Precision Measurement of the Ratio $\mathcal{B}(\mathrm{\ensuremath{\Upsilon}}(3S)\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}})/\mathcal{B}(\mathrm{\ensuremath{\Upsilon}}(3S)\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})$

Open Access

Precision Measurement of the Ratio $B (ϒ (3 S) \to τ^{+} τ^{-}) / B (ϒ (3 S) \to μ^{+} μ^{-})$

J. P. Lees et al. (BABAR Collaboration)

Phys. Rev. Lett. 125, 241801 – Published 8 December 2020

Abstract

We report on a precision measurement of the ratio $R_{τ μ}^{ϒ (3 S)} = B (ϒ (3 S) \to τ^{+} τ^{-}) / B (ϒ (3 S) \to μ^{+} μ^{-})$ using data collected with the BABAR detector at the SLAC PEP-II $e^{+} e^{-}$ collider. The measurement is based on a $28 {fb}^{- 1}$ data sample collected at a center-of-mass energy of 10.355 GeV corresponding to a sample of 122 million $ϒ (3 S)$ mesons. The ratio is measured to be $R_{τ μ}^{ϒ (3 S)} = 0.966 \pm 0.00 8_{stat} \pm 0.01 4_{syst}$ and is in agreement with the standard model prediction of 0.9948 within 2 standard deviations. The uncertainty in $R_{τ μ}^{ϒ (3 S)}$ is almost an order of magnitude smaller than the only previous measurement.

Received 13 May 2020
Accepted 20 October 2020

DOI:https://doi.org/10.1103/PhysRevLett.125.241801

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Published by the American Physical Society