Fragmentation of Relativistic Gold Nuclei with Energies between 0.92 and 4.0AGeV in Hydrogen

Abstract

Modeling the propagation of ultraheavy (UH) cosmic-ray nuclei through the interstellar medium requires a knowledge of the fragmentation cross sections. The cross sections for the production of fragments from the interactions of relativistic gold nuclei in hydrogen have been measured from 0.56 to 10.6 A GeV, using the Lawrence Berkeley Laboratory (LBL) Bevalac and the Brookhaven alternating gradient synchrotron (AGS). The total charge-changing cross sections are found to be essentially independent of energy. The partial elemental cross sections vary significantly with energy but show a transition to energy independence at the highest energies. These cross sections can be scaled to apply to neighboring elements, corrected for the effects of radio active decay, and applied to propagation models to deduce source abundances of the heaviest UH elements from those observed near Earth. There are serious uncertainties involved in deducing the cross sections applicable in space from those measured on Earth. Hence calculations of propagation must be regarded with caution.