Measurement of K^+ \to \pi^0 \mu^+ \nu \gamma decay using stopped kaons
  The K^+ \to \pi^0 \mu^+ \nu \gamma ($K_{\mu 3 \gamma}$) decay has been measured with stopped positive kaons at the KEK 12 GeV proton synchrotron. A $K_{\mu 3 \gamma}$ sample containing 125 events was obtained. The partial branching ratio $Br(K_{\mu 3 \gamma}, E_{\gamma}>30 {\rm MeV}, \theta_{\mu^+ \gamma}>20^{\circ})$ was found to be $[2.4 \pm 0.5(stat) \pm 0.6(syst)]\times 10^{-5}$, which is in good agreement with theoretical predictions. 
KEK-E470 Collaboration: S. Shimizu, K. Horie, M.A. Aliev, Y. Asano, T.   Baker, P. Depommier, M. Hasinoff, Y. Igarashi, J. I...