Testing lepton non-unitarity with the next generation of Germanium-based CE$ν$NS reactor experiments

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Autori principali: Chuliá, Salvador Centelles, Lindner, Manfred, Rink, Thomas
Natura: Preprint
Pubblicazione: 2025
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author Chuliá, Salvador Centelles
Lindner, Manfred
Rink, Thomas
author_facet Chuliá, Salvador Centelles
Lindner, Manfred
Rink, Thomas
contents Coherent elastic neutrino-nucleus scattering (CE$ν$NS) has been experimentally confirmed using neutrinos from pion decay at rest, solar neutrinos and reactor antineutrinos. Future CE$ν$NS experiments will foreseeable lead to precision measurements which will be a powerful tool to search for new physics beyond the Standard Model. In this work, we investigate possible deviations from unitarity in the $3\times3$ leptonic mixing matrix that controls the propagation of active neutrinos. Such deviations may originate from the mixing with additional gauge singlet fermions and depending on their mass scale and mixing, the resulting phenomenology can differ substantially. We explore two well-motivated regimes: the \textit{seesaw limit}, where the new fermions are heavy and kinematically inaccessible, leading to effective deviations from unitarity in the active sector; and the \textit{light sterile limit}, where they are light enough to be produced and participate in neutrino propagation and scattering processes. We show how these scenarios modify both CE$ν$NS and elastic neutrino--electron scattering (E$νe$S), and we present the corresponding sensitivity projections for a future CE$ν$NS reactor experiment obtained by upscaling the CONUS+ experiment, which reported the first observation of reactor CE$ν$NS. We identify the leading experimental systematics relevant for such an upscaling and demonstrate the resulting capability to probe TeV-scale new physics. Our results highlight the strong potential of CE$ν$NS to test the structure of the lepton sector and to search for physics beyond the Standard Model.
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id arxiv_https___arxiv_org_abs_2512_09027
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Testing lepton non-unitarity with the next generation of Germanium-based CE$ν$NS reactor experiments
Chuliá, Salvador Centelles
Lindner, Manfred
Rink, Thomas
High Energy Physics - Phenomenology
High Energy Physics - Experiment
Coherent elastic neutrino-nucleus scattering (CE$ν$NS) has been experimentally confirmed using neutrinos from pion decay at rest, solar neutrinos and reactor antineutrinos. Future CE$ν$NS experiments will foreseeable lead to precision measurements which will be a powerful tool to search for new physics beyond the Standard Model. In this work, we investigate possible deviations from unitarity in the $3\times3$ leptonic mixing matrix that controls the propagation of active neutrinos. Such deviations may originate from the mixing with additional gauge singlet fermions and depending on their mass scale and mixing, the resulting phenomenology can differ substantially. We explore two well-motivated regimes: the \textit{seesaw limit}, where the new fermions are heavy and kinematically inaccessible, leading to effective deviations from unitarity in the active sector; and the \textit{light sterile limit}, where they are light enough to be produced and participate in neutrino propagation and scattering processes. We show how these scenarios modify both CE$ν$NS and elastic neutrino--electron scattering (E$νe$S), and we present the corresponding sensitivity projections for a future CE$ν$NS reactor experiment obtained by upscaling the CONUS+ experiment, which reported the first observation of reactor CE$ν$NS. We identify the leading experimental systematics relevant for such an upscaling and demonstrate the resulting capability to probe TeV-scale new physics. Our results highlight the strong potential of CE$ν$NS to test the structure of the lepton sector and to search for physics beyond the Standard Model.
title Testing lepton non-unitarity with the next generation of Germanium-based CE$ν$NS reactor experiments
topic High Energy Physics - Phenomenology
High Energy Physics - Experiment
url https://arxiv.org/abs/2512.09027