Search for Rare Radiative Decay $W\rightarrow\pi\gamma$ in ppbar Collisions at $\sqrt{s} = 1.96$ TeV

We present a search for the rare radiative decay $W\rightarrow\pi\gamma$ using 4.3$fb^{-1}$ of data collected from proton-anti proton collisions at $\sqrt{s} = 1.96$ TeV by the CDF experiment at Fermilab. As no signal is observed, we set a 95\% CL upper limit on the relative branching fraction bratio at $6.4\times 10^{-5}$, a factor of 10 improvement over the existing limit.