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  • richardmitnick 2:49 pm on October 26, 2018 Permalink | Reply
    Tags: , , , , J-PARC accelerator, , SNOLAB, Super Kamiokande experiment, T2K (Tokai to Kamiokande) experiment   

    From Live Science: “Could Misbehaving Neutrinos Explain Why the Universe Exists?” 

    Livescience
    From Live Science

    October 24, 2018

    FNAL’s Don Lincoln

    1
    Credit: Shutterstock

    Scientists revel in exploring mysteries, and the bigger the mystery, the greater the enthusiasm. There are many huge unanswered questions in science, but when you’re going big, it’s hard to beat “Why is there something, instead of nothing?”

    That might seem like a philosophical question, but it’s one that is very amenable to scientific inquiry. Stated a little more concretely, “Why is the universe made of the kinds of matter that makes human life possible so that we can even ask this question?” Scientists conducting research in Japan have announced a measurement last month that directly addresses that most fascinating of inquiries. It appears that their measurement disagrees with the simplest expectations of current theory and could well point toward an answer of this timeless question.

    Their measurement seems to say that for a particular set of subatomic particles, matter and antimatter act differently.

    Matter v. Antimatter

    Using the J-PARC accelerator, located in Tokai, Japan, scientists fired a beam of ghostly subatomic particles called neutrinos and their antimatter counterparts (antineutrinos) through the Earth to the Super Kamiokande experiment, located in Kamioka, also in Japan.

    J-PARC Facility Japan Proton Accelerator Research Complex , located in Tokai village, Ibaraki prefecture, on the east coast of Japan

    Super-Kamiokande experiment. located under Mount Ikeno near the city of Hida, Gifu Prefecture, Japan

    This experiment, called T2K (Tokai to Kamiokande), is designed to determine why our universe is made of matter. A peculiar behavior exhibited by neutrinos, called neutrino oscillation, might shed some light on this very vexing problem.

    T2K map, T2K Experiment, Tokai to Kamioka, Japan

    Asking why the universe is made of matter might sound like a peculiar question, but there is a very good reason that scientists are surprised by this. It’s because, in addition to knowing of the existence of matter, scientists also know of antimatter.

    In 1928, British physicist Paul Dirac proposed the existence of antimatter — an antagonistic sibling of matter. Combine equal amounts of matter and antimatter and the two annihilate each other, resulting in the release of an enormous amount of energy. And, because physics principles usually work equally well in reverse, if you have a prodigious quantity of energy, it can convert into exactly equal amounts of matter and antimatter. Antimatter was discovered in 1932 by American Carl Anderson and researchers have had nearly a century to study its properties.

    However, that “into exactly equal amounts” phrase is the crux of the conundrum. In the brief moments immediately after the Big Bang, the universe was full of energy. As it expanded and cooled, that energy should have converted into equal parts matter and antimatter subatomic particles, which should be observable today. And yet our universe consists essentially entirely of matter. How can that be?

    By counting the number of atoms in the universe and comparing that with the amount of energy we see, scientists determined that “exactly equal” isn’t quite right. Somehow, when the universe was about a tenth of a trillionth of a second old, the laws of nature skewed ever-so-slightly in the direction of matter. For every 3,000,000,000 antimatter particles, there were 3,000,000,001 matter particles. The 3 billion matter particles and 3 billion antimatter particles combined — and annihilated back into energy, leaving the slight matter excess to make up the universe we see today.

    Since this puzzle was understood nearly a century ago, researchers have been studying matter and antimatter to see if they could find behavior in subatomic particles that would explain the excess of matter. They are confident that matter and antimatter are made in equal quantities, but they have also observed that a class of subatomic particles called quarks exhibit behaviors that slightly favor matter over antimatter. That particular measurement was subtle, involving a class of particles called K mesons which can convert from matter to antimatter and back again. But there is a slight difference in matter converting to antimatter as compared to the reverse. This phenomenon was unexpected and its discovery led to the 1980 Nobel prize, but the magnitude of the effect was not enough to explain why matter dominates in our universe.

    Ghostly beams

    Thus, scientists have turned their attention to neutrinos, to see if their behavior can explain the excess matter. Neutrinos are the ghosts of the subatomic world. Interacting via only the weak nuclear force, they can pass through matter without interacting nearly at all. To give a sense of scale, neutrinos are most commonly created in nuclear reactions and the biggest nuclear reactor around is the Sun. To shield one’s self from half of the solar neutrinos would take a mass of solid lead about 5 light-years in depth. Neutrinos really don’t interact very much.

    Between 1998 and 2001, a series of experiments — one using the Super Kamiokande detector, and another using the SNO detector in Sudbury, Ontario ­­— proved definitively that neutrinos also exhibit another surprising behavior. They change their identity.

    SNOLAB, a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario


    SNOLAB, Sudbury, Ontario, Canada.

    Physicists know of three distinct kinds of neutrinos, each associated with a unique subatomic sibling, called electrons, muons and taus. Electrons are what causes electricity and the muon and tau particle are very much like electrons, but heavier and unstable.

    The three kinds of neutrinos, called the electron neutrino, muon neutrino and tau neutrino, can “morph” into other types of neutrinos and back again. This behavior is called neutrino oscillation.

    Neutrino oscillation is a uniquely quantum phenomenon, but it is roughly analogous to starting out with a bowl of vanilla ice cream and, after you go and find a spoon, you come back to find that the bowl is half vanilla and half chocolate. Neutrinos change their identity from being entirely one type, to a mix of types, to an entirely different type, and then back to the original type.

    Antineutrino oscillations

    Neutrinos are matter particles, but antimatter neutrinos, called antineutrinos, also exist. And that leads to a very important question. Neutrinos oscillate, but do antineutrinos also oscillate and do they oscillate in exactly the same way as neutrinos? The answer to the first question is yes, while the answer to the second is not known.

    Let’s consider this a little more fully, but in a simplified way: Suppose that there were only two neutrino types — muon and electron. Suppose further that you had a beam of purely muon type neutrinos. Neutrinos oscillate at a specific speed and, since they move near the speed of light, they oscillate as a function of distance from where they were created. Thus, a beam of pure muon neutrinos will look like a mix of muon and electron types at some distance, then purely electron types at another distance and then back to muon-only. Antimatter neutrinos do the same thing.

    However, if matter and antimatter neutrinos oscillate at slightly different rates, you’d expect that if you were a fixed distance from the point at which a beam of pure muon neutrinos or muon antineutrinos were created, then in the neutrino case you’d see one blend of muon and electron neutrinos, but in the antimatter neutrino case, you’d see a different blend of antimatter muon and electron neutrinos. The actual situation is complicated by the fact that there are three kinds of neutrinos and the oscillation depends on beam energy, but these are the big ideas.

    The observation of different oscillation frequencies by neutrinos and antineutrinos would be an important step towards understanding the fact that the universe is made of matter. It’s not the entire story, because additional new phenomena must also hold, but the difference between matter and antimatter neutrinos is necessary to explain why there is more matter in the universe.

    In the current prevailing theory describing neutrino interactions, there is a variable that is sensitive to the possibility that neutrinos and antineutrinos oscillate differently. If that variable is zero, the two types of particles oscillate at identical rates; if that variable differs from zero, the two particle types oscillate differently.

    When T2K measured this variable, they found it was inconsistent with the hypothesis that neutrinos and antineutrinos oscillate identically. A little more technically, they determined a range of possible values for this variable. There is a 95 percent chance that the true value for that variable is within that range and only a 5 percent chance that the true variable is outside that range. The “no difference” hypothesis is outside the 95 percent range.

    In simpler terms, the current measurement suggests that neutrinos and antimatter neutrinos oscillate differently, although the certainty does not rise to the level to make a definitive claim. In fact, critics point out that measurements with this level of statistical significance should be viewed very, very skeptically. But it is certainly an enormously provocative initial result, and the world’s scientific community is extremely interested in seeing improved and more precise studies.

    The T2K experiment will continue to record additional data in hopes of making a definitive measurement, but it’s not the only game in town. At Fermilab, located outside Chicago, a similar experiment called NOvA is shooting both neutrinos and antimatter neutrinos to northern Minnesota, hoping to beat T2K to the punch.

