2017/12/15 by Yannick Ulrich, Ulrich, Y.
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High Energy Physics - Phenomenology (hep-ph) #Neutrino Physics Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions
paper · pdf · doi:10.48550/arxiv.1712.05633
openalex publication_date 2017/12/15 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We present a general purpose, parton-level Monte Carlo program for the calculation of the radiative (L→ννl+γ) and rare (L→ννl'+ l+l-) muon and tau decays at NLO in the effective Fermi theory. In the case of muon, these processes are irreducible Standard Model backgrounds to searches for lepton flavour violation at the PSI experiments MEG and Mu3e as they become indistinguishable from the corresponding signals when the neutrinos carry little energy. Furthermore, we argue that fully differential NLO corrections are very important for the analysis of measurements aiming at the percent level or better. This is especally true if very stringent phase-space cuts are applied. To illustrate this, we use a tension between BaBar's recent measurement of the radiative tau decay and the Standard Model prediction as an example of such an analysis. Finally, we present the branching ratios of the rare tau decay τ→ννl' l+l- at NLO. We generally find that QED corrections of O(10%) are very well possible.