LZ experiment sets new record in search for Dark Matter

Detector explores weaker dark matter interactions than ever searched for before.

Exploring weakly interacting massive particles

Figuring out the nature of dark matter, the invisible substance that makes up most of the mass in our universe, is one of the greatest puzzles in physics. New results from the world’s most sensitive dark matter detector, LUX-ZEPLIN (LZ), have narrowed down possibilities for one of the leading dark matter candidates: weakly interacting massive particles, or WIMPs.

LZ hunts for dark matter from a cavern nearly one mile underground at the Sanford Underground Research Facility in South Dakota. The experiment’s new results explore weaker dark matter interactions than ever searched before and further limit what WIMPs could be.

The scientists involved in this latest work have noted that the detector and analysis techniques are performing even better than expected.

LZ uses 10 tonnes of liquid xenon to provide a dense, transparent material for dark matter particles to potentially bump into. The hope is for a WIMP to knock into a xenon nucleus, causing it to move, much like a hit from a cue ball in a game of pool. By collecting the light and electrons emitted during interactions, LZ captures potential WIMP signals alongside other data.

What is dark matter?

Dark matter, so named because it does not emit, reflect, or absorb light, is estimated to make up 85% of the mass in the universe but has never been directly detected, though it has left its fingerprints on multiple astronomical observations. We wouldn’t exist without this mysterious yet fundamental piece of the universe; dark matter’s mass contributes to the gravitational attraction that helps galaxies form and stay together.

International collaboration

LZ is a collaboration of roughly 250 scientists from 38 institutions in the United States, United Kingdom, Portugal, Switzerland, South Korea, and Australia; much of the work building, operating, and analysing the record-setting experiment is done by early career researchers.

At the School of Physics and Astronomy, Professor Alex Murphy and Dr Sally Shaw lead a group of researchers contributing to many aspects of LZ, including neutron backgrounds and searches for other dark matter candidates such as axions.  Sally served as LZ’s Physics Coordinator from 2022 to earlier this year, overseeing most of the data-taking and leading a substantial part of the analysis for the new results.

Dr Sally Shaw said:

This result was only possible due to many excellent physicists working very hard together, despite spanning most of the world's time zones! Doing science on this scale is a team game, and the LZ team has done a brilliant job once again delivering world-leading dark matter constraints.

The collaboration is already looking forward to analysing the next data set and using new analysis tricks to look for even lower-mass dark matter.