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

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 data were examined for NHLs decaying into muonic final states ( $\ensuremath{\mu}\ensuremath{\mu}\ensuremath{\nu}$, $\ensuremath{\mu}e\ensuremath{\nu}$, $\ensuremath{\mu}\ensuremath{\pi}$, and $\ensuremath{\mu}\ensuremath{\rho}$); 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.