Heavy neutral fermions at the high-luminosity LHC

TL;DR

This paper evaluates the potential of upcoming LHC experiments like FASER, CODEX-b, and MATHUSLA to detect heavy neutral fermions, which are long-lived particles predicted by theories extending the standard model.

Contribution

It compares the sensitivity and advantages of recent experimental proposals for detecting heavy neutral fermions at the high-luminosity LHC.

Findings

FASER, CODEX-b, and MATHUSLA have complementary sensitivities.

These experiments can probe new parameter space for heavy neutral fermions.

The paper highlights the relative merits of each experimental setup.

Abstract

Long-lived light particles (LLLPs) appear in many extensions of the standard model. LLLPs are usually motivated by the observed small neutrino masses, by dark matter or both. Typical examples for fermionic LLLPs (a.k.a. heavy neutral fermions, HNFs) are sterile neutrinos or the lightest neutralino in R-parity violating supersymmetry. The high luminosity LHC is expected to deliver up to 3/ab of data. Searches for LLLPs in dedicated experiments at the LHC could then probe the parameter space of LLLP models with unprecedented sensitivity. Here, we compare the prospects of several recent experimental proposals, FASER, CODEX-b and MATHUSLA, to search for HNFs and discuss their relative merits.