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  • richardmitnick 10:24 am on April 2, 2018 Permalink | Reply
    Tags: , , , Neutrinoless double beta decay, , , ,   

    From CNN: “Why the universe shouldn’t exist at all” 

    1
    CNN

    April 1, 2018

    FNAL’s Don Lincoln

    Don Lincoln, a senior physicist at Fermilab, does research using the Large Hadron Collider. He is the author of The Large Hadron Collider: The Extraordinary Story of the Higgs Boson and Other Stuff That Will Blow Your Mind, and produces a series of science education videos. Follow him on Facebook. The opinions expressed in this commentary are his.

    Why is there something, rather than nothing?” could be the oldest and deepest question in all of metaphysics. Long exclusively the province of philosophy, in recent years this question has become one that can be addressed by scientific methods. What’s more, a new scientific advance has made it more likely that we will finally be able to answer this cosmic conundrum. This is a big deal, because the simplest scientific answer to that question is “We shouldn’t exist at all.”

    Obviously, we know that there must be something, because we’re here. If there were nothing, we couldn’t ask the question. But why? Why is there something? Why is the universe not a featureless void? Why does our universe have matter and not only energy? It might seem surprising, but given our current theories and measurements, science cannot answer those questions.

    However, give some scientists 65 pounds of a rare isotope of germanium, cool it to temperatures cold enough to liquify air, and place their equipment nearly a mile underground in an abandoned gold mine, and you’ll have the beginnings of an answer. Their project is called the Majorana Demonstrator and it is located at the Sanford Underground Research Facility, near Lead, South Dakota.

    U Washington Majorana Demonstrator Experiment at SURF

    Science paper om Majorana Demonstrator project
    Initial Results from the Majorana Demonstrator
    Journal of Physics: Conference Series

    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

    To grasp why science has trouble explaining why matter exists — and to understand the scientific achievement of Majorana — we must first know a few simple things. First, our universe is made exclusively of matter; you, me, the Earth, even distant galaxies. All of it is matter.

    However, our best theory for explaining the behavior of the matter and energy of the universe contradicts the realities that we observe in the universe all around us. This theory, called the Standard Model, says that the matter of the universe should be accompanied by an identical amount of antimatter, which, as its name suggests, is a substance antagonistic to matter. Combine equal amounts of matter and antimatter and it will convert into energy.

    And the street goes both ways: Enough energy can convert into matter and antimatter. (Fun fact: Combining a paper clip’s worth of matter and antimatter will result in the same energy released in the atomic explosion at Hiroshima. Don’t worry though; since antimatter’s discovery in 1931, we have only been able to isolate enough of it to make about 10 pots of coffee.)

    An enigma about the relative amounts of matter and antimatter in the universe arises when we think about how the universe came to be. Modern cosmology says the universe began in an unimaginable Big Bang — an explosion of energy. In this theory, equal amounts of matter and antimatter should have resulted.

    So how is our universe made exclusively of matter? Where did the antimatter go?

    The simplest answer is that we don’t know. In fact, it remains one of the biggest unanswered problems of modern physics.

    Just because the question of missing antimatter is unanswered doesn’t mean that scientists are completely clueless. Beginning in 1964 and continuing through to the present day, physicists have studied the problem and we have found out that early in the universe there was a slight asymmetry in the laws of nature that treated matter and antimatter differently.

    Very approximately, for every billion antimatter subatomic particles that were made in the Big Bang, there were a billion-and-one matter particles. The billion matter and antimatter particles were annihilated, leaving the small amount of leftover matter (the “one”) that went on to make up the universe we see around us. This is accepted science.

    However, we don’t know the process whereby the asymmetry in the laws of the universe arose. One possible explanation revolves around a class of subatomic particles called leptons.

    The most well-known of the leptons is the familiar electron, found around atoms. However, a less known lepton is called the neutrino. Neutrinos are emitted in a particular kind of nuclear radiation, called beta decay. Beta decay occurs when a neutron in an atom decays into a proton, an electron, and a neutrino.

    Neutrinos are fascinating particles. They interact extremely weakly; a steady barrage of neutrinos from the nuclear reactions in the sun pass through the entire Earth essentially without interacting. Because they interact so little, they are very difficult to detect and study. And that means that there are properties of neutrinos that we still don’t understand.

    Still a mystery to scientists is whether there is a difference between neutrino matter and neutrino antimatter. While we know that both exist, we don’t know if they are different subatomic particles or if they are the same thing. That’s a heavy thought, so perhaps an analogy will help.

    Imagine you have a set of twins, with each twin standing in for the matter and antimatter neutrinos. If the twins are fraternal, you can tell them apart, but if they are identical, you can’t. Essentially, we don’t know which kind of twins the neutrino matter/antimatter pair are.

    If neutrinos are their own antimatter particle, it would be an enormous clue in the mystery of the missing antimatter. So, naturally, scientists are working to figure this out.

    The way they do that is to look first for a very rare form of beta decay, called double beta decay. That’s when two neutrons in the nucleus of an atom simultaneously decay. In this process, two neutrinos are emitted. Scientists have observed this kind of decay.

    However, if neutrinos are their own antiparticle, an even rarer thing can occur called “neutrinoless double beta decay.” In this process, the neutrinos are absorbed before they get outside of the nucleus. In this case, no neutrinos are emitted. This process has not been observed and this is what scientists are looking for. The observation of a single, unambiguous neutrinoless double beta decay would show that matter and antimatter neutrinos were the same.

    If indeed neutrinoless double beta decay exists, it’s very hard to detect and it’s important that scientists can discriminate between the many types of radioactive decay that mimic that of a neutrino. This requires the design and construction of very precise detectors.

    So that’s what the Majorana Demonstrator scientists achieved. They developed the technology necessary to make this very difficult differentiation. This demonstration paints a way forward for a follow-up experiment that can, once and for all, answer the question of whether matter and antimatter neutrinos are the same or different. And, with that information in hand, it might be possible to understand why our universe is made only of matter.

    For millennia, introspective thinkers have pondered the great questions of existence. Why are we here? Why is the universe the way it is? Do things have to be this way? With this advance, scientists have taken a step forward in answering these timeless questions.

    See the full article here .

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  • richardmitnick 12:53 pm on March 29, 2018 Permalink | Reply
    Tags: , Gran Sasso National Laboratories (LNGS), Is the neutrino is its own antiparticle?, , Neutrinoless double beta decay   

    From MIT News: “Scientists report first results from CUORE neutrino experiment” 

    MIT News

    MIT Widget

    MIT News

    March 26, 2018
    Jennifer Chu

    1
    Researchers working on the cryostat. Image: CUORE Collaboration

    Data could shed light on why the universe has more matter than antimatter.

    This week, an international team of physicists, including researchers at MIT, is reporting the first results from an underground experiment designed to answer one of physics’ most fundamental questions: Why is our universe made mostly of matter?

