Extending Sensitivity for Low-Mass Neutral Heavy Lepton Searches

Abstract

We point out the importance of two-body final states of weak isosinglet neutral heavy leptons predicted in several models of new physics beyond the standard model. We concentrate on muon-type neutral heavy leptons $L_μ^0$ with mass $M<2$ GeV which can be searched for with increased sensitivity at a new round of neutrino experiments at CERN and Fermilab. Providing explicit decay rate formulae for the $e e ν$, $eμν$, $μμν$, $πμ$, $ρμ$, and $a_1μ$ final states, we use general scaling features to estimate sensitivity of $L_μ^0$ searches in current and future experiments, emphasizing the importance of the $πμ$ decay mode.