Search for Right-Handed Currents by Means of Muon Spin Rotation

Abstract

A muon-spin-rotation technique has been used to place limits on right-handed currents in ${\ensuremath{\mu}}^{+}$ decay. The spins of polarized ${\ensuremath{\mu}}^{+}$ stopped in metal targets were precessed by 70-G or 110-G transverse fields. The muon-spin-rotation signal amplitude produced by high-momentum decay ${e}^{+}$ emitted near the beam direction implies $\frac{\ensuremath{\xi}{P}_{\ensuremath{\mu}}\ensuremath{\delta}}{\ensuremath{\rho}}>0.9955$ and $M({W}_{2})>370$ GeV (90% confidence), where ${W}_{2}$ is a predominantly right-handed gauge boson. The present result combined with our previous spin-held analysis yields $\frac{\ensuremath{\xi}{P}_{\ensuremath{\mu}}\ensuremath{\delta}}{\ensuremath{\rho}}>0.9966$ and $M({W}_{2})>400$ GeV.