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.
Categories: hep-ex nucl-ex