LZ’s central detector, the time projection chamber, in a floor lab blank room sooner than supply underground. Credit score: Matthew Kapust/Sanford Underground Analysis Facility
Working out the character of darkish topic, the invisible substance that makes up many of the mass in our universe, is among the biggest puzzles in physics. New effects from the sector’s maximum delicate darkish topic detector, LUX-ZEPLIN (LZ), have narrowed down chances for one of the vital main darkish topic applicants: weakly interacting huge debris, or WIMPs.
LZ, led through the Division of Power’s Lawrence Berkeley Nationwide Laboratory (Berkeley Lab), hunts for darkish topic from a cavern just about one mile underground on the Sanford Underground Analysis Facility in South Dakota. The experiment’s new effects discover weaker darkish topic interactions than ever researched sooner than and extra restrict what WIMPs may well be.
“Those are new world-leading constraints through a large margin on darkish topic and WIMPs,” stated Chamkaur Ghag, spokesperson for LZ and a professor at College School London (UCL). He famous that the detector and research ways are acting even higher than the collaboration anticipated.
“If WIMPs were throughout the area we searched, we would had been in a position to robustly say one thing about them. We all know we have now the sensitivity and gear to look whether or not they are there as we seek decrease energies and accrue the majority of this experiment’s lifetime.”
The collaboration discovered no proof of WIMPs above a mass of 9 gigaelectronvolts/c2 (GeV/c2). (For comparability, the mass of a proton is rather lower than 1 GeV/c2.) The experiment’s sensitivity to faint interactions is helping researchers reject possible WIMP darkish topic fashions that do not have compatibility the information, leaving considerably fewer puts for WIMPs to cover.
The brand new effects had been introduced at two physics meetings on August 26: TeV Particle Astrophysics 2024 in Chicago, Illinois, and LIDINE 2024 in São Paulo, Brazil. A paper will likely be printed within the coming weeks.
An array of photomultiplier tubes which might be designed to discover alerts from particle interactions happening inside of LZ’s liquid xenon detector. Credit score: Matthew Kapust/Sanford Underground Analysis Facility
The effects analyze 280 days’ price of knowledge: a brand new set of 220 days (accumulated between March 2023 and April 2024) mixed with 60 previous days from LZ’s first run. The experiment plans to gather 1,000 days’ price of knowledge sooner than it leads to 2028.
“Should you bring to mind the seek for darkish topic like searching for buried treasure, we have now dug virtually 5 instances deeper than any person else has prior to now,” stated Scott Kravitz, LZ’s deputy physics coordinator and a professor on the College of Texas at Austin. “That is one thing you do not do with one million shovels—you do it through inventing a brand new instrument.”
LZ’s sensitivity comes from the myriad techniques the detector can cut back backgrounds, the false alerts that may impersonate or cover a depressing topic interplay. Deep underground, the detector is protected against cosmic rays coming from house.
To cut back herbal radiation from on a regular basis items, LZ used to be constructed from hundreds of ultraclean, low-radiation portions. The detector is constructed like an onion, with every layer both blocking off outdoor radiation or monitoring particle interactions to rule out darkish topic mimics. And complex new research ways lend a hand rule out background interactions, in particular the ones from the most typical offender: radon.
This outcome may be the primary time that LZ has implemented “salting”—one way that provides faux WIMP alerts all through information assortment. Through camouflaging the true information till “unsalting” on the very finish, researchers can keep away from subconscious bias and stay from overly deciphering or converting their research.
Individuals of the LZ crew within the LZ water tank after the outer detector set up. Credit score: Matthew Kapust/Sanford Underground Analysis Facility
“We are pushing the boundary right into a regime the place other folks have now not regarded for darkish topic sooner than,” stated Scott Haselschwardt, the LZ physics coordinator and a up to date Chamberlain Fellow at Berkeley Lab who’s now an assistant professor on the College of Michigan. “There is a human tendency to wish to see patterns in information, so it is truly vital while you input this new regime that no bias wanders in. If you’re making a discovery, you wish to have to get it proper.”
Darkish topic, so named as it does now not emit, replicate, or soak up gentle, is estimated to make up 85% of the mass within the universe however hasn’t ever been at once detected, regardless that it has left its fingerprints on more than one astronomical observations. We would not exist with out this mysterious but basic piece of the universe; darkish topic’s mass contributes to the gravitational appeal that is helping galaxies shape and keep in combination.
LZ makes use of 10 heaps of liquid xenon to offer a dense, clear subject material for darkish topic debris to probably stumble upon. The hope is for a WIMP to knock right into a xenon nucleus, inflicting it to transport, similar to successful from a cue ball in a sport of pool. Through amassing the sunshine and electrons emitted all through interactions, LZ captures possible WIMP alerts along different information.
“We have now demonstrated how sturdy we’re as a WIMP seek system, and we are going to stay operating and getting even higher—however there may be plenty of different issues we will do with this detector,” stated Amy Cottle, lead at the WIMP seek effort and an assistant professor at UCL.
“The following level is the use of those information to take a look at different attention-grabbing and uncommon physics processes, like uncommon decays of xenon atoms, neutrinoless double beta decay, boron-8 neutrinos from the solar, and different beyond-the-Usual-Fashion physics. And that is along with probing one of the most maximum attention-grabbing and up to now inaccessible darkish topic fashions from the final two decades.”
Individuals of the LZ collaboration accumulate on the Sanford Underground Analysis Facility in June 2023, in a while after the experiment started the new science run. Credit score: Stephen Kenny/Sanford Underground Analysis Facility
LZ is a collaboration of more or less 250 scientists from 38 establishments in the US, United Kingdom, Portugal, Switzerland, South Korea, and Australia; a lot of the paintings construction, working, and examining the record-setting experiment is finished through early occupation researchers.
The collaboration is already taking a look ahead to examining the following information set and the use of new research tips to search for even lower-mass darkish topic. Scientists also are pondering via possible upgrades to additional beef up LZ, and making plans for a next-generation darkish topic detector referred to as XLZD.
“Our skill to seek for darkish topic is bettering at a fee quicker than Moore’s Regulation,” Kravitz stated. “Should you have a look at an exponential curve, the whole thing prior to now is not anything. Simply wait till you notice what comes subsequent.”
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Experiment units new checklist in seek for darkish topic (2024, August 26)
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