Neutrino Portals, Terrestrial Upscattering, and Atmospheric Neutrinos

Understand

We consider the upscattering of atmospheric neutrinos in the interior of the Earth producing heavy neutral leptons (HNLs) which subsequently decay inside large volume detectors (e.g.

• Super-Kamiokande or DUNE).
• We compute the flux of upscattered HNLs arriving at a detector, and the resultant event rate of visible decay products.
• Using Super-Kamiokande's atmospheric neutrino dataset we find new leading constraints for dipole couplings to any flavor with HNL masses between roughly 10 MeV and 100 MeV.