Observation of the radiative kaon decay K- --> mu-pi0gammanu
  Using data collected with the ISTRA+ spectrometer during the 2001 run of the U-70 proton synchrotron in Protvino, we report the first observation of the radiative kaon decay K- -->mu-pi0gammanu. We find Br(Kmu3g)/Br(Kmu3) for two regions 5<Eg<30 and 30<Eg<60 MeV consistent with theoretical predictions. The measured angular distribution asymmetry for the first region,   0.093+/-0.141, is two standard deviations away from the theoretical prediction of 0.354. The measured asymmetry in the T-odd variable is -0.03+/-0.13. 
O.Tchikilev, S.Akimenko, G.Britvich, K.Datsko, A.Filin, A.Inyakin,   V.Khmelnikov, S.Konstantinov, I.Korolkov, V.Leontiev, V...