Search for right-handed currents in the decay chain of [ital K][sup +][r arrow][mu][sup +][nu][sub [mu]], [mu][sup +][r arrow][ital e][sup +][nu][sub [ital e]][bar [nu]][sub [mu]]

The asymmetry of positrons in the [ital K][sup +][r arrow][mu][sup +][nu], [mu][sup +][r arrow][ital e][sup +][nu][sub [ital e]][bar [nu]][sub [mu]] decay chain was measured in a search for right-handed weak currents in [Delta][ital S]=1 semileptonic decay. High-intensity low-background monoenergetic polarized muons of 236 MeV/[ital c] momentum resulting from kaon decay at rest were directly extracted from a primary production target which was hit by a proton beam of the KEK 12-GeV proton synchrotron. Muons were stopped in a pure-aluminum plate, and the energy-integrated asymmetry of the decay positrons with respect to the incoming muon direction was determined to high precision. The observed asymmetry yielded [xi][ital P][sub [mu]]=[minus]0.9996[plus minus]0.0030(stat)[plus minus]0.0048(syst). This result revealed no evidence of right-handed currents in this kaon-decay chain, and set a stringent bound on the mass of the right-handed weak boson.