Experimental study of direct photon emission in K- --> pi- pi0 gamma   decay using ISTRA+ detector
  The branching ratio in the charged-pion kinetic energy region of 55 to 90 MeV for the direct photon emission in the K- --> pi- pi0 gamma decay has been measured using in-flight decays detected with the ISTRA+ setup operating in the 25 GeV/c negative secondary beam of the U-70 PS. The value Br(DE)=[0.37+-0.39(stat)+-0.10(syst)]*10^(-5) obtained from the analysis of 930 completely reconstructed events is consistent with the average value of two stopped-kaon experiments, but it differs by 2.5 standard deviations from the average value of three in-flight-kaon experiments. The result is also compared with recent theoretical predictions. 
V.A. Uvarov, S.A. Akimenko, G.I. Britvich, K.V. Datsko, A.P. Filin,   A.V. Inyakin, V.A. Khmelnikov, A.S. Konstantinov, V.F....