Measurement of the Absolute Branching Fraction of D0→K-π+

We measure the absolute branching fraction for D0→K-π+ using partial reconstruction of B̅ 0→D*+Xℓ-ν̅ ℓ decays, in which only the charged lepton and the pion from the decay D*+→D0π+ are used. Based on a data sample of 230×106 BB̅ pairs collected at the Υ(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC, we obtain B(D0→K-π+)=(4.007±0.037±0.072)%, where the first uncertainty is statistical and the second is systematic.