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Neutrino decays as a natural explanation of the neutrino mass tension

Guillermo Franco Abellán*

  • Instituto de Física Corpuscular (IFIC), CSIC–Universitat de València, Parc Científic UV, c/ Catedrático José Beltrán, 2, E-46980 Paterna (València), Spain and GRAPPA Institute, Institute for Theoretical Physics Amsterdam, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands

  • *Contact author: g.francoabellan@ific.uv.es
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Phys. Rev. D 113, 123527 – Published 11 June, 2026

DOI: https://doi.org/10.1103/lwdv-qrcc

Abstract

A new tension is emerging between the tight cosmological upper bounds on the total neutrino mass (∑mν≲0.06  eV) and the lower limits from oscillation experiments, with potentially far-reaching implications for cosmology and particle physics. Neutrinos decaying into massless Beyond the Standard Model (BSM) particles with lifetimes τν∼0.01–1  Gyr represent a theoretically well-motivated mechanism to reconcile such measurements. Using Dark Energy Spectroscopic Instrument Data Release 2 and cosmic microwave background datasets, we show that such invisible decays relax the bound on the total neutrino mass up to ∑mν<0.23  eV (95%), restoring full agreement with oscillation data. We also present the first late-time cosmological analysis of invisible neutrino decays into lighter neutrinos in a manner consistent with the measured mass splittings. In contrast to the decays into massless BSM particles, we find that this scenario only marginally alleviates—or even tightens—the cosmological neutrino mass bounds, depending on the mass ordering.

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Physics Subject Headings (PhySH)

synopsis

Dodging Neutrino-Mass Tension with Decays

Published 11 June, 2026

A disagreement over neutrino-mass estimates might be resolved by assuming that neutrinos decay into hypothetical massless particles.

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Article Text

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Phys. Rev. D 113, 123527– Published 11 June, 2026
  • Received 26 January 2026
  • Accepted 20 April 2026
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