Measurement of the $\bar{B}$⁰ → D^*+ℓ^-$\bar{v}$ Branching Fraction with a Partial Reconstruction Technique

Presented is a precise measurement of the {bar B}{sup 0} {yields} D*{sup +}{ell}{sup -}{bar {nu}}{sub {ell}} branching fraction using 81.47 fb{sup -1} of data collected with the BABAR detector at the PEP-II e{sup +}e{sup -} storage ring at the Stanford Linear Accelerator Center. The measurement was performed by partially reconstructing the D*{sup +} meson from {bar B}{sup 0} {yields} D*{sup +}{ell}{sup -}{bar {nu}}{sub {ell}} decays using only the soft pion of the D*{sup +} {yields} D{sup 0}{pi}{sup +} decay to reconstruct its four vector. The branching fraction was measured to be {Beta}({bar B}{sup 0} {yields} D*{sup +}{ell}{sup -}{bar {nu}}{sub {ell}}) = (4.91 {+-} 0.01{sub stat} {+-} 0.15{sub syst})%