Long-lived heavy neutral leptons with a displaced shower signature at CMS

TL;DR

This paper explores the potential of the CMS detector at the LHC to discover heavy neutral leptons through a novel displaced shower signature, especially sensitive to tau lepton mixings, and demonstrates the ability to probe new parameter space.

Contribution

It introduces a new detection strategy for heavy neutral leptons using displaced showers in the CMS muon detector and reinterprets existing searches to extend sensitivity to tau sector mixings.

Findings

Sensitive to HNL masses 1-6 GeV

Can detect mixings as low as 10^{-7} in the tau sector

Probes unique regions of parameter space

Abstract

We study the LHC discovery potential in the search for heavy neutral leptons (HNL) with a new signature: a displaced shower in the CMS muon detector, giving rise to a large cluster of hits forming a displaced shower. A new Delphes module is used to model the CMS detector response for such displaced decays. We reinterpret a dedicated CMS search for neutral long-lived particles decaying in the CMS muon endcap detectors for the minimal HNL scenario. We demonstrate that this new strategy is particularly sensitive to active-sterile mixings with $\tau$ leptons, due to hadronic $\tau$ decays. HNL masses between $\sim 1 - 6$ GeV can be accessed for mixings as low as $|V_{\tau N}|^{2}\sim 10^{-7}$, probing unique regions of parameter space in the $\tau$ sector.