Unstable fragment emission from 25 GeV/c proton stars in nuclear emulsion

Abstract

The heavy prongs from 8000 25 GeV proton interactions in Ilford G5 emulsions giving 4 or more heavy prongs have been followed in the pellicle containing the primary interaction and all secondary interactions recorded. 379 secondary interactions were found including 129 hammer tracks, 6 mesonic hyperfragments, and 5, definite nonmesonic hyperfragments. The range spectrum of connecting tracks of other secondary stars shows a marked peaking below 50 microns. Statistical arguments are used to show that there are 26 unidentified nonmesonic hyperfragments with connecting track less than 50 microns. The hyperfragment production rate is ∼ 0.5% and the hammer track production rate is R~1.6% for the star sample scanned. An attempt is made to interpret the rise from lower bombarding energies of the former rate. An isotropic angular distribution of the hammer tracks is found and the energy spectrum fits the evaporation model with parametersT = 12 andV = 0 MeV. Possible explanations of these features are discussed.