A Super-Sensitive Dark Matter Detector Just Booted Up

A super-sensitive dark matter detector has just started up

The LUX-ZEPLIN (LZ) experiment team today announced the results of its first scientific run; the experiment is the world’s most sensitive dark matter detector, and although it found no dark matter in this first round, the team confirmed that the experiment is working as expected.

The LZ experiment detector consists of nested tanks of liquid xenon, each 1.5 meters high and 1.5 meters wide, buried under North Dakota. The idea is that a particle of dark matter whizzing through space will eventually bounce off one of the xenon atoms, knocking electrons loose in a flash captured by the experiment. The tank is buried about a mile below the Earth’s surface to minimize the amount of background noise. Today’s announcement comes after 60 live days of data collection stretching from December 25 to May 12.

“We’re looking for very, very energy-efficient recoils according to the standards of particle physics. It’s a very, very rare process, if at all visible,” Hugh Lippincott, a UC Santa Barbara physicist and member of the LZ team, said at a news conference today. “You can shoot a particle of dark matter through 10 million light-years of lead and expect only one interaction at the end of that light-year.”

Dark matter is the collective name for the unknown that seems to make up about 27% of the universe. It almost never interacts with ordinary matter, hence its “darkness” to us. But we know it’s out there because, while it’s never directly detected, it has gravitational effects that can be observed on cosmic scales. (NASA breaks down the concept pretty well) here

There are many candidates for dark matter. One is the WIMP, or a weakly interactive solid particle. Unlike others dark matter hypotheses such as axions or dark photons, which are so small and diffuse that they can behave more like waves, WIMPs would have mass but hardly interact with ordinary matter. So to detect them, you need a device that pretty much muffles all other physics.

LZ is super sensitive, making it good for spotting such volatile and rare interactions. The experiment is 30 times larger and 100 times more sensitive than its predecessor, the Large Underground Xenon experiment, according to a Sanford Underground Research Facility release† LZ is “basically an onion,” Lippincott said, with each layer of the experiment isolating against noise that could obscure a potential WIMP interaction.

The LZ Outer Detector, which guards against unwanted signals. (Photo: Matthew Kapust, Sanford Underground Research Facility)

“The collaboration worked well to calibrate and understand the detector’s response,” said Aaron Manalaysay, a physicist at Berkeley Laboratory and member of the LZ team, in a Berkeley Lab. press release† “Since we just turned it on a few months ago and during the COVID restrictions, it’s impressive that we already have such significant results.”

Of the many detections the LZ experiment made during its 60-day run, 335 seemed promising, but none turned out to be WIMPs. That doesn’t mean WIMPs aren’t there, but it does eliminate a massive range of contention. (This is the gist of what dark matter detectors do: bit by bit they exclude the mass of the particles) can not to be.) Several physicists have recently addressed Gizmodo. told that they think the next big discovery in particle physics will come from a dark matter detector like LZ.

This scientific run started with what is expected to be a 1000-day schedule. The recent round was also unblinded so the LZ team could monitor how the technology behaved. Since it has performed as expected, the results of the next scientific run will be ‘salted’, or laced with fake signals, to reduce bias

Twenty times more data will be collected in the coming years, so perhaps the wimpy WIMPs should finally face the music of their own existence. Then again, maybe they don’t exist at all. We won’t know until we look.

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