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Improved Upper Limits on the Flavor-Changing Neutral Current Decays<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">B</mml:mi><mml:mi /><mml:mo>→</mml:mo><mml:mi /><mml:mi mathvariant="italic">K</mml:mi><mml:mrow><mml:msup><mml:mrow><mml:mi>ℓ</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow><mml:mrow><mml:msup><mml:mrow><mml:mi>ℓ</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msup></mml:mrow></…
We have searched a sample of $9.6\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ events for the flavor-changing neutral current decays $B\ensuremath{\rightarrow}K{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ and $B\ensuremath{\rightarrow}{K}^{*}(892){\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$. We subject the latter decay to the requirement that the dilepton mass ${m}_{\ensuremath{\ell}\ensuremath{\ell}}$ exceed 0.5 GeV. There is no indication of a signal. We obtain the $90%$ confidence level upper limits $B(B\ensuremath{\rightarrow}K{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}})<1.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ …