heavy targets is shown. A strong increase of nuclear-charge pickup cross sections, forming $_{83}\mathrm{Bi}$, is observed in comparison to similar measurements at $10.6A\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}$. This process is attributed to the electromagnetic production of a negative pion by an equivalent photon, which is quantitatively described by the RELDIS model.