A robust search for lepton flavour violating axions at Mu3e

Abstract We propose a search at Mu3e for lepton flavor violating axion(-like) particles in μ → 3e + a decays. By requiring an additional e + e − pair from internal conversion, one can circumvent the calibration challenges which plague the μ → e + a channel for axions lighter than 20 MeV. Crucially,...

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Main Authors: Simon Knapen, Kevin Langhoff, Toby Opferkuch, Diego Redigolo
Format: Article
Language:English
Published: SpringerOpen 2025-07-01
Series:Journal of High Energy Physics
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Online Access:https://doi.org/10.1007/JHEP07(2025)243
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author Simon Knapen
Kevin Langhoff
Toby Opferkuch
Diego Redigolo
author_facet Simon Knapen
Kevin Langhoff
Toby Opferkuch
Diego Redigolo
author_sort Simon Knapen
collection DOAJ
description Abstract We propose a search at Mu3e for lepton flavor violating axion(-like) particles in μ → 3e + a decays. By requiring an additional e + e − pair from internal conversion, one can circumvent the calibration challenges which plague the μ → e + a channel for axions lighter than 20 MeV. Crucially, the corresponding reduction in signal rate is to a large extent compensated for by Mu3e’s ability to resolve highly collimated tracks. For phase I of Mu3e, we project a sensitivity to decay constants as high as 6 × 109 GeV which probes uncharted parameter space in scenarios of axion dark matter. The sensitivity to axions which couple primarily to right-handed leptons can be further improved by leveraging the polarisation of the muon beam.
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institution Kabale University
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series Journal of High Energy Physics
spelling doaj-art-a9dfefc09c684d049457c28556aea0972025-08-20T04:01:43ZengSpringerOpenJournal of High Energy Physics1029-84792025-07-012025711210.1007/JHEP07(2025)243A robust search for lepton flavour violating axions at Mu3eSimon Knapen0Kevin Langhoff1Toby Opferkuch2Diego Redigolo3Berkeley Center for Theoretical Physics, University of CaliforniaBerkeley Center for Theoretical Physics, University of CaliforniaBerkeley Center for Theoretical Physics, University of CaliforniaINFN, Sezione di FirenzeAbstract We propose a search at Mu3e for lepton flavor violating axion(-like) particles in μ → 3e + a decays. By requiring an additional e + e − pair from internal conversion, one can circumvent the calibration challenges which plague the μ → e + a channel for axions lighter than 20 MeV. Crucially, the corresponding reduction in signal rate is to a large extent compensated for by Mu3e’s ability to resolve highly collimated tracks. For phase I of Mu3e, we project a sensitivity to decay constants as high as 6 × 109 GeV which probes uncharted parameter space in scenarios of axion dark matter. The sensitivity to axions which couple primarily to right-handed leptons can be further improved by leveraging the polarisation of the muon beam.https://doi.org/10.1007/JHEP07(2025)243Axions and ALPsBaryon/Lepton Number ViolationNew Light ParticlesTheories of Flavour
spellingShingle Simon Knapen
Kevin Langhoff
Toby Opferkuch
Diego Redigolo
A robust search for lepton flavour violating axions at Mu3e
Journal of High Energy Physics
Axions and ALPs
Baryon/Lepton Number Violation
New Light Particles
Theories of Flavour
title A robust search for lepton flavour violating axions at Mu3e
title_full A robust search for lepton flavour violating axions at Mu3e
title_fullStr A robust search for lepton flavour violating axions at Mu3e
title_full_unstemmed A robust search for lepton flavour violating axions at Mu3e
title_short A robust search for lepton flavour violating axions at Mu3e
title_sort robust search for lepton flavour violating axions at mu3e
topic Axions and ALPs
Baryon/Lepton Number Violation
New Light Particles
Theories of Flavour
url https://doi.org/10.1007/JHEP07(2025)243
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