Kavli Affiliate: T. Higuchi
| First 5 Authors: Belle II Collaboration, I. Adachi, K. Adamczyk, L. Aggarwal, H. Aihara
| Summary:
We present a measurement of the ratio $R_mu = mathcal{B}(tau^-to
mu^-barnu_munu_tau) / mathcal{B}(tau^-to e^-barnu_enu_tau)$ of
branching fractions $mathcal{B}$ of the $tau$ lepton decaying to muons or
electrons using data collected with the Belle II detector at the SuperKEKB
$e^+e^-$ collider. The sample has an integrated luminosity of
$362!pm!2,text{fb}^{-1}$ at a centre-of-mass energy of
$10.58,text{GeV}$. Using an optimised event selection, a binned maximum
likelihood fit is performed using the momentum spectra of the electron and muon
candidates. The result, $R_mu = 0.9675 pm 0.0007 pm 0.0036$, where the first
uncertainty is statistical and the second is systematic, is the most precise to
date. It provides a stringent test of the light-lepton universality,
translating to a ratio of the couplings of the muon and electron to the $W$
boson in $tau$ decays of $0.9974 pm 0.0019$, in agreement with the standard
model expectation of unity.
| Search Query: ArXiv Query: search_query=au:”T. Higuchi”&id_list=&start=0&max_results=3