Isospin Violation Measurement at the Upsilon(4S) Resonance

Isospin violation at the Upsilon(4S) resonance is an important input for many B meson measurements at B Factories. It may be at the level of a few percent mostly due to electromagnetic interactions and the mass different \newline of the up and the down quarks. We partially reconstruct neutral B meson in the semileptonic decay of $\backslash $bar\textbraceleft B\textbraceright \textasciicircum 0 $\to $ D\textasciicircum \textbraceleft *$+$\textbraceright lepton\textasciicircum - $\backslash $bar\textbraceleft $\backslash $nu\textbraceright . We discuss a model independent measurement of the branching fraction of Upsilon(4S) decays to neutral BB pairs based on a data sample of 470 million BB pairs collected at the Upsilon(4S) resonance with the BABAR detector at SLAC.