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September 27, 2021 to October 1, 2021
Indiana University
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Precision measurement of the B[Υ(3S) → τ+τ−) / B(Υ(3S) → μ+μ−] ratio at BABAR

Sep 28, 2021, 1:40 PM
Virtual (Indiana University)


Indiana University


Alexei Sibidanov (University of Victoria)


We report on a precision measurement of the ratio R^Υ(3S)_τμ = B[Υ(3S) → τ+τ−] / B[Υ(3S) → 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(3S) mesons. The ratio is measured to be R^Υ(3S)_τμ = 0.966 ± 0.008 (stat) ± 0.014 (syst) and is in agreement with the Standard Model prediction of 0.9948 within 2 standard deviations. The uncertainty in R^Υ(3S)_τμ is almost an order of magnitude smaller than the only previous measurement.

What is your topic? Lepton universality and flavour violation

Primary authors

Alberto Lusiani (Scuola Normale Superiore and INFN, sezione di Pisa) Alexei Sibidanov (University of Victoria)

Presentation materials