Preprint IHEP  IHEP IHEP 2005-20, hep-ex/0506023

Authors: O.Tchikilev, et al.
"Observation of the radiative kaon decay K- --> mu-pi0gammanu"


        Abstract

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.