Success! First Outcomes From World’s Most Delicate Darkish Matter Detector

Success! First Outcomes From World’s Most Delicate Darkish Matter Detector

LZ Water Tank

Members of the LZ group within the LZ water tank after the outer detector set up. Credit score: Matthew Kapust, Sanford Underground Analysis Facility

Berkeley Lab Researchers File Profitable Startup of LUX-ZEPLIN Darkish Matter Detector at Sanford Underground Analysis Facility

An modern and uniquely delicate darkish matter detector – the LUX-ZEPLIN (LZ) experiment – has handed a check-out part of startup operations and delivered first outcomes. LZ is situated deep under the Black Hills of South Dakota within the Sanford Underground Analysis Facility (SURF) and is led by the DOE’s Lawrence Berkeley Nationwide Laboratory (Berkeley Lab).

The take-home message from this profitable startup: “We’re prepared and every part’s wanting good,” stated Berkeley Lab senior physicist and previous LZ spokesperson Kevin Lesko. “It’s a fancy detector with many elements to it and they’re all functioning nicely inside expectations,” he stated.

In a paper posted on July 7 on the experiment’s web site, LZ scientists report that with the preliminary run, LZ is already the world’s most delicate darkish matter detector. The paper will seem on the web preprint archive arXiv.org later. LZ spokesperson Hugh Lippincott of the College of California Santa Barbara stated, “We plan to gather about 20 occasions extra information within the coming years, so we’re solely getting began. There’s lots of science to do and it’s very thrilling!”

LZ Outer Detector

Trying up into the LZ Outer Detector, used to veto radioactivity that may mimic a darkish matter sign. Credit score: Matthew Kapust/Sanford Underground Analysis Facility

Whereas darkish matter particles have by no means really been detected, they might not be true for for much longer. The countdown could have begun already with outcomes from LZ’s first 60 “stay days” of testing. These information have been collected over a three-and-a-half-month interval of preliminary operations starting on the finish of December. This period was lengthy sufficient to substantiate that each one points of the detector have been functioning correctly.

Though it’s unseen, as a result of it doesn’t emit, soak up, or scatter mild, darkish matter’s presence and gravitational pull are nonetheless elementary to our understanding of the universe. For instance, the presence of darkish matter, which is estimated to be about 85 % of the entire mass of the universe, shapes the shape and motion of galaxies, and it’s invoked by researchers to clarify what is understood in regards to the large-scale construction and enlargement of the universe.

Two nested titanium tanks full of ten tonnes of very pure liquid xenon and considered by two arrays of photomultiplier tubes (PMTs) capable of detect faint sources of sunshine type the center of the LZ darkish matter detector. The titanium tanks reside in a bigger detector system to catch particles that may mimic a darkish matter sign.

LUX ZEPLIN Schematic

A schematic of the LZ detector. Credit score: LZ collaboration

“I’m thrilled to see this complicated detector prepared to handle the long-standing concern of what darkish matter is product of,” stated Berkeley Lab Physics Division Director Nathalie Palanque-Delabrouille. “The LZ group now has in hand probably the most formidable instrument to take action!”

The design, manufacturing, and set up phases of the LUX-ZEPLIN detector have been led by Berkeley Lab mission director Gil Gilchriese along with a global group of 250 scientists and engineers from over 35 establishments within the US, UK, Portugal, and South Korea. The LZ operations supervisor is Berkeley Lab’s Simon Fiorucci. Collectively, the collaboration is hoping to make use of the instrument to document the primary direct proof of darkish matter, the so-called lacking mass of the cosmos.

Henrique Araújo, from Imperial College London, leads the UK groups and previously the last phase of the UK-based ZEPLIN-III program. He worked very closely with the Berkeley team and other colleagues to integrate the international contributions. “We started out with two groups with different outlooks and ended up with a highly tuned orchestra working seamlessly together to deliver a great experiment,” Araújo said.

