Mu3e Experiment

Searching for Lepton Flavour Violation
with utmost precision.

The observation of lepton flavour violation (LFV) would be a clear sign of physics beyond the Standard Model (SM). The Mu3e Collaboration aims to search for the LFV decay \(\mu\rightarrow eee\) with a precision of one in \(10^{16}\) muon decays.

Mu3e Experiment

The Mu3e experiment is currently being built at the Paul-Scherrer Institut (PSI).

Signal and Background

The invariant mass of \(\mu\rightarrow eee\) signal decays equals the muon rest mass invariant mass \(m_{\mu}\).
In background from rare SM muon decay \(\mu^+\rightarrow e^+e^-e^+\nu\nu\), part of the energy is carried by the undetected neutrinos. Additional backgrounds stem from accidental combinations of three tracks.


A high-intensity muon beam is stopped on a target. The tracks of the decay particles are measured in a lightweight tracking detector built from ultra-thin pixel sensors, scintillating fibres and tiles.

Data acquisition

Triggerless, continuous data readout and online track and vertex reconstruction on a GPU based filterfarm.

Exotic muon decays @ ETP

At the ETP, we develop data acquisition for Mu3e and prepare the analysis for various exotic muon decays.

Effective field theories

The underlying interaction defines the kinematics of \(\mu\rightarrow eee\) decays. Modelling is done in effective field theories.

Two-body muon decays

The data acquisition is modified to record \(\mu\rightarrow eX\) events in which the \(X\) escapes undetected.


Publications (non-exhaustive)
Recent talks