Search for Neutral Heavy Leptons in a High-Energy Neutrino Beam

TL;DR

This study conducted a search for neutral heavy leptons in a high-energy neutrino beam at Fermilab, finding no evidence but setting more restrictive limits on their mixing with standard neutrinos in the 0.25-2.0 GeV mass range.

Contribution

First search for NHLs using an instrumented decay channel at Fermilab, improving existing limits on NHL mixing in the specified mass range.

Findings

No evidence of NHL decays detected.

Set more restrictive limits on NHL mixing.

Extended the mass range for NHL searches.

Abstract

A search for neutral heavy leptons (NHLs) has been performed using an instrumented decay channel at the NuTeV (E-815) experiment at Fermilab. The decay channel was composed of helium bags interspersed with drift chambers, and was used in conjunction with the NuTeV neutrino detector to search for NHL decays. The data were examined for NHLs decaying into muonic final states (mu mu nu, mu e nu, mu pi, and mu rho); no evidence has been found for NHLs in the 0.25 - 2.0 GeV mass range. This analysis places limits on the mixing of NHLs with standard light neutrinos at a level up to an order of magnitude more restrictive than previous search limits in this mass range.