    FNAL NOvA Near Detector


    FNAL/NOvA experiment map


    FNAL NOvA far detector in northern Minnesota


    NOvA Far Detector Block

    And, looking more to the future, Fermilab is working hard on what will be its flagship experiment, called DUNE (Deep Underground Neutrino Experiment), which will have far superior capabilities to study this important phenomenon.


    FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA


    SURF DUNE LBNF Caverns at Sanford Lab

    While the T2K result is not definitive and caution is warranted, it is certainly tantalizing. Given the enormity of the question of why our universe seems to have no appreciable antimatter, the world’s scientific community will avidly await further updates.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

     
  • richardmitnick 5:14 pm on September 20, 2018 Permalink | Reply
    Tags: An ultrasensitive microphone for dark matter, , Dark Matter hunt, , Searching for much lighter dark matter candidates, SNOLAB, SuperCDMS experiment, , The predecessor of SuperCDMS SNOLAB—the SuperCDMS Soudan experiment housed in the Soudan mine in Minnesota—required the charge from 70 electron-hole pairs to make a detection. SuperCDMS SNOLAB wil,   

    From Symmetry: “Dark matter vibes” 

    Symmetry Mag
    From Symmetry

    09/20/18
    Manuel Gnida

    1
    Dawn Harmer, SLAC

    SuperCDMS physicists are testing a way to amp up dark matter vibrations to help them search for lighter particles.

    A dark matter experiment scheduled to go online at the Canadian underground laboratory SNOLAB in the early 2020s will conduct one of the most sensitive searches ever for hypothetical particles known as weakly interacting massive particles, or WIMPs.

    SNOLAB, a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario


    SNOLAB, a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario

    Scientists consider WIMPs strong dark matter candidates. But what if dark matter turns out to be something else? After all, despite an intense hunt with increasingly sophisticated detectors, scientists have yet to directly detect dark matter.

    That’s why researchers on the SuperCDMS dark matter experiment at SNOLAB are looking for ways to broaden their search. And they found one: They have tested a prototype detector that would allow their experiment to search for much lighter dark matter candidates as well.

    SLAC SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)


    SLAC SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)


    LBNL Super CDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)

    “This development is exciting because it gives us access to a new sector of particle masses where alternatives to WIMPs could be hiding,” says Priscilla Cushman from the University of Minnesota, spokesperson for the SuperCDMS collaboration. “It also demonstrates the flexibility of our detector technology, now reaching energy thresholds and resolutions that weren’t possible a few years ago.”

    The collaboration published the results of the first low-mass dark matter search with the new technology in Physical Review Letters. Some scientists on the team also described the prototype in an earlier paper in Applied Physics Letters.

    An ultrasensitive mic for dark matter

    The core of the SuperCDMS experiment is made of very sensitive detectors on the top and bottom of hockey puck-shaped silicon and germanium crystals. The detectors are able to observe very small vibrations caused by dark matter particles rushing through the crystals. The challenge in using this technology to find light dark matter particles is that, the lighter the particle, the smaller the vibrations.

    “To pick those vibrations up, you need an extraordinary ‘microphone’,” says Matt Pyle from the University of California, who contributed to both papers. “Our goal is to build microphones—detectors—that are sensitive enough to detect signals of very light particles. Our technology is at the leading edge of what’s currently possible.”

    The vibrations caused by a dark matter interaction can also dislodge negatively charged electrons in the crystal. This leaves positively charged spots, or holes, at the locations where the electrons once were. If an electric field is applied, the pairs of electrons and holes traverse the crystal in opposite directions, and the detector can measure their charge.

    One way of making the experiment more sensitive is to increase the efficiency with which it measures the charge of the electron-hole pairs. This approach has been the major factor in improving sensitivity until now. The predecessor of SuperCDMS SNOLAB—the SuperCDMS Soudan experiment, housed in the Soudan mine in Minnesota—required the charge from 70 electron-hole pairs to make a detection. SuperCDMS SNOLAB will require just half as much.

    “But that’s not the type of improvement we did here,” says Roger Romani, a recent undergraduate student in Blas Cabrera’s group at Stanford University and lead author of the Applied Physics Letters paper. The team found a different way to make the experiment even more sensitive.

    “In our approach, we counted the number of electron-hole pairs by looking at the vibrations they caused when traveling through our detector crystal,” he says.

    To do so, Cabrera’s team, joined by Pyle and Santa Clara University’s Betty Young, applied a high voltage that pushed the electron-hole pairs through the crystal. The acceleration led to the production of more vibrations, on top of those created without voltage.

    “As a result, our prototype is sensitive to a single electron-hole pair,” says Francisco Ponce, a postdoctoral researcher on Cabrera’s team. “Being able to measure a smaller charge gives us a higher resolution in our experiment and lets us detect particles with smaller mass.”

    4
    This refrigeration unit in the Cabrera lab at Stanford keeps the experiment’s detector crystals at nearly absolute zero temperature. Dawn Harmer, SLAC

    First search for light dark matter

    The SuperCDMS collaboration has used the prototype detector for a first light dark matter search, and the outcome is promising.

    “The experiment demonstrates that we’re sensitive to a mass range in which we had no sensitivity at all before,” says Cabrera, former SuperCDMS SNOLAB project director from the Kavli Institute for Particle Astrophysics and Cosmology, a joint institute of the Department of Energy’s SLAC National Accelerator Laboratory and Stanford.

    Noah Kurinsky, a recent PhD student in Cabrera’s group, says, “Although the technology is in the early stages of its development, we’re able to set limits on the properties of light dark matter and are already competitive to other experiments that operate in the same mass range.”

    The result is even more compelling considering the experimental circumstances: Located in Cabrera’s lab in a basement at Stanford, the experiment wasn’t shielded from the unwanted cosmic-ray background (SuperCDMS SNOLAB will operate 6800 feet underground); it used a very small prototype crystal, limiting the size of the signal (SuperCDMS Soudan’s crystals were 1500 times heavier); and it ran for a relatively short time, limiting the amount of data for the analysis (XENON10 had 20,000 times more exposure).

    Eventually, the researchers want to scale up the size of their crystal and use it in a future generation of SuperCDMS SNOLAB. However, much more R&D work needs to be done before that can happen.

    At the moment, they’re working on improving the quality of the crystal and on better understanding its fundamental physics: for instance, how to deal with a quantum mechanical effect that randomly creates electron-hole pairs for no apparent reason and can cause a background signal that looks exactly like a signal from dark matter.

    The team is hopeful that their efforts will lead to new detector designs that continue to make SuperCDMS SNOLAB more powerful, Pyle says: “Then, we’ll have an even better shot at studying unknown dark matter territory.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 5:34 pm on August 30, 2018 Permalink | Reply
    Tags: , Borexino observatory, , , , , DarkSide experiment, Davide D’Angelo-physical scientist, , , , , , , Pobbile dark matter candidates-axions gravitinos Massive Astrophysical Compact Halo Objects (MACHOs) and Weakly Interacting Massive Particles (WMIPs.)), SABRE-Sodium Iodide with Active Background Rejection Experiment, SNOLAB, Solar neutrinos-recently caught at U Wisconsin IceCube at the South Pole, , , , , , WIMPs that go by names like the gravitino sneutrino and neutralino   

    From Gran Sasso via Motherboard: “The New Hunt for Dark Matter Is Taking Place Under a Mountain” 

    From Gran Sasso

    via

    Motherboard

    1

    Aug 30 2018
    Daniel Oberhaus

    Davide D’Angelo wasn’t always interested in dark matter, but now he’s at the forefront of the hunt to find the most elusive particle in the universe.

    About an hour outside of Rome there’s a dense cluster of mountains known as the Gran Sasso d’Italia. Renowned for their natural beauty, the Gran Sasso are a popular tourist destination year round, offering world-class skiing in the winter and plenty of hiking and swimming opportunities in the summer. For the 43-year old Italian physicist Davide D’Angelo, these mountains are like a second home. Unlike most people who visit Gran Sasso, however, D’Angelo spends more time under the mountains than on top of them.

    It’s here, in a cavernous hall thousands of feet beneath the earth, that D’Angleo works on a new generation of experiments dedicated to the hunt for dark matter particles, an exotic form of matter whose existence has been hypothesized for decades but never proven experimentally.