    According to theory, the Big Bang should have produced equal amounts of matter and antimatter — the latter consisting of “antiparticles” that are essentially mirror images of matter, only bearing charges opposite to those of protons, electrons, neutrons, and other particle counterparts. And yet, we live in a decidedly material universe, made mostly of galaxies, stars, planets, and everything we see around us — and very little antimatter.

    Physicists posit that some process must have tilted the balance in favor of matter during the first moments following the Big Bang. One such theoretical process involves the neutrino — a particle that, despite having almost no mass and interacting very little with other matter, is thought to permeate the universe, with trillions of the ghostlike particles streaming harmlessly through our bodies every second.

    There is a possibility that the neutrino may be its own antiparticle, meaning that it may have the ability to transform between a matter and antimatter version of itself. If that is the case, physicists believe this might explain the universe’s imbalance, as heavier neutrinos, produced immediately after the Big Bang, would have decayed asymmetrically, producing more matter, rather than antimatter, versions of themselves.

    One way to confirm that the neutrino is its own antiparticle, is to detect an exceedingly rare process known as a “neutrinoless double-beta decay,” in which a stable isotope, such as tellurium or xenon, gives off certain particles, including electrons and antineutrinos, as it naturally decays. If the neutrino is indeed its own antiparticle, then according to the rules of physics the antineutrinos should cancel each other out, and this decay process should be “neutrinoless.” Any measure of this process should only record the electrons escaping from the isotope.

    The underground experiment known as CUORE, for the Cryogenic Underground Observatory for Rare Events, is designed to detect a neutrinoless double-beta decay from the natural decay of 988 crystals of tellurium dioxide.

    CUORE experiment,at the Italian National Institute for Nuclear Physics’ (INFN’s) Gran Sasso National Laboratories (LNGS) in Italy,a search for neutrinoless double beta decay

    In a paper published this week in Physical Review Letters, researchers, including physicists at MIT, report on the first two months of data collected by CUORE (Italian for “heart”). And while they have not yet detected the telltale process, they have been able to set the most stringent limits yet on the amount of time that such a process should take, if it exists at all. Based on their results, they estimate that a single atom of tellurium should undergo a neutrinoless double-beta decay, at most, once every 10 septillion (1 followed by 25 zeros) years.

    Taking into account the massive number of atoms within the experiment’s 988 crystals, the researchers predict that within the next five years they should be able to detect at least five atoms undergoing this process, if it exists, providing definitive proof that the neutrino is its own antiparticle.

    “It’s a very rare process — if observed, it would be the slowest thing that has ever been measured,” says CUORE member Lindley Winslow, a member of the Laboratory for Nuclear Science, and the Jerrold R. Zacharias Career Development Assistant Professor of Physics at MIT, who led the analysis. “The big excitement here is that we were able to run 998 crystals together, and now we’re on a path to try and see something.”

    The CUORE collaboration includes some 150 scientists primarily from Italy and the U.S., including Winslow and a small team of postdocs and graduate students from MIT.

    Coldest cube in the universe

    The CUORE experiment is housed underground, in the Italian National Institute for Nuclear Physics’ (INFN) Gran Sasso National Laboratories, buried deep within a mountain in central Italy, in order to shield it from external stimuli such as the constant bombardment of radiation from sources in the universe.

    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy

    The heart of the experiment is a detector consisting of 19 towers, each containing 52 cube-shaped crystals of tellurium dioxide, totaling 988 crystals in all, with a mass of about 742 kilograms, or 1,600 pounds. Scientists estimate that this amount of crystals embodies around 100 septillion atoms of the particular tellurium isotope. Electronics and temperature sensors are attached to each crystal to monitor signs of their decay.

    The entire detector resides within an ultracold refrigerator, about the size of a vending machine, which maintains a steady temperature of 6 millikelvin, or -459.6 degrees Fahrenheit. Researchers in the collaboration have previously calculated that this refrigerator is the coldest cubic meter that exists in the universe.

    The experiment needs to be kept exceedingly cold in order to detect minute changes in temperature generated by the decay of a single tellurium atom. In a normal double-beta decay process, a tellurium atom gives off two electrons, as well as two antineutrinos, which amount to a certain energy in the form of heat. In the event of a neutrinoless double-beta decay, the two antineutrinos should cancel each other out, and only the energy released by the two electrons would be generated. Physicists have previously calculated that this energy must be around 2.5 megaelectron volts (Mev).

    In the first two months of CUORE’s operation, scientists have essentially been taking the temperature of the 988 tellurium crystals, looking for any miniscule spike in energy around that 2.5 Mev mark.

    “CUORE is like a gigantic thermometer,” Winslow says. “Whenever you see a heat deposit on a crystal, you end up seeing a pulse that you can digitize. Then you go through and look at these pulses, and the height and width of the pulse corresponds to how much energy was there. Then you zoom in and count how many events were at 2.5 Mev, and we basically saw nothing. Which is probably good because we weren’t expecting to see anything in the first two months of data.”

    The heart will go on

    The results more or less indicate that, within the short window in which CUORE has so far operated, not one of the 1,000 septillion tellurium atoms in the detector underwent a neutrinoless double-beta decay. Statistically speaking, this means that it would take at least 10 septillion years, or years, for a single atom to undergo this process if a neutrino is in fact its own antiparticle.

    “For tellurium dioxide, this is the best limit for the lifetime of this process that we’ve ever gotten,” Winslow says.

    CUORE will continue to monitor the crystals for the next five years, and researchers are now designing the experiment’s next generation, which they have dubbed CUPID — a detector that will look for the same process within an even greater number of atoms. Beyond CUPID, Winslow says there is just one more, bigger iteration that would be possible, before scientists can make a definitive conclusion.

    “If we don’t see it within 10 to 15 years, then, unless nature chose something really weird, the neutrino is most likely not its own antiparticle,” Winslow says. “Particle physics tells you there’s not much more wiggle room for the neutrino to still be its own antiparticle, and for you not to have seen it. There’s not that many places to hide.”

    This research is supported by the National Institute for Nuclear Physics (INFN) in Italy, the National Science Foundation, the Alfred P. Sloan Foundation, and the U.S. Department of Energy.

    See the full article here .

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  • richardmitnick 1:05 pm on March 26, 2018 Permalink | Reply
    Tags: Gan Sasso Laboratory, , , , Neutrinoless double beta decay,   

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

    Berkeley Logo

    Berkeley Lab

    March 26, 2018
    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 486-5582

    1
    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.

    3
    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.

    NERSC PDSF


    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.

    4
    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.

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  • richardmitnick 10:06 am on February 26, 2018 Permalink | Reply
    Tags: , , Neutrinoless double beta decay,   

    From ScienceNews: “The quest to identify the nature of the neutrino’s alter ego is heating up” 


    ScienceNews

    February 26, 2018
    Emily Conover

    Physicists are trying to see if the particle’s matter and antimatter versions are the same.

    1
    ANTIMATTER MYSTERY Physicists suspect that the neutrino may be its own antiparticle. Experiments such as GERDA (shown) are attempting to determine whether that hunch is correct by searching for a rare type of nuclear decay. K. Freund/GERDA collaboration

    Galaxies, stars, planets and life, all are formed from one essential substance: matter.

