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

The newest hunt for darkish matter has come up empty handed to this point, 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 clarification for it.

Darkish matter doesn’t work together a lot with common matter or with gentle, so we are able to’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 clarification for darkish matter has lengthy been that it’s made up of weakly interacting huge 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 essentially the most delicate but – however after 280 days of looking, it hasn’t discovered any WIMPs. “We’re the world’s finest at not discovering darkish matter,” says LZ spokesperson Chamkaur Ghag at College Faculty London.

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

“It’s as if we’ve been advised there’s some magical fish that lives within the ocean and we don’t know the place it’s,” says Ghag. “We get into the ocean, swim round, get out, get a snorkel, swim round, nonetheless don’t discover 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.

“That is the following huge step ahead, and it’s one in a protracted line of such steps,” says Dan Hooper on the Fermi Nationwide Accelerator Laboratory in Illinois, who wasn’t concerned on this work. “In any certainly one of these steps ahead, it is perhaps honest to say we don’t count on to see something. However for those who take sufficient of those steps, it appears not unlikely that we may see one thing.”

At this level, many initially common concepts for potential varieties of WIMPs have been dominated out. There are nonetheless some left, however LZ isn’t completed 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 following era detector, XLZD, doesn’t see WIMPs, it’s form of over for WIMPs,” says Ghag. The XLZD challenge continues to be within the planning section.

If WIMPs don’t make up darkish matter, that will probably be an enormous paradigm shift, however physicists received’t hand over totally on discovering darkish matter. “In the event you’re attempting to resolve a homicide investigation, and also you’ve received 20 suspects, and you discover out that 10 of them have good [alibis], you don’t go, ‘properly I suppose there wasn’t a homicide’. You simply have a greater concept of who the precise suspect is perhaps,” says Hooper. “We cross a few of our suspects off the record, and the search will get narrower and extra targeted – that’s what progress appears like on this area.”