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  • richardmitnick 1:05 pm on March 26, 2018 Permalink | Reply
    Tags: Gan Sasso Laboratory, GERDA collaboration, , , ,   

    From LBNL: “Underground Neutrino Experiment Could Provide Greater Clarity on Matter-Antimatter Imbalance” 

    Berkeley Logo

    Berkeley Lab

    March 26, 2018
    Glenn Roberts Jr.
    (510) 486-5582

    Stacks of lead bricks (gray) and a copper chamber make up the innermost layers of the MAJORANA DEMONSTRATOR’s multilayered shield. The shielding materials weigh about 57 tons. (Credit: Matthew Kapust/Sanford Underground Research Facility)

    By Dawn Levy

    If equal amounts of matter and antimatter had formed in the Big Bang more than 13 billion years ago, one would have annihilated the other upon meeting, and today’s universe would be full of energy – but no matter – to form stars, planets, and life.

    So the very existence of matter suggests something is wrong with Standard Model equations describing symmetry between subatomic particles and their antiparticles.

    In a study published March 26 in Physical Review Letters, nuclear physicists from the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and other institutions working on the MAJORANA DEMONSTRATOR experiment have shown that they can shield a sensitive, scalable, 44-kilogram germanium detector array from background radioactivity. The experiment is led by Oak Ridge National Laboratory (ORNL).

    This accomplishment is critical to developing and proposing a much larger future experiment – with approximately a ton of detectors – to study the nature of neutrinos. These electrically neutral particles interact only weakly with matter, making their detection exceedingly difficult.

    “We’re trying to figure out the really basic question: Are neutrinos their own antiparticles?” said Alan Poon, the detector group leader for the MAJORANA DEMONSTRATOR. “Another goal is to demonstrate that we can actually build a bigger detector.”

    John Wilkerson, a nuclear physicist from ORNL and the University of North Carolina at Chapel Hill who led the construction of the experiment, said, “The excess of matter over antimatter is one of the most compelling mysteries in science.” The collaboration involves 129 researchers from 27 institutions and 6 nations.

    The experiment seeks to observe a phenomenon in atomic nuclei called “neutrinoless double-beta decay.” This observation would prove that neutrinos are their own antiparticles. The existence of this type of decay would have “profound implications for our understanding of the universe,” Wilkerson added. These measurements could also provide a better understanding of neutrino mass.

    Berkeley Lab was responsible for fashioning a specially prepared form of germanium crystals into working detectors for the experiment, and building the detector array’s front-end electronics that sit very close to the detectors. Decades ago, Berkeley Lab pioneered the technique for making high-purity germanium detectors and invented the type of germanium detectors that were adapted for the MAJORANA DEMONSTRATOR experiment.

    Poon noted that the electronics and other components surrounding the detectors are made of ultrapure materials to reduce background “noise,” or unwanted signals from naturally occurring radiation. “They are the lowest-radioactivity front-end electronics in the world,” he said.

    A researcher works on the delicate wiring of a MAJORANA cryostat, which is like a thermos under vacuum that chills the detectors at the heart of the experiment. The experiment’s two cryostats each house 29 germanium detectors. Berkeley Lab fashioned a specialized form of germanium crystals into working detectors for the experiment. (Credit: Matthew Kapust/Sanford Underground Research Facility)

    The collaboration also used Berkeley Lab’s National Energy Research Scientific Computing Center (NERSC) to process and analyze data from the experiment. NERSC will be the principal site for data processing and analyses throughout the course of the experiment.

    NERSC Cray XC40 Cori II supercomputer

    LBL NERSC Cray XC30 Edison supercomputer

    The Genepool system is a cluster dedicated to the DOE Joint Genome Institute’s computing needs. Denovo is a smaller test system for Genepool that is primarily used by NERSC staff to test new system configurations and software.


    PDSF is a networked distributed computing cluster designed primarily to meet the detector simulation and data analysis requirements of physics, astrophysics and nuclear science collaborations.

    In a 2015 report of the U.S. Nuclear Science Advisory Committee to the Department of Energy and the National Science Foundation, a U.S.-led ton-scale experiment to detect neutrinoless double-beta decay was deemed a top priority for the nuclear physics community. Nearly a dozen experiments have sought neutrinoless double-beta decay, and as many future experiments have been proposed. One of their keys to success depends on avoiding background radiation that could mimic the signal of neutrinoless double-beta decay.

