$\bar{B}\to D^{(\ast )}\ell \bar{\nu }$ Branching Ratios and Evidence for Isospin Breaking in ${\rm Y}(4S)$ Decays

Martin Jung, Stefan Schacht

We introduce a new method for the determination of the ratio of production fractions $R^{\pm 0}=\mathcal{B}({\rm Y}(4S)\to B^{+}{B}^{-})/\mathcal{B}({\rm Y}(4S)\to B^0{\bar{B}}^0)$ based on $\bar B\to D^{…