Detecting dark matter with far-forward emulsion and liquid argon detectors at the LHC

New light particles may be produced in large numbers in the far-forward region at the LHC and then decay to dark matter, which can be detected through its scattering in far-forward experiments. We consider the example of invisibly decaying dark photons, which decay to dark matter through A' -> chi chi. The dark matter may then be detected through its scattering off electrons chi e(-) -> chi e(-). We consider the discovery potential of detectors placed on the beam collision axis 480 m from the ATLAS interaction point, including an emulsion detector (FASER nu 2) and, for the first time, a Forward Liquid Argon Experiment (FLArE). For each of these detector technologies, we devise cuts that effectively separate the single e(-) signal from the leading neutrino- and muon-induced backgrounds. We find that 10- to 100-tonne detectors may detect hundreds to thousands of dark matter events in the high-luminosity Large Hadron Collider (HL-LHC) era and will sensitively probe the thermal relic region of parameter space. These results motivate the construction of far-forward emulsion and liquid argon detectors at the LHC, as well as a suitable location to accommodate them, such as the proposed Forward Physics Facility.

Automated summary

Research suggests that new light particles may be produced at the LHC's far-forward region and decay into dark matter, which can be detected through scattering. Specific detectors can effectively detect these dark matter events, sensitively probing the thermal relic region of parameter space.