Members of the LZ equipment in the LZ water tank after the installation of the external detector. Credit: Matthew Kapust / Sanford Underground Research Facility
In the depths of the Black Hills of South Dakota, at the Sanford Underground Research Facility (SURF), an innovative and unique dark matter detector, the LUX-ZEPLIN (LZ) experiment, led by Lawrence Berkeley National Laboratory (Berkeley Lab), has gone through a phase of verification of the initial operations and first results obtained.
The message from this successful startup: “We’re ready and everything looks good,” said Berkeley Lab senior physicist and former LZ spokesman Kevin Lesko. “It’s a complex detector with many parts and they all work well as expected,” he said.
In an article posted online today on the experiment’s website, LZ researchers report that with the initial test, LZ is already the most sensitive dark matter detector in the world. The document will appear later today in the online prepress archive arXiv.org. LZ spokesman Hugh Lippincott of the University of California Santa Barbara said, “We plan to collect about 20 times more data in the next few years, so we’re just getting started. There’s a lot of science to do and it’s very exciting.” .
Dark matter particles have never been detected, but perhaps not for much longer. The countdown may have started with the results of the first 60 “live days” of LZ testing. These data were collected over a period of three and a half months of initial operations from the end of December. This was a long enough period to confirm that all aspects of the detector worked well.
Unseen, because it does not emit, absorb, or scatter light, the presence of dark matter and gravitational attraction are, however, fundamental to our understanding of the universe. For example, the presence of dark matter, estimated at about 85 percent of the total mass of the universe, shapes the shape and motion of galaxies, and is relied upon by researchers to explain what is known. on large-scale structure and expansion. of the universe.
Looking at the LZ outdoor detector, used to veto radioactivity that can mimic a dark matter signal. Credit: Matthew Kapust / Sanford Underground Research Facility
The heart of the LZ dark matter detector consists of two niified titanium tanks filled with ten tons of very pure liquid xenon and seen by two arrays of photomultiplier tubes (PMT) capable of detecting dim light sources. Titanium tanks reside in a larger detector system to trap particles that can mimic a dark matter signal.
“I am delighted to see this complex detector ready to address the long-standing problem of what dark matter is made of,” said Berkeley Laboratory’s physics division director Nathalie Palanque-Delabrouille. “The LZ team now has the most ambitious instrument in hand to do so.”
The design, manufacturing and installation phases of the LZ detector were led by Berkeley Lab project director Gil Gilchriese, along with an international team of 250 scientists and engineers from more than 35 institutions in the US, UK, Portugal and South Korea. LZ’s operations manager is Simon Fiorucci of Berkeley Lab. Together, the collaboration hopes to use the instrument to record the first direct evidence of dark matter, the so-called missing mass of the cosmos.
Henrique Araújo, of 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 international contributions. “We started with two groups with different perspectives and ended up with a very fine-tuned orchestra that worked perfectly together to deliver a great experiment,” Araújo said.
An underground detector
Hidden a mile underground at SURF in Lead, SD, LZ is designed to capture dark matter in the form of weakly interacting massive particles (WIMP). The experiment is underground to protect it from cosmic radiation at the surface that could drown out signs of dark matter.
(Left) A diagram of the LZ detector. (Right) Illustration of Operation LZ: Particles interact in liquid xenon, releasing a flash of light and charge that are collected by arrays of photomultiplier tubes at the top and bottom. Credit: Outline of the left: LZ collaboration. Right image: LZ / SLAC
Xenon particle collisions produce visible flashes or flashes of light, which are recorded by PMTs, said Aaron Manalaysay of the Berkeley Lab, who as physics coordinator led the collaboration’s efforts to produce these early physics results. “The collaboration worked well to calibrate and understand the detector response,” Manalaysay said. “Given that we launched it a few months ago and during COVID restrictions, it’s impressive that we already have such significant results.”
Collisions will also drop electrons from xenon atoms, sending them adrift to the top of the chamber under an applied electric field where they produce another flash that allows the reconstruction of space events. The characteristics of scintillation help determine the types of particles that interact in the xenon.
Mike Headley, CEO of SURF Lab, said: “The entire SURF team congratulates LZ’s collaboration on achieving this important milestone. The LZ team has been a wonderful partner and we are proud to welcome them. and SURF “.
Fiorucci said the on-site team deserves special praise at this initial milestone, as the detector was transported underground in late 2019, just before the start of the COVID-19 pandemic. He said with the trips very restricted, only a few LZ scientists could make the trip to help the site. The South Dakota team took excellent care of LZ.
“I would like to commend the SURF team and would also like to express my gratitude to the large number of people who provided remote support during the construction, commissioning and operations of LZ, many of whom worked full time from home.institutions making sure the experiment would be a success and continue to do so now, “said Tomasz Biesiadzinski of SLAC, the LZ detector’s operations manager.
The central LZ detector in the clean room of the Sanford Underground Research Facility after assembly, before beginning its underground journey. Credit: Matthew Kapust, Sanford Underground Research Facility
“Many subsystems began to come together as we began to gather data for detector start-up, calibrations, and scientific execution. Starting a new experiment is a challenge, 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 of Pennsylvania State University, which coordinates planning the operation of the detector.
Maria Elena Monzani of SLAC, Deputy Director of Computer and Software Operations, said: “We had amazing scientists and software developers throughout the collaboration, who tirelessly supported data movement, data processing and in the simulations, allowing an impeccable operation of the detector.The support of NERSC [National Energy Research Scientific Computing Center] it was invaluable. “
With confirmation that LZ and its systems are working successfully, Lesko said, it is time for large-scale observations to begin in the hope that a particle of dark matter will collide with a xenon atom on the LZ detector very soon.
An important milestone for an underground dark matter search experiment More information: DS Akerib et al, The LUX-ZEPLIN experiment (LZ), Nuclear instruments and methods in physics research Section A: Accelerators, spectrometers, detectors and associated equipment (2019). DOI: 10.1016 / j.nima.2019.163047
Projected WIMP sensitivity of the dark matter experiment LUX-ZEPLIN (LZ), arXiv: 1802.06039v2 [astro-ph.IM] doi.org/10.48550/arXiv.1802.06039
Provided by Lawrence Berkeley National Laboratory
Citation: Investigators record successful start of dark matter detector in underground research facilities (2022, July 7) recovered on July 7, 2022 …