The muon to electron conversion process and the Mu2e experiment at Fermilab

Abstract

The Mu2e experiment at Fermilab aims to measure the charged-lepton flavor violating (CLFV) neutrino-less conversion of a negative muon into an electron in the field of an aluminum nucleus. In the Standard Model, the CLFV processes in the muon sector have negligible rates.However, in many Beyond the Standard Model scenarios their rates are within reach of next generation experiments. Goal of the Mu2e experiment is to improve of four orders of magnitude the best previous measurement and reach a single event sensitivity of 2.5 $\times 10^{-17}$ on the conversion rate with respect to the muon capture rate. The distinctive signature of the muon to electron conversion is a mono-energetic electron with momentumvery close to the muon rest mass. In this paper, we explain the sensitivity to new physics scale and the Mu2e experimental technique that is based on four elements: the high muon intensity, the used pulsed beam structure , the extinction of out of time particles and a precise electron identification in the detector solenoid. Production and transport of the muons is done with a sophisticated magnetic system composed by a production, a transport and a detector solenoid. The experiment goal is achieved by stopping 10$^{18}$ low momentum muons on an Aluminium target in three years of running. This paper focuses on the design and status of the experiment.