The Time Distribution of Decay Electrons from Mesons Stopped in Magnesium at 3500 Meter Altitude

The time distribution of decay electrons from the natural mixture of positive and negative mesons stopped in 13.2 g/cm² magnesium at Climax, Colorado has been measured. The apparatus recorded delayed coincidences in ten contiguous 0.6 {μ}sec. channels covering delays from 0.5 to 6.5 {μ}sec. The time distribution of false delayed coincidences due to G-M tube lags was also measured. These lags are shown to affect only the data from the first delay channel (0.5 to 1.1 {μ}sec.), and an approximate correction for this effect can be made. Corrections for accidental delayed coincidences are also applied. The results (based on 2869 delayed coincidences) lie on a smooth differential decay curve, closely fitting the composite decay curve calculated on the assumption of competition between capture and decay for negative mesons. The effective mean life of the negative mesons is definitely less than 2.15 {μ}sec., and appears to be approximately one {μ}sec. The results can also be fitted by a single exponential of mean life 1.7±{}0.1 {μ}sec.