Fully differential NLO predictions for the rare muon decay

TL;DR

This paper presents automated NLO calculations for the rare muon decay process, providing precise predictions crucial for background estimation in lepton-flavour violation searches, and extends to tau decays with minor adjustments.

Contribution

It introduces a fully automated NLO computation framework for muon decay, enabling detailed predictions of branching ratios and observables relevant to experimental searches.

Findings

Computed NLO corrections for muon decay process.

Provided precise branching ratio predictions.

Enabled analysis of tau decay processes with minimal modifications.

Abstract

Using the automation program GoSam, fully differential NLO corrections were obtained for the rare decay of the muon $\mu\to e\nu\bar\nu ee$. This process is an important Standard Model background to searches of the Mu3e collaboration for lepton-flavour violation, as it becomes indistinguishable from the signal $\mu\to 3e$ if the neutrinos carry little energy. With our NLO program we are able to compute the branching ratio as well as custom-tailored observables for the experiment. With minor modifications, related decays of the tau can also be computed.