    Dark matter is thought to make up about 27 percent of the universe and characterizing this elusive substance is one of the most profound problems in contemporary physics. Although D’Angelo is optimistic that a breakthrough will occur in his lifetime, so was the last generation of physicists. In fact, there’s a decent chance that the particles D’Angelo is looking for don’t exist at all. Yet for physicists probing the fundamental nature of the universe, the possibility that they might spend their entire career “hunting ghosts,” as D’Angelo put it, is the price of advancing science.

    WHAT’S UNDER THE ‘GREAT STONE’?

    In 1989, Italy’s National Institute for Nuclear Physics opened the Gran Sasso National Laboratory, the world’s largest underground laboratory dedicated to astrophysics. Gran Sasso’s three cavernous halls were purposely built for physics, which is something of a luxury as far as research centers go. Most other underground astrophysics laboratories like SNOLAB are ad hoc facilities that repurpose old or active mine shafts, which limits the amount of time that can be spent in the lab and the types of equipment that can be used.


    SNOLAB, Sudbury, Ontario, Canada.

    Buried nearly a mile underground to protect it from the noisy cosmic rays that bathe the Earth, Gran Sasso is home to a number of particle physics experiments that are probing the foundations of the universe. For the last few years, D’Angelo has divided his time between the Borexino observatory and the Sodium Iodide with Active Background Rejection Experiment (SABRE), which are investigating solar neutrinos and dark matter, respectively.

    Borexino Solar Neutrino detector

    SABRE experiment at INFN Gran Sasso

    2
    Davide D’Angelo with the SABRE proof of concept. Image: Xavier Aaronson/Motherboard

    Over the last 100 years, characterizing solar neutrinos and dark matter was considered to be one of the most important tasks of particle physics. Today, the mystery of solar neutrinos is resolved, but the particles are still of great interest to physicists for the insight they provide into the fusion process occurring in our Sun and other stars. The composition of dark matter, however, is still considered to be one of the biggest questions in particle physics. Despite the radically different nature of the particles, they are united insofar as they both can only be discovered in environments where the background radiation is at a minimum: Thousands of feet beneath the Earth’s surface.

    “The mountain acts as a shield so if you go below it, you have so-called ‘cosmic silence,’” D’Angelo said. “That’s the part of my research I like most: Going into the cave, putting my hands on the detector and trying to understand the signals I’m seeing.”

    After finishing grad school, D’Angelo got a job with Italy’s National Institute for Nuclear Physics where his research focused on solar neutrinos, a subatomic particle with no charge that is produced by fusion in the Sun. For the better part of four decades, solar neutrinos [recently caught at U Wisconsin IceCube at the South Pole] were at the heart of one of the largest mysteries in astrophysics.

    IceCube neutrino detector interior


    U Wisconsin ICECUBE neutrino detector at the South Pole

    The problem was that instruments measuring the energy from solar neutrinos returned results much lower than predicted by the Standard Model, the most accurate theory of fundamental particles in physics.

    Given how accurate the Standard Model had proven to be for other aspects of cosmology, physicists were reluctant to make alterations to it to account for the discrepancy. One possible explanation was that physicists had faulty models of the Sun and better measurements of its core pressure and temperature were needed. Yet after a string of observations in the 60s and 70s demonstrated that the models of the sun were essentially correct, physicists sought alternative explanations by turning to the neutrino.

    A TALE OF THREE NEUTRINOS

    Ever since they were first proposed by the Austrian physicist Wolfgang Pauli in 1930, neutrinos have been called upon to patch holes in theories. In Pauli’s case, he first posited the existence of an extremely light, chargeless particle as a “desperate remedy” to explain why the law of the conservation of energy appeared to be violated during radioactive decay. Three years later, the Italian physicist Enrico Fermi gave these hypothetical particles a name. He called them “neutrinos,” Italian for “little neutrons.”

    A quarter of a century after Pauli posited their existence, two American physicists reported the first evidence of neutrinos produced in a fission reactor. The following year, in 1957, Bruno Pontecorvo, an Italian physicist working in the Soviet Union, developed a theory of neutrino oscillations. At the time, little was known about the properties of neutrinos and Pontecorvo suggested that there might be more than one type of neutrino. If this were the case, Pontecorvo theorized that it could be possible for the neutrinos to switch between types.

    By 1975, part of Pontecorvo’s theory had been proven correct. Three different types, or “flavors,” of neutrino had been discovered: electron neutrinos, muon neutrinos, and tau neutrinos. Importantly, observations from an experiment in a South Dakota mineshaft had confirmed that the Sun produced electron neutrinos. The only issue was that the experiment detected far fewer neutrinos than the Standard Model predicted.

    FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA


    FNAL DUNE Argon tank at SURF


    Surf-Dune/LBNF Caverns at Sanford



    SURF building in Lead SD USA

    Prior to the late 90s, there was scant indirect evidence that neutrinos could change from one flavor to another. In 1998, a group of researchers working in Japan’s Super-Kamiokande Observatory observed oscillations in atmospheric neutrinos, which are mostly produced by the interactions between photons and the Earth’s atmosphere.

    Super-Kamiokande experiment. located under Mount Ikeno near the city of Hida, Gifu Prefecture, Japan

    Three years later, Canada’s Sudbury Neutrino Observatory (SNO) provided the first direct evidence of oscillations from solar neutrinos.

    Sudbury Neutrino Observatory, no longer operating

    This was, to put it lightly, a big deal in cosmological physics. It effectively resolved the mystery of the missing solar neutrinos, or why experiments only observed about a third as many neutrinos radiating from the Sun compared to predictions made by the Standard Model. If neutrinos could oscillate between flavors, this means a neutrino that is emitted in the Sun’s core could be a different type of neutrino by the time it reaches Earth. Prior to the mid-80s, most experiments on Earth were only looking for electron neutrinos, which meant they were missing the other two flavors of neutrinos that were created en route from the Sun to the Earth.

    When SNO was dreamt up in the 80s, it was designed so that it would be capable of detecting all three types of neutrinos, instead of just electron neutrinos. This decision paid off. In 2015, the directors of the experiments at Super-Kamiokande and SNO shared the Nobel Prize in physics for resolving the mystery of the missing solar neutrinos.

    Although the mystery of solar neutrinos has been solved, there’s still plenty of science to be done to better understand them. Since 2007, Gran Sasso’s Borexino observatory has been refining the measurements of solar neutrino flux, which has given physicists unprecedented insight into the fusion process powering the Sun. From the outside, the Borexino observatory looks like a large metal sphere, but on the inside it looks like a technology transplanted from an alien world.

    Borexino detector. Image INFN

    In the center of the sphere is basically a large, transparent nylon sack that is almost 30 feet in diameter and only half a millimeter thick. This sack contains a liquid scintillator, a chemical mixture that releases energy when a neutrino passes through it. This nylon sphere is suspended in 1,000 metric tons of a purified buffer liquid and surrounded by 2,200 sensors to detect energy released by electrons that are freed when neutrinos interact with the liquid scintillator. Finally, an outer buffer of nearly 3,000 tons of ultrapure water helps provide additional shielding for the detector. Taken together, the Borexino observatory has the most protection from outside radiation interference of any liquid scintillator in the world.

    For the last decade, physicists at Borexino—including D’Angelo, who joined the project in 2011—have been using this one-of-a-kind device to observe low energy solar neutrinos produced by proton collisions during the fusion process in the Sun’s core. Given how difficult it is to detect these chargless, ultralight particles that hardly ever interact with matter, detecting the low energy solar neutrinos would be virtually impossible without such a sensitive machine. When SNO directly detected the first solar neutrino oscillations, for instance, it could only observe the highest energy solar neutrinos due to interference from background radiation. This amounted to only about 0.01 percent of all the neutrinos emitted by the Sun. Borexino’s sensitivity allows it to observe solar neutrinos whose energy is a full order of magnitude lower than those detected by SNO, opening the door for an incredibly refined model of solar processes as well as more exotic events like supernovae.

    “It took physicists 40 years to understand solar neutrinos and it’s been one of the most interesting puzzles in particle physics,” D’Angelo told me. “It’s kind of like how dark matter is now.”

    SHINING A LIGHT ON DARK MATTER

    If neutrinos were the mystery particle of the twentieth century, then dark matter is the particle conundrum for the new millenium. Just like Pauli proposed neutrinos as a “desperate remedy” to explain why experiments seemed to be violating one of the most fundamental laws of nature, the existence of dark matter particles is inferred because cosmological observations just don’t add up.

