New constraints on Heavy Neutral Leptons from Super-Kamiokande data

TL;DR

This paper uses Super-Kamiokande data to search for heavy neutral leptons produced in atmospheric showers, setting new limits on their mixing with standard neutrinos and constraining models with additional interactions.

Contribution

It provides the first comprehensive limits on heavy neutral leptons from atmospheric neutrino data, including branching ratios and lifetimes, for various neutrino flavors.

Findings

Stringent limits on mixing angles with electron, muon, and tau neutrinos.

Constraints on heavy neutral lepton mass and lifetime parameter space.

Limits on branching ratios versus lifetime for non-minimal models.

Abstract

Heavy neutral leptons are predicted in many extensions of the Standard Model with massive neutrinos. If kinematically accessible, they can be copiously produced from kaon and pion decays in atmospheric showers, and subsequently decay inside large neutrino detectors. We perform a search for these long-lived particles using Super-Kamiokande multi-GeV neutrino data and derive stringent limits on the mixing with electron, muon and tau neutrinos as a function of the long-lived particle mass. We also present the limits on the branching ratio versus lifetime plane, which are helpful in determining the constraints in non-minimal models where the heavy neutral leptons have new interactions with the Standard Model.