Radiativeτ-Meson Decay

Abstract

The characteristics of the decay process ${\tau }^{\pm }\to {\pi }^{\pm }+{\pi }^{+}+{\pi }^{-}+\gamma$ are considered. For a pseudoscalar $\tau$-meson, the probability $R\left(k\right)\mathrm{}$, relative to the $3\pi$-decay, for emission of a photon of energy $k$ Mev or greater is found to be 1.06×${10}^{-3\mathrm{}}$ for $k=10\mathrm{} \mathrm{and} 1.1\times {10}^{-4\mathrm{}}$ for $k=30\mathrm{}$. Quite similar values are obtained for other spin values compatible with the $\tau$-meson decay data. Branching ratios for other decay processes are briefly discussed and it is suggested that the absence of the decay mode ${\pi }^{\pm }+\gamma$ or ${\pi }^{\pm }+e^{+}+e^{-}$ may provide some evidence against a nonzero $\tau$-meson spin. Competing decay processes involving a neutrino are not considered.