A seesaw model for large neutrino masses in concordance with cosmology

M. Escudero, T. Schwetz and J. Terol-Calvo

JHEP 02 (2023) 142; Addendum: JHEP 06 (2024) 119

arXiv:2211.01729 · Journal version

What it is about

There is a long-standing tension in neutrino physics: cosmology requires the neutrino masses to sum to a very small value, while laboratory experiments such as KATRIN are designed to look for masses that cosmology appears to have excluded. We construct a model in which both can hold, with neutrinos heavy today but effectively massless in the early universe. The addendum adds a mechanism that opens the parameter space further.

The mechanism that hides the neutrino mass from cosmology. Above, neutrinos annihilate into the mediator X, which decays into massless dark states. Below, the resulting number densities: the active neutrino density is depleted between BBN and recombination, relaxing the cosmological mass bound.
The mechanism that hides the neutrino mass from cosmology. Above, neutrinos annihilate into the mediator X, which decays into massless dark states. Below, the resulting number densities: the active neutrino density is depleted between BBN and recombination, relaxing the cosmological mass bound.

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