Multilepton and Lepton Jet Probes of Sub-Weak-Scale Right-Handed Neutrinos

TL;DR

This paper proposes novel LHC search strategies for sterile neutrinos below the W boson mass, utilizing prompt leptons and lepton jets to significantly improve sensitivity to their mixing angles.

Contribution

It introduces new search methods for sub-weak-scale sterile neutrinos at the LHC, enhancing detection sensitivity for a range of neutrino masses and mixing angles.

Findings

LHC can probe mixing angles of 10^{-4} to 10^{-3} for GeV-scale sterile neutrinos.

Run II can explore small mixing angles for neutrinos above 15 GeV.

Sensitivity improves by up to two orders of magnitude compared to previous methods.

Abstract

We propose new searches that exploit the unique signatures of decaying sterile neutrinos with masses below $M_W$ at the LHC, where they can be produced in rare decays of Standard Model gauge bosons. We show that for few-GeV-scale sterile neutrinos, the LHC experiments can probe mixing angles at the level of $10^{-4}-10^{-3}$ through powerful searches that look for prompt leptons in association with displaced lepton jets. For higher-mass sterile neutrinos, ${\it i.e.}$, $M_N \gtrsim 15$ GeV, Run II can explore similarly small mixing angles in prompt multilepton final states. This represents an improvement of up to two orders of magnitude in sensitivity to the sterile neutrino production rate.