A measurement of the electronic widths Γ ee of the ϒ(1S), ϒ(2S), and ϒ(4S) resonances, and of the total decay width Γ of the ϒ(4S)

Abstract

The partial decay width into electrons, Γ ee , of the ϒ(1S) and ϒ(2S) resonances have been measured with the detector ARGUS at thee+e− storage ring DORISII of DESY. Applying the formula of Kuraev and Fadin for the radiative corrections we find: Γ ee (ϒ(1S))= (1.32±0.04±0.03) keV and Γ ee (ϒ(2S))=(0.52±0.03±0.01) keV. The total decay width of the ϒ(4S) resonance and its partial width into electrons have been determined as well. Fitting the data with a generalized Breit-Wigner function with an energy dependent decay width Γ(s) and a mass shift functionm(s), we obtain the following resonance parameters: Γ(M2)=(10.0±2.8±2.7) MeV, Γ ee =(0.28±0.05±0.01)keV andB ee =(2.77±0.50±0.49)·10−5. We argue that the disagrecment of this result with the world average originates from our more adequate parametrization of the observed ϒ(4S) resonance cross section.