NEW MEASUREMENT OF THE RATE FOR PION BETA DECAY

The conserved-vector-current hypothesis, together with measured nuclear-beta-decay rates, predicts a value of the rate for the decay ..pi../sup +/..--> pi../sup 0/e/sup +/..nu.. of 0.4027 +- 0.0018 s/sup -1/. With use of a decay-in-flight technique the authors have made the most precise measurement to date of this rate, obtaining the value 0.398 +- 0.015 s/sup -1/, in good agreement with the prediction.