Search for the rare decay [Formula Presented] in proton-antiproton collisions at [Formula Presented]

We have searched for the rare decay ${W}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}+\ensuremath{\gamma}$ in $83 {\mathrm{pb}}^{\mathrm{\ensuremath{-}}1}$ of data taken in proton-antiproton collisions at $\sqrt{s}=1.8 \mathrm{TeV}$ with the Collider Detector at Fermilab. We find three events in the signal region and estimate the background to be 5.2\ifmmode\pm\else\textpm\fi{}1.5 events. We set a 95% confidence level upper limit of $7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ on the ratio of partial widths, $\ensuremath{\Gamma}{(W}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}+\ensuremath{\gamma})/\ensuremath{\Gamma}{(W}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{e}^{\ifmmode\pm\else\textpm\fi{}}+\ensuremath{\nu}).$