Search for the rare decay of the muon to three electrons in the Mu3e experiment.

The Mu3e experiment searches for the extremely rare decay of the muon to three electrons. This is a process that potentially occurs in less than 1 in 10,000,000,000,000,000 muon decays and its observation would provide unequivocal evidence for new physics beyond the Standard Model. Mu3e uses the high intensity muon facility at the Paul Scherrer Institute (PSI) near Zurich, Switzerland.

The muons are brought to rest on a target and are left to decay. Around the target, a detector composed of several layers of tracking detectors which will be able to reconstruct the electrically charged decay products of the muon. The detector is currently under construction and it is expected to start data-taking starting in 2025.

The data-taking will continue for several years before the experiment is upgraded for a second phase in which even higher muon rates will be studied, starting from 2029.

The search for extremely rare processes requires experiments that deploy detectors with fast response and high-bandwidth to produce data at very high rates. Current experiments operate multi-staged trigger systems that select events based on relatively crude event features and thus succeeding in reducing the event rate. Mu3e will use instead a high bandwidth electronics to stream the full detector data to an online GPU filter and analysis farm.

There, a large data reduction will be achieved through a much more complete processing and background rejection of the data. We want to take this one step further by removing the need for permanent storage entirely for certain classes of analysis.

This PhD project will focus on the development of the software for the fast processing and physics analysis on the Mu3e GPU farm. The student will work on the implementation of calibration and alignment procedures on the GPU farm and develop the tolls to apply the required corrections to the data. In parallel they will have a direct involvement in the commissioning of the full online processing system at the experiment at PSI.

Benefiting from their deep knowledge of the experiment's data processing, they will be able to develop online data-analyses to look for new physics beyond the rare muon decay to three electrons, including searching for potentially long-lived axions and dark photons.