Sub-GeV Dark Matter Direct Detection with Neutrino Observatories
Rebecca K. Leane, John F. Beacom
TL;DR
The paper tackles the challenge of probing sub-GeV dark matter by proposing a novel detection channel: DM-electron scattering in a neutrino observatory like JUNO excites or ionizes LAB scintillator molecules, producing photons that generate PMT hits. Although single scatter events are indistinguishable, the authors exploit the annual modulation of the Earth’s motion to extract the aggregate DM-induced signal from the dominant PMT dark rate, without requiring per-event reconstruction. They derive the expected DM signal rate, incorporating molecular form factors and DM form factors, and show that JUNO’s large target mass and low excitation threshold enable competitive sensitivity in certain mass ranges, potentially surpassing other techniques and approaching key theory benchmarks. The approach can be generalized to other scintillator-based or large-volume neutrino detectors and motivates coordinated multi-detector searches, though substantial experimental and modeling work remains to validate backgrounds, signal response, and systematics. If realized, this method would open a new frontier in DM detection by repurposing existing neutrino observatories for sub-GeV DM searches.
Abstract
We present a new technique for sub-GeV dark matter (DM) searches and a new use of neutrino observatories. DM-electron scattering in an observatory can excite or ionize target molecules, which then produce light that can be detected by the photomultiplier tubes (PMTs). While individual DM scatterings are indistinguishable, the aggregate rate from many independent scatterings can be isolated from the total PMT dark rate using the expected DM annual modulation. We showcase this technique with the example of JUNO, a 20,000-ton scintillator detector, showing that its potential sensitivity in some mass ranges exceeds other techniques and reaches key particle-theory benchmarks.