Search for right-handed currents in the decay K+--> micro+ nu.

The longitudinal polarization of the muon emitted in the decay ${K}^{+}$\ensuremath{\rightarrow}${\ensuremath{\mu}}^{+}$\ensuremath{\nu} was measured to search for right-handed weak currents in a strangeness-changing process. The 236-MeV/c muons from the decay of stopped ${K}^{+}$ were identified and were collected by a magnetic spectrometer. The muons were then slowed down in a carbon degrader and were brought to rest in an aluminum target. The muon spins were precessed by a 220-G transverse field, and a muon-spin-rotation technique was employed to measure the muon-spin polarization. The polarization was determined to be -0.970\ifmmode\pm\else\textpm\fi{}0.047, which is consistent with the V-A hypothesis.