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Photos: World’s most sensitive dark matter detector sets new limits

A cutting-edge experiment called LUX-ZEPLIN (LZ) is offering new clues about dark matter.

Published: Aug 27, 2024 07:26 AM EST

a day ago

An array of photomultiplier tubes that are designed to detect signals from particle interactions occurring within LZ’s liquid xenon detector.

Matthew Kapust/Sanford Underground Research Facility

A mystery substance lurks deep within the cosmos, invisible yet powerful. It’s called dark matter, and it makes up the majority of the mass in the universe.

The nature of dark matter remains one of the most perplexing mysteries in physics.

Scientists have been searching for dark matter for decades, and now, a cutting-edge experiment called LUX-ZEPLIN (LZ) is offering new clues.

LZ, located deep down in South Dakota, is the world’s most sensitive detector of dark matter. It is intended to detect weakly interacting massive particles (WIMPs), one of the most promising candidates for dark matter.

Despite 280 days of searching, LZ has found no WIMPs. However, the press release mentions: “New results from the world’s most sensitive dark matter detector put the best-ever limits on particles called WIMPs.”

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LZ is an underground facility
Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) is leading the LZ experiment. LZ is located in a deep underground cavern at the Sanford Underground Research Facility in South Dakota. In this new experiment, LZ has delved deeper than ever before into the realm of WIMPs. “If WIMPs had been within the region we searched, we’d have been able to robustly say something about them. We know we have the sensitivity and tools to see whether they’re there as we search lower energies and accrue the bulk of this experiment’s lifetime,” said Chamkaur Ghag, spokesperson for LZ and a professor at University College London (UCL).
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LZ's new limits of WIMPs
LZ has ruled out WIMPs with a mass greater than 9 GeV/c2 (gigaelectronvolts/c2). This is a significant constraint, as a proton's mass is only slightly less than 1 GeV/c2. Moreover, its ability to detect even weak interactions has helped scientists rule out many potential WIMP models. This could bring scientists closer to understanding the nature of dark matter.
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Meticulous design ensures exceptional sensitivity
LZ's exceptional sensitivity is a result of its meticulous design. It is constructed from thousands of ultra-clean, low-radiation parts to minimize background noise. Interestingly, its layered design (like an onion) further shields the detector from external radiation. Plus, the detector’s underground location protects it from cosmic rays. Overall, this enables accurate detection of potential dark matter interactions.
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Consists of liquid xenon
LZ's innovative approach to dark matter detection utilizes 10 tonnes of liquid xenon as a target material to capture the faint signals produced by WIMP collisions. If a WIMP were to collide with a xenon nucleus in the detector, it would create a signal that LZ could detect.
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LZ will function until 2028
“If you think of the search for dark matter like looking for buried treasure, we’ve dug almost five times deeper than anyone else has in the past,” said Scott Kravitz, LZ’s deputy physics coordinator and a professor at the University of Texas at Austin. “That’s something you don’t do with a million shovels – you do it by inventing a new tool.” The search for dark matter is far from over. The hunt for dark matter will continue with LZ until 2028, as it strives to collect 1,000 days of crucial data.
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LZ is a result of international collaboration
Th LZ experiment is an international collaboration. It brings together 250 scientists from 38 institutions in the United States, United Kingdom, Portugal, Switzerland, South Korea, and Australia. “We’re pushing the boundary into a regime where people have not looked for dark matter before. There’s a human tendency to want to see patterns in data, so it’s really important when you enter this new regime that no bias wanders in. If you make a discovery, you want to get it right,” said Scott Haselschwardt, the LZ physics coordinator, in the press release.
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Dark matter's elusive nature
Dark matter constitutes 85% of the universe's mass. Dark matter's elusive nature, characterized by its inability to emit, reflect, or absorb light, makes it a formidable target for direct detection. But this unseen force shapes the universe in myriad ways. For instance, its gravitational pull plays a vital role in galaxy formation and stability.