Measurement of thepi→eνbranching ratio

A measurement of the ..pi -->..e..nu.. branching ratio using a NaI(Tl) spectrometer yields a value GAMMA((..pi -->..e..nu..)+(..pi -->..e..nu gamma..))/ GAMMA((..pi --> mu nu..)+(..pi --> mu nu gamma..)) = (1. 218 +- 0.014) x 10/sup -4/. The result is consistent with expectations of the standard electroweak theory incorporating electron-muon universality.