Advancing the quest for dark matter: New insights from the LUX-ZEPLIN experiment

In 2022, the detector passed a check-out phase of startup operations and delivered its first results, proving itself to be world's most sensitive detector of dark matter and placing what were until now the strictest limits on how strongly WIMPs should interact with ordinary matter. To get the latest result, the analysis combined 220 days of new data taken in 2023 and 2024 with 60 days from the experiment's first run, which started in 2022. LZ is still in its early phases, too. By 2028, the LZ team plans to gather over 1,000 days of data.

"This is how science works," Gaitskell said. "This is a huge question we are trying to answer: 'What is most of the matter in the universe made of?' It won't get answered in a matter of weeks, months or even years necessarily. This is one that will take decades to answer, and that is actually pretty typical of most major scientific questions. If you go back and look at the history books, you'll realize that major discoveries are separated by long periods of time and happened step-by-step."

This new results marks the first time that LZ has applied "salting"- a technique that adds fake WIMP signals during data collection. By camouflaging the real data until "unsalting" at the very end, researchers can avoid unconscious bias and keep from overly interpreting or changing their analysis before knowing the outcome.

"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," said Scott Haselschwardt, the LZ physics coordinator and an assistant professor at the University of Michigan. "If you make a discovery, you want to get it right."

Brown's role in the experiment

Since its start, early-career researchers have played a significant role in building and operating the experiment. Brown's team, for instance, was crucial in building the PMT arrays, which serve as the experiment's "eyes."

The group worked with Berkeley Lab and Imperial College London researchers to design, test and assemble the arrays and its more than 14,000 components in cleanrooms at Brown's Department of Physics, where the components also underwent two years of testing.