A new tension is emerging between the tight cosmological upper bounds on the total neutrino mass ($\sum m_{\nu }\lesssim 0.06\mathrm{eV}$) 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 ${\tau }_{\nu }\sim 0.01–1\mathrm{Gyr}$ 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 $\sum m_{\nu }<0.23\mathrm{eV}$ (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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• Baryon acoustic oscillations
• Cosmic microwave background
• Cosmological parameters
• Neutrino interactions
• Neutrinos
• Neutrino mass