Observation of Υ(3S)→τ+τ- and Tests of Lepton Universality in Υ Decays

Using data collected with the CLEO III detector at the CESR e⁺e^- collider, we report on a first observation of the decay Υ(3S)→τ⁺τ^-, and precisely measure the ratio of branching fractions of Υ(nS), n=1, 2, 3, to τ⁺τ^- and μ⁺μ^- final states, finding agreement with expectations from lepton universality. We derive absolute branching fractions for these decays, and also set a limit on the influence of a low mass CP-odd Higgs boson in the decay of the Υ(1S).