Measurement of the semileptonic decays (B)over-bar -> D tau(-)(nu)over-bar(tau) and (B)over-bar -> D*tau(-)(nu)over-bar(tau)

Abstract

We present measurements of the semileptonic decays B- -> D-0 tau(-)(nu) over bar (tau), B- -> D*(0)tau(-)(nu) over bar tau, (B) over bar (0) -> D+tau(-)(nu) over bar (tau), and (B) over bar (0) -> D*(+)tau(-)(nu) over bar (tau), which are sensitive to non-standard model amplitudes in certain scenarios. The data sample consists of 232 x 10(6) Y(4S) -> B (B) over bar decays collected with the BABAR detector at the PEP-II e(+)e(-) squared to distinguish signalcollider. We select events with a D or D* meson and a light lepton (l = e or mu) recoiling against a fully reconstructed B meson. We perform a fit to the joint distribution of lepton momentum and missing mass (B) over bar -> D-(*())tau(-)(nu) over bar (tau) events from the backgrounds, predominantly R(D*) equivalent to B((B) over bar -> D*tau(-)(nu) over bar (tau))/B((B) over bar -> D*l(-)(nu) over bar (l)) and, from a combined fit to B- and (B) over bar (0) channels, obtain the results R(D) = (41.6 +/- 11.7 +/- 5.2)% and R(D*) = (29.7 +/- 5.6 +/- 1.8)%, where the uncertainties are statistical and systematic. Normalizing to measured B- -> D-(*()0)l(-)(nu) over bar (l) branching fractions, we obtain B((B) over bar -> D tau(-)(nu) over bar (tau)) = (0.86 +/- 0.24 +/- 0.06)% and B((B) over bar -> D*tau(-)(nu) over bar (tau)) = (1.62 +/- 0.31 +/- 0.10 +/- 0.05)%, where the additional third uncertainty is from the normalization mode. We also present, for the first time, distributions of the lepton momentum vertical bar P-l*vertical bar, and the squared momentum transfer, q(2).