    That was the key accomplishment of the MAJORANA DEMONSTRATOR. Its implementation was completed in South Dakota in September 2016, nearly a mile underground at the Sanford Underground Research Facility.

    SURF-Sanford Underground Research Facility

    SURF Above Ground

    SURF Out with the Old

    SURF An Empty Slate

    SURF Carving New Space

    SURF Shotcreting

    SURF Bolting and Wire Mesh

    SURF Outfitting Begins

    SURF circular wooden frame was built to form a concrete ring to hold the 72,000-gallon (272,549 liters) water tank that would house the LUX dark matter detector

    SURF LUX water tank was transported in pieces and welded together in the Davis Cavern

    SURF Ground Support

    SURF Dedicated to Science

    SURF Building a Ship in a Bottle

    SURF Tight Spaces

    SURF Ready for Science

    SURF Entrance Before Outfitting

    SURF Entrance After Outfitting

    SURF Common Corridior

    SURF Davis

    SURF Davis A World Class Site

    SURF Davis a Lab Site

    SURF DUNE LBNF Caverns at Sanford Lab

    FNAL DUNE Argon tank at SURF

    U Washington LUX Xenon experiment at SURF

    SURF Before Majorana

    U Washington Majorana Demonstrator Experiment at SURF

    Siting the experiment under nearly a mile of rock was the first of many steps collaborators took to reduce interference from background levels of radiation. Other steps included a cryostat made of the world’s purest copper and a complex six-layer shield to eliminate interference from cosmic rays, radon, dust, fingerprints, and naturally occurring radioactive isotopes.

    “If you’re going to search for neutrinoless double-beta decay, it’s critical to know that radioactive background is not going to overwhelm the signal you seek,” said ORNL’s David Radford, a lead scientist in the experiment.

    There are many ways for an atomic nucleus to fall apart. A common decay mode happens when a neutron inside the nucleus emits an electron (called a “beta”) and an antineutrino to become a proton. In two-neutrino double-beta decay, two neutrons decay simultaneously to produce two protons, two electrons, and two antineutrinos. This process has been observed. The MAJORANA Collaboration seeks evidence for a similar decay process that has never been observed, in which no neutrinos are emitted.

    Conservation of the number of leptons – subatomic particles such as electrons, muons, or neutrinos that do not take part in strong interactions – was written into the Standard Model of particle physics. “There is no really good reason for this, just the observation that it appears that’s the case,” said Radford. “But if lepton number is not conserved, when added to processes that we think happened during the very early universe, that could help explain why there is more matter than antimatter.”

    Many theorists believe that the lepton number is not conserved: that the neutrino and the antineutrino – which were assumed to have opposite lepton numbers – are really the same particle spinning in different ways. Italian physicist Ettore Majorana introduced that concept in 1937, predicting the existence of particles that are their own antiparticles.

    The MAJORANA DEMONSTRATOR uses germanium crystals as both the source of double-beta decay and the means to detect it. Germanium-76 (Ge-76) decays to become selenium-76, which has a smaller mass. When germanium decays, mass gets converted to energy that is carried away by the electrons and the antineutrinos. “If all that energy goes to the electrons, then none is left for neutrinos,” Radford said. “That’s a clear identifier that we found the event we’re looking for.”

    The scientists distinguish two-neutrino vs. neutrinoless decay modes by their energy signatures. “It’s a common misconception that our experiments detect neutrinos,” said Jason Detwiler of the University of Washington, who is a co-spokesperson for the MAJORANA Collaboration and a former Glenn T. Seaborg Postdoctoral Fellow at Berkeley Lab. “It’s almost comical to say it, but we are searching for the absence of neutrinos. In the neutrinoless decay, the released energy is always a particular value. In the two-neutrino version, the released energy varies but is always smaller than it is for neutrinoless double-beta decay.”

    The MAJORANA DEMONSTRATOR has shown that the neutrinoless double-beta decay half-life of Ge-76 is at least 1025 years – 15 orders of magnitude longer than the age of the universe. So it’s impossible to wait for a single germanium nucleus to decay. “We get around the impossibility of watching one nucleus for a long time by instead watching on the order of 1026 nuclei for a shorter amount of time,” explained co-spokesperson Vincente Guiseppe of the University of South Carolina.

