SciPost Submission Page
High-precision muon decay predictions for ALP searches
by Pulak Banerjee, Antonio Coutinho, Tim Engel, Andrea Gurgone, Adrian Signer, Yannick Ulrich
This Submission thread is now published as
Submission summary
| Ontological classification |
| Academic field: |
Physics |
| Specialties: |
- High-Energy Physics - Theory
- High-Energy Physics - Phenomenology
|
| Approaches: |
Theoretical, Phenomenological |
Abstract
We present an improved theoretical prediction of the positron energy spectrum for the polarised Michel decay $\mu^+\to e^+ \nu_e\bar{\nu}_\mu$. In addition to the full next-to-next-to-leading order correction of order $\alpha^2$ in the electromagnetic coupling, we include logarithmically enhanced terms at even higher orders. Logarithms due to collinear emission are included at next-to-leading accuracy up to order $\alpha^4$. At the endpoint of the Michel spectrum, soft photon emission results in large logarithms that are resummed up to next-to-next-to-leading logarithmic accuracy. We apply our results in the context of the MEG II and Mu3e experiments to estimate the impact of the theory error on the branching ratio sensitivity for the lepton-flavour-violating decay $\mu^+\to e^+ X$ of a muon into an axion-like particle $X$.
Author comments upon resubmission
We have revised the submission following guidance from the reviewers.
List of changes
The changes we have made as a response to the reviewer's comments are listed in our replies to the report.