    But the abundance of matter is one of the biggest unsolved mysteries of physics. The Big Bang, 13.8 billion years ago, spawned equal amounts of matter and its bizarro twin, antimatter. Matter and antimatter partners annihilate when they meet, so an even-stephen universe would have ended up full of energy — and nothing else. Somehow, the balance tipped toward matter in the early universe.

    A beguiling subatomic particle called a neutrino may reveal how that happened. If neutrinos are their own antiparticles — meaning that the neutrino’s matter and antimatter versions are the same thing — the lightweight particle might point to an explanation for the universe’s glut of matter.

    So scientists are hustling to find evidence of a hypothetical kind of nuclear decay that can occur only if neutrinos and antineutrinos are one and the same. Four experiments have recently published results showing no hint of the process, known as neutrinoless double beta decay (SN: 7/6/02, p. 10). But another attempt, set to begin soon, may have a fighting chance of detecting this decay, if it occurs. Meanwhile, planning is under way for a new generation of experiments that will make even more sensitive measurements.

    “Right now, we’re standing on the brink of what potentially could be a really big discovery,” says Janet Conrad, a neutrino physicist at MIT not involved with the experiments.

    A league of its own

    Each matter particle has an antiparticle, a partner with the opposite electric charge. Electrons have positrons as partners; protons have antiprotons. But it’s unclear how this pattern applies to neutrinos, which have no electric charge.

    Rather than having distinct matter and antimatter varieties, neutrinos might be the lone example of a theorized class of particle dubbed a Majorana fermion (SN: 8/19/17, p. 8), which are their own antiparticles. “No other particle that we know of could have this property; the neutrino is the only one,” says neutrino physicist Jason Detwiler of the University of Washington in Seattle, who is a member of the KamLAND-Zen and Majorana Demonstrator neutrinoless double beta decay experiments.

    Neutrinoless double beta decay is a variation on standard beta decay, a relatively common radioactive process that occurs naturally on Earth. In beta decay, a neutron within an atom’s nucleus converts into a proton, releasing an electron and an antineutrino. The element thereby transforms into another one further along the periodic table.

    ______________________________________________________
    Beta decays

    The standard type of beta decay (left) occurs when a neutron in an atom’s nucleus converts into a proton and releases an electron (blue, e-) and an antineutrino (red). For certain species of atoms, two such decays can happen at once (middle). If the neutrino is its own antiparticle, those double beta decays could also occur without any emitted antineutrinos (right).

    2
    ______________________________________________________

    In certain isotopes of particular elements — species of atoms characterized by a given number of protons and neutrons — two beta decays can occur simultaneously, emitting two electrons and two antineutrinos. Although double beta decay is exceedingly rare, it has been detected. If the neutrino is its own antiparticle, a neutrino-free version of this decay might also occur: In a rarity atop a rarity, the antineutrino emitted in one of the two simultaneous beta decays might be reabsorbed by the other, resulting in no escaping antineutrinos.

    Such a process “creates asymmetry between matter and antimatter,” says physicist Giorgio Gratta of Stanford University, who works on the EXO-200 neutrinoless double beta decay experiment.

    SLAC EXO-200 Enriched Xenon Observatory near Carlsbad, New Mexico

    In typical beta decay, one matter particle emitted — the electron — balances out the antimatter particle — the antineutrino. But in neutrinoless double beta decay, two electrons are emitted with no corresponding antimatter particles. Early in the universe, other processes might also have behaved in a similarly asymmetric way.

    On the hunt

    To spot the unusual decay, scientists are building experiments filled with carefully selected isotopes of certain elements and monitoring the material for electrons of a particular energy, which would be released in the neutrinoless decay.

    If any experiment observes this process, “it would be a huge deal,” says particle physicist Yury Kolomensky of the University of California, Berkeley, a member of the CUORE neutrinoless double beta decay experiment. “It is a Nobel Prize‒level discovery.”

    CUORE experiment UC Berkeley, experiment at the Italian National Institute for Nuclear Physics’ (INFN’s) Gran Sasso National Laboratories (LNGS), a search for neutrinoless double beta decay

    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy

    Unfortunately, the latest results won’t be garnering any Nobels. In a paper accepted in Physical Review Letters, the GERDA experiment spotted no signs of the decay. Located in the Gran Sasso underground lab in Italy, GERDA looks for the decay of the isotope germanium-76. (The number indicates the quantity of protons and neutrons in the atom’s nucleus.) Since there were no signs of the decay, if the process occurs it must be extremely rare, the scientists concluded, and its half-life must be long — more than 80 trillion trillion years.

    Three other experiments have also recently come up empty. The Majorana Demonstrator experiment, located at the Sanford Underground Research Facility in Lead, S.D., which also looks for the decay in germanium, reported no evidence of neutrinoless double beta decay in a paper accepted in Physical Review Letters.

    U Washington Majorana Demonstrator Experiment at SURF

    Meanwhile, EXO-200, located in the Waste Isolation Pilot Plant, underground in a salt deposit near Carlsbad, N.M., reported no signs of the decay in xenon-136 in a paper published in the Feb. 16 Physical Review Letters.

    Likewise, no evidence for the decay materialized in the CUORE experiment, in results reported in a paper accepted in Physical Review Letters. Composed of crystals containing tellurium-130, CUORE is also located in the Gran Sasso underground lab.

    The most sensitive search thus far comes from the KamLAND-Zen neutrinoless double beta decay experiment located in a mine in Hida, Japan, which found a half-life longer than 100 trillion trillion years for the neutrinoless double beta decay of xenon-136.


    KamLAND at the Kamioka Observatory in located in a mine in Hida, Japan

    That result means that, if neutrinos are their own antiparticles, their mass has to be less than about 0.061 to 0.165 electron volts depending on theoretical assumptions, the KamLAND-Zen collaboration reported in a 2016 paper in Physical Review Letters. (An electron volt is particle physicists’ unit of energy and mass. For comparison, an electron has a much larger mass of half a million electron volts.)

    Neutrinos, which come in three different varieties and have three different masses, are extremely light, but exactly how tiny those masses are is not known. Mass measured by neutrinoless double beta decay experiments is an effective mass, a kind of weighted average of the three neutrino masses. The smaller that mass, the lower the rate of the neutrinoless decays (and therefore the longer the half-life), and the harder the decays are to find.

    KamLAND-Zen looks for decays of xenon-136 dissolved in a tank of liquid. Now, KamLAND-Zen is embarking on a new incarnation of the experiment, using about twice as much xenon, which will reach down to even smaller masses, and even rarer decays. Finding neutrinoless double beta decay may be more likely below about 0.05 electron volts, where neutrino mass has been predicted to lie if the particles are their own antiparticles.

    Supersizing the search

    KamLAND-Zen’s new experiment is only a start. Decades of additional work may be necessary before scientists clinch the case for or against neutrinos being their own antiparticles. But, says KamLAND-Zen member Lindley Winslow, a physicist at MIT, “sometimes nature is very kind to you.” The experiment could begin taking data as early as this spring, says Winslow, who is also a member of CUORE.

