Search for the Flavor-Changing Neutral Current Decays ${\mathit{B}}^{+}\to {\mu }^{+}{\mu }^{-}{\mathit{K}}^{+}$ and ${\mathit{B}}^0\to {\mu }^{+}{\mu }^{-}{\mathit{K}}^{*0}$

We report on a search for the flavor-changing neutral current decays $B^{+}\to {\mu }^{+}{\mu }^{-}{K}^{+}$ and $B^0\to {\mu }^{+}{\mu }^{-}{K}^{*0\mathrm{}}$ using $88{\mathrm{pb}}^{-1\mathrm{}}$ of data from $\overline{p}p$ collisions at $\sqrt{s}=1.8\mathrm{}\mathrm{TeV}$, collected with the Collider Detector at Fermilab. Finding no evidence for these decays, we set upper limits on the branching fractions $B(B^{+}\to {\mu }^{+}{\mu }^{-}{K}^{+})<5.2\mathrm{}\times {10}^{-6\mathrm{}}$ and $B(B^0\to {\mu }^{+}{\mu }^{-}{K}^{*0\mathrm{}})<4.0\mathrm{}\times {10}^{-6\mathrm{}}$ at the $90\%$ confidence level.