Observation of $\ensuremath{\Upsilon}(3S)\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$ and Tests of Lepton Universality in $\ensuremath{\Upsilon}$ Decays

Observation of $Υ (3 S) \to τ^{+} τ^{-}$ and Tests of Lepton Universality in $Υ$ Decays

D. Besson et al. (CLEO Collaboration)

Phys. Rev. Lett. 98, 052002 – Published 29 January 2007

Abstract

Using data collected with the CLEO III detector at the CESR $e^{+} e^{-}$ collider, we report on a first observation of the decay $Υ (3 S) \to τ^{+} τ^{-}$ , and precisely measure the ratio of branching fractions of $Υ (n S)$ , $n = 1$ , 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 $C P$ -odd Higgs boson in the decay of the $Υ (1 S)$ .