Muon Polarization inKμ30Decay

An experiment to measure the polarization of muons from ${K_{\mu 3}}^0$ decay was carried out at the Bevatron with counter techniques. All three components of the polarization were measured. The time-reversal-violating component transverse to the decay plane was found to be $〈{P_T}^{\mathrm{c}.\mathrm{m}.\mathrm{}}〉=-0.005\mathrm{}\pm 0.019$, which is consistent with $T$ invariance. The result for the form-factor ratio $\xi \equiv \frac{f_{-}}{f_{+}}$ was $\mathrm{Re}\xi =-{{1.81}_{-0.26\mathrm{}}}^{+0.50\mathrm{}}$, $\mathrm{Im}\xi =-0.02\mathrm{}\pm 0.08$, $\mathrm{Arg}\left(\xi \right)-\pi =(0.6\mathrm{}\pm 2.6)°$, if $\xi$ is assumed to be independent of $q^2$. If $\xi$ is not too strongly dependent on $q^2$, this result still holds true for $\xi$ at $q^2\cong 2.65{m_{\pi }}^2$, the average $q^2$ selected by our apparatus.