The first dilepton yield measurements from excited nuclear states obtained with a new Positron-Electron Pair Spectroscopic Instrument (PEPSI) are reported. Nuclear states in 28Si, with an initial excitation energy E* = 50 MeV, were populated via the isospin T = 0 reaction 4He + 24Mg and the mixed-isospin 3He + 25Mg reaction. In both reactions the dilepton (e+e-) and photon decay yields were measured concurrently. An excess of counts in the e+e- spectrum, over the converted photon yield, is observed in the energy region above 15 MeV. An analyses is discussed whereby the observed excess counts are assumed to represent the isoscalar E0 strength in excited nuclear states.
ASJC Scopus subject areas
- Nuclear and High Energy Physics