Search for the rare radiative decay W -> pi gamma in p(p)over-bar collisions at root s=1.96 TeV

We present a search for the rare radiative decay W+ -> pi(+)gamma using data corresponding to an integrated luminosity of 4.3 fb(-1) of proton-antiproton collisions at a center-of-mass energy of 1.96 TeV collected by the CDF experiment at Fermilab. As no statistically significant signal is observed, we set a 95%-confidence- level upper limit on the relative branching fraction Gamma(W+ -> pi(+)gamma)/Gamma(W+ -> e(+) nu) at 6.4 x 10(-5), a factor of 10 improvement over the previous limit.