The search for the decay η → e+e- was carried out using the WASA detector at the COSY storage ring. Data were taken during a two week experimental run in Sept-Nov 2008 in which about 107 η mesons were collected from the reaction of pp → ppη at energy of 1.4 GeV. Background studies were performed for several different reactions. The performance of the WASA detector for the measurement of electron-positron pairs based on the single Dalitz decay of the η meson was studied. We also identified a statistically significant data sample of other more frequent leptonic decays.
The Electron-Positron Storage Ring Petra, Plans and Status
