Measurement of the $K^+rightarrow{mu^+}{ u_{mu}}{gamma}$ decay form factors in the OKA experiment

A precise measurement of the vector and axial-vector form factors difference $F_V-F_A$ in the $K^+rightarrow{mu^+}{ u_{mu}}{gamma}$ decay is presented. About 95K events of $K^+rightarrow{mu^+}{ u_{mu}}{gamma}$ are selected in the OKA experiment. The result is $F_V-F_A=0.134pm0.021(stat)pm0.027(syst)$. Both errors are smaller than in the previous $F_V-F_A$ measurements.