High-energy electrons from the muon decay in orbit: radiative corrections

We determine the $\mathcal{O}(\alpha)$ correction to the energy spectrum of electrons produced in the decay of muons bound in atoms. We focus on the high-energy end of the spectrum that constitutes a background for the muon-electron conversion and will be precisely measured by the upcoming experiments Mu2e and COMET. The correction suppresses the background by about 15\%.Comment: 7 pages, v2: corrected and improved versio

General description of neutrino oscillations with non-standard interactions

We present a formalism describing neutrino oscillations in any application beyond the Standard Model theory. Instead of using the standard pure states approach, we apply the density matrix formalism. In general, in New Physics models, neutrino states are no longer as pure as they are in the Standard Model. We discuss the details of the appearance of a mixed state, following which possible New Physics effects are taken at the levels of both the production and detection processes. We present a number of examples of calculations with our formalism, using muons as a source of neutrinos and different detection process. We also show the connection between normal formulae, derived by assuming pure states, and proper results based on the density matrix approach. The difference occurs at the second order in parameters describing the departure from the Standard Model. Finally, as an application of our formalism, we also demonstrate that it is possible to distinguish Dirac and Majorana neutrinos in oscillations when New Physics scalar interactions are present

Rare muon decays

In this paper, we present a short review of searches for charged lepton flavour violation on the example of rare muon decays. We discuss the evaluation of electron spectrum for muon decay in orbit which is a background process for conversion experiments