Status of the Mu3e Experiment at PSI

TL;DR

The Mu3e experiment at PSI is developing a high-sensitivity search for the rare muon decay $ ext{mu}^+ ightarrow ext{e}^+ ext{e}^+ ext{e}^-$, aiming to improve detection sensitivity to new physics beyond current limits.

Contribution

This paper reports on the current status and development of the Mu3e experiment's detector components and its potential to probe lepton-flavour violation with unprecedented sensitivity.

Findings

Development of thin pixel sensors for tracking

Implementation of scintillating fibres and tiles for timing

Preparation for detector construction and operation

Abstract

The Mu3e experiment aims to search for the lepton-flavour violating decay $\mu^+\rightarrow\ \text{e}^+ \text{e}^+ \text{e}^-$ with a sensitivity to one signal decay in $10^{16}$ muon decays at a muon stopping rate of $2\times 10^9 \frac{\mu}{\text{s}}$. With currently available rates of $10^8 \frac{\mu}{\text{s}}$, a sensitivity on the branching ratio of $10^{-15}$ is the aim of the first phase. This will allow for tests of new physics models with enhanced branching ratios for lepton-flavour violating processes with an unprecedented precision. The experiment must be operated at very high muon rates all the while suppressing the background of the decay $\mu^+\rightarrow\ \text{e}^+ \text{e}^- \text{e}^+ \overline{\nu}_\mu \nu_\text{e}$ and accidental electron-positron combinations. Therefore, a tracking detector made of thin pixel sensors with additional scintillating fibres and tiles for precise time measurement will be built. The development of the subdetectors is ongoing while detector construction is still in preparation.