    To keep searching, experiments must get bigger, while remaining extremely clean, free from any dust or contamination that could harbor radioactive isotopes. “What we are searching for is a decay that is very, very, very rare,” says GERDA collaborator Riccardo Brugnera, a physicist at the University of Padua in Italy. Anything that could mimic the decay could easily swamp the real thing, making the experiment less sensitive. Too many of those mimics, known as background, could limit the ability to see the decays, or to prove that they don’t occur.

    In a 2017 paper in Nature, the GERDA experiment deemed itself essentially free from background — a first among such experiments. Reaching that milestone is good news for the future of these experiments. Scientists from GERDA and the Majorana Demonstrator are preparing to team up on a bigger and better experiment, called LEGEND, and many other teams are also planning scaled-up versions of their current detectors.

    Antimatter whodunit

    If scientists conclude that neutrinos are their own antiparticles, that fact could reveal why antimatter is so scarce. It could also explain why neutrinos are vastly lighter than other particles. “You can kill multiple problems with one stone,” Conrad says.

    Theoretical physicists suggest that if neutrinos are their own antiparticles, undetected heavier neutrinos might be paired up with the lighter neutrinos that we observe. In what’s known as the seesaw mechanism, the bulky neutrino would act like a big kid on a seesaw, weighing down one end and lifting the lighter neutrinos to give them a smaller mass. At the same time, the heavy neutrinos — theorized to have existed at the high energies present in the young universe — could have given the infant cosmos its early preference for matter.

    Discovering that neutrinos are their own antiparticles wouldn’t clinch the seesaw scenario. But it would provide a strong hint that neutrinos are essential to explaining where the antimatter went. And that’s a question physicists would love to answer.

    “The biggest mystery in the universe is who stole all the antimatter. There’s no bigger theft that has occurred than that,” Conrad says.

    Citations

    J.B. Albert et al. Search for neutrinoless double-beta decay with the upgraded EXO-200 detector. Physical Review Letters. Vol. 120, February 16, 2018, p. 072701. doi: 10.1103/PhysRevLett.120.072701.

    C.E. Aalseth et al. Search for zero-neutrino double beta decay in 76Ge with the Majorana demonstrator. Physical Review Letters, in press, 2018.

    M. Agostini et al. Improved limit on neutrinoless double beta decay of 76Ge from GERDA Phase II. Physical Review Letters, in press, 2018.

    CUORE Collaboration. First results from CUORE: a search for lepton number violation via 0νββ decay of 130Te. Physical Review Letters, in press, 2018.

    KamLAND-Zen Collaboration. Search for majorana neutrinos near the inverted mass hierarchy region with KamLAND-Zen. Physical Review Letters. Vol. 117, August 19, 2017, p. 082503. doi:10.1103/PhysRevLett.117.082503.

    The GERDA Collaboration. Background-free search for neutrinoless double-β decay of 76Ge with GERDA. Nature. Vol. 544, April 6, 2017, p. 47. doi:10.1038/nature21717.

    See the full article here .

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  • richardmitnick 3:54 pm on December 12, 2017 Permalink | Reply
    Tags: , How Neutrinos Could Solve The Three Greatest Open Questions In Physics, Neutrinoless double beta decay, Standard Model of cosmology, Standard Model of Cosmology Timeline, ,   

    From Ethan Siegel: “How Neutrinos Could Solve The Three Greatest Open Questions In Physics” 

    Ethan Siegel
    Dec 12, 2017

    Dark matter, dark energy, and why there’s more matter than antimatter? There’s an experiment to explore if neutrinos could solve all three.

    1
    A detailed look at the Universe reveals that it’s made of matter and not antimatter, that dark matter and dark energy are required, and that we don’t know the origin of any of these mysteries. Image credit: Chris Blake and Sam Moorfield.

    When you take a look at the Universe in great detail, a few facts jump out at you that might be surprising. All the stars, galaxies, gas, and plasma out there are made of matter and not antimatter, even though the laws of nature appear symmetric between the two. In order to form the structures we see on the largest scales, we require a huge amount of dark matter: about five times as much as all the normal matter we possess. And to explain how the expansion rate has changed over time, we need a mysterious form of energy inherent to space itself that’s twice as important (as far as energy is concerned) as all the other forms combined: dark energy. These three puzzles may be the greatest cosmological problems for the 21st century, and yet the one particle that goes beyond the standard model — the neutrino — just might explain them all.

    2
    The particles and antiparticles of the Standard Model of particle physics are exactly in line with what experiments require, with only massive neutrinos providing a difficulty. Image credit: E. Siegel / Beyond the Galaxy.

    Standard Model of Particle Physics from Symmetry Magazine

    Here in the physical Universe, we have two types of Standard Model:

    The Standard Model of particle physics (above), with six flavors of quarks and leptons, their antiparticles, the gauge bosons, and the Higgs.
    The Standard Model of cosmology (below), with the inflationary Big Bang, matter and not antimatter, and a history of structure formation that leads to stars, galaxies, clusters, filaments, and the present-day Universe.

    4
    The matter and energy content in the Universe at the present time (left) and at earlier times (right). Note the presence of dark energy, dark matter, and the prevalence of normal matter over antimatter, which is so minute it does not contribute at any of the times shown. Image credit: NASA, modified by Wikimedia Commons user 老陳, modified further by E. Siegel.

    Both Standard Models are perfect in the sense that they explain everything we can observe, but both contain mysteries we cannot explain. From the particle physics side, there’s the mystery of why the particle masses have the values that they do, while on the cosmology side, there are the mysteries of what dark matter and dark energy are, and why (and how) they came to dominate the Universe.

    The Universe according to the Standard Model

    Standard Model of Cosmology Timeline

    The big problem in all of this is that the Standard Model of particle physics explains everything we’ve ever observed — every particle, interaction, decay, etc. — perfectly. We’ve never observed a single interaction in a collider, a cosmic ray, or any other experiment that runs counter to the Standard Model’s predictions. The only experimental hint we have that the Standard Model doesn’t give us everything we observe is the fact of neutrino oscillations: where one type of neutrino transforms into another as it passes through space, and through matter in particular. This can only happen if neutrinos have a small, tiny, non-zero mass, as opposed to the massless properties predicted by the Standard Model.

    5
    If you begin with an electron neutrino (black) and allow it to travel through either empty space or matter, it will have a certain probability of oscillating into one of the other two types, something that can only happen if neutrinos have very small but non-zero masses. Image credit: Wikimedia Commons user Strait.

    So, then, why and how do neutrinos get their masses, and why are those masses so tiny compared to everything else?

    6
    The mass difference between an electron, the lightest normal Standard Model particle, and the heaviest possible neutrino is more than a factor of 4,000,000, a gap even larger than the difference between the electron and the top quark. Image credit: Hitoshi Murayama.

