Precision Measurement of theμ+Lifetime

A new precision measurement of the mean lifetime of the positive muon, $\tau \left({\mu }^{+}\right)$, is described. On the basis of 12 internally consistent, independent determinations performed under a variety of experimental conditions we obtain $\tau \left({\mu }^{+}\right)=(2.203\mathrm{}\pm 0.004)$ μsec. These determinations were performed by means of an improved version of Swanson's "digitron"—a digital electronic time interval measuring device—embodying a continuous wave (CW) oscillator and several protective features. The available experimental conditions, in particular concerning the percentage of background events, were greatly superior to those available in earlier experiments here and elsewhere. Particular attention was paid to sources of systematic error, such as time dependence of background events and rate dependence of the over-all measuring process. All sources of background have been localized, their effects quantitatively exhibited and, in general, suppressed electronically during actual lifetime determinations.