An underground detector

Tucked away about a mile underground at SURF in Lead, South Dakota, LUX-ZEPLIN is designed to capture dark matter in the form of weakly interacting massive particles (WIMPs). The experiment is underground to protect it from cosmic radiation at the surface that could drown out dark matter signals.

Particle collisions in the xenon produce visible scintillation or flashes of light, which are recorded by the PMTs, explained Aaron Manalaysay from Berkeley Lab who, as physics coordinator, led the collaboration’s efforts to produce these first physics results. “The collaboration worked well together to calibrate and to understand the detector response,” Manalaysay said. “Considering we just turned it on a few months ago and during COVID restrictions, it is impressive we have such significant results already.”

LZ Detector Event Diagram

When a WIMP – a hypothetical dark matter particle – collides with a xenon atom, the xenon atom emits a flash of light (gold) and electrons. The flash of light is detected at the top and bottom of the liquid xenon chamber. An electric field pushes the electrons to the top of the chamber, where they generate a second flash of light (red). LZ will be searching for a particular sequence of flashes that cannot be due to anything other than WIMPs. Credit: LZ/SLAC

The collisions will also knock electrons off xenon atoms, sending them to drift to the top of the chamber under an applied electric field where they produce another flash permitting spatial event reconstruction. The characteristics of the scintillation help determine the types of particles interacting in the xenon.

The South Dakota Science and Technology Authority, which manages SURF through a cooperative agreement with the U.S. Department of Energy, secured 80 percent of the xenon in LZ. Funding came from the South Dakota Governor’s office, the South Dakota Community Foundation, the South Dakota State University Foundation, and the University of South Dakota Foundation.

Mike Headley, executive director of SURF Lab, said, “The entire SURF team congratulates the LZ Collaboration in reaching this major milestone. The LZ team has been a wonderful partner and we’re proud to host them at SURF.”

Vacuum Distillation System for LZ Dark Matter Experiment

Chemists at Brookhaven Lab used this custom-made vacuum distillation system to purify linear alkyl benzene needed to produce liquid scintillator for the LZ dark matter experiment. Credit: Brookhaven Lab

Fiorucci said the onsite team deserves special praise at this startup milestone, given that the detector was transported underground late in 2019, just before the onset of the COVID-19 pandemic. He said with travel severely restricted, only a few LZ scientists could make the trip to help on site. The team in South Dakota took excellent care of LZ.

“I’d like to second the praise for the team at SURF and would also like to express gratitude to the large number of people who provided remote support throughout the construction, commissioning and operations of LZ, many of whom worked full time from their home institutions making sure the experiment would be a success and continue to do so now,” said Tomasz Biesiadzinski of SLAC, the LZ detector operations manager.

“Lots of subsystems started to come together as we started taking data for detector commissioning, calibrations and science running. Turning on a new experiment is challenging, but we have a great LZ team that worked closely together to get us through the early stages of understanding our detector,” said David Woodward from Pennsylvania State University who coordinates the detector run planning.

LZ Central Detector in Clean Room

The LZ central detector in the clean room at Sanford Underground Research Facility after assembly, before beginning its journey underground. Credit: Matthew Kapust, Sanford Underground Research Facility

Maria Elena Monzani of SLAC, the Deputy Operations Manager for Computing and Software, said “We had amazing scientists and software developers throughout the collaboration, who tirelessly supported data movement, data processing, and simulations, allowing for a flawless commissioning of the detector. The support of NERSC [National Energy Research Scientific Computing Center] was invaluable.”

With affirmation that LZ and its programs are working efficiently, Lesko stated, it’s time for full-scale observations to start in hopes {that a} darkish matter particle will collide with a xenon atom in the LZ detector very soon.

LZ is supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics and the National Energy Research Scientific Computing Center, a DOE Office of Science user facility. LZ is also supported by the Science & Technology Facilities Council of the United Kingdom; the Portuguese Foundation for Science and Technology; and the Institute for Basic Science, Korea. Over 35 institutions of higher education and advanced research provided support to LZ. The LZ collaboration acknowledges the assistance of the Sanford Underground Research Facility.

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