One other blow for darkish matter as largest hunt but finds nothing

The most recent hunt for darkish matter has come up empty handed thus far, however the upside is that physicists can now set the tightest constraints ever on the character of this mysterious substance. New measurements from the LUX-ZEPLIN (LZ) experiment in South Dakota imply we’re both nearer than ever to discovering particles of darkish matter or ruling out the most well-liked rationalization for it.

Darkish matter doesn’t work together a lot with common matter or with mild, so we will’t see it. We solely know that it exists due to its gravitational results, however these results point out it makes up over 80 per cent of all matter. The main rationalization for darkish matter has lengthy been that it’s made up of weakly interacting large particles (WIMPs), however hunts for these elementary entities have discovered nothing but.

LUX-ZEPLIN, a darkish matter detector made of seven tonnes of liquid xenon buried 1.5 kilometres underground, is probably the most delicate but – however after 280 days of looking, it hasn’t discovered any WIMPs. “We’re the world’s best at not finding dark matter,” says LZ spokesperson Chamkaur Ghag at College Faculty London.

Whereas this consequence could appear to be a disappointment, it has allowed physicists to put tight constraints on the character of darkish matter, lowering the vary of properties it might have. The constraints are practically 5 instances tighter than the earlier finest, drastically narrowing down the probabilities for WIMPs. This work was introduced at two physics conferences – TeV Particle Astrophysics within the US and LIDINE in Brazil – on 26 August.

“It’s as if we’ve been told there’s some magical fish that lives in the ocean and we have no idea where it is,” says Ghag. “We get into the ocean, swim around, get out, get a snorkel, swim around, still don’t find it, get a submarine.” If the magical fish is a WIMP, researchers have now explored about 75 per cent of the ocean with out discovering it, he says.

“This is the next big step forward, and it’s one in a long line of such steps,” says Dan Hooper on the Fermi Nationwide Accelerator Laboratory in Illinois, who wasn’t concerned on this work. “In any one of these steps forward, it might be fair to say we don’t expect to see anything. But if you take enough of these steps, it seems not unlikely that we could see something.”

At this level, many initially fashionable concepts for doable kinds of WIMPs have been dominated out. There are nonetheless some left, however LZ isn’t achieved but – it’s anticipated to make 1000 days of observations in whole earlier than it ends in 2028. “If LZ doesn’t see WIMPs, and the next generation detector, XLZD, does not see WIMPs, it’s kind of over for WIMPs,” says Ghag. The XLZD venture remains to be within the planning section.

If WIMPs don’t make up darkish matter, that will probably be a enormous paradigm shift, however physicists received’t surrender completely on discovering darkish matter. “If you’re trying to solve a murder investigation, and you’ve got 20 suspects, and you find out that 10 of them have good [alibis], you don’t go, ‘well I guess there wasn’t a murder’. You just have a better idea of who the right suspect might be,” says Hooper. “We cross some of our suspects off the list, and the search gets narrower and more focused – that’s what progress looks like in this field.”