Underground, there is a large tank filled with liquid xenon. One day, one of the atomic nuclei in this tank received a weak kick and recoiled, like a billiard ball struck by an invisible ball. The LUX-ZEPLIN detector recorded this kick, but scientists could not figure out what caused it. All the usual culprits, cosmic rays, radioactivity, did not fit.

Then an idea emerged: maybe it was a dark matter particle. Dark matter is invisible stuff that does not shine and barely interacts with ordinary matter, yet its gravity holds galaxies together. One possible dark matter particle is called the higgsino. It is a heavy partner of the Higgs boson, the particle discovered in 2012 at the Large Hadron Collider.

Scientists calculated what the interaction strength of the higgsino with a nucleus should be if its mass is around 1 TeV. The resulting number falls within the range measured by the detector. This means that the higgsino could leave exactly such a trace. But so far only one event has been recorded, and that is too few to confidently say: yes, this is dark matter. More data are needed to distinguish a fluke from a real signal.