Muon Decay Experiments and Charged Lepton Flavor Violation

The talk summarizes the ongoing and upcoming experimental searches for charged lepton flavor violation (CLFV) with muons. This work focuses on the MEG II experiment ($\mu^{+} \rightarrow e^{+} \gamma$), the Mu3e experiment ($\mu^{+} \rightarrow e^{+} e^{-} e^{+}$), and the Mu2e experiment ($\mu^{-} N \rightarrow e^{-} N$). These are the three 'golden channels' of CLFV with muons, which are sensitive to a broad range of physics models. Over their full lifetimes, the experiments are expecting $10-10^{4}$ improvements in sensitivity beyond their predecessors.

The MEG II experiment at PSI is in its final years of data-taking. The collaboration is on track to reach its goal of $6 \cdot 10^{-14}$, with the 2021-2022 runs reaching a world-leading upper limit of $1.5 \cdot 10^{-13}$ at the 90\% confidence level. The Mu3e experiment at PSI has commissioned its Phase-I detectors and is preparing for physics data-taking in 2026. Mu3e Phase-I is expected to reach a sensitivity of $\sim 2 \cdot 10^{-15}$. The Mu2e experiment at Fermilab aims for all detectors ready for cosmic ray commissioning starting at the end of 2025. The collaboration is expecting an engineering+physics run before the Fermilab long shutdown starting in 2028. 

This talk details the three experiment's experimental design, the CLFV signal, expected backgrounds, detector resolutions, timelines, and additional 'exotic' searches planned. The talk will also detail the latest MEG II result.