3.1 Pion Beta Decay Experiments
The pion beta decay has been observed for the first time in 1962 at CERN [Dep
62]. In the years from 1962-1965 several experiments on this decay were
published and lead to results with errors of 20-30%. Since then, two
experiments have been carried out with errors below 10%. The first of these was
an experiment using stopped pions [Dep 68], whereas the second one [McFa 85]
was a decay-in-flight measurement.