Measurement of the Absolute Branching Fraction of $D^0\to K^{-}{\pi }^{+}$

We measure the absolute branching fraction for $D^0\to K^{-}{\pi }^{+}$ using partial reconstruction of ${\overline{B}}^0\to D^{*+}X{\ell }^{-}{\overline{\nu }}_{\ell }$ decays, in which only the charged lepton and the pion from the decay $D^{*+}\to D^0{\pi }^{+}$ are used. Based on a data sample of $230\times {10}^6$ $B\overline{B}$ pairs collected at the ${\rm Y}(4S)$ resonance with the BABAR detector at the PEP-II asymmetric-energy $B$ factory at SLAC, we obtain $\mathcal{B}(D^0\to K^{-}{\pi }^{+})=(4.007\pm 0.037\pm 0.072)\%$, where the first uncertainty is statistical and the second is systematic.

Figure 1

The ${\mathcal{M}}_{\nu }^2$ distribution of the inclusive sample, for right-charge (a) and wrong-charge (b) samples. The data are represented by solid points with uncertainty. The MC fit results are overlaid to the data, as explained in the figure.

Figure 2

Continuum-subtracted $\Delta M$ distribution for data (points with error bars) and backgrounds overlaid as explained in the figure.