# Measurements of Charged Current Lepton Universality and $|V_{us}|$ using Tau Lepton Decays to $e^- \bar{\nu}_e \nu_\tau$, $\mu^- \bar{\nu}_\mu \nu_\tau$, $\pi^- \nu_\tau$ and $\K^- \nu_\tau$

Abstract : Using 467 $fb^{-1}$ of $e^+e^-$ annihilation data collected with the BaBar detector, we measure $\frac{{\cal{B}}(\tau^- \to \mu^- \bar{\nu}_\mu \nu_\tau)}{{\cal{B}}(\tau^- \to e^- \bar{\nu}_e \nu_\tau)} = (0.9796 \pm 0.0016 \pm 0.0036)$, $\frac{{\cal{B}}(\tau^- \to \pi^- \nu_\tau)}{{\cal{B}}(\tau^- \to e^- \bar{\nu}_e \nu_\tau)} = (0.5945 \pm 0.0014 \pm 0.0061)$, and $\frac{{\cal{B}}(\tau^- \to \K^- \nu_\tau)}{{\cal{B}}(\tau^- \to e^- \bar{\nu}_e \nu_\tau)} = (0.03882 \pm 0.00032 \pm 0.00057)$, where the uncertainties are statistical and systematic, respectively. From these precision measurements we test the Standard Model assumption of $\mu$-$e$ and $\tau$-$\mu$ charged current lepton universality and also obtain a value for $|V_{us}| = 0.2255 \pm 0.0024$, which is consistent with the prediction from the unitarity of the Cabibbo-Kobayashi-Maskawa matrix.
Document type :
Journal articles

http://hal.in2p3.fr/in2p3-00438613
Contributor : Swarna Bassava <>
Submitted on : Friday, December 4, 2009 - 11:01:42 AM
Last modification on : Tuesday, December 22, 2020 - 12:40:02 PM

### Citation

B. Aubert, Y. Karyotakis, J. P. Lees, V. Poireau, E. Prencipe, et al.. Measurements of Charged Current Lepton Universality and $|V_{us}|$ using Tau Lepton Decays to $e^- \bar{\nu}_e \nu_\tau$, $\mu^- \bar{\nu}_\mu \nu_\tau$, $\pi^- \nu_\tau$ and $\K^- \nu_\tau$. Physical Review Letters, American Physical Society, 2010, 105, pp.051602. ⟨10.1103/PhysRevLett.105.051602⟩. ⟨in2p3-00438613⟩

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