The LUX-ZEPLIN experiment has not discovered dark matter. It has found something more modest and, for particle physicists, unusually provocative: one very energetic nuclear recoil that is difficult to explain cleanly.
The event appeared in a 2.84 tonne-year exposure of LZ's liquid-xenon detector. A xenon nucleus recoiled with an energy of about 248 kiloelectronvolts, while the data did not show the lower-energy recoils that most ordinary dark-matter interactions should also produce. As Science News reported, the signal could have come from a dark-matter particle, but it could also be a fluctuation or a known physical process. One event is nowhere near enough to settle the question.
Why a higgsino fits the shape
The odd energy pattern has put a familiar candidate back in the conversation: the higgsino, a hypothetical partner of the Higgs boson predicted by supersymmetry. Supersymmetry proposes a heavier partner for every known particle. No such partner has turned up in collider searches, which is one reason the theory has lost ground in recent years.
