Positron asymmetry in the decay of muons produced in K++ has been precisely measured in a search for right-handed currents. A novel technique utilizing a K2 muon beam from the at-rest decay of positive kaons in a primary-proton-beam target was employed. A limit of P>0.990 (90% C.L.) was obtained from the energy-integrated positron asymmetry observed in muon spin precession under a transverse magnetic field. This limit sets a new constraint on the mass of a second weak boson (MW2) as well as on the Cabibbo angle of the right-handed sector.
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