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

Understand

A precise measurement of the vector and axial-vector form factors difference $F_V-F_A$ in the $K^+\rightarrow{\mu^+}{\nu_{\mu}}{\gamma}$ decay is presented.

• About 95K events of $K^+\rightarrow{\mu^+}{\nu_{\mu}}{\gamma}$ are selected in the OKA experiment.
• The result is $F_V-F_A=0.134\pm0.021(stat)\pm0.027(syst)$.
• Both errors are smaller than in the previous $F_V-F_A$ measurements.