Muon Polarization inKμ30Decay

Abstract

An experiment to measure the polarization of muons from ${{K}_{\ensuremath{\mu}3}}^{0}$ 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 $〈{{P}_{T}}^{\mathrm{c}.\mathrm{m}.}〉=\ensuremath{-}0.005\ifmmode\pm\else\textpm\fi{}0.019$, which is consistent with $T$ invariance. The result for the form-factor ratio $\ensuremath{\xi}\ensuremath{\equiv}\frac{{f}_{\ensuremath{-}}}{{f}_{+}}$ was $\mathrm{Re}\ensuremath{\xi}=\ensuremath{-}{{1.81}_{\ensuremath{-}0.26}}^{+0.50}$, $\mathrm{Im}\ensuremath{\xi}=\ensuremath{-}0.02\ifmmode\pm\else\textpm\fi{}0.08$, $\mathrm{Arg}(\ensuremath{\xi})\ensuremath{-}\ensuremath{\pi}=(0.6\ifmmode\pm\else\textpm\fi{}2.6)\ifmmode^\circ\else\textdegree\fi{}$, if $\ensuremath{\xi}$ is assumed to be independent of ${q}^{2}$. If $\ensuremath{\xi}$ is not too strongly dependent on ${q}^{2}$, this result still holds true for $\ensuremath{\xi}$ at ${q}^{2}\ensuremath{\cong}2.65{{m}_{\ensuremath{\pi}}}^{2}$, the average ${q}^{2}$ selected by our apparatus.