The LUX-ZEPLIN (LZ) experiment team announced today the results of their first scientific work; the experiment is the world’s most sensitive dark matter detector, and although it didn’t find any dark matter in this first round, the team confirmed that the experiment worked as expected.
The LZ experimental detector consists of liquid xenon tanks, each 1.5 meters high and 1.5 meters wide, buried under the south. Dakota. The idea is that a dark matter particle whizzing through space will eventually bounce off one of the xenon atoms and knock loose electrons in a flash recorded 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 days of live data collection from December 25 to May 12.
“We’re looking for very, very low-energy recoils by particle physics standards. It’s a very, very rare process, if it’s seen at all,” said Hugh Lippincott, a physicist at UC Santa Barbara and a member of the LZ team, at today’s press conference. “You can shoot a dark matter particle 10 million light-years through a lead, and that light-year you can only expect one interaction at the end.”
Dark matter is an all-encompassing term for the apparently unknown substances that make up about 27% of the universe. It almost never interacts with ordinary matter, hence its “darkness” to us. But we know it’s there because it has gravitational effects that can be seen on a cosmic scale, although never directly detected. (NASA breaks down the concept pretty well here.)
There are many candidates for dark matter. One of these is the WIMP, or Weakly Interacting Massive Particle. Unlike others dark matter hypotheses such as axions or dark photonsWIMPs that are so small and diffuse that they can behave more like waves will have mass, but they will hardly interact with ordinary matter. So to detect them, you need a device that pretty much silences all the other physics going on.
LZ is very sensitive, which makes it good for detecting such frequent and infrequent interactions. According to the Sanford Underground Research Facility, the experiment is 30 times larger and 100 times more sensitive than its predecessor, the Large Underground Xenon experiment. release. “It’s effectively an onion,” Lippincott said, with each layer of the experiment insulating against noise that could mask potential WIMP interactions.
“The collaboration worked well together to calibrate and understand the detector’s response,” said Berkeley Lab physicist and LZ team member Aaron Manalaysay. press release. “Given that we launched it a few months ago and during the COVID restrictions, we already have such significant results.”
Of the many detections the LZ experiment made over 60 days, 335 looked promising, but none were WIMPs. That’s not to say WIMPs aren’t out there, but it removes mass range from the argument. (This is the essence of what dark matter detectors do: they gradually rule out what masses the particles have. to read to be.) Several physicists recently spoke to Gizmodo They think the next big breakthrough in particle physics will come from a dark matter detector like LZ.
This science run kicked off what was expected to be a 1,000-day schedule. The final round was also not blinded, so the LZ team was able to watch how the technology behaved. As expected, the results of the next scientific study will be peppered with “salted” or spurious signals. reduce bias.
Twenty times as much data will be collected in the coming years, so maybe the puny WIMPs will finally have to face the music of their existence. Then again, maybe they don’t exist at all. We won’t know until we see.
Read more: 10 years after the Higgs Boson, what’s the next big thing for Physics?
