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In an underground mine in South Dakota, researchers unravel mysteries of dark matter

July 22, 2019
Components needed to fully assemble the dark matter-search experiment LZ—including digital electronics developed at Rochester—are transported down a shaft and installed in the nearly mile-deep research cavern at the Sanford Underground Research Facility (SURF) in South Dakota. SURF, the site of a former gold mine, is now dedicated to a broad spectrum of scientific research. (Sanford Underground Research Facility photo)

Scientists around the world have attempted for decades to solve the mystery of dark matter, which accounts for about 85 percent of all matter in the universe. Proof of dark matter particles would fundamentally change our understanding of the makeup of the universe. However, researchers have so far only inferred dark matter indirectly by observing gravitational effects that cannot be explained by standard theories of gravity.

Researchers from the University of Rochester are involved in an international collaboration of about 250 scientists from 37 institutions assembling an innovative underground dark matter-search experiment called LUX-ZEPLIN (LZ). When it is completed, LZ will be the largest, most sensitive U.S.-based experiment designed to directly detect dark matter particles. Many of the components needed to fully assemble LZ—including digital electronics developed at Rochester—arrived at LZ’s home recently at the Sanford Underground Research Facility (SURF) in South Dakota. Compiling the various pieces brings researchers one step closer to their goal of completing the installation of the experiment later this year and beginning to collect data in 2020.

The digital electronics designed, developed, delivered, and installed at SURF in June by Rochester researchers are an integral piece of the puzzle in detecting dark matter; the electronics will enable the readout of signals from particle interactions.

Lower and upper photomultiplier tube arrays being prepared for installation for the underground dark matter-search experiment called LZ. More than 28 miles of coaxial cable will connect these photomultiplier tubes to the digitizing electronics developed at Rochester. (SURF photo / Matt Kapust)

“All of our electronics have been designed specifically for LZ with the goal of maximizing our sensitivity for the smallest possible signals,” says Frank Wolfs, a professor of physics and astronomy at Rochester, who is overseeing Rochester’s efforts.

LZ is particularly focused on finding a type of theoretical particle called weakly interacting massive particles, or WIMPs, by triggering sequences of light and electrical signals in a tank filled with 10 metric tons of highly purified liquid xenon, which is among Earth’s rarest elements. The properties of xenon atoms allow them to produce light in certain particle interactions.

Assembly of the liquid xenon time projection chamber for LZ is now about 80 percent complete. When it is fully assembled, this inner detector will contain about 500 photomultiplier tubes. The tubes are designed to amplify and transmit signals produced within the chamber. More than 28 miles of coaxial cable will connect photomultiplier tubes and their amplifying electronics to the digitizing electronics developed at Rochester.

“The successful installation of the digital electronics and the online network and computing infrastructure in June makes us eager to see the first signals emerge from LZ,” Wolfs says.

group photo of six scientists in hard hats.

The team of Rochester researchers, faculty, and alumni who completed the installation of the LZ dark matter experiment’s electronics pose for a photo 4,800 feet below the surface, in Lead, South Dakota. Team members include, from left, Erik Druszkiewicz ’17 (PhD), research engineer; Dev Ashish Khaitan ’11, physics PhD student; Yufan Qie ’20; Jean Wolfs ’18; Frank Wolfs, professor of physics and astronomy; and Marcus Converse, physics PhD student. (University of Maryland photo / Douglas Tiedt )

SURF, the site of a former gold mine, is now dedicated to a broad spectrum of scientific research. All of the components for LZ will be transported down a shaft and installed in a nearly mile-deep research cavern. The rock above provides a natural shield against much of the constant bombardment of particles raining down on the planet’s surface that produce unwanted “noise.”

“LZ achieved major milestones in June. It was the busiest single month for delivering things to SURF—it was the peak,” says LZ Project Director Murdock Gilchriese of the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), the lead institution for the LZ project.

The University of Rochester’s contribution to LZ is the latest example of Rochester physics researchers developing technologies for groundbreaking projects that seek to understand the mysterious particles in our universe. Segev BenZvi, an assistant professor of physics, is involved in research to detect gamma rays and dark matter in Mexico while Rochester researchers Arie Bodek, Regina Demina, Aran Garcia-Bellido, and Sergei Korjenevski were part of an experimental team whose results made possible the discovery of the Higgs boson. Wolfs was also involved in developing signal processing electronics for LUX, the predecessor to LZ.

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Category: Featured