PROVIDENCE, R.I. [Brown University] — A Brown University physicist will play a key role in a future experiment aimed at detecting and characterizing dark matter, the mysterious stuff thought to account for most of the matter in the universe.
The XENON/DARWIN and LUX-ZEPLIN collaborations — which operate two current and ongoing dark matter experiments — have now joined forces to work together on the design, construction and operation of a new multi-ton-scale xenon observatory to explore dark matter. Xenon experiments have proven to be the most sensitive dark matter detection systems in the world over the last 20 years, says Richard Gaitskell, a physics professor at Brown who will participate in the new experiment. The primary science goal of the new joint observatory is to reach a sensitivity for detecting dark matter in the Earth’s galaxy by at least a factor of 10 beyond that of the current generation of detectors.
“Nature has presented us with an enormous challenge in identifying the dominant form of matter in our universe,” said Gaitskell, who is currently a member of the LUX-ZEPLIN research team. “The dark matter reacts so weakly with conventional material that we have to build massive detectors in order to potentially collect only a handful of identifiable interactions a year. The larger the detector, the greater the chance of seeing an interaction.”
Dark matter makes up 85% of the matter in the universe, but its nature remains a mystery. Scientists can see the effects of its gravity in the rotation of galaxies and in the way light bends as it travels across the universe, but no one has directly detected a dark matter particle. The direct identification of the dark matter particle is among the highest priorities in science and also one of the most challenging.
The current xenon-based experiments XENONnT and LUX-ZEPLIN will start their first science runs in 2021. The experiments employ 5.9 and 7.0 tons of liquid xenon for the search, respectively. Both research teams are hopeful that one or both of these experiments will make the world’s first direct detection of a dark matter particle. But whatever the outcome, Gaitskell says that the new detector is necessary to confirm or clarify those results.
“If we see a dark matter signal using our 10-ton detectors, we will then need a much larger detector to accurately determine the properties of that elusive dark matter,” he said. “If we see nothing over the next few years with the 10-ton detectors, we will need the much larger detector to probe additional hiding places of the dark matter. The work on the research and design for the new even more massive next-generation detector has begun.”
Beyond its sensitivity to dark matter, the new detector’s large mass and low level of background interference will also enable world-leading searches for additional signatures of physics beyond the Standard Model of particle physics, collaboration scientists say. In particular, the secondary science goal will be the search for neutrinoless 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.
The current LUX-ZEPLIN experiment operates at the Sanford Underground Research Facility in South Dakota. The XENONnT experiment is located at the INFN Gran Sasso Laboratory in Italy. DARWIN is the evolution of the XENON program and includes additional groups, focusing on several research and development aspects required for the much larger detector. The new multi-ton liquid xenon detector will combine the most successful technologies employed in rare-event searches with xenon detectors, including those developed for XENONnT and LUX-ZEPLIN, and from targeted research and development including work supported under DARWIN.
After a joint workshop in April 2021, 104 research group leaders from 16 countries have signed a memorandum of understanding to work together on the design, construction and operation of the new detector.