New Measurement of theπ→eνBranching Ratio

Abstract

A new measurement of the $\pi \to e\nu$ branching ratio yields $\frac{\Gamma (\pi \to e\nu +\pi \to e\nu \gamma )}{\Gamma (\pi \to \mu \nu +\pi \to \mu \nu \gamma )}=(1.218\mathrm{}\pm 0.014)\times {10}^{-4\mathrm{}}$. The measured value is in good agreement with the standard-model prediction incorporating electron-muon universality.