Investigating Lepton Flavour violating Muon decays with the Mu3e experiment at PSI

Student: Sean Hughes
Supervisor: Nikolaos Rompotis

The Mu3e experiment aims to search for the Muon decay μ → eee, a decay heavily suppressed in the Standard Model due to conservation of Lepton Flavour. The decay, occurring through current SM interactions, would occur through the means of neutrino mixing, at an unobservable branching fraction of 10^−54. The experiment aims for a sensitivity of 10^−16, 4 orders of magnitude larger than the previous sensitivity achieved of 10^−12 at SINDRUM, a previous experiment looking into this Muon decay. Mu3e therefore has sensitivity to physics beyond the SM, as the detection of such a decay would be a clear indication of the breaking of Lepton Flavour (a symmetry currently conserved in the SM), and thus new physics. To reach the required sensitivity of 10^−16, the Mu3e experiment requires a muon beam capable of producing up to 10^8 muons per second, which is possible through the use of the upgraded πE5 beamline at PSI. 

The project will investigate and develop simulation software created by the Mu3e collaboration. For example, this will involve the investigation of the timing responses of the scintillating fibre and tile layers present in the experiment. The aim will be to optimise the performance of both the physical detectors present in the experiment and the simulated detectors. A significant section of the project will involve the analysis of the first data set taken from the experiment. Particular studies using this data will include the validation of the simulation with particular regard to the timing response of the silicon, fibre and tile detectors. Other studies could involve the analysis of a particular sections of the detector at later phases of the Mu3e experiment. 

Further studies into software will involve improving the scope of the Mu3e experiment through the use of neural networks to better analyse the GPU-reconstructed vertices in real time. This involves the development and optimisation of software that will be used by these GPU farms to select μ → eeeX decays (where X is a new particle, dark photon for example). This will expand the Mu3e experiment’s potential through investigations into these new particles that new models suggest exist.