    In the early 1930s, the American astronomer Fritz Zwicky was studying the movement of a handful of galaxies in the Coma cluster, a collection of over 1,000 galaxies approximately 320 million light years from Earth.

    Fritz Zwicky, the Father of Dark Matter research.No image credit after long search

    Vera Rubin did much of the work on proving the existence of Dark Matter. She and Fritz were both overlooked for the Nobel prize.

    Vera Rubin measuring spectra (Emilio Segre Visual Archives AIP SPL)


    Astronomer Vera Rubin at the Lowell Observatory in 1965. (The Carnegie Institution for Science)

    Using data published by Edwin Hubble, Zwicky calculated the mass of the entire Coma galaxy cluster.

    Coma cluster via NASA/ESA Hubble

    When he did, Zwicky noticed something odd about the velocity dispersion—the statistical distribribution of the speeds of a group of objects—of the galaxies: The velocity distribution was about 12 times higher than it should be based on the amount of matter in the galaxies.

    Inside Gran Sasso- Image- Xavier Aaronson-Motherboard

    This was a surprising calculation and its significance wasn’t lost on Zwicky. “If this would be confirmed,” he wrote, “we would get the surprising result that dark matter is present in much greater amount than luminous matter.”

    The idea that the universe was made up mostly of invisible matter was a radical idea in Zwicky’s time and still is today. The main difference, however, is that astronomers now have much stronger empirical evidence pointing to its existence. This is mostly due to the American astronomer Vera Rubin, whose measurement of galactic rotations in the 1960s and 70s put the existence of dark matter beyond a doubt. In fact, based on Rubin’s measurements and subsequent observations, physicists now think dark matter makes up about 27 percent of the “stuff” in the universe, about seven times more than the regular, baryonic matter we’re all familiar with. The burning question, then, is what is it made of?

    Since Rubin’s pioneering observations, a number of dark matter candidate particles have been proposed, but so far all of them have eluded detection by some of the world’s most sensitive instruments. Part of the reason for this is that physicists aren’t exactly sure what they’re looking for. In fact, a small minority of physicists think dark matter might not be a particle at all and is just an exotic gravitational effect. This makes designing dark matter experiments kind of like finding a car key in a stadium parking lot and trying to track down the vehicle it pairs with. There’s a pretty good chance the car is somewhere in the parking lot, but you’re going to have to try a lot of doors before you find your ride—if it even exists.

    Among the candidates for dark matter are subatomic particles with goofy names like axions, gravitinos, Massive Astrophysical Compact Halo Objects (MACHOs), and Weakly Interacting Massive Particles (WMIPs.) D’Angelo and his colleagues at Gran Sasso have placed their bets on WIMPs, which until recently were considered to be the leading particle candidate for dark matter.

    Over the last few years, however, physicists have started to look at other possibilities after some critical tests failed to confirm the existence of WIMPs. WIMPs are a class of hypothetical elementary particles that hardly ever interact with regular baryonic matter and don’t emit light, which makes them exceedingly hard to detect. This problem is compounded by the fact that no one is really sure how to characterize a WIMP. Needless to say, it’s hard to find something if you’re not even really sure what you’re looking for.

    So why would physicists think WIMPs exist at all? In the 1970s, physicists conceptualized the Standard Model of particle physics, which posited that everything in the universe was made out of a handful of fundamental particles.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.


    Standard Model of Particle Physics from Symmetry Magazine

    The Standard Model works great at explaining almost everything the universe throws at it, but it’s still incomplete since it doesn’t incorporate gravity into the model.

    Gravity measured with two slightly different torsion pendulum set ups and slightly different results

    In the 1980s, an extension of the Standard Model called Supersymmetry emerged, which hypothesizes that each fundamental particle in the Standard Model has a partner.

    Standard model of Supersymmetry DESY

    These particle pairs are known as supersymmetric particles and are used as the theoretical explanation for a number of mysteries in Standard Model physics, such as the mass of the Higgs boson and the existence of dark matter. Some of the most complex and expensive experiments in the world like the Large Hadron Collider particle accelerator were created in an effort to discover these supersymmetric particles, but so far there’s been no experimental evidence that these particles actually exist.

    LHC

    CERN map


    CERN LHC Tunnel

    CERN LHC particles

    Many of the lightest particles theorized in the supersymmetric model are WIMPs and go by names like the gravitino, sneutrino and neutralino. The latter is still considered to be the leading candidate for dark matter by many physicists and is thought to have formed in abundance in the early universe. Detecting evidence of this ancient theoretical particle is the goal of many dark matter experiments, including the one D’Angelo works on at Gran Sasso.

    D’Angelo told me he became interested in dark matter a few years after joining the Gran Sasso laboratory and began contributing to the laboratory’s DarkSide experiment, which seemed like a natural extension of his work on solar neutrinos. DarkSide is essentially a large tank filled with liquid argon and equipped with incredibly sensitive sensors. If WIMPs exist, physicists expect to detect them from the ionization produced through their collision with the argon nuclei.

    Dark Side-50 Dark Matter Experiment at Gran Sasso

    The set up of the SABRE experiment is deliberately similar to another experiment that has been running at Gran Sasso since 1995 called DAMA. In 2003, the DAMA experiment began looking for seasonal fluctuations in dark matter particles that was predicted in the 1980s as a consequence of the relative motion of the sun and Earth to the rest of the galaxy. The theory posited that the relative speed of any dark matter particles detected on Earth should peak in June and bottom out in December.

    The DarkSide experiment has been running at Gran Sasso since 2013 and D’Angelo said it is expected to continue for several more years. These days, however, he’s found himself involved with a different dark matter experiment at Gran Sasso called SABRE [above], which will also look for direct evidence of dark matter particles based on the light produced when energy is released through their collision with Sodium-Iodide crystals.

    Over the course of nearly 15 years, DAMA did in fact register seasonal fluctuations in its detectors that were in accordance with this theory and the expected signature of a dark matter particle. In short, it seemed as if DAMA was the first experiment in the world to detect a dark matter particle. The problem, however, was that DAMA couldn’t completely rule out the possibility that the signature it had detected was in fact due to some other seasonal variation on Earth, rather than the ebb and flow of dark matter as the Earth revolved around the Sun.

    SABRE aims to remove the ambiguities in DAMA’s data. After all the kinks are worked out in the testing equipment, the Gran Sasso experiment will become one half of SABRE. The other half will be located in Australia in a converted gold mine. By having a laboratory in the northern hemisphere and another in the southern hemisphere, this should help eliminate any false positives that result from normal seasonal fluctuations. At the moment, the SABRE detector is still in a proof of principle phase and is expected to begin observations in both hemispheres within the next few years.

    When it comes to SABRE, it’s possible that the experiment may disprove the best evidence physicists have found so far for a dark matter particle. But as D’Angelo pointed out, this type of disappointment is a fundamental part of science.

    “Of course I am afraid that there might not be any dark matter there and we are hunting ghosts, but science is like this,” D’Angelo said. “Sometimes you spend several years looking for something and in the end it’s not there so you have to change the way you were thinking about things.”

    For D’Angelo, probing the subatomic world with neutrino and dark matter research from a cave in Italy is his way of connecting to the universe writ large.

    “The tiniest elements of nature are bonded to the most macroscopic phenomena, like the expansion of the universe,” D’Angelo said. “The infinitely small touches the infinitely big in this sense, and I find that fascinating. The physics I do, it’s goal is to push over the boundary of human knowledge.”

    See the full article here .

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

    INFN Gran Sasso National Laboratory (LNGS) is the largest underground laboratory in the world devoted to neutrino and astroparticle physics, a worldwide research facility for scientists working in this field of research, where particle physics, cosmology and astrophysics meet. It is unequalled anywhere else, as it offers the most advanced underground infrastructures in terms of dimensions, complexity and completeness.

    LNGS is funded by the National Institute for Nuclear Physics (INFN), the Italian Institution in charge to coordinate and support research in elementary particles physics, nuclear and sub nuclear physics

    Located between L’Aquila and Teramo, at about 120 kilometres from Rome, the underground structures are on one side of the 10-kilometre long highway tunnel which crosses the Gran Sasso massif (towards Rome); the underground complex consists of three huge experimental halls (each 100-metre long, 20-metre large and 18-metre high) and bypass tunnels, for a total volume of about 180.000 m3.

