New limits on neutrino decay from the Glashow resonance of high-energy cosmic neutrinos

Understand

Discovering neutrino decay would be strong evidence of physics beyond the Standard Model.

• Presently, there are only lax lower limits on the lifetime $\tau$ of neutrinos, of $\tau/m \sim 10^{-3}$ s eV$^{-1}$ or worse, where $m$ is the unknown neutrino mass.
• High-energy cosmic neutrinos, with TeV-PeV energies, offer superior sensitivity to decay due to their cosmological-scale baselines.
• To tap into it, we employ a promising method, recently proposed, that uses the Glashow resonance $\bar{\nu}_e + e \to W$, triggered by $\bar{\nu}_e$ of 6.3 PeV, to test decay with only a handful of detected events.