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Aubert, B.; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Prencipe, E.; Prudent, X.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M.; Palano, A.; Pappagallo, M.; Eigen, G.; Stugu, B.; Sun, L.; Battaglia, M.; Brown, D.N.; Kerth, L.T.; Kolomensky, Yu. G.; Lynch, G.; Osipenkov, I.L.; Tackmann, K.; Tanabe, T.; Hawkes, C.M.; Soni, N.; Watson, A.T.; Koch, H.; Schroeder, T.; Asgeirsson, D.J.; Fulsom, B.G.; Hearty, C.; Mattison, T.S.; Mckenna, J.A.; Barrett, M.; Khan, A.; Randle-Conde, A.; Blinov, V.E.; Bukin, A.D.; Buzykaev, A.R.; Druzhinin, V.P.; Golubev, V.B.; Onuchin, A.P.; Serednyakov, S.I.; Skovpen, Yu. I.; Solodov, E.P.; Todyshev, K. Yu; Bondioli, M.; Curry, S.; Eschrich, I.; Kirkby, D.; Lankford, A.J.; Lund, P.; Mandelkern, M.; Martin, E.C.; Stoker, D.P.; Atmacan, H.; Gary, J.W.; Liu, F.; Long, O.; Vitug, G.M.; Yasin, Z.; Sharma, V.; Campagnari, C.; Hong, T.M.; Kovalskyi, D.; Mazur, M.A.; Richman, J.D.; Beck, T.W.; Eisner, A.M.; Heusch, C.A.; Kroseberg, J.; Lockman, W.S.; Martinez, A.J.; Schalk, T.; Schumm, B.A.; Seiden, A.; Wang, L.; Winstrom, L.O.; Cheng, C.H.; Doll, D.A.; Echenard, B.; Fang, F.; Hitlin, D.G.; Narsky, I.; Ongmongkolkul, P.; Piatenko, T.; Porter, F.C.; Andreassen, R.; Mancinelli, G.; Meadows, B.T.; Mishra, K.; Sokoloff, M.D.; Bloom, P.C.; Ford, W.T.; Gaz, A.; Hirschauer, J.F.; Nagel, M.; Nauenberg, U.; Smith, J.G.; Wagner, S.R.
Physical review letters, 2010, Volume: 105Journal Article
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.
