The world's most sensitive dark matter detector just delivered 'significant results'

The hope is that a dark matter particle will fly through space and eventually bounce off one of the xenon atoms. This will agitate loose electrons into a flash that will be recorded by the experiment. 

The first run for the LZ detector lasted 60 days between December 25 and May 16. However, the scientists emphasized the fact that they're playing a long waiting game.

"We're looking for very, very low-energy recoils by the standards of particle physics. It’s a very, very rare process, if it's visible at all," Hugh Lippincott, a physicist at UC Santa Barbara and a member of the LZ team, said a press conference yesterday, July 7. "You can shoot a dark matter particle through 10 million light-years of lead and expect only one interaction at the end of that light-year."

Dark matter refers to the mysterious unaccounted-for matter that makes up roughly 85 percent of the entire mass of the universe. Though it has never directly been detected, we know it's out there because of the gravitational effect it has on observable space objects.

One of the main candidates targeted by dark matter detection experiments, such as the DAMA/LIBRA experiment in Italy, is the WIMP, or Weakly Interacting Massive Particle. These particles have mass but barely ever interact with ordinary matter, which is why a super sensitive machine is required to detect them.

The LZ detector has 1,000 days of experiments scheduled

LZ is 30 times larger and 100 times more sensitive than its predecessor, the Large Underground Xenon experiment. Though construction started on the new detector in 2018, experiments were delayed by Covid-19. Now things seem to be running smoothly. "The collaboration worked well together to calibrate and to understand the detector response," said Aaron Manalaysay, a physicist at Berkeley Laboratory and a member of the LZ team, in a Berkeley Lab press release. "Considering we just turned it on a few months ago and during COVID restrictions, it is impressive we have such significant results already."

The LZ detector researchers highlighted a total of 335 detections that looked promising during the machine's initial 60-day run. None turned out to be WIMPs, but the team was able to eliminate a mass range from future experiments. Ultimately, the team will be able to gradually eliminate mass ranges by pinpointing what masses the particles can't be. This will continually narrow the parameters for future experiments, making it more likely that WIMPs will be detected in subsequent attempts.

The LZ detector has 1,000 operational days scheduled, meaning roughly 20 times more data will be collected. And every data set is more likely than the last to finally uncover the great mystery of dark matter.