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The xenon detector at the core of the LUX-ZEPLIN experiment

Hundreds of global researchers, including from Imperial College London, are planning the most sensitive dark matter detector ever built.

Dark matter makes up 85 percent of the matter in the Universe, but its nature remains a mystery, with several possible candidate particles. In addition, because it is predicted to interact only very weakly with ordinary matter, it has so far not been detected.

If nature has been kind enough to put dark matter within the reach of any direct detection experiment, then this technology is the best shot we have. Professor Henrique Araújo

The DARWIN and LUX-ZEPLIN collaborations have joined forces to work together on the design, construction, and operation of a new, single, multi-tonne scale observatory that will use xenon to explore dark matter. It will be highly sensitive to a wide range of proposed dark matter particles and their interactions with visible matter.

The primary science goal of the new joint observatory is to improve sensitivity for detecting dark matter in our galaxy by at least a factor of 10 beyond that of the current generation of detectors.

Xenon experiments

Professor Henrique Araújo, from the Department of Physics at Imperial, leads the UK contribution to the LUX-ZEPLIN (LZ) experiment – the current state-of-the-art detector. He said: “If nature has been kind enough to put dark matter within the reach of any direct detection experiment, then this technology is the best shot we have – and one which we are proud to have helped pioneer.”

The current xenon-based experiments XENONnT and LUX-ZEPLIN will start their first science runs in 2021, to lead the race to detect the first signs of new particles and interactions. These experiments employ 5.9 and 7.0 tonnes of liquid xenon for the search, respectively. Xenon is used because candidate dark matter particles – particularly ‘weakly interacting massive particles’, or WIMPs – are thought to interact with the heavy nuclei of xenon atoms.

The LUX-ZEPLIN experiment operates at the Sanford Underground Research Facility (SURF) in the USA. The XENONnT experiment is located at the INFN Gran Sasso Laboratory (LNGS) in Italy. DARWIN is the evolution of the XENON program and includes additional groups, focusing on several research and design aspects required for the new, much larger detector.

Further revolutionary physics

Beyond its unparalleled sensitivity to dark matter, the new detector’s large mass and unprecedented low background levels of radiation will also enable world-leading searches for additional signatures of physics beyond the Standard Model of particle physics that would similarly revolutionize our understanding of the universe.

In particular, the secondary science goal will be the search for neutrino-less double-beta decay in xenon, shedding light on the nature of the neutrino and the imbalance of matter and antimatter in the universe. The observatory will also perform searches for other rare processes and particles such as axions, hypothetical particles that might be emitted from the Sun. It will also measure neutrinos created in the Sun, the Earth’s atmosphere, and potentially those from galactic supernovae.

After a very successful first joint workshop in April 2021, more than 100 research senior scientists from 16 countries signed a memorandum of understanding on July 6, 2021.  Scientific cooperation has now begun to realize this next-generation rare event observatory.

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Adapted from a press released by the Sanford Underground Research Facility (SURF) and Gran Sasso National Laboratory (LNGS) on behalf of the DARWIN and LZ collaborations.

Top image credit: Matt Kapust, Sanford Underground Research Facility, USA