    There’s even more bizarreness afoot when you take a closer look at these particles. You see, every neutrino we’ve ever observed is left-handed, meaning if you point your left-hand’s thumb in a certain direction, your fingers curl in the direction of the neutrino’s spin. Every anti-neutrino, on the other hand (literally), is right-handed: your right thumb points in its direction of motion and your fingers curl in the direction of the anti-neutrino’s spin. Every other fermion that exists has a symmetry between particles and antiparticles, including equal numbers of left-and-right-handed types. This bizarre property suggests that neutrinos are Majorana (rather than the normal Dirac) fermions, where they behave as their own antiparticles.

    Why could this be? The simplest answer is through an idea known as the see-saw mechanism.

    If you had “normal” neutrinos with typical masses — comparable to the other Standard Model particles (or the electroweak scale) — that would be expected. Left-handed neutrino and right-handed neutrinos would be balanced, and would have a mass of around 100 GeV. But if there were very heavy particles, like the yellow one (above) that existed at some ultra-high scale (around 10¹⁵ GeV, typical for the grand unification scale), they could land on one side of the see-saw. This mass would get mixed together with the “normal” neutrinos, and you’d get two types of particles out:

    . a stable, neutral, weakly interacting ultra-heavy right-handed neutrino (around 10¹⁵ GeV), made heavy by the heavy mass that landed on one side of the see-saw, and
    . a light, neutral, weakly interacting left-handed neutrino of the “normal” mass squared over the heavy mass: about (100 GeV)²/(10¹⁵ GeV), or around 0.01 eV.

    That first type of particle could easily be the mass of the dark matter particle we need: a member of a class of cold dark matter candidates known as WIMPzillas. This could successfully reproduce the large-scale structure and gravitational effects we need to recover the observed Universe. Meanwhile, the second number lines up extremely well with the actual, allowable mass ranges of the neutrinos we have in our Universe today. Given the uncertainties of one or two orders of magnitude, this could describe exactly how neutrinos work. It gives a dark matter candidate, an explanation for why neutrinos would be so light, and three other interesting things.

    7
    The expected fates of the Universe (top three illustrations) all correspond to a Universe where the matter and energy fights against the initial expansion rate. In our observed Universe, a cosmic acceleration is caused by some type of dark energy, which is hitherto unexplained. Image credit: E. Siegel / Beyond the Galaxy.

    Dark energy. If you try and calculate what the zero-point energy, or vacuum energy, of the Universe is, you get a ridiculous number: somewhere around Λ ~ (10¹⁹ GeV)⁴. If you’ve ever heard of people saying that the prediction for dark energy is too large by about 120 orders of magnitude, this is where they get that number from. But if you replace that number of 10¹⁹ GeV with the mass of the neutrino, at 0.01 eV, you get a number that’s right around Λ ~ (0.01 eV)⁴, which comes out to match the value we measure almost exactly. This isn’t a proof of anything, but it’s extremely suggestive.

    8
    When the electroweak symmetry breaks, the combination of CP-violation and baryon number violation can create a matter/antimatter asymmetry where there was none before, owing to the effect of sphaleron interactions working on a neutrino excess. Image credit: University of Heidelberg.

    A baryon asymmetry. We need a way to generate more matter than antimatter in the early Universe, and if we have this see-saw scenario, it gives us a viable way to do it. These mixed-state neutrinos can create more leptons than anti-leptons through the neutrino sector, giving rise to a Universe-wide asymmetry. When the electroweak symmetry breaks, a series of interactions known as sphaleron interactions can then give rise to a Universe with more baryons than leptons, since baryon number (B) and lepton number (L) aren’t individually conserved: just the combination B — L. Whatever lepton asymmetry you start with, they’ll get converted into equal parts baryon and lepton asymmetry. For example, if you start with a lepton asymmetry of X, these sphalerons will naturally give you a Universe with an “extra” amount of protons and neutrons that equals X/2, while giving you that same X/2 amount of electrons and neutrinos combined.

    9
    When a nucleus experiences a double neutron decay, two electrons and two neutrinos get emitted conventionally. If neutrinos obey this see-saw mechanism and are Majorana particles, neutrinoless double beta decay should be possible. Experiments are actively looking for this. Image credit: Ludwig Niedermeier, Universitat Tubingen / GERDA.

    U Washington Majorana Demonstrator Experiment at SURF

    U Washington Majorana Demonstrator Experiment at SURF


    SURF building in Lead SD USA

    A new type of decay: neutrinoless double beta decay. The theoretical idea of a source for dark matter, dark energy, and the baryon asymmetry is fascinating, but you need an experiment to detect it. Until we can directly measure neutrinos (and anti-neutrinos) left over from the Big Bang, a feat that’s practically impossible due to the low cross-section of these low-energy neutrinos, we won’t know how to test whether neutrinos have these properties (Majorana) or not (Dirac). But if a double beta decay that emits no neutrinos occurs, we’ll know that neutrinos do have these (Majorana) properties after all, and all of this suddenly could be real.

    Perhaps ironically, the greatest advance in particle physics — a great leap forward beyond the Standard Model — might not come from our greatest experiments and detectors at high-energies, but from a humble, patient look for an ultra-rare decay. We’ve constrained neutrinoless double beta decay to have a lifetime of more than 2 × 10²⁵ years, but the next decade or two of experiments should measure this decay if it exists. So far, neutrinos are the only hint of particle physics beyond the Standard Model. If neutrinoless double beta decay turns out to be real, it might be the future of fundamental physics. It could solve the biggest cosmic questions plaguing humanity today. Our only choice is to look. If nature is kind to us, the future won’t be supersymmetry, extra dimensions, or string theory. We just might have a neutrino revolution on our hands.

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 12:39 pm on November 14, 2017 Permalink | Reply
    Tags: GERDA (GERmanium Detector Array), In 1937 Italian physicist Ettore Majorana hypothesized the existence of the Majorana fermion a particle that is its own anti-particle, LEGEND - Large Enriched Germanium Experiment for Neutrinoless ββ Decay, , Neutrinoless double beta decay,   

    From SURF: “MAJORANA collaboration releases results” 

    SURF logo
    Sanford Underground levels

    Sanford Underground Research facility

    November 13, 2017
    Constance Walter

    2
    Dr. Vincente Guiseppe talked about Majorana Demonstrator’s new results at the November Deep Talks. Matthew Kapust

    U Washington Majorana Demonstrator Experiment at SURF

    In 1937, Italian physicist Ettore Majorana hypothesized the existence of the Majorana fermion, a particle that is its own anti-particle. His hypothesis informed the basis for decades of neutrino-based experiments, including the Majorana Demonstrator Project, which is looking for a rare form of decay called neutrinoless double-beta decay.

    “If the neutrino is its own antiparticle, it could explain a lot about our universe,” said Vincente Guiseppe, co-spokesperson for the Majorana collaboration and an assistant professor of physics and astronomy at the University of South Carolina. “Such a discovery could help explain why there is more matter than anti-matter in the universe—and why we exist at all.”

