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ISSN - 09205632, Nuclear Physics B - Proceedings Supplements, 2007, vol. 169, p. 76-81

Measurement of B+ → τ+ ντ at Belle

Eidelman S.

We present the first evidence of the decay B+ → τ+ ντ, using 414  fb-1 of data collected at the Υ{hooked} (4 S) 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. The significance of the signal is 3.5 standard deviations including systematics, and the branching fraction is measured to be B (B+ → τ+ ντ) = (1.79-0.49 +0.56 (stat)-0.51 +0.46 (syst)) × 10-4. This implies that fB = 0.229-0.031 +0.036 (stat)-0.037 +0.034 (syst)  GeV; this is the first direct measurement of this quantity. © 2007 Elsevier B.V. All rights reserved.