Search for new Physics with the $\pi\rightarrow e\nu$ Decay

TL;DR

This paper discusses a high-precision experiment measuring the ratio of pion decays to test lepton universality, which could reveal new physics beyond the Standard Model.

Contribution

The paper presents the TRIUMF PIENU experiment aiming to measure the decay ratio with 0.1% precision, improving constraints on new physics.

Findings

Expected to improve constraints on physics beyond the Standard Model.

Potential to uncover deviations from lepton universality.

Provides the most precise test of the $R_{e / f}$ ratio to date.

Abstract

In the Standard Model, lepton universality refers to the identical electroweak gauge interactions among charged leptons. The measurement of the branching ratio $R_{e / \mu} = \frac{\Gamma(\pi\rightarrow\ e \nu)}{\Gamma(\pi\rightarrow\mu\nu)}$ is one of the most stringent tests of lepton universality between the first two generations. The TRIUMF PIENU experiment aims at the most precise test of universality measuring $R_{e / \mu}$ with 0.1% precision. The measurement will provide improved constraints to physics beyond the Standard Model or uncover new scenarios if a disagreement is found.