    After years of planning, building the experiment and collecting data, the collaboration has something to celebrate. At last week’s Deep Talks, Guiseppe announced the initial physics results. And although neutrinoless double-beta decay was not observed, the Majorana collaboration still has much to celebrate, Guiseppe said.

    “We know that we created an environment that is incredibly clean and quiet. These initial results give us a better understanding of the always-elusive neutrino and how it shaped the universe.”

    The collaboration went to great lengths to create such a quiet environment. For the past six years, the team grew the world’s purest copper to build the demonstrator. Two ultra-pure copper cryostats each hold approximately 22 kg of enriched and natural germanium. And both are housed inside a six-layered shield deep underground at Sanford Lab to escape cosmic radiation and other impurities that could create noisy events.

    To observe this type of rare physics event in just two atoms, you’d have to wait over 2 x 1025 years. That’s a 2 followed by 25 zeroes.

    “You might say that’s improbable—the universe is only 13.8 billion years old,” Guiseppe said in his presentation. “But so is the lottery. To increase your chances, you buy more lottery tickets.” In the case of Majorana, they had to increase the number of germanium atoms.

    Still, they didn’t expect to see neutrinoless double-beta decay. The project is, first and foremost, a demonstrator, a research and development project built on a moderate scale to determine whether a larger version is feasible. And for it to be feasible, “We had to show that backgrounds can be low enough to justify building a next-generation experiment,” Guiseppe said.

    Ettore Majorana disappeared mysteriously in 1938 while traveling by ship from Palermo to Naples, Italy. For decades rumors abounded about his disappearance: he committed suicide, he fell overboard and drowned or took refuge in a convent. An article from the 1950s suggests he resurfaced in Venezuela, South America, under an assumed name.

    The Majorana collaboration, however, has no intention of disappearing.

    “We plan to continue operating the Demonstrator to study its performance, better estimate the backgrounds we observe and test some hardware upgrades,” Guiseppe said. “In a few years, we’ll hit a point of diminishing returns. At that time, we can make better use of the detectors along a path towards a next-generation experiment.”

    That next generation is LEGEND, the Large Enriched Germanium Experiment for Neutrinoless ββ Decay, which will contain up to 1,000 kg of germanium. Last year, the collaboration joined forces with members of GERDA (GERmanium Detector Array), as well as other researchers in this field to begin planning for LEGEND. GERDA, another neutrinoless double-beta decay experiment, used commercial copper and shielded its detector inside a tank of liquid argon, which scintillates, or lights up, when backgrounds enter.

    How can they be sure the next generation will work? They can’t. Still, they are compelled to keep searching.

    “We live in a curious world. And as humans, we want to know what things are, how they came to be and why we exist,” Guiseppe said. “That’s why our collaboration is studying neutrinos. That’s why so many other experiments around the world study neutrinos.”

    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
    LBNE

     
  • richardmitnick 12:55 pm on November 7, 2017 Permalink | Reply
    Tags: Neutrinoless double beta decay, , ,   

    From SURF: “Deep Talks delves into MAJORANA results” 

    SURF logo
    Sanford Underground levels

    Sanford Underground Research facility

    November 3, 2017
    Contact
    Constance Walter
    Communications Director
    605.722.4025
    Contact by email

    What do the results look like and what do they mean for the experiment? For science? For Sanford Lab?

    1
    The Majorana experiment sits inside a six-layered shield. Matt Kapust

    U Washington Majorana Demonstrator Experiment at SURF

    The MAJORANA DEMONSTRATOR Collaboration recently released its first physics results at a neutrino conference. What do those results mean for the experiment? For science? For Sanford Lab?

    Join Dr. Vincente Guiseppe Thursday, Nov. 9, for “Released from the Depths: What do Majorana’s results look like and what do they mean?,” at the Sanford Lab Homestake Visitor Center, 160 W. Main Street, in Lead, S.D. Guiseppe, co-spokesperson for the collaboration, will take us on a journey deep inside the Majorana experiment, explaining the collaboration’s effort to build an extremely quiet experiment that could tell us more about the origins of our universe.

    “These initial results will give us a better understanding of the always-elusive neutrino and how it shaped the universe,” Guiseppe said.

    Collaborators with the Majorana Demonstrator built their experiment on the 4850 Level of the Sanford Lab to escape cosmic radiation that constantly bombards the earth. The experiment, which uses enriched germanium crystals to look for a rare form of radioactive decay called neutrinoless double-beta decay, is further protected by a six-layered shield. The collaboration hopes to answer one of the most challenging and important questions in physics: are neutrinos their own antiparticles? If the answer is yes, we could finally learn why matter is more abundant than antimatter and why we exist at all.

    Guiseppe, an assistant professor of physics and astronomy at the University of South Carolina, oversaw the design and construction of the shield. His experimental nuclear and astroparticle physics research focuses on neutrino physics and ultra-low background experiments conducted deep underground.

    Deep Talks begins at 5 p.m. with a social hour; the talk begins at 6 p.m. Free beer from Crow Peak Brewing Company in Spearfish is available for those 21 and older. Deep Talks is sponsored by Sanford Lab, the Sanford Lab Homestake Visitor Center, Crow Peak Brewing Company and First National Bank in Lead. The event is free to the public.

    Deep Talks is a lecture series created by the Sanford Underground Research Facility and the Sanford Lab Homestake Visitor Center. The event is held the second Thursday of each month, October through May. Deep Talks is free to the public. Donations to support community education are welcome.

    Sanford Lab is operated by the South Dakota Science and Technology Authority (SDSTA) with funding from the Department of Energy. Our mission is to advance compelling underground, multidisciplinary research in a safe work environment and to inspire and educate through science, technology, and engineering. Visit us at http://www.SanfordLab.org.

    Visit the Sanford Lab Homestake Visitor Center at http://sanfordlabhomestake.com

    See the full article here .

    Please help promote STEM in your local schools.
    STEM Icon

    Stem Education Coalition

    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
    LBNE

     
  • richardmitnick 10:08 am on October 23, 2017 Permalink | Reply
    Tags: , , , , , Neutrinoless double beta decay,   

    From LBNL: “Experiment Provides Deeper Look into the Nature of Neutrinos” 

    Berkeley Logo

    Berkeley Lab

    October 23, 2017
    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 486-5582

    The first glimpse of data from the full array of a deeply chilled particle detector operating beneath a mountain in Italy sets the most precise limits yet on where scientists might find a theorized process to help explain why there is more matter than antimatter in the universe.

    This new result, submitted today to the journal Physical Review Letters, is based on two months of data collected from the full detector of the CUORE (Cryogenic Underground Observatory for Rare Events) experiment at the Italian National Institute for Nuclear Physics’ (INFN’s) Gran Sasso National Laboratories (LNGS) in Italy. CUORE means “heart” in Italian.

    The CUORE detector array, shown here in this rendering is formed by 19 copper-framed “towers” that each house a matrix of 52 cube-shaped crystals Credit CUORE collaboration

    CUORE experiment UC Berkeley, experiment at the Italian National Institute for Nuclear Physics’ (INFN’s) Gran Sasso National Laboratories (LNGS), a search for neutrinoless double beta decay

    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy

    The Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) leads the U.S. nuclear physics effort for the international CUORE collaboration, which has about 150 members from 25 institutions. The U.S. nuclear physics program has made substantial contributions to the fabrication and scientific leadership of the CUORE detector.

