Laser polarized muonic helium

Abstract

We have formed polarized muonic $^{3}\mathrm{He}$ by stopping unpolarized negative muons in a gaseous $^{3}\mathrm{He}$ target which was polarized by spin exchange with laser optically pumped Rb vapor. We measured ${\mathit{P}}_{\mathrm{\ensuremath{\mu}}}^{\mathit{N}}$, the resulting muon polarization normalized to the nuclear polarization of the $^{3}\mathrm{He}$. In addition to being a property that characterizes the muon cascade in the \ensuremath{\mu}${\mathrm{\ensuremath{-}}}^{3}$He system, ${\mathit{P}}_{\mathrm{\ensuremath{\mu}}}^{\mathit{N}}$ is of practical value for future experiments on nuclear muon capture. Our result, ${\mathit{P}}_{\mathrm{\ensuremath{\mu}}}^{\mathit{N}}$=0.072\ifmmode\pm\else\textpm\fi{}0.008, is a factor of 2 smaller than predicted by simple atomic cascade theory.