Observation of $\mathit{B}\to \mathit{\phi }\mathit{K}$ and $\mathit{B}\to {\mathit{\phi }\mathit{K}}^{*}$

We have studied two-body charmless hadronic decays of $B$ mesons into the final states $\phi K$ and $\phi K^{*}$. Using 9.7 million $B\overline{B}$ pairs collected with the CLEO II detector, we observe the decays $B^{-}\to \phi K^{-}$ and $B^0\to \phi K^{*0\mathrm{}}$ with the following branching fractions: $B(B^{-}\to \phi K^{-})=({5.5}_{-1.8\mathrm{}}^{+2.1\mathrm{}}\pm 0.6)\times {10}^{-6\mathrm{}}$ and $B(B^0\to \phi K^{*0\mathrm{}})=\left({11.5}_{-3.7-1.7\mathrm{}}^{+4.5+1.8\mathrm{}}\right)\times {10}^{-6\mathrm{}}$. We also see evidence for the decays $B^0\to \phi K^0$ and $B^{-}\to \phi K^{*-}$. However, since the statistical significance is not overwhelming for these modes, we determine upper limits of $<12.3\mathrm{}\times {10}^{-6\mathrm{}}$ and $<22.5\mathrm{}\times {10}^{-6\mathrm{}}$ ( $90\%$ confidence level), respectively.