    CUORE is considered one of the most promising efforts to determine whether tiny elementary particles called neutrinos, which interact only rarely with matter, are “Majorana particles” – identical to their own antiparticles. Most other particles are known to have antiparticles that have the same mass but a different charge, for example. CUORE could also help us home in on the exact masses of the three types, or “flavors,” of neutrinos – neutrinos have the unusual ability to morph into different forms.

    “This is the first preview of what an instrument this size is able to do,” said Oliviero Cremonesi, a senior faculty scientist at INFN and spokesperson for the CUORE collaboration. Already, the full detector array’s sensitivity has exceeded the precision of the measurements reported in April 2015 after a successful two-year test run that enlisted one detector tower. Over the next five years CUORE will collect about 100 times more data.

    Yury Kolomensky, a senior faculty scientist in the Nuclear Science Division at Lawrence Berkeley National Laboratory (Berkeley Lab) and U.S. spokesperson for the CUORE collaboration, said, “The detector is working exceptionally well and these two months of data are enough to exceed the previous limits.” Kolomensky is also a professor in the UC Berkeley Physics Department.

    The new data provide a narrow range in which scientists might expect to see any indication of the particle process it is designed to find, known as neutrinoless double beta decay.

    “CUORE is, in essence, one of the world’s most sensitive thermometers,” said Carlo Bucci, technical coordinator of the experiment and Italian spokesperson for the CUORE collaboration. Its detectors, formed by 19 copper-framed “towers” that each house a matrix of 52 cube-shaped, highly purified tellurium dioxide crystals, are suspended within the innermost chamber of six nested tanks.

    Cooled by the most powerful refrigerator of its kind, the tanks subject the detector to the coldest known temperature recorded in a cubic meter volume in the entire universe: minus 459 degrees Fahrenheit (10 milliKelvin).

    The detector array was designed and assembled over a 10-year period. It is shielded from many outside particles, such as cosmic rays that constantly bombard the Earth, by the 1,400 meters of rock above it, and by thick lead shielding that includes a radiation-depleted form of lead rescued from an ancient Roman shipwreck. Other detector materials were also prepared in ultrapure conditions, and the detectors were assembled in nitrogen-filled, sealed glove boxes to prevent contamination from regular air.

    “Designing, building, and operating CUORE has been a long journey and a fantastic achievement,” said Ettore Fiorini, an Italian physicist who developed the concept of CUORE’s heat-sensitive detectors (tellurium dioxide bolometers), and the spokesperson-emeritus of the CUORE collaboration. “Employing thermal detectors to study neutrinos took several decades and brought to the development of technologies that can now be applied in many fields of research.”

    Together weighing over 1,600 pounds, CUORE’s matrix of roughly fist-sized crystals is extremely sensitive to particle processes, especially at this extreme temperature. Associated instruments can precisely measure ever-slight temperature changes in the crystals resulting from these processes.

    Berkeley Lab and Lawrence Livermore National Laboratory scientists supplied roughly half of the crystals for the CUORE project. In addition, the Berkeley Lab team designed and fabricated the highly sensitive temperature sensors – called neutron transmutation doped thermistors – invented by Eugene Haller, a senior faculty scientist in Berkeley Lab’s Materials Sciences Division and a UC Berkeley faculty member.

    2
    CUORE was assembled in this specially designed clean room to help protect it from contaminants. (Credit: CUORE collaboration)

    Berkeley Lab researchers also designed and built a specialized clean room supplied with air depleted of natural radioactivity, so that the CUORE detectors could be installed into the cryostat in ultraclean conditions. And Berkeley Lab scientists and engineers, under the leadership of UC Berkeley postdoc Vivek Singh, worked with Italian colleagues to commission the CUORE cryogenic systems, including a uniquely powerful cooling system called a dilution refrigerator.

    Former UC Berkeley postdoctoral students Tom Banks and Tommy O’Donnell, who also had joint appointments in the Nuclear Science Division at Berkeley Lab, led the international team of physicists, engineers, and technicians to assemble over 10,000 parts into towers in nitrogen-filled glove boxes. They bonded almost 8,000 gold wires, measuring just 25 microns in diameter, to 100-micron sized pads on the temperature sensors, and on copper pads connected to detector wiring.

    CUORE measurements carry the telltale signature of specific types of particle interactions or particle decays – a spontaneous process by which a particle or particles transform into other particles.

    In double beta decay, which has been observed in previous experiments, two neutrons in the atomic nucleus of a radioactive element become two protons. Also, two electrons are emitted, along with two other particles called antineutrinos.

    Neutrinoless double beta decay, meanwhile – the specific process that CUORE is designed to find or to rule out – would not produce any antineutrinos. This would mean that neutrinos are their own antiparticles. During this decay process the two antineutrino particles would effectively wipe each other out, leaving no trace in the CUORE detector. Evidence for this type of decay process would also help scientists explain neutrinos’ role in the imbalance of matter vs. antimatter in our universe.

    Neutrinoless double beta decay is expected to be exceedingly rare, occurring at most (if at all) once every 100 septillion (1 followed by 26 zeros) years in a given atom’s nucleus. The large volume of detector crystals is intended to greatly increase the likelihood of recording such an event during the lifetime of the experiment.

    There is growing competition from new and planned experiments to resolve whether this process exists using a variety of search techniques, and Kolomensky noted, “The competition always helps. It drives progress, and also we can verify each other’s results, and help each other with materials screening and data analysis techniques.”

    Lindley Winslow of the Massachusetts Institute of Technology, who coordinated the analysis of the CUORE data, said, “We are tantalizingly close to completely unexplored territory and there is great possibility for discovery. It is an exciting time to be on the experiment.”

    CUORE is supported jointly by the Italian National Institute for Nuclear Physics Istituto Nazionale di Fisica Nucleare (INFN) in Italy, and the U.S. Department of Energy’s Office of Nuclear Physics, the National Science Foundation, and the Alfred P. Sloan Foundation in the U.S. The CORE collaboration includes about 150 scientists from Italy, U.S., China, France, and Spain, and is based in the underground Italian facility called INFN Gran Sasso National Laboratories (LNGS) of the INFN.

    CUORE collaboration members include: Italian National Institute for Nuclear Physics (INFN), University of Bologna, University of Genoa, University of Milano-Bicocca, and Sapienza University in Italy; California Polytechnic State University, San Luis Obispo; Berkeley Lab; Lawrence Livermore National Laboratory; Massachusetts Institute of Technology; University of California, Berkeley; University of California, Los Angeles; University of South Carolina; Virginia Polytechnic Institute and State University; and Yale University in the US; Saclay Nuclear Research Center (CEA) and the Center for Nuclear Science and Materials Science (CNRS/IN2P3) in France; and the Shanghai Institute of Applied Physics and Shanghai Jiao Tong University in China.

