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arXiv · 2311.17915

A Robust Search for Lepton Flavour Violating Axions at Mu3e

Simon Knapen·Kevin Langhoff·Toby Opferkuch·Diego Redigolo
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Abstract

We propose a search at Mu3e for lepton flavor violating axion(-like) particles in $\mu\to 3e + a$ decays. By requiring an additional $e^+e^-$ pair from internal conversion, one can circumvent the calibration challenges which plague the $\mu \to e+a$ 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 $6\times 10^9$ 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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Simon Knapen, Kevin Langhoff, Toby Opferkuch, Diego Redigolo. 2023-11-29. A Robust Search for Lepton Flavour Violating Axions at Mu3e. https://arxiv.org/abs/2311.17915

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