ELECTROMAGNETIC DISSOCIATION OF 60 A GeV16O IN EMULSION

Abstract

The electromagnetic dissociations (EDs) of 60 A GeV16O in nuclear emu lsion is investigated with high statistics for the first time. It is found that the interaction cross section for EDs increases with increasing beam energy, and the charge distribution of projectile fragments is the same as the results at 2 00 A GeV, but the production probability of projectile fragments with charge 3≤ Z≤5 is smaller than that of the results at 200 A GeV. These results can be expl ained by use of the Weizscker-Williams method for calculating the EDs contributi ons. The percentage abundances of various decay modes for EDs at 60 A GeV is the same as the results at 200 A GeV,but different from the results at 14.6 A GeV. The EDs of 60 A GeV16O is mainly caused by the giant dipole and quadr upole resonance of E1 and E2 and by the quasi deuteron effect, which can be qual itatively explained by the multiplicity distribution of projectile fragmentation proton in EDs. The multiplicity distribution of α fragments in EDs and nuclear events have different functional forms. This difference may be a consequence of the different reaction mechanisms involved in EDs and nuclear events.