Speaker
Michael Roney
Description
We report a measurement of $R(D) = B(B\to D\tau\bar\nu_\tau)/B(B\to D\ell\bar\nu_\ell)$
and $R(D^*) = B(B\to D^*\tau\bar\nu_\tau)/B(B\to D^*\ell\bar\nu_\ell)$, where $\ell$
refers to either an electron or muon. The dataset consists of
426 fb$^{-1}$ collected at the $\Upsilon(4S)$ resonance by the BABAR detector at the
PEP-II asymmetric storage ring collider. We select samples by reconstructing tag-side $B$ mesons in semileptonic decays and signal-side $\tau$ in a purely leptonic decay.
