For the better part of a century, people have been trying to understand dark matter. This invisible substance makes up roughly 85% of the mass in the universe but has never been directly detected. Determining exactly what it is remains one of the biggest open questions in science.
Now, a new analysis from the LUX-ZEPLIN (LZ) experiment has recorded a single particle interaction, known as LZ.230616 for the date it occurred, that researchers have great difficulty explaining with known background signals from regular matter. The result does not yet meet the statistical threshold required to claim a discovery, but is the most compelling hint of dark matter reported by the LZ experiment to date.
“We can’t explain LZ.230616 with the backgrounds we know about,” said UC Santa Barbara physics professor Hugh Lippincott, who led the internal review of the analysis. “The work of young LZ researchers held up to intense scrutiny during our review. No matter what happens, I’m extremely proud of this team.”
Lippincott also led construction of a skin-like layer of liquid xenon that surrounds the main dark-matter sensitive cylinder of liquid xenon. The xenon skin detector has proved critical in rejecting dark matter imposters that could have faked LZ230616.
Co-founded by UCSB physics professor Harry Nelson, LZ is an international collaboration of 250 scientists and engineers from 39 institutions. LZ held its first collaboration meeting on the 5th floor of Broida Hall on the UCSB campus in 2012. Operating nearly one mile below ground at the Sanford Underground Research Facility (SURF) in South Dakota, the experiment uses 10 tonnes of ultrapure liquid xenon to search for dark matter and is optimized to look for WIMPs, or weakly interacting massive particles.