Characteristics of Fragments Produced in the Interaction of 5.5-GeV Protons with Silver

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Abstract

The energy spectra of nuclear fragments produced by the interaction of 5.5-GeV protons with silver were determined at several laboratory angles by means of $\frac{\mathrm{dE}}{dx\ensuremath{-}E}$ measurements with semiconductor-detector telescopes. Individual isotopes of the elements from hydrogen to nitrogen were resolved. From oxygen to silicon the elements were determined without isotopic separation. For the case of the isotopes of He through Be enough of the evaporation-like energy spectra were recorded so that it was possible to perform integrations to obtain angular distributions and total cross sections. For elements above beryllium, an experimental cutoff on the low-energy side precluded these integrations, and only the high-energy portions of the spectra were recorded. The energy spectra of the neutron-deficient isotopes differ from the others in that the high-energy parts of the spectra are more pronounced and flatter, and the angular distributions are more forward-peaked.Some of the energy spectra were fitted with calculated curves based on the isotropic evaporation of fragments from an excited nucleus moving along the beam axis. The apparent Coulomb barriers obtained from this analysis were about one half the nominal Coulomb barriers, and the apparent nuclear temperatures fell in the 8-11-MeV range. However, no one temperature could fit the entire energy range, and for the highest-energy fragments observed at 90\ifmmode^\circ\else\textdegree\fi{} the apparent temperature rose to 20 MeV or higher. From the forward-backward shifts of the most probable energy it was deduced that the average velocity of the moving system emitting Li and Be fragments is $0.008c$. However, all of the data are more forward-peaked in intensity than can be explained by the simple two-step model. The energy analysis carried out on these new data is compared with those given in the literature for silver targets or emulsions bombarded with protons, cosmic rays, pions, kaons, and other particles. Comparisons are made of these results with those obtained in an earlier study of fragments from a uranium target.

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