    Chances of spotting a neutrinoless double-beta decay in Ge-76 are rare – no more than 1 for every 100,000 two-neutrino double-beta decays, Guiseppe said. Using detectors containing large amounts of germanium atoms increases the probability of spotting the rare decays. Between June 2015 and March 2017, the scientists observed no events with the energy profile of neutrinoless decay, the process that has not yet been observed. (This was expected given the small number of germanium nuclei in the detector). However, they were encouraged to see many events with the energy profile of two-neutrino decays, verifying the detector could spot the decay process that has been observed.

    Strings of MAJORANA detectors are shown here. Each cylindrical “string” features stacks of germanium crystals separated by ultrapure copper components. (Credit: Matthew Kapust/Sanford Underground Research Facility).

    The MAJORANA Collaboration’s results coincide with new results from a competing experiment in Italy called GERDA (for GERmanium Detector Array), which takes a complementary approach to studying the same phenomenon.

    MPG GERmanium Detector Array (GERDA) at Gran Sasso, Italy

    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in L’Aquila, Italy

    “The MAJORANA DEMONSTRATOR and GERDA together have the lowest background of any neutrinoless double-beta decay experiment,” said Radford.

    The DEMONSTRATOR was designed to lay the groundwork for a ton-scale experiment by demonstrating that backgrounds can be low enough to justify building a larger detector. Just as bigger telescopes collect more light and enable viewing of fainter objects, increasing the mass of germanium allows for a greater probability of observing the rare decay. With 30 times more germanium than the current experiment, the planned one-ton experiment would be able to spot the neutrinoless double-beta decay of just one germanium nucleus per year.

    The MAJORANA DEMONSTRATOR is planned to continue taking data for two or three years. Meanwhile, a merger with GERDA is in the works to develop a possible one-ton detector called LEGEND, planned to be built in stages at an as-yet-to-be-determined site.

    Poon said, “Our data demonstrates that the background signals are low enough that we can actually build a bigger detector.”

    LEGEND 200, the LEGEND demonstrator, represents a step toward a possible future ton-scale experiment that will be a combination of GERDA, MAJORANA, and new detectors. Scientists hope to start on the first stage of LEGEND 200 by 2021. A ton-scale experiment, LEGEND 1000, would be the next stage, if approved.

    “This merger leverages public investments in the MAJORANA DEMONSTRATOR and GERDA by combining the best technologies of each,” said LEGEND Collaboration co-spokesperson (and long-time MAJORANA spokesperson up until last year) Steve Elliott of Los Alamos National Laboratory.

    Funding came from the U.S. Department of Energy Office of Science and the U.S. National Science Foundation. The Russian Foundation for Basic Research and Laboratory Directed Research and Development programs of DOE’s Los Alamos, Lawrence Berkeley, and Pacific Northwest national laboratories provided support. The research used resources of the Oak Ridge Leadership Computing Facility and NERSC, which are DOE Office of Science User Facilities at ORNL and Berkeley Lab, respectively. Sanford Underground Research Facility hosted and collaborated on the experiment.

    See the full article here .

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  • richardmitnick 9:17 am on September 19, 2017 Permalink | Reply
    Tags: GERDA collaboration, LEGEND 200, , ,   

    From SURF: “Majorana Demonstrator: Preparing to scale up” 

    SURF logo
    Sanford Underground levels

    Sanford Underground Research facility

    September 11, 2017
    Constance Walter

    John Wilkerson (left) and Cabot-Ann Christofferson work on the systems for the Majorana experiment, which sits inside a six-layered shield to block backgrounds. Photo by Matt Kapust

    For years, the Majorana Demonstrator laboratories and machine shop bustled with activity. Dozens of collaboration members worked on various elements of the experiment— from electroforming copper to building a shield to machining every component for the detectors and cryostats. Today, nestled deep within its six-layered shield, Majorana quietly collects data with just a handful of team members to ensure things are working.

    “We’ve made the transition from managing construction to overseeing an operation,” said Vince Guiseppe, assistant professor of physics at the University of South Carolina. “Since the winter, we’ve been running smoothly.”

    The Majorana Demonstrator uses natural and enriched germanium crystals to look for neutrinoless double-beta decay. Such a discovery could determine whether the neutrino is its own antiparticle.