    Access to experimental halls is horizontal and it is made easier by the highway tunnel. Halls are equipped with all technical and safety equipment and plants necessary for the experimental activities and to ensure proper working conditions for people involved.

    The 1400 metre-rock thickness above the Laboratory represents a natural coverage that provides a cosmic ray flux reduction by one million times; moreover, the flux of neutrons in the underground halls is about thousand times less than on the surface due to the very small amount of uranium and thorium of the Dolomite calcareous rock of the mountain.

    The permeability of cosmic radiation provided by the rock coverage together with the huge dimensions and the impressive basic infrastructure, make the Laboratory unmatched in the detection of weak or rare signals, which are relevant for astroparticle, sub nuclear and nuclear physics.

    Outside, immersed in a National Park of exceptional environmental and naturalistic interest on the slopes of the Gran Sasso mountain chain, an area of more than 23 acres hosts laboratories and workshops, the Computing Centre, the Directorate and several other Offices.

    Currently 1100 scientists from 29 different Countries are taking part in the experimental activities of LNGS.
    LNGS research activities range from neutrino physics to dark matter search, to nuclear astrophysics, and also to earth physics, biology and fundamental physics.

     
    • Marco Pereira 2:43 pm on September 1, 2018 Permalink | Reply

      I created a theory called the Hypergeometrical Universe Theory (HU). This theory uses three hypotheses:
      a) The Universe is a lightspeed expanding hyperspherical hypersurface. This was later proven correct by observations by the Sloan Digital Sky Survey
      https://hypergeometricaluniverse.quora.com/Proof-of-an-Extra-Spatial-Dimension
      b) Matter is made directly and simply from coherences between stationary states of deformation of the local metric called Fundamental Dilator or FD.
      https://hypergeometricaluniverse.quora.com/The-Fundamental-Dilator
      c) FDs obey the Quantum Lagrangian Principle (QLP). Yves Couder had a physical implementation (approximation) of the Fundamental Dilator and was perplexed that it would behave Quantum Mechanically. FDs and the QLP are the reason for Quantum Mechanics. QLP replaces Newtonian Dynamics and allows for the derivation of Quantum Gravity or Gravity as applied to Black Holes.

      HU derives a new law of Gravitation that is epoch-dependent. That makes Type 1a Supernovae to be epoch-dependent (within the context of the theory). HU then derives the Absolute Luminosity of SN1a as a function of G and showed that Absolute Luminosity scales with G^{-3}.
      Once corrected the Photometrically Determined SN1a distances, HU CORRECTLY PREDICTS all SN1a distances given their redshifts z.

      The extra dimension refutes all 4D spacetime theories, including General Relativity and L-CDM. HU also falsifies all Dark Matter evidence:
      https://www.quora.com/Are-dark-matter-and-dark-energy-falsifiable/answer/Marco-Pereira-1
      including the Spiral Galaxy Conundrum and the Coma Cluster Conundrum.

      Somehow, my theory is still been censored by the community as a whole (either directly or by omission).

      I hope this posting will help correct this situation.

      Like

  • richardmitnick 12:01 pm on May 15, 2018 Permalink | Reply
    Tags: Dark Matter experiments, , SNOLAB, SuperCDMS (Cryogenic Dark Matter Search), ,   

    From Sanford Underground Research Facility: “SD Mines develops radon reduction system for LZ, SuperCDMS” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    May 14, 2018
    Constance Walter

    1
    Radon reduction researchers pictured with the machine they designed from left): SD Mines physics graduate student Joseph Street, Richard Schnee, Ph.D., along with lab technicians David Molash and Christine Hjelmfelt. Charles Michael Ray, SD Mines

    In the coming months, researchers will begin building the LUX-ZEPLIN dark matter experiment in a surface cleanroom at the Sanford Underground Research Facility (Sanford Lab).

    LBNL Lux Zeplin project at SURF

    Once the detector is assembled, a team will carefully move the highly sensitive physics equipment to its home on the 4850 Level of Sanford Lab.

    But before that can happen, there’s some work that needs to be done to ensure the experiment remains free of backgrounds that could interfere with the results. That’s where Dr. Richard Schnee and a team from the South Dakota School of Mines & Technology come in. Schnee, who is head of the physics department at SD Mines and a collaborator with LZ, heads up the SD Mines team that designed a radon reduction system for the experiment.

    “Our detectors need very low levels of radon,” Schnee said. While the radon levels at the 4850 Level are safe for humans, they are too high for sensitive experiments like LZ, which go deep underground to escape cosmic radiation, Schnee explained. “We will take regular air from the facility and the systems will reduce the levels by 1,000 times or more.”

    LZ, a second-generation dark matter experiment, will continue the search for WIMPs—weakly interacting massive particles—begun by its much smaller predecessor LUX (Large Underground Xenon), which was named the most sensitive of its kind in 2013 and again in 2016.

    U Washington Large Underground Xenon at SURF, Lead, SD, USA

    LZ will hold 10 tons of liquid xenon, making it approximately 30 times larger and 100 times more sensitive than LUX.

    LZ is designed so that if a dark matter particle collides with a xenon atom, it will produce a flash of light followed by a second flash of light when the electrons produced in the liquid xenon chamber drift to its top. The light pulses, picked up by a series of about 500 photo multiplier tubes lining the massive tank—over four times more than were installed in LUX—will carry the telltale fingerprint of the particles that created them.

    Additionally, LZ will include a component not present in LUX—nine acrylic tanks filled with a liquid scintillator will form a veto system around the experiment, allowing researchers to better recognize a WIMP if they see one.

    The system designed by the SD Mines team focuses specifically on filtering out radon particles to produce the ultra-pure air needed for the acrylic tanks and other components of LZ located in the same water tank that held LUX. The team is also helping ensure the parts used to build the experiments are relatively free of radon.

    “The real problem for these super sensitive dark mater detectors are the radon daughters that are radioactive,” Schnee said. Even miniscule amounts of radioactive particles could contaminate and throw off the experiments—so the work of Schnee and his team is critical.

    “We are very excited to have SD Mines as a partner in producing a major component for LZ, a world-leading dark matter experiment,” said Mike Headley, executive director the South Dakota Science and Technology Authority.

    LZ is in a global race to discover dark matter. One competitor, SuperCDMS (Cryogenic Dark Matter Search), which will be located at SNOLab in Canada, is using germanium to search for WIMPs. And SD Mines is designing a radon reduction system for that experiment as well, Schnee said.

    SNOLAB, a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario


    SNOLAB, Sudbury, Ontario, Canada.

    LBNL SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)


    LBNL SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)


    LBNL Super CDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)

    SNOLab is the deepest underground laboratory in North America at 6,800 feet deep. Although the experiments are competitors, Schnee said they actually complement each other as they are searching for dark matter in different areas. To use a metaphor, if dark matter were a lost child in a large cornfield, LZ would be looking in one part of the field, and SuperCDMS would be looking in another. Both projects will begin operations in the early 2020s. SD Mines is one of 26 institutions working on the SuperCDMS and one of 37 institutions working on LZ.

    Headley attributes the expanding role of SD Mines’ in research at Sanford Lab and other international experiments to the Ph.D. program in South Dakota. SD Mines and the University of South Dakota offer a joint program and each graduated Ph.D. students in 2017.

    “With the implementation of the Ph.D. program in 2012, South Dakota institutions are attracting high-quality professors and students,” Headley said. “It’s impressive to see them deliver such an important component for LZ, but also on other experiments around the world.”

    To learn more about the physics program at SD Mines, go to http://www.sdsmt.edu; to read the full press release about SD Mines work on LZ and SuperCDMS, go to https://www.sdsmt.edu/Research/.

    You can learn more about LZ at http://lz.lbl.gov/detector/and SCDMS at https://supercdms.slac.stanford.edu.

    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 2:31 pm on May 11, 2018 Permalink | Reply
    Tags: Arthur B. McDonald Canadian Astroparticle Physics Research Institute, , , , , , , , SNOLAB   

    From Perimeter Institute: “New centre for astroparticle physics launches in Canada” 

    Perimeter Institute

    From Perimeter Institute

    May 10, 2018

    Perimeter Institute is among 13 partner organizations contributing to a new national hub of astroparticle physics at Queen’s University in Kingston, Ontario.

