Heavy Neutral Leptons at Beam Dump Experiments of Future Lepton Colliders

TL;DR

Future high-energy electron-positron collider beam dump experiments offer a promising new method to search for heavy neutral leptons, expanding the exploration of dark sector particles beyond current experimental capabilities.

Contribution

This paper demonstrates the potential sensitivity of future electron-positron collider beam dump experiments to heavy neutral leptons, highlighting their complementarity to other search methods.

Findings

Experiments at ILC, C3, and CLIC can probe new HNL parameter space.

Beam dump experiments provide sensitivity beyond past experiments.

Complementary to proton beam and neutrino experiments.

Abstract

A new beam dump experiment that utilizes the beam of future high energy electron-positron colliders could be an excellent avenue to search for dark sector particles due to its unprecedented high energy and intensity. We consider heavy neutral leptons (HNLs) as a specific example to demonstrate the sensitivity of searches for dark sector particles at future electron-positron collider beam dump experiments. This includes the study of the reach at the International Linear Collider (ILC), the Cool Copper Collider ($\rm C^3$), and the Compact Linear Collider (CLIC). We comprehensively examine the HNL production and detector acceptance at these electron beam dump experiments. We show that these experiments will probe a large range of HNL parameter space, not yet probed by past experiments. These experiments will be complementary to other proposed experiments such as proton beam dump experiments, neutrino experiments, and LHC auxiliary detectors. Our study also motivates a more detailed analysis of heavy meson productions in high-energy electron-nucleon collisions in thick targets.