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

Abstract

We measure the absolute branching fraction for D 0 → K − π + using partial reconstruction of ¯¯¯ B 0 → D * + X ℓ − ¯ ν ℓ decays, in which only the charged lepton and the pion from the decay D * + → D 0 π + are used. Based on a data sample of 230 × 10 6 B ¯¯¯ B pairs collected at the Υ ( 4 S ) resonance with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC, we obtain B ( D 0 → K − π + ) = ( 4.007 ± 0.037 ± 0.072 ) % , where the first uncertainty is statistical and the second is systematic.