Determination of the electronic branching ratio of the Υ(9.46) and an upper limit for its total width

We have measured the reaction e⁺e^- → e⁺e^- at the ϒ Using athe excess of electron pairs over the QED expectation we obtain an electronic branching ratio of B_ee = (5.1 ± 3.0) %. Combining this with publishe values of the muonic branching ratio B_μμ we conclude that the ϒ is a narrow state with a total width < 180 keV at 95% C.L.