Speaker
Description
The PIENU experiment at TRIUMF aims to make a high-precision measurement of the $ \pi \rightarrow e \nu $ branching ratio: $ R_{\pi} = \frac{\Gamma\left(\pi \rightarrow e \nu \hspace{1 mm} + \hspace{1 mm} \pi \rightarrow e \nu \gamma \right)}{\Gamma\left(\pi \rightarrow \mu \nu \hspace{1 mm} + \hspace{1 mm} \pi \rightarrow \mu \nu \gamma \right)}. $ Measurement of $R_{\pi}$ provides a sensitive test of lepton universality and tight constraints on many new physics scenarios. In addition, a heavy neutrino lighter than the pion could be detected through its effect on the $\pi \rightarrow e \nu$ energy spectrum.
New results will be presented, using the full PIENU dataset, placing limits on the mixing of a neutrino of mass 60-135 MeV/$c^2$ with the electron neutrino. These limits are improved by up to an order of magnitude over previous results. The status of the branching ratio analysis will be presented as well.
