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${{\mathit K}^{\pm}}$ $\rightarrow$ ${{\mathit \ell}^{\pm}}{{\mathit \nu}}{{\mathit \gamma}}$ FORM FACTORS

For definitions of the axial-vector $\mathit F_{\mathit A}$ and vector $\mathit F_{\mathit V}$ form factor, see the “Note on ${{\mathit \pi}^{\pm}}$ $\rightarrow$ ${{\mathit \ell}^{\pm}}{{\mathit \nu}}{{\mathit \gamma}}$ and ${{\mathit K}^{\pm}}$ $\rightarrow$ ${{\mathit \ell}^{\pm}}{{\mathit \nu}}{{\mathit \gamma}}$ Form Factors” in the ${{\mathit \pi}^{\pm}}$ section. In the kaon literature, often different definitions $\mathit a_{\mathit K}$ = $\mathit F_{\mathit A}/\mathit m_{\mathit K}$ and $\mathit v_{\mathit K}$ = $\mathit F_{\mathit V}/{\mathit m}_{{{\mathit K}}}$ are used.

$\mathit F_{\mathit A}$ $−$ $\mathit F_{\mathit V}$, DIFFERENCE OF AXIAL-VECTOR AND VECTOR FORM FACTOR FOR ${{\mathit K}}$ $\rightarrow$ ${{\mathit \mu}}{{\mathit \nu}_{{\mu}}}{{\mathit \gamma}}$

INSPIRE   PDGID:

S010F-M

VALUE CL% EVTS DOCUMENT ID TECN CHG $\bf{ -0.153 \pm0.033}$ OUR AVERAGE  Error includes scale factor of 1.1. $-0.134$ $\pm0.021$ $\pm0.027$ 95k KRAVTSOV 2019 OKA + $-0.21$ $\pm0.06$ 22k DUK 2011 ISTR - • • We do not use the following data for averages, fits, limits, etc. • • $-0.24\text{ to }0.04 $ 90 2588 ADLER 2000 B B787 + $-2.2\text{ to }0.6 $ 90 DEMIDOV 1990 XEBC $-2.5\text{ to }0.3 $ 90 AKIBA 1985 SPEC

References:

KRAVTSOV 2019 EPJ C79 635 Measurement of the $K^+\rightarrow{\mu^+}{\nu_{\mu}}{\gamma}$ decay form factors in the OKA experiment DUK 2011 PL B695 59 Extraction of Kaon Formfactors from ${{\mathit K}^{-}}$ $\rightarrow$ ${{\mathit \mu}}{{\mathit \nu}}{{\mathit \gamma}}$ Decay at ISTRA+ Setup ADLER 2000B PRL 85 2256 Measurement of Structure-Dependent ${{\mathit K}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{\mu}}}{{\mathit \gamma}}$ Decay DEMIDOV 1990 SJNP 52 1006 Measurement of the ${{\mathit K}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}}{{\mathit \gamma}}$ Decay Probability AKIBA 1985 PR D32 2911 A Study of the Radiative Decay ${{\mathit K}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{\mu}}}{{\mathit \gamma}}$

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