A next-generation dark matter detector is operational and is already delivering initial results showing it is the most sensitive machine of its kind on Earth.
The machine could help unravel one of physics’ greatest mysteries – the nature of Dark matter— by the first direct detection of its components.
Deep beneath the Black Hills of South Dakota, the LUX-ZEPLIN (LZ) experiment – operated by a team of 250 scientists led by the Lawrence Berkeley National Lab (Berkeley Lab) – has entered the check-up phase of its launch process with flying passed colors.
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The LZ detector has been operational since December 2021 and these initial results represent the first 60 days of live operation. “We’re ready and everything’s looking good,” said Kevin Lesko, lead physicist and former LZ spokesman for Berkeley Lab expression (opens in new tab). “It’s a complex detector with many parts, all of which work well and perform as expected.”
Dark matter makes up about 85% of known matter universe , but since it doesn’t interact with light, it’s practically invisible. Whatever the constituent particles of dark matter, they don’t interact strongly with other matter either.
In fact, scientists can only infer dark matter from their presence gravitational influence which literally holds most galaxies together and prevents their components from flying apart as they rotate.
That means researchers know that dark matter isn’t made up of protons and neutrons like the everyday matter — or baryonic matter — we see around us every day.
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The LUX-ZEPLIN detector is designed to search specifically for a hypothetical type of dark matter, called dark matter weakly interacting massive particles,or WIMP’s. These particles are expected to very rarely collide with matter and when they do, interact extremely weakly.
No dark matter particles have been directly detected at this time, but the hope is that the LZ detector could change that by detecting the weak interactions of these mysterious particles with xenon atoms. This requires a sensitive detector that eliminates all possible interference that could interfere with detection.
The LZ experiment’s xenon is housed in two nested titanium tanks containing ten tons of the element in a liquid state. These tanks are monitored by two photomultiplier tube (PMT) arrays ready to detect weak light sources.
The tanks and associated detectors are also housed in a larger detection system that can catch any particles that might mimic the dark matter signal and exclude them from searching for real dark matter.
In order to detect these weak interactions, the xenon tanks must be kept at minus 148 degrees Fahrenheit (minus 100 degrees Celsius). In addition, the LZ team must remove all natural background radiation from the detector. A water tank surrounds the experiment from the natural radiation emitted by radiation from the walls of the laboratory.
The underground location of the dark matter detector helps protect it from high-energy protons and atomic nuclei, which travel through space at nearly the speed of light and originate from the sun and outside the solar system, known as cosmic rays.
The sensitivity of the LZ detector will continue to increase over the next 1000 days, meaning this is just the beginning of the experiment.
“We plan to collect about 20 times more data in the coming years, so we’re just getting started,” said LZ spokesman Hugh Lippincott of the University of California Santa Barbara in a expression (opens in new tab). “There’s a lot of science to do and it’s very exciting!”
The first results of the detector were published on the website (opens in new tab) of the LZ experiments on Thursday (7 July).
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