Muon Polarization inKμ30-Meson Decay

The polarization of the muon in the decay ${K_L}^0\to {\pi }^{-}{\mu }^{+}\nu$ was measured in a spark-chamber experiment. For the decay phase space measured in this experiment, the results are $\alpha {\overline{P}}_L=0.31\mathrm{}\pm 0.07$, $\alpha {\overline{P}}_T=-0.02\mathrm{}\pm 0.07$, and $\alpha {\overline{P}}_P=-0.10\mathrm{}\pm 0.07$, where ${\overline{P}}_L$, ${\overline{P}}_T$, and ${\overline{P}}_P$ are the average components of polarization along the muon momentum, transverse to the decay plane, and perpendicular to the muon in the decay plane. The analyzing parameter $\alpha$ of the muon decay is about 0.35 in this experiment. From the above polarization results, assuming energy-independent form factors, we obtain the ratio of form factors $\xi =\frac{f_{-}}{f_{+}}$; the results are $\mathrm{Re}\xi =-1.6\mathrm{}\pm 0.5$ and $\mathrm{Im}\xi =-0.2\mathrm{}\pm 0.6$.