While the idea of dark matter has long fascinated scientists and amateur astronomers alike, no one has ever come close to understanding it, much less detecting and containing it. However, an international physics collaboration has planned an experiment to change that.
The second generation Large Underground Xenon experiment, called the LUX-ZEPLIN (LZ), is being led by University of California, Santa Barbara physicists.
The team will construct the largest dark matter detector in the world at a site a below ground in the Black Hills of South Dakota.
Since it was first hypothesized in 1932, dark matter has eluded characterisation. It makes up most of the matter in the universe, is void of light and affects the gravity of galaxies, but beyond that little else is known.
Scientists have theorized that dark matter is comprised of weakly interacting massive particles (WIMPS). To detect dark matter, scientists will focus on finding WIMPS.
The LZ detector will contain seven tonnes of active liquid xenon, a chemical element naturally occurring in small amounts in Earth’s atmosphere.
When WIMPS collide with xenon atoms, they produce photons (light) and electrons, and these signals are precisely mapped by measuring their brightness.
However, these WIMP collisions do not happen frequently. Scientists hope that with this new, highly sensitive technology they will be able to record up to five events in three years.
“Our dream would be after about a year’s worth of data that there would be a signal of dark matter,” said UC Santa Barbara physics professor Harry Nelson, the leader of the LZ collaboration. “That’s how rare a dark matter event is.”
The assembly of the detector is no easy task, either. In addition to the liquid xenon, the outer part will contain 27 tonnes of scintillator liquid, a type of oil that becomes illuminated in the presence of neutrons and gamma rays. The detector will then be contained within a tank of water.
The experiment must be conducted deep underground to keep the detectors from exposure to cosmic rays, but radiation from the decay of elements in the detectors’ surroundings can still affect the accuracy of the results. The LZ detector will be equipped with extra layers of particle detection outside the liquid xenon to ensure reliability.
The LZ project will be funded by the Department of Energy and the National Science Foundation. Equipment building could begin in 2015, based on when the funding becomes available, with experiment operations beginning in 2018.
Perhaps by LZ’s conclusion, scientists will have shed some light on the seemingly unsolvable mystery of dark matter.
First body image courtesy of Matthew Kapust, Sanford Lab, second body image courtesy of the UC Santa Barbara Current.