Speaker
Description
Since the discovery of the muon, the lack of understanding of flavor is one of the most intriguing and persistent problems in particle physics. Many hypotheses which extend the Standard Model suggest that observations of non-universal charged current interactions could be due to effects at high mass scales, possibly approaching 1000 TeV, or to the existence of sterile neutrinos. Measurement of the pion decay branching ratio $R_{\pi\rightarrow e}=\frac{\Gamma(\pi^+\to e^+\nu +\pi^+\to e^+\nu\gamma)}{ \Gamma(\pi^+\to \mu^+\nu +\pi^+\to \mu^+\nu\gamma)} $ in comparison with the extraordinarily precise Standard Model prediction provides one of the best tests of universality, currently indicating consistency with $e-\mu$ universality at the 0.1 % level. This presentation will discuss the PIENU experiment at TRIUMF which aims to improve the precision of the measurement of $R_{\pi\to e}$ and to search for evidence of sterile neutrinos involved in pion decay.
