Neutrino decays as a natural explanation of the neutrino mass tension

Fuente: arXiv
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Autor principal: Abellán, Guillermo Franco
Formato: Preprint
Publicado: 2026
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author Abellán, Guillermo Franco
author_facet Abellán, Guillermo Franco
contents A new tension is emerging between the tight cosmological upper bounds on the total neutrino mass ($\sum m_ν\lesssim 0.06 \, \rm{eV}$) and the lower limits from oscillation experiments, with potentially far-reaching implications for cosmology and particle physics. Neutrinos decaying into massless BSM particles with lifetimes $τ_ν\sim 0.01-1\, \rm{Gyr}$ represent a theoretically well-motivated mechanism to reconcile such measurements. Using DESI DR2 and CMB datasets, we show that such decays relax the bound on the total neutrino mass up to $\sum m_ν< 0.23 \, \rm{eV}$ (95%), restoring full agreement with oscillation data. We also present the first late-time cosmological analysis of 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.
format Preprint
id arxiv_https___arxiv_org_abs_2601_04312
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Neutrino decays as a natural explanation of the neutrino mass tension
Abellán, Guillermo Franco
Cosmology and Nongalactic Astrophysics
High Energy Physics - Phenomenology
High Energy Physics - Theory
A new tension is emerging between the tight cosmological upper bounds on the total neutrino mass ($\sum m_ν\lesssim 0.06 \, \rm{eV}$) and the lower limits from oscillation experiments, with potentially far-reaching implications for cosmology and particle physics. Neutrinos decaying into massless BSM particles with lifetimes $τ_ν\sim 0.01-1\, \rm{Gyr}$ represent a theoretically well-motivated mechanism to reconcile such measurements. Using DESI DR2 and CMB datasets, we show that such decays relax the bound on the total neutrino mass up to $\sum m_ν< 0.23 \, \rm{eV}$ (95%), restoring full agreement with oscillation data. We also present the first late-time cosmological analysis of 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.
title Neutrino decays as a natural explanation of the neutrino mass tension
topic Cosmology and Nongalactic Astrophysics
High Energy Physics - Phenomenology
High Energy Physics - Theory
url https://arxiv.org/abs/2601.04312