    The U.S.-CUORE team was lead by late Prof. Stuart Freedman until his untimely passing in 2012. Other current and former Berkeley Lab members of the CUORE collaboration not previously mentioned include US Contractor Project Manager Sergio Zimmermann (Engineering Division), former U.S. Contractor Project Manager Richard Kadel, staff scientists Jeffrey Beeman, Brian Fujikawa, Sarah Morgan, Alan Smith, postdocs Giovanni Benato, Raul Hennings-Yeomans, Ke Han, Yuan Mei, Bradford Welliver, Benjamin Schmidt, graduate students Adam Bryant, Alexey Drobizhev, Roger Huang, Laura Kogler, Jonathan Ouellet, and Sachi Wagaarachchi, and engineers David Biare, Luigi Cappelli, Lucio di Paolo, and Joseph Wallig.

    See the full article here .

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  • richardmitnick 9:17 am on September 19, 2017 Permalink | Reply
    Tags: , LEGEND 200, , Neutrinoless double beta decay,   

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

    SURF logo
    Sanford Underground levels

    Sanford Underground Research facility

    September 11, 2017
    Constance Walter

    1
    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.

    3
    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
    LBNE

     
  • richardmitnick 9:06 pm on July 1, 2017 Permalink | Reply
    Tags: In contrast the quadruple form of the decay would allow the neutrino to be a Dirac particle: like every other particle in the Standard Model, It would defy the never previously violated conservation of lepton number, , NEMO-3 hunts for ultra-rare beta decay, Neutrinoless double beta decay, Neutrinoless double beta decay would also mean that the neutrino is its own antiparticle: a so-called Majorana particle, Neutrinoless quadruple beta decay, , says Rodejohann: "We pointed out that Dirac particles can in fact violate lepton number but by four units say rather than two.", Such a violation in turn might explain the dominance of matter over antimatter, The potential prize on offer: an explanation for the universe's matter/antimatter asymmetry   

    From physicsworld.com: “NEMO-3 hunts for ultra-rare beta decay” 

    physicsworld
    physicsworld.com

    Jun 30, 2017

    1
    Out of the blue: NEMO-3 being built. NO image credit.

    For the best part of 30 years, physicists have been looking for a very rare nuclear process known as neutrinoless double beta decay. With discovery still elusive, researchers in France have now turned their attention to an even rarer process called neutrinoless quadruple beta decay. As expected, their first search has drawn a blank. But they say it is worth persisting, given the potential prize on offer: an explanation for the universe’s matter/antimatter asymmetry.

    In normal beta decay, an electron and an antineutrino are emitted from a nucleus within which a neutron transforms into a proton. There are also several dozen isotopes that have been shown to undergo double beta decay, in which two neutrons turn into two protons and emit two electrons plus two antineutrinos. But what physicists have been keen to observe, so far without success, is the neutrinoless version without the emission of any antineutrinos.

    The discovery of this phenomenon, if real, would be huge news in physics, since it would defy the never previously violated conservation of lepton number – protons and neutrons having a lepton number of zero while electrons and neutrinos are +1 and their antimatter counterparts –1. Such a violation in turn might explain the dominance of matter over antimatter, since it would reveal a process that yields a slight excess of matter.

    Majorana particles

    Neutrinoless double beta decay would also mean that the neutrino is its own antiparticle, a so-called Majorana particle. This is because an antineutrino emitted by one of the two decaying neutrons could be absorbed by the other neutron as a neutrino, leading to no neutrino output. In contrast, the quadruple form of the decay would allow the neutrino to be a Dirac particle, like every other particle in the Standard Model, which is not the mirror image of itself.

    Neutrinoless quadruple beta decay was proposed theoretically by Julian Heeck and Werner Rodejohann of the Max Planck Institute for Nuclear Physics in Heidelberg, Germany, in 2013. The pair found that by adding three right-handed neutrinos to the existing trio of left-handed neutrinos in the Standard Model, as well as two new scalar particles, which are similar to the Higgs boson, the (virtual) neutrinos emitted in the simultaneous beta decay of four neutrons would annihilate one another before they could be emitted from the nucleus in question.

    “Before we published our paper the common opinion was that Dirac neutrinos conserve lepton number,” says Rodejohann. “We pointed out that Dirac particles can in fact violate lepton number, but by four units, say, rather than two.”

    Energy boost

    The Heidelberg researchers point out that the only nuclei that could undergo this decay are those for which the transformation of just one neutron into a proton boosts their energy – so forbidding normal beta decay, which would otherwise predominate – while the transformation of four neutrons makes them less energetic. They have identified just three such isotopes – zirconium-96, xenon-136 and neodymium-150 – of which the latter is best, they say, because it releases the greatest amount of energy during the decay, so making it more detectable.

    Indeed, it is that nucleus that has been used in the experimental work. The work was carried out at the NEMO-3 experiment at the Modane Underground Laboratory in France.

    Edelweiss Dark Matter Experiment, located at the Modane Underground Laboratory in France

    This comprises a 3 × 5 m cylindrical detector consisting of thin foils of various isotopes – including 37 g of neodymium-150 – surrounded by tracking chambers and calorimeters. Although optimized to search for neutrinoless double beta decay, the detector’s ability to plot the trajectories of individual emitted particles also makes it well suited to the new line of research.

    NEMO-3 has not collected new data, but rather physicists have analysed existing events recorded in its detector between 2003 and 2011. The researchers looked for events generating either three or four particles (in the former, one of the emitted electrons would be reabsorbed by the neodymium foil). Doing so, they found no evidence for events beyond those expected from background radioactive processes. But they were able to stipulate a first lower bound on the process’s half-life – some 1021 years.

    Forty orders of magnitude

    Steven Elliott of the Los Alamos National Laboratory in the US praises NEMO-3 for reaching “an interesting milestone that no other existing experiment can reach”. But he doubts that the group will be able to detect the putative decay, pointing out that Heeck and Rodejohann predicted a half-life (of around 1065 years) that is “at least 40 orders of magnitude” beyond the experiment’s sensitivity. Ettore Fiorini of the University of Milano-Bicocca shares that scepticism, arguing that a positive sighting “seems to be outside any realistic hope”.

    Former NEMO-3 member Xavier Sarazin of the Linear Accelerator Laboratory in Orsay, France, acknowledges that the group is very unlikely to make a discovery. But he maintains that it will still be worthwhile carrying out a new search with the upgraded “SuperNEMO”, which should start taking data in about a year and which could contain up to a kilogram of neodymium-150. “You would never design an experiment from scratch to look for this decay,” he says, “but if you can increase the amount of neodymium, why not?”

    Indeed, Heeck says that potential alternatives to the model developed by himself and Rodejohann might feature much shorter decay half-lives. “Our hope would be that NEMO-3’s first experimental search for quadruple beta decay will motivate people to explore models that could lead to testable rates,” he says.

    The research has been accepted for publication in Physical Review Letters.

    See the full article here .

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    PhysicsWorld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
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