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

## TL;DR

This paper reports a precise measurement of the difference between vector and axial-vector form factors in the $K^+
ightarrow \mu^+
u_\mu \gamma$ decay, using about 95,000 events from the OKA experiment, with improved accuracy over previous results.

## Contribution

The study provides the most precise measurement to date of the $F_V - F_A$ form factor difference in this decay mode, reducing uncertainties compared to prior measurements.

## Key findings

- Measured $F_V - F_A = 0.134 \, extpm \, 0.021 (stat) \, extpm \, 0.027 (syst)$.
- Selected about 95,000 decay events in the OKA experiment.
- Achieved smaller errors than previous measurements.

## Abstract

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.