A Hydrogen Trap for Dark Matter express
Dark matter is invisible, but you can catch it on the rebound. Hydrogen embedded in a carbon film acts like a billiard ball: when a dark matter particle hits it, the proton flies out. That ejection is the signal you're looking for.
The authors of the idea suggest coating a detector with hydrogenated carbon — a material that can already be made in thin layers. A dark matter particle with a mass between 1 and 100 MeV (about the mass of a few electrons) strikes a hydrogen nucleus and knocks out a proton with almost no energy loss. This process is called quasi-elastic: as if a billiard ball barely slowed down after the hit, while the second ball shot forward.
A detector based on such a film is simple and cheap. It doesn't require cryogenic temperatures or complex electronics. Moreover, the ejected proton preserves the direction of the impact: this allows distinguishing a dark matter signal from random noise, just as an echo in the mountains helps locate the source of a sound.
Original abstract
as written by the authors arXiv:2602.02694
We propose hydrogenated carbon structures as targets with a remarkable sensitivity to dark matter-nucleon interactions, in the mass range between the 1 MeV and 100 MeV. The ejection of a proton following the interaction with a dark matter particle is a quasi-elastic process, with an extremely small energy threshold, and a clear experimental signature. The proposed detectors are simple, technologically ready, and inexpensive. Yet, they can be considerably more sensitive than current experiments. They also allow strong directionality, to be used towards efficient background rejection.
Hydrogen is the most abundant element in the universe, and it's perfect for catching dark matter because its nucleus, a single proton, is easy to knock out even with a weak hit.