    Queen’s University has officially launched the Arthur B. McDonald Canadian Astroparticle Physics Research Institute, a national research network dedicated to understanding some of the universe’s deepest mysteries.

    The namesake of the institute, Arthur B. McDonald, is the 2015 Nobel laureate in physics for his pioneering neutrino work at SNOLAB, and is a member of Perimeter Institute’s Board of Directors.

    SNOLAB, a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario

    SNOLAB, Sudbury, Ontario, Canada.

    The newly announced institute is the result of a $63.7 million investment from the Government of Canada’s Canada First Research Excellence Fund given to Queen’s University in 2016.

    Perimeter Institute is among the five affiliated research organizations and eight universities in partnership with the McDonald Institute. Together, the partners aim to facilitate the exchange of research and ideas at the intersections of cosmology and particle physics.

    “Although the dimensions of the particles we are studying are minute, the implications of these discoveries are monumental and fundamental to the very properties of science and our understanding of the formation and evolution of the universe,” said McDonald Institute Scientific Director Tony Noble at the May 8 launch in Kingston.

    Perimeter Faculty Chair Luis Lehner said partnering with the McDonald Institute will facilitate “collaborative research in pursuit of answers to some of the deepest mysteries in science, and mutually strengthen the training and educational outreach activities of both institutes.”

    Over the past year and a half, the McDonald Institute has appointed a scientific director and recruited 13 new faculty members (out of 15 designated positions) from around the world.

    In addition to advancing research into areas such as the mysteries surrounding dark matter and neutrino science, the McDonald Institute has a mandate for scientific outreach and to develop unique undergraduate and graduate student programming and opportunities.

    Visit http://www.mcdonaldinstitute.ca for more information.

    See the full article here .

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    About Perimeter

    Perimeter Institute is the world’s largest research hub devoted to theoretical physics. The independent Institute was founded in 1999 to foster breakthroughs in the fundamental understanding of our universe, from the smallest particles to the entire cosmos. Research at Perimeter is motivated by the understanding that fundamental science advances human knowledge and catalyzes innovation, and that today’s theoretical physics is tomorrow’s technology. Located in the Region of Waterloo, the not-for-profit Institute is a unique public-private endeavour, including the Governments of Ontario and Canada, that enables cutting-edge research, trains the next generation of scientific pioneers, and shares the power of physics through award-winning educational outreach and public engagement.

     
  • richardmitnick 9:01 am on May 7, 2018 Permalink | Reply
    Tags: , , Construction Begins on One of the World’s Most Sensitive Dark Matter Experiments, , , , , SNOLAB, SuperCDMS SNOLAB experiment,   

    From SLAC Lab: “Construction Begins on One of the World’s Most Sensitive Dark Matter Experiments” 


    From SLAC Lab

    May 7, 2018

    Press Office Contact: Andrew Gordon,
    agordon@slac.stanford.edu
    (650) 926-2282

    Written by Manuel Gnida

    1
    The future SuperCDMS SNOLAB experiment will hunt for weakly interacting massive particles (WIMPs), hypothetical components of dark matter. If a WIMP (white trace) strikes an atom inside the experiment’s detector crystals (gray), it will cause the crystal lattice to vibrate (blue). The collision will also send electrons (red) through the crystal that enhance the vibrations. (Greg Stewart/SLAC National Accelerator Laboratory)

    2
    The future SuperCDMS SNOLAB experiment will hunt for weakly interacting massive particles (WIMPs), hypothetical components of dark matter. This photo shows one of the experiment’s detector crystals within its protective copper housing. (Andy Freeberg/SLAC National Accelerator Laboratory)

    3
    SLAC’s Paul Brink handles the SuperCDMS SNOLAB engineering tower. (Chris Smith/SLAC National Accelerator Laboratory)

    4
    A SuperCDMS SNOLAB detector, fabricated at Texas A&M University. (Matt Cherry/SuperCDMS collaboration/SLAC National Accelerator Laboratory)

    5
    Dan Bauer (left) and Mark Ruschman in Fermilab’s Lab G , where the SuperCDMS SNOLAB project is preparing to test the cryogenics system for the new experiment. (Reidar Hahn/Fermi National Accelerator Laboratory)

    6
    Fermilab’s Mark Ruschman tests prototypes for the SuperCDMS SNOLAB cryogenics system. (Reidar Hahn/Fermi National Accelerator Laboratory)

    The SuperCDMS SNOLAB project, a multi-institutional effort led by SLAC, is expanding the hunt for dark matter to particles with properties not accessible to any other experiment.

    SNOLAB, Sudbury, Ontario, Canada.

    The U.S. Department of Energy has approved funding and start of construction for the SuperCDMS SNOLAB experiment, which will begin operations in the early 2020s to hunt for hypothetical dark matter particles called weakly interacting massive particles, or WIMPs. The experiment will be at least 50 times more sensitive than its predecessor, exploring WIMP properties that can’t be probed by other experiments and giving researchers a powerful new tool to understand one of the biggest mysteries of modern physics.

    The DOE’s SLAC National Accelerator Laboratory is managing the construction project for the international SuperCDMS collaboration of 111 members from 26 institutions, which is preparing to do research with the experiment.

    “Understanding dark matter is one of the hottest research topics – at SLAC and around the world,” said JoAnne Hewett, head of SLAC’s Fundamental Physics Directorate and the lab’s chief research officer. “We’re excited to lead the project and work with our partners to build this next-generation dark matter experiment.”

    With the DOE approvals, known as Critical Decisions 2 and 3, the researchers can now build the experiment. The DOE Office of Science will contribute $19 million to the effort, joining forces with the National Science Foundation ($12 million) and the Canada Foundation for Innovation ($3 million).

    “Our experiment will be the world’s most sensitive for relatively light WIMPs – in a mass range from a fraction of the proton mass to about 10 proton masses,” said Richard Partridge, head of the SuperCDMS group at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), a joint institute of SLAC and Stanford University. “This unparalleled sensitivity will create exciting opportunities to explore new territory in dark matter research.”

    An Ultracold Search 6,800 Feet Underground

    Scientists know that visible matter in the universe accounts for only 15 percent of all matter. The rest is a mysterious substance, called dark matter. Due to its gravitational pull on regular matter, dark matter is a key driver for the evolution of the universe, affecting the formation of galaxies like our Milky Way. It therefore is fundamental to our very own existence.

    But scientists have yet to find out what dark matter is made of. They believe it could be composed of dark matter particles, and WIMPs are top contenders. If these particles exist, they would barely interact with their environment and fly right through regular matter untouched. However, every so often, they could collide with an atom of our visible world, and dark matter researchers are looking for these rare interactions.

    7
    The centerpiece of the SuperCDMS SNOLAB experiment will be four detector towers (left), each containing six detector packs. The towers will be mounted inside the SNOBOX (right), a vessel in which the detector packs will be cooled to almost absolute zero temperature. (Greg Stewart/SLAC National Accelerator Laboratory)

    In the SuperCDMS SNOLAB experiment, the search will be done using silicon and germanium crystals, in which the collisions would trigger tiny vibrations. However, to measure the atomic jiggles, the crystals need to be cooled to less than minus 459.6 degrees Fahrenheit – a fraction of a degree above absolute zero temperature. These ultracold conditions give the experiment its name: Cryogenic Dark Matter Search, or CDMS. The prefix “Super” indicates an increased sensitivity compared to previous versions of the experiment.

    The collisions would also produce pairs of electrons and electron deficiencies that move through the crystals, triggering additional atomic vibrations that amplify the signal from the dark matter collision. The experiment will be able to measure these “fingerprints” left by dark matter with sophisticated superconducting electronics.

    The experiment will be assembled and operated at the Canadian laboratory SNOLAB – 6,800 feet underground inside a nickel mine near the city of Sudbury. It’s the deepest underground laboratory in North America. There it will be protected from high-energy particles, called cosmic radiation, which can create unwanted background signals.

    8
    The SuperCDMS dark matter experiment will be located at the Canadian laboratory SNOLAB, 2 kilometers (6,800 feet) underground inside a nickel mine near the city of Sudbury. It’s the deepest underground laboratory in North America. There it will be protected from high-energy particles, called cosmic radiation, which can create unwanted background signals. (Greg Stewart/SLAC National Accelerator Laboratory; inset: SNOLAB)

    “SNOLAB is excited to welcome the SuperCDMS SNOLAB collaboration to the underground lab,” said Kerry Loken, SNOLAB project manager. “We look forward to a great partnership and to supporting this world-leading science.”

