Measurement of the $B^{+}{/B}^0$ production ratio from the ${\rm Y}\mathrm{}\left(4S\right)\mathrm{}$ meson using $B^{+}\to J/\psi K^{+}$ and $B^0\to J/\psi K_S^0$ decays

We report a measurement of the production ratio of charged and neutral B mesons from ${\rm Y}\mathrm{}\left(4S\right)\mathrm{}$ decays based on the ratio of efficiency-corrected yields for the charmonium modes $J/\psi K^{+}$ and $J/\psi K_s^0$ with 81.9 ${\mathrm{fb}}^{\mathrm{-}1}$ of data collected with the BABAR detector on the ${\rm Y}\mathrm{}\left(4S\right)\mathrm{}$ resonance at 10.580 GeV. We find a value of $1.006\pm 0.036\left(\mathrm{stat}\right)\pm 0.031\left(\mathrm{syst}\right)$ for the ratio $R^{+/0\mathrm{}}=\Gamma \left({\rm Y}\mathrm{}\right(4S)\mathrm{}\to B^{+}{B}^{-})/\Gamma \left({\rm Y}\mathrm{}\right(4S)\mathrm{}\to B^0{B}^0).$