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

Abstract

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.