The Energy Spectrum of Positrons from the Decay of theμ-Meson

Abstract

The energy of the positrons from $301\pi \to \mu \to \beta$ decays have been determined in electron sensitive emulsions by measuring the multiple scattering of the positron tracks. The annihilation properties of the charged particle emitted in the decay of the ${\mu }^{+}$ meson confirm its identity as a positron. This spectrum has a maximum about 36 Mev and a nonzero cutoff at the high energy end. A statistical analysis of the data, using the Michel theory, yields a value of $\rho =0.41\mathrm{}\pm 0.13$.