LUX-ZEPLIN (LZ), a next-generation dark matter detector that will be at least 100 times more sensitive than its predecessor, has cleared another approval milestone and is on schedule to begin its deep-underground hunt for theoretical particles known as WIMPs, or weakly interacting massive particles, in 2020.
WIMPs are among the top prospects for explaining dark matter, the unseen stuff that we have observed only through gravitational effects.
Last month, LZ received an important U.S. Department of Energy approval (known as Critical Decision 2 and 3b) for the project’s overall scope, cost and schedule. The latest approval step sets in motion the buildout of major components and the preparation of its nearly mile-deep lair at the Sanford Underground Research Facility (SURF) in Lead, S.D.
The experiment is designed to tease out dark matter signals from within a chamber filled with 10 metric tons of purified liquid xenon, one of the rarest elements on Earth. The project is supported by a collaboration of more than 30 institutions and about 200 scientists worldwide.
“Nobody looking for dark matter interactions with matter has so far convincingly seen anything, anywhere, which makes LZ more important than ever,” said Murdock “Gil” Gilchriese, LZ project director and Berkeley Lab physicist.
Harry Nelson, LZ spokesperson and a physics professor at University of California, Santa Barbara, said, “The nature of the dark matter, which comprises 85 percent of all matter in the universe, is one of the most perplexing mysteries in all of contemporary science. Just as science has elucidated the nature of familiar matter—from the periodic table of elements to subatomic particles, including the recently discovered Higgs boson—the LZ project will lead science in testing one of the most attractive hypotheses for the nature of the dark matter.”
LZ is named for the merger of two dark matter detection experiments: the Large Underground Xenon experiment (LUX) and the U.K.-based ZonEd Proportional scintillation in Liquid Noble gases experiment (ZEPLIN). LUX, a smaller liquid xenon-based underground experiment at SURF will be dismantled to make way for the new project.
“Liquid xenon has turned out to be a nearly magical substance for WIMP detection, as demonstrated by the sensitivities achieved by ZEPLIN and LUX,“ said Professor Henrique Araujo from Imperial College London, who leads the project in the U.K.
The SURF site shields the experiment from many particle types that are constantly showering down on the Earth’s surface and would obscure the signals LZ is seeking.
Dan McKinsey, a Lawrence Berkeley National Laboratory (Berkeley Lab) faculty senior scientist and UC Berkeley Physics professor who is a part of the LZ collaboration, said, “A major reason for LZ is surprises: We’re really pushing way into the low-energy, low-background parameter space where no one has ever looked, and this is where surprises could await. That’s where new things get discovered. While we are looking for dark matter, we may see something else that has a rare interaction with matter at low energies.”
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