Measurement of the Branching Fraction of Y(4S) to B0-B0bar

Based on a data sample of 476 million B-meson anti-B-meson pairs collected at the Upsilon(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy B-Factory at SLAC, we measure a model independent measurement of the branching fraction of Upsilon(4S) decays to B0 and anti-B0 pair. The B mesons are reconstructed in the channel anti-B0 decays to D*+ lepton anti-neutrino using a partial reconstruction method. Our result does not depend on any branching fractions, the simulated reconstruction efficiency, the ratio of the charged and neutral B-meson lifetimes, or assumption of isospin symmetry. This measurement is important for normalizing many B-decay branching fractions.