    U Washington Majorana Demonstrator Experiment at SURF

    But the project is, first and foremost, a demonstrator, a research and development project built on a small scale to determine whether a 1-ton version is feasible, said Steve Elliott of Los Alamos National Laboratory. “For it to be feasible, we have to show that backgrounds can be low enough to justify building such a next-generation experiment.”

    Which Majorana has done, Guiseppe said. “We’ve only been running for about a year and we appear to be meeting those goals. Our backgrounds are excellent.”

    Guiseppe recently became a co-spokesperson for the project, along with Jason Detwiler of the University of Washington. The two replace Elliott, who will become co-spokesperson for LEGEND, the recently formed collaboration that will develop a much larger next-generation neutrinoless double-beta decay experiment

    The Large Enriched Germanium Experiment for Neutrinoless ββ Decay, or LEGEND, collaboration was formed a year ago and includes members of the Majorana Demonstrator collaboration, the GERDA (GERmanium Detector Array) collaboration, and other researchers in this field.

    The GERDA experiment has been proposed in 2004 as a new 76Ge double-beta decay experiment at LNGS. The GERDA installation is a facility with germanium detectors made out of isotopically enriched material. The detectors are operated inside a liquid argon shield. The experiment is located in Hall A of LNGS.

    GERDA and Majorana are searching for the same thing, but they’ve used different technologies to reach their goals. For example, where Majorana used electroformed copper and built a complicated six-layered shield to keep backgrounds out, GERDA used commercial copper and shielded its detector inside a tank of liquid argon, which scintillates, or lights up, when backgrounds enter.

    And both are seeing what they hoped to see: low backgrounds. “They’ve done a lot of nice things, we’ve done a lot of nice things and there are some things we both did very well.” Guiseppe said. “And we’ve both demonstrated we can get the backgrounds we want. LEGEND will take the best features of each experiment.”

    The LEGEND collaboration wants to scale up to 1,000 kg of enriched germanium. By comparison, Majorana and GERDA each use approximately 30 kg in their experiments. But the plan is to start smaller, with a 200-kg experiment.

    “LEGEND 200 will be the first incarnation and will be the roadmap to get to the ton-scale experiment,” Guiseppe said.

    “The good news is we have a great collaboration with great people. We have a common vision and design and funding plans are moving forward. This is not something one of us can do alone. It’s important to have international partners.”

    Although he’s looking to the future, Guiseppe remains focused on the here and now. “Both GERDA and Majorana have to complete their life cycles,” he said. “And there’s still a lot we can learn from running our current experiments.”

    See the full article here .

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    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.
    LUX/Dark matter experiment at SURFLUX/Dark matter experiment at SURF

    In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    Fermilab LBNE

  • richardmitnick 5:32 pm on April 5, 2017 Permalink | Reply
    Tags: , GERDA collaboration, , , Scientists Are Getting Closer to Understanding Where All the Antimatter Has Gone   

    From GIZMODO: “Scientists Are Getting Closer to Understanding Where All the Antimatter Has Gone’ 

    GIZMODO bloc


    Ryan F. Mandelbaum

    From Nature: “The fiber shroud of the liquid argon veto and the copper head for mounting the germanium strings. View from bottom.” Image: V. Wagner, GERDA collaboration

    You and me, we’re matter. Everyone you know is matter. Everything on Earth, spare a few particles, is matter. Most of the things in space are matter. But we don’t have convincing reasons why there should be so much more matter than antimatter. So where’s all the antimatter?

    A team of European scientists have taken a major step in understanding this conundrum, using a house-sized detector called the Germanium Detector Array, or GERDA, buried inside a mountain in Grand Sasso, Italy. GERDA’s scientists are looking for a strange behavior in radioactive atoms, called “neutrinoless double beta decay” (I’ll get to that in a second). Some versions of the rules of particle physics says this behavior could help explain where all the antimatter went. But for now, the experiment is reporting some important results: it works.

    “A discovery of [neutrinoless double beta] decay would have far-reaching consequences for our understanding of particle physics and cosmology,” the researchers write in the paper, published today in the journal Nature. It’s important that we understand why there is more matter than antimatter today. The Big Bang probably should have created equal amounts… but it didn’t [CERN].