    Over the past months, a detector prototype has been successfully tested at SLAC. “These tests were an important demonstration that we’re able to build the actual detector with high enough energy resolution, as well as detector electronics with low enough noise to accomplish our research goals,” said KIPAC’s Paul Brink, who oversees the detector fabrication at Stanford.

    Together with seven other collaborating institutions, SLAC will provide the experiment’s centerpiece of four detector towers, each containing six crystals in the shape of oversized hockey pucks. The first tower could be sent to SNOLAB by the end of 2018.

    “The detector towers are the most technologically challenging part of the experiment, pushing the frontiers of our understanding of low-temperature devices and superconducting readout,” said Bernard Sadoulet, a collaborator from the University of California, Berkeley.

    A Strong Collaboration for Extraordinary Science

    In addition to SLAC, two other national labs are involved in the project. Fermi National Accelerator Laboratory is working on the experiment’s intricate shielding and cryogenics infrastructure, and Pacific Northwest National Laboratory is helping understand background signals in the experiment, a major challenge for the detection of faint WIMP signals.

    9
    Slideshow of SuperCDMS SNOLAB photos. For more images, visit the SuperCDMS SNOLAB photostream on Flickr.

    A number of U.S. and Canadian universities also play key roles in the experiment, working on tasks ranging from detector fabrication and testing to data analysis and simulation. The largest international contribution comes from Canada and includes the research infrastructure at SNOLAB.

    “We’re fortunate to have a close-knit network of strong collaboration partners, which is crucial for our success,” said KIPAC’s Blas Cabrera, who directed the project through the CD-2/3 approval milestone. “The same is true for the outstanding support we’re receiving from the funding agencies in the U.S. and Canada.”

    Fermilab’s Dan Bauer, spokesperson of the SuperCDMS collaboration said, “Together we’re now ready to build an experiment that will search for dark matter particles that interact with normal matter in an entirely new region.”

    SuperCDMS SNOLAB will be the latest in a series of increasingly sensitive dark matter experiments. The most recent version, located at the Soudan Mine in Minnesota, completed operations in 2015.

    “The project has incorporated lessons learned from previous CDMS experiments to significantly improve the experimental infrastructure and detector designs for the experiment,” said SLAC’s Ken Fouts, project manager for SuperCDMS SNOLAB. “The combination of design improvements, the deep location and the infrastructure support provided by SNOLAB will allow the experiment to reach its full potential in the search for low-mass dark matter.”

    For more information on the SuperCDMS SNOLAB project and the SuperCDMS collaboration, check out this website:

    SuperCDMS SNOLAB Website

    See the full article here .

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    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 12:50 pm on March 20, 2018 Permalink | Reply
    Tags: , Beyond the WIMP: Unique Crystals Could Expand the Search for Dark Matter, , , , SNOLAB,   

    From LBNL: “Beyond the WIMP: Unique Crystals Could Expand the Search for Dark Matter” 

    Berkeley Logo

    Berkeley Lab

    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 486-5582

    1
    A computerized simulation of the large-scale distribution of dark matter in the universe. An overlay graph (in white) shows how a crystal sample intensely scintillates, or glows, when exposed to X-rays during a lab test. This and other properties could make it a good material for a dark matter detector. (Credit: Millennium Simulation, Berkeley Lab)

    A new particle detector design proposed at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) could greatly broaden the search for dark matter – which makes up 85 percent of the total mass of the universe yet we don’t know what it’s made of – into an unexplored realm.

    While several large physics experiments have been targeting theorized dark matter particles called WIMPs, or weakly interacting massive particles, the new detector design could scan for dark matter signals at energies thousands of times lower than those measurable by more conventional WIMP detectors.

    The ultrasensitive detector technology incorporates crystals of gallium arsenide that also include the elements silicon and boron. This combination of elements causes the crystals to scintillate, or light up, in particle interactions that knock away electrons.

    This scintillation property of gallium arsenide has been largely unexplored, said Stephen Derenzo, a senior physicist in the Molecular Biophysics and Integrated Bioimaging Division at Berkeley Lab and lead author of a study published March 20 in the Journal of Applied Physics that details the material’s properties.

    “It’s hard to imagine a better material for searching in this particular mass range,” Derenzo said, which is measured in MeV, or millions of electron volts. “It ticks all of the boxes. We are always worried about a ‘Gotcha!’ or showstopper. But I have tried to think of some way this detector material can fail and I can’t.”

    The breakthrough came from Edith Bourret, a senior staff scientist in Berkeley Lab’s Materials Sciences Division who decades earlier had researched gallium arsenide’s potential use in circuitry. She gave him a sample of gallium arsenide from this previous work that featured added concentrations, or “dopants,” of silicon and boron.

    Derenzo had previously measured some lackluster performance in a sample of commercial-grade gallium arsenide. But the sample that Bourret handed him exhibited a scintillation luminosity that was five times brighter than in the commercial material, owing to the silicon and boron that imbued the material with new and enhanced properties. This enhanced scintillation meant it was far more sensitive to electronic excitations.

    “If she hadn’t handed me this sample from more than 20 years ago, I don’t think I would have pursued it,” Derenzo said. “When this material is doped with silicon and boron, this turns out to be very important and, accidentally, a very good choice of dopants.”

    Derenzo noted that he has had a longstanding interest in scintillators that are also semiconductors, as this class of materials can produce ultrafast scintillation useful for medical imaging applications such as PET (positron emission tomography) and CT (computed tomography) scans, for example, as well as for high-energy physics experiments and radiation detection.

    The doped gallium arsenide crystals he studied appear well-suited for high-sensitivity particle detectors because extremely pure crystals can be grown commercially in large sizes, the crystals exhibit a high luminosity in response to electrons booted away from atoms in the crystals’ atomic structure, and they don’t appear to be hindered by typical unwanted effects such as signal afterglow and dark current signals.

    Some of the larger WIMP-hunting detectors – such as that of the Berkeley Lab-led LUX-ZEPLIN project now under construction in South Dakota, and its predecessor, the LUX experiment – incorporate a liquid scintillation detector. A large tank of liquid xenon is surrounded by sensors to measure any light and electrical signals expected from a dark matter particle’s interaction with the nucleus of a xenon atom. That type of interaction is known as a nuclear recoil.

    2
    A crystal of gallium arsenide. (Credit: Wikimedia Commons)

    In contrast, the crystal-based gallium arsenide detector is designed to be sensitive to the slighter energies associated with electron recoils – electrons ejected from atoms by their interaction with dark matter particles. As with LUX and LUX-ZEPLIN, the gallium arsenide detector would need to be placed deep underground to shield it from the typical bath of particles raining down on Earth.

    It would also need to be coupled to light sensors that could detect the very few infrared photons (particles of light) expected from a low-mass dark matter particle interaction, and the detector would need to be chilled to cryogenic temperatures. The silicon and boron dopants could also possibly be optimized to improve the overall sensitivity and performance of the detectors.

    Because dark matter’s makeup is still a mystery – it could be composed of one or many particles of different masses, for example, or may not be composed of particles at all – Derenzo noted that gallium arsenide detectors provide just one window into dark matter particles’ possible hiding places.

    While WIMPs were originally thought to inhabit a mass range measured in billions of electron volts, or GeV, the gallium arsenide detector technology is well-suited to detecting particles in the mass range measured in millions of electron volts, or MeV.

    Berkeley Lab physicists are also proposing other types of detectors to expand the dark matter search, including a setup that uses an exotic state of chilled helium known as superfluid helium to directly detect low-mass dark matter particles.

    “Superfluid helium is scientifically complementary to gallium arsenide since helium is more sensitive to dark matter interactions with atomic nuclei, while gallium arsenide is sensitive to dark matter interacting with electrons,” said Dan McKinsey, a faculty senior scientist at Berkeley Lab and physics professor at UC Berkeley who is a part of the LZ Collaboration and is conducting R&D on dark matter detection using superfluid helium.

    LBNL LZ project at SURF, Lead, SD, USA

    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

    “We don’t know whether dark matter interacts more strongly with nuclei or electrons – this depends on the specific nature of the dark matter, which is so far unknown,” he said.

