Proton Helicity from a Decay

Abstract

S>A necessary consequence of parity nonconservation is the longitudinal polarization of the decay proton from unpolarized LAMBDA hyperons decaying at rest. This longitudinal polarization appears as a partial transverse polarization when a LAMBDA decays in flight. Measurements of the helicity of the proton were obtained in scattering experiments. For each analyzed event the angle between the spin and direction of motion of the proton was computed. The sine of this angle divided into the transverse polarization, found as a function of incoming momentum and scattering angle, gave the longitudinal polarization. The data gave a value of -0.45 plus or minus 0.4 for the longitudinal polarization. This indicated a positive helicity for the proton in contradiction to theory. (M.C.G.)