The MicroBooNE Experiment, the NuMI Absorber, and Heavy Neutral Leptons

TL;DR

This paper shows how the MicroBooNE experiment's data can be repurposed to set new constraints on Heavy Neutral Leptons, particles that could explain neutrino masses, by analyzing existing search results.

Contribution

It demonstrates a novel reinterpretation of MicroBooNE data to constrain Heavy Neutral Leptons, expanding the experimental bounds in a previously unexplored mass range.

Findings

Excluded new parameter space for Heavy Neutral Leptons between 30 and 150 MeV.

Recasted existing experimental results to derive new constraints.

Made Monte Carlo tools publicly available for further research.

Abstract

Motivated by the recent search for a Higgs-Portal Scalar decaying inside the MicroBooNE detector, we demonstrate that the same search can be used to constrain Heavy Neutral Leptons. These are gauge-singlet fermions that interact with the Standard Model by mixing with neutrinos only and could be related to the origin of neutrino masses. By recasting the results of the MicroBooNE Collaboration's analysis, we show that, for a Heavy Neutral Lepton that mixes predominantly with muon-flavored neutrinos, previously unexplored parameter space can be excluded for masses between 30 and 150 MeV. Additionally, we make our Monte Carlo tools publicly available.