Measurement of the $$K^+\rightarrow {\mu ^+}{\nu _{\mu }}{\gamma }$$ K+→μ+νμγ decay form factors in the OKA experiment

Abstract A precise measurement of the vector and axial-vector form factors difference $$F_V-F_A$$ FV-FA in the $$K^+\rightarrow {\mu ^+}{\nu _{\mu }}{\gamma }$$ K+→μ+νμγ decay is presented. About 95K events of $$K^+\rightarrow {\mu ^+}{\nu _{\mu }}{\gamma }$$ K+→μ+νμγ are selected in the OKA experiment. The result is $$F_V-F_A=0.134\pm 0.021(stat)\pm 0.027(syst)$$ FV-FA=0.134±0.021(stat)±0.027(syst) . Both errors are smaller than in the previous $$F_V-F_A$$ FV-FA measurements.