Sub-GeV dark matter search at ILC beam dumps

TL;DR

This paper proposes the ILC-BDX experiment to detect sub-GeV dark matter particles produced in ILC beam dumps, using a specialized detector setup to identify scattering and decay signals amidst backgrounds.

Contribution

It introduces a novel experimental design for dark matter detection at the ILC beam dumps, including background analysis and sensitivity projections.

Findings

ILC-BDX can probe new parameter space for dark photon models.

The experiment can reach below the relic density target in many scenarios.

Backgrounds from neutrinos and cosmic rays are manageable with the proposed setup.

Abstract

Light dark matter particles may be produced in electron and positron beam dumps of the International Linear Collider (ILC). We propose an experimental setup to search for such events, the Beam-Dump eXperiment at the ILC (ILC-BDX). The setup consists of a muon shield placed behind the beam dump, followed by a multi-layer tracker and an electromagnetic calorimeter. The calorimeter can detect electron recoils due to elastic scattering of dark matter particles produced in the dump, while the tracker is sensitive to decays of excited dark-sector states into the dark matter particle. We study the production, decay and scattering of sub-GeV dark matter particles in this setup in several models with a dark photon mediator. Taking into account beam-related backgrounds due to neutrinos produced in the beam dump as well as the cosmic-ray background, we evaluate the sensitivity reach of the ILC-BDX experiment. We find that the ILC-BDX will be able to probe interesting regions of the model parameter space and, in many cases, reach well below the relic target.