New Result from the LUX-ZEPLIN Experiment
17 Sep 2026
An intriguing new result from the LUX-ZEPLIN (LZ) experiment presents a possible detection of a dark matter particle, though more data is needed before any claim can be made.
Hosted at the Sanford Underground Research Facility (SURF) in South Dakota, USA, LZ is an international collaboration of around 250 scientists and engineers and uses liquid xenon technology to search for dark matter particles. Dark matter is thought to make up around 85% of all the matter in the universe, yet it has never been directly detected.
Recently, the LZ group at the University of Bristol have identified a single particle interaction that researchers have struggled to explain using any known background process.
Sam Eriksen, a senior research associate at the University of Bristol and lead author of the study said
“This was a detailed study in a region we hadn’t explored within this dataset, and we spent months of additional effort to understand all the possible causes of background events. We understand our detector and the backgrounds so well that even a single outstanding event, like the one we found, is important. We expect dark matter events to be extremely rare, so only a handful could mark the first detection of WIMP dark matter.”
Professor Henrique Araújo, from Imperial College London and STFC Particle Physics Department, leads the LZ project in the UK. He said
“Many in the UK team contributed to this analysis, but clearly the Bristol group had to endure the level of scrutiny one reserves to such a big result. I’m happy to report that, after a couple of years of analysis, they came out the other end. I’m already looking forward to examining more data. I also want to say that we’re only in this prime position because we helped design and build a fantastic instrument!”
Researchers and engineers from STFC’s national laboratories, including the Particle Physics and Technology Departments (PPD and TD), and the Boulby Underground Laboratory, have been central to designing, testing and delivering the experiment’s most vital elements. Notable contributions to the construction of the experiment include:
- Design, fabrication and deployment of a radiopure titanium cryostat
- Design and fabrication of a radioactive sources deployment system for the detector calibration
- Material assays at Boulby Underground Laboratory, accounting for 50% of the entire international material screening campaign
and contributions to the experiment operations:
- Maintenance and operation of the external radioactive deployment sources systems
- Covering experimental shifts, which can largely be done remotely due to the highly developed instrumental monitoring and controls in place
- UK operations and financial management
See here for more information on the contributions to the LZ experiment by PPD.
If the event was caused by dark matter, it would point to a particle with a mass of at least 200 GeV/c² (gigaelectron volts), or more than 200 times the mass of a proton, interacting with ordinary matter in a way not covered by the simplest theoretical models. The result stands at 2.6 sigma significance, meaning there is roughly a 0.5% chance it could be explained by known backgrounds alone. This is well short of the 5-sigma threshold that physics requires before a result can be called a discovery. LZ will continue collecting data at SURF, allowing researchers to test whether the signal grows stronger, weakens, or disappears as more data is gathered.
LZ’s achievements so far include the most significant observation of solar boron-8 neutrinos, and today’s result, reflecting years of collaborative work. Drawing on the successful double-phase xenon technology pioneered in the UK, and decades of experience in building the most sensitive dark matter experiments to date, the UK team is already preparing the next phase with international partners. Funded by a UKRI Infrastructure Fund Preliminary Activity, XENON-LUX-ZEPLIN-DARWIN (XLZD) is the next-generation rare event observatory for dark matter detection and neutrino physics, which could be hosted at the Boulby Underground Laboratory.
Professor Pawel Majewski, Dark Matter group leader at PPD and LZ co-investigator, said
“Years of LZ’s exploitation and scientific achievements have demonstrated the maturity of liquid xenon technology and underscore the need to continue scientific exploration with a much larger experiment, enabling discoveries that, with today’s announcement, could be literally around the corner.”
Further Information
The double-phase xenon technology used in the LZ experiment, was originally developed in the 2000s at Boulby Underground Laboratory (by PPD and other UK institutes). Dark matter particles are expected to collide with the xenon atoms to produce small signals in the detector. These interactions are so rare that a detailed understanding of the sources of background signals is required, so that these can be distinguished from real dark matter events. At this level of precision, even natural radioactivity from everyday materials must be avoided. To minimise this, the LZ experiment is 1 mile underground and the detector itself uses shielding materials.
The signals are also compared with a high-precision Background Model, which is based on screening the materials used to identify their signal levels. While the materials chosen are due to their radiological purity, they will contain trace amounts of radiation that must be accounted for. This procedure is a type of material assay, and is an area of Boulby expertise. Find out more here: Material Assay (BUGS) – Boulby Underground Laboratory
Looking beyond LZ, its successor XLZD will be significantly larger (by an order of magnitude on detector volume) and aims to achieve world leading sensitivity to dark matter candidates, investigate neutrino decay and explore phenomena beyond our current understanding of physics. Find out more more about XLZD here.
For the XLZD experiment, PPD and TD are:
- Working on the design for the cryostat
- Leading the engineering and installation planning
- Responsible for xenon procurement
with significant international leadership roles and strong involvement in project management.
See here for more information on how PPD and TD will contribute towards the next generation experiment, XLZD.
