Mott Scattering of Polarized Muons

An experimental determination has been made of the helicity of muons from ${\pi }^{-}$ decays and the cross sections for scattering from lead by Mott scattering. With (2.0±0.3)×${10}^8$ muons incident on the scatterers, a left-right asymmetry of -0.090±0.031 was measured for a total of 1163±60 scattering events. Extensive checks indicated negligible systematic asymmetries. The sign of the asymmetry shows a positive helicity for the negative muon in pion decay in agreement with $V-A$ theory. Agreement of the magnitude of the asymmetry and of the number of events with the ones predicted for the experimental arrangement (0.081±0.001 and 1210±220, respectively) confirms the results of other experiments which have indicated a purely electromagnetic behavior for muon scattering. This experiment, at an average momentum transfer of 110 Mev/c, has the added interest of being the only measurement of the Mott scattering of transversely polarized fermions in this momentum transfer region.