Speaker
Description
Mu3e is an experiment currently under construction at PSI, designed to search for the charged lepton flavour violating decay µ⁺ → e⁺e⁻e⁺. It will make use of the πE5 intense DC surface muon beam of 10⁸ µ⁺/s to reach a sensitivity of 2 × 10⁻¹⁵. The nature of this decay imposes strict requirements on the detector system, especially concerning design compactness, material budget, efficiency and time resolution. This can be achieved only by implementing depleted Monolithic Active Pixel Sensors (dMAPS) in the Pixel Tracker, ultra-thin Aluminum-Kapton HDIs for the services and mechanical support, and several other technical features. A first version of the Vertex detector, the two innermost layers of the tracking system, has been produced and operated in 2025 at πE5 experimental conditions and with the design DAQ system. This campaign successfully validated many key features and proved the integration of the Pixel Tracker with the high-intensity muon beamline under a 1 T magnetic field. These results represent a major milestone towards readiness for Phase I measurements. This contribution will cover the experimental design, the sensor qualification and the first results from the recent commissioning run campaign at PSI, along with the perspectives for the next data taking campaigns.