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Evidence of the Purely Leptonic Decay B- --> tau- nu_tau-bar

K. Ikado
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Abstract

We present the first evidence of the decay B- --> tau- nu_tau-bar using 414 fb^-1 of data collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. Events are tagged by fully reconstructing one of the B mesons in hadronic modes. We detect the signal with a significance of 3.5 standard deviations including systematics, and measure the branching fraction to be Br(B- --> tau- nu_tau-bar) = (1.79 +0.56-0.49(stat) +0.46-0.51(syst))*10^-4. This implies that f_B = 0.229 +0.036-0.031(stat) +0.034-0.037(syst) GeV and is the first direct measurement of this quantity.

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K. Ikado. 2006-12-02. Evidence of the Purely Leptonic Decay B- --> tau- nu_tau-bar. https://doi.org/10.1103/physrevlett.97.251802

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