Isospin Asymmetry

Isospin asymmetry in radiative and FCNC decays with leptons of $B$ mesons. In some of the $B$-factory results it is assumed that $\mathcal{B}(\mathrm{{\rm Y}}(4S)\to B^{+}{B}^{-})=\mathcal{B}(\mathrm{{\rm Y}}(4S)\to B^0\bar{B}{}^0)$, and in others a measured value of the ratio of branching fractions is used. See original papers for details. The averages quoted here are computed naively and should be treated with caution