Experimental study of the mechanism of production of intermediate-mass fragments in relativistic /ital p/+Au and /sup 4/He+Au interactions

Differential cross sections for production of intermediate-mass fragments (/ital Z/=5--12) have been measured in the reactions /ital p/+Au/r arrow//ital Z/+/ital X/ and /sup 4/He+Au/r arrow//ital Z/+/ital X/ at angles 35--135/degree/. The energy range of the proton beam was 2.6--7.5 GeV, and that of the /sup 4/He beam 1.3--13.5 GeV. Total cross sections have been measured for production of fragments with /ital Z/=5--9 and have been approximated by the function sigma(/ital Z/)/similar to//ital Z//sup /minus//tau//. For the reaction /sup 4/He+Au a minimum of the function /tau/(/ital E//sub /sup 4/He/) is observed at /ital E//congruent/6 GeV. The cross sections are analyzed in the framework of a model which assumes the existence of two sources of fragments with different transport velocity. The nonmonotonic behavior of the parameter /tau/ is related to the cross-section component due to decay of the fast source of fragments.