    If you’ve got a good handle on what neutrinoless double beta decay is, you can skip the next three paragraphs. If not, it’s time for a break from our regular programming.

    Matter is stuff, and it’s made of particles. Antimatter is also stuff, made from the particles’ antiparticle counterparts. We’ve made it in labs and some radioactive elements produce it. Every particle has an antiparticle, like electrons and positrons, which have the same mass, but opposite electric charge. If they meet, they annihilate each other in a burst of energy. There is not a lot of antimatter in the universe. Capisce?

    From Nature: “The inner walls of the water tank are covered by a reflecting foil improving the light detection. This permits the identification of cosmic muons.” Image: K. Freund, GERDA collaboration

    Neutrinos, they’re weird. Scientists don’t know how much they weigh, but even at the upper limit of what we guess their mass is, they’re many times lighter than electrons. They’re also really common—for example, the sun sending almost a hundred billion of them per square centimeter of your body every second. They don’t interact via electromagnetism, though, so they don’t harm us in any way. If they were their own antiparticle, what scientists call “Majorana particles,” they should annihilate one another. Most extensions of our main theory of particle physics, called the Standard Model, say this is true.

    So, the key is to build an experiment that can test whether neutrinos are annihilating one another, and to look for a process that should usually create neutrinos, but doesn’t. In this case, that process is radioactive beta decay, where the neutral neutron turns into a positive proton, a negative electron, and an antineutrino. Some forms of some atoms, like germanium should go through double beta decay, where two neutrons decay simultaneously. If scientists observe double beta decay without any neutrinos (or antineutrinos), then they can say they’ve spotted this neutrinoless double beta decay. This would demonstrate that neutrinos and antineutrinos are essentially the same, and convince us that our physics theories can explain why there’s more matter than antimatter.

    From Nature: “Working on the germanium detector array within the glove box which is located in the clean room on top of the liquid argon cryostat.” (Image: J. Suvorov, GERDA collaboration)

    That’s what GERDA is looking for. They’re watching 35.6 kilograms of a special form of germanium, the shiny semiconducting metal, sitting inside a vat of liquid argon inside a bigger vat of water, waiting however long it takes for it to experience a neutrinoless double beta decay. No, they haven’t found any evidence of the process yet. But their experiment works really, really well—there’s no background noise, which is an incredible feat. Otherwise, we might see a false signal. And there’s radiation that could set off the detector everywhere, from the sun to the air we breathe.

    “Imagine running a radiation detector for a year and seeing nothing! It’s quite an experience,” said Duke physicist Phillip Barbeau, who is not involved in the GERDA collaboration, in an interview with Gizmodo. “We need discerning detectors, ones that avoid sources of these backgrounds by going deep underground, avoiding dust, building them in clean rooms, avoiding cosmic activation of these materials. After all, they can turn radioactive simply by being above ground.”

    Scientists are at least sure that the experiment is working, and not just turned off, by the way. “People would give them the benefit of the doubt,” said Barbeau. But “it’s a difficult experiment to run because you see nothing in the detector.”

    But there are plenty of other complicating factors in this process aside from getting rid of all the outside noise. Most processes we’ve observed in the universe conserves a property called lepton number. In theory, the number of leptons (neutrinos and electrons are examples of leptons) minus the number of antileptons should remain the same before and after some physical reaction. Regular beta decay starts with a lepton number of zero and ends with zero (one electron minus one antineutrino). Neutrinoless double beta decay starts with zero and ends with two. As a note, we want to see this violation happen. I’m just pointing out that this decay is breaking a not-that-well-supported rule.

    And the neutrinoless double beta decay is really, really rare—its half life, the amount of time it takes for half of the possible events to happen, is several times the age of the universe. So scientists might have to sit and watch this vat for a very, very long time. But hey, that’s why they have so much germanium.

    GERDA isn’t the only experiment looking for this decay—there’s the MAJORANA experiment, the CUORE-0, COBRA, and others.

    U Washington Majorana Demonstrator Experiment at SURF

    Yale CUORE-0

    Anyway, now that we’ve got the working GERDA detector…it’s time to watch and wait.

    Yale CUORE-0

    If we don’t spot this decay, we might just have to go looking for other evidence of neutrinos being their own antiparticles. And there’s so much more about neutrinos we don’t know—we can’t even accurately measure their mass, for example.

    See the full article here .

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