Observation of the Semileptonic Decays B→D∗τ−¯ντ and Evidence for B→Dτ−¯ντ

Abstract

We present measurements of the semileptonic decays B − → D 0 τ − ¯ ν τ , B − → D * 0 τ − ¯ ν τ , ¯¯¯ B 0 → D + τ − ¯ ν τ , and ¯¯¯ B 0 → D * + τ − ¯ ν τ , which are potentially sensitive to non-standard model amplitudes. The data sample comprises 232 × 10 6 Υ ( 4 S ) → B ¯¯¯ B decays collected with the BABAR detector. From a combined fit to B − and ¯¯¯ B 0 channels, we obtain the branching fractions B ( B → D τ − ¯ ν τ ) = ( 0.86 ± 0.24 ± 0.11 ± 0.06 ) % and B ( B → D ∗ τ − ¯ ν τ ) = ( 1.62 ± 0.31 ± 0.10 ± 0.05 ) % (normalized for the ¯¯¯ B 0 ), where the uncertainties are statistical, systematic, and normalization-mode-related.