$$\boldsymbol{K^{+}\to}\pi^{\mathbf{0}}\mu^{\boldsymbol{+}}{\nu\gamma}$$ Radiative Decay: Recent Results from the ‘‘OKA’’ Experiment

The $$K^{+}\to\pi^{0}\mu^{+}\nu\gamma$$ ( $$K_{\mu 3\gamma}$$ ) decay is measured with OKA detector at the RF-separated 17.7 GeV/c momentum kaon beam from the U-70 synchrotron. The data obtained corresponds to the value of $$2.62\times 10^{10}$$ ‘‘live’’ kaons passing to the decay volume. About 1000 $$K_{\mu 3\gamma}$$ events are extracted. The ratio of $$\textrm{Br}(K_{\mu 3\gamma})/\textrm{Br}(K_{\mu 3}$$ ) is measured. The T-odd correlation $${\xi}_{\pi\mu\gamma}$$ , which is the mixed product of the momenta of $$\mu^{+},\pi^{0}$$ , and $$\gamma$$ in the kaon rest frame, is measured. The asymmetry of the distribution in $$\xi$$ is characterized by the ratio $$A_{\xi}=(N_{+}-N_{-})/(N_{+}+N_{-})$$ , where $$N_{+}$$ ( $$N_{-}$$ ) is the number of events with positive (negative) $$\xi$$ . The values of $$A_{\xi}$$ is obtained. Our results are preliminary, with systematic errors being estimated.