Speaker
Description
The Mu3e experiment at the Paul Scherrer Institute (PSI) searches for the charged lepton flavour violating decay $\mu^+ \to e^+ e^- e^+$, aiming to improve the current best limit set by the SINDRUM experiment by four orders of magnitude.
The experiment will proceed in two phases. Phase I, currently under construction at the $\pi$E5 beamline at PSI, will utilise a DC surface muon beam of $10^8\ \mu^+/\mathrm{s}$ to achieve a single-event sensitivity of $2 \times 10^{-15}$. Phase II will leverage the upcoming High-Intensity Muon Beam (HIMB) to push this further to the $10^{-16}$ regime. This improvement is made possible by combining high-intensity muon beams with a low-material-budget tracking system based on ultra-thin HV-MAPS silicon pixel detectors, fast scintillating fibre and tile detectors providing sub-ns timing resolution, and a high-rate data acquisition system. Operating in a $1\ \mathrm{T}$ solenoidal magnetic field, the detector is optimised for the $\mu^+ \to e^+ e^- e^+$ signature, enabling precise reconstruction of the decay vertex and invariant mass.
In preparation for Phase I data-taking, a crucial commissioning campaign took place in June 2025 at the PSI $\pi$E5 beamline. This campaign successfully validated essential detector components—including vertex, scintillating fibre, and tile modules—and demonstrated their integration with the high-intensity muon beamline under a $1\ \mathrm{T}$ magnetic field. These achievements mark a major milestone towards readiness for Phase I measurements.
This contribution will present first results from the 2025 commissioning run, the current status of the experiment, and an outlook on the 2026 campaign leading towards the physics run, anticipated in 2027.
| Are you an early career researcher? | Yes, a Postdoc |
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