The Mu2e collaboration uploaded a technical design report for the project, which is planned to be built at Fermilab. It’s a huge document (almost 900 pages) but if you want to read about every aspect of the project in excruciating detail there’s a lot there. Mu2e would be part of what the DoE calls the “intensity frontier,” where lab-created high-intensity but not particularly high-energy beams are used in experiments.
As the name suggests, Mu2e is designed to look for muon conversion to electrons. While muons decay into electrons, there are also neutrinos so that flavor (lepton number) is not violated. Mu2e looks for flavor violating interactions, which could yield hints about presently unknown physics beyond the Standard Model. Their signal is to look for muons captured by an aluminum target that then convert to electrons due to their interactions with the target material. The paper mentions that in most models, a tensor interaction of an electron and muon field with a vector field and a scalar interaction with quarks are the two most important terms in an effective Lagrangian. Some models mentioned as leading to flavor violating interactions are grand unified theories and leptoquarks.