    Another effort would employ gallium arsenide crystals in a different approach to the light dark matter search based on vibrations in the atomic structure of the crystals, known as optical phonons. This setup could target “light dark photons,” which are theorized low-mass particles that would serve as the carrier of a force between dark matter particles – analogous to the conventional photon that carries the electromagnetic force.

    Still another next-gen experiment, known as the Super Cryogenic Dark Matter Search experiment, or SuperCDMS SNOLAB, will use silicon and germanium crystals to hunt for low-mass WIMPs.

    LBNL SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)

    LBNL SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)


    LBNL Super CDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)

    SNOLAB, a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario

    SNOLAB, a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario

    “These would be complementary experiments,” Derenzo said of the many approaches. “We need to look at all of the possible mass ranges. You don’t want to be fooled. You can’t exclude a mass range if you don’t look there.”

    Stephen Hanrahan, a staff scientist in Berkeley Lab’s Molecular Biophysics and Integrated Bioimaging Division; and Gregory Bizarri, a senior lecturer in manufacturing at Cranfield University in the U.K., also participated in this study. The work was supported by Advanced Crystal Technologies Inc.

    See the full article here .

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    A U.S. Department of Energy National Laboratory Operated by the University of California

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  • richardmitnick 10:48 am on October 17, 2017 Permalink | Reply
    Tags: Carleton U, , DEAP-3600 experiment, Ottawa Citizen, SNOLAB   

    From Carleton U via Ottawa Citizen: “Dark matter: Carleton physicist gets $3.35M to help unravel mysteries of the universe” 

    Carleton University
    1
    Carleton University experimental physicist Mark Boulay has been warded $3.35 million for a new lab. Tony Caldwell

    A Carleton University experimental physicist has been awarded $3.35 million to build a lab to help gain insight into the nature of neutrinos and dark matter. The elusive answers to those questions could lead to nothing less than a better understanding of how the universe was formed.

    Neutrinos are much smaller than other known particles, and are very difficult to detect. The actually mass of the neutrino is not known. A measurement that would shed light on its mass and the origin of that mass would offer some insight into the formation of the universe.

    Dark matter is even more mysterious.

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    LUX Dark matter Experiment at SURF, Lead, SD, USA

    ADMX Axion Dark Matter Experiment, U Uashington

    It has never been observed, but scientists have known for a long time that it’s out there because its gravitational effects can be seen — galaxies move faster than expected, for example.

    Dark matter outweighs conventional matter by five-to-one, said Mark Boulay, who is the Canada Research Chair in Particle Astrophysics and Subatomic Physics. Essentially, most of the matter in the universe is invisible.

    “There’s a large amount of mass that goes unaccounted for. We know that there’s matter out there, but we haven’t directly seen it,” he said.

    The $3.35 million in funding from the Canada Foundation for Innovation will be used to develop and build detectors that use liquified noble gases to identify extremely rare subatomic processes.

    Boulay has been leading the DEAP-3600 experiment in SNOLAB, an underground laboratory in a mine two kilometres under the surface of the earth near Sudbury.

    SNOLAB, a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario

    SNOLAB, a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario

    One hypothesis suggests that dark matter consists of Weakly Interacting Massive Particles, known as WIMPs. The rock overburden at SNOLAB filters out cosmic rays that would interfere with WIMP detection. The DEAP-3600 experiments searches for dark matter particle interactions using a detector containing 3,600 kilograms of liquid argon.

    Dark matter research is one of the highest-profile areas of particle physics — and it’s highly competitive. The detectors being developed for the Carleton lab will support the study of neutrinos and dark matter at SNOLAB. The lab will be used by researchers at Carleton and others in its network, which includes TRIUMF, Canada’s national laboratory for particle and nuclear physics, as well as the University of British Columbia, McGill University and Université de Sherbrooke.

    “In my field we’ve been looking to demonstrate conclusively the existence of this particle. We’ve been looking for two or three decades. We haven’t found it yet. We don’t know what the mass of the particle is, or how likely it is to interact with other matter,” said Boulay. “We understand that we have a lot of work ahead of us.”

    He estimates it will take a year to construct the first set of prototype detectors for the lab at Carleton. The lab will occupy about 2,000 square feet of space in the Herzberg building.

    “We want to be able to define future programs — what detectors we will be able to build in the next 20 years,” said Boulay. “We’re at the leading edge of what’s possible, and we want to push that.”

    See the full article here .

    Please help promote STEM in your local schools.

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    Situated on unceded Algonquin territory beside the historic Rideau Canal, an official UNESCO World Heritage Site, Carleton University was founded by the community in 1942 to meet the needs of veterans returning from the Second World War.

    What defines Carleton?

    We strive for innovation in research, teaching and learning.
    Our location in Ottawa, the nation’s capital, connects us to the world.
    We encourage hands-on experience in the classroom.
    We offer exceptional student support.

     
  • richardmitnick 4:11 pm on September 1, 2017 Permalink | Reply
    Tags: , , DEAP3600, , SNOLAB, ,   

    From TRIUMF: “New results surface from world’s most sensitive argon dark matter experiment” 

    TRIUMF

    31. August 2017

    1

    Argon in its natural form is a colourless, odorless, and non-flammable gas. It is also utterly unreactive – chemists and physicists have long wielded argon to formulate nonreactive and inert conditions. These qualities earned this noble gas its name, derived from the Greek word for ‘inactive.’

    What use, then, is a 3600-kilogram sphere of liquid argon, buried under two kilometers of Ontario bedrock?

    If you ask Dr. Pietro Giampa, a newly-joined TRIUMF scientist and recipient of the Otto Hausser Postdoctoral Fellowship, the simple answer (accompanied by a knowing smile) is: “Possibly changing our entire understanding of physics beyond the Standard Model, but also potentially the entire universe.” He delivers this response with the ease of repetition, a common trait among dark matter physicists. And while it may seem like a lofty claim, for Giampa and a dedicated team of particle physicists, astrophysicists, and astronomers at SNOLAB in Sudbury, ON, the proof may very well be in the depths of liquid argon.

    SNOLAB, Sudbury, Ontario, Canada.

    Deeper understanding

    The sphere of argon is a dark matter detector, and the central component of a state-of-the-art system called DEAP-3600: ‘Dark Matter Experiment using Argon Pulse-shape’ (with the argon weighing in at just over 3600 kilograms). Giampa and the DEAP-3600 team are working to characterize the fundamental properties of dark matter, a nebulous substance that makes up 23% of the mass of our universe and which we know next to nothing about.

    DEAP-3600 is in search of a host of particles widely considered the most viable candidates for dark matter: weakly interacting massive particles, or WIMPs. WIMPs behave similarly to the building-block particles of our universe like protons and neutrons, except that they don’t interact via any forces other than the electroweak and gravitational. This means that most WIMPs pass through our world without any interaction with atoms, subatomic particles, or nearly anything else.

    DEAP-3600 works by listening for collisions between dark matter and the nuclei of argon atoms. The impacts will be faint, and the apparatus can only listen in on one bandwidth at a time. Theoretical models beyond the Standard Model point to a WIMP of mass 100 gigaelectronvolts (GeV) or greater, a range DEAP is uniquely capable of investigating.

    Essentially, the detector provides a small sphere of space where collision events between WIMPs and the nuclei of argon atoms can be quietly recorded. Inactive argon, which undergoes no radioactive decay unless perturbed, is the perfect target for incoming dark matter particles; situating the argon sphere 2070 meters below Earth’s surface only heightens DEAP’s senses, eliminating the white noise of WIMP-like cosmic rays and muons. With a sufficiently large detector space and a sufficiently sensitive detection apparatus, there’s a chance that we’ll bear witness to the first WIMP ever observed as it glances off an argon atom.

    2
    DEAP-3600 takes a long, hard listen; silence.

    The DEAP team’s first results have surfaced: a new paper published by the group on August 1st, 2017 describes preliminary results from the experiment, and conclusions gleaned from just four and a half days of data-taking immediately following the completion of the detector system in August 2016. The paper details an extremely sensitive system, and a similarly sensitive, high-performance mathematical model for discriminating between the energy signals of WIMPs of different masses near the 100 GeV range.

    The experiment didn’t observe any dark matter-argon collisions during its initial monitoring period, but this absence of signal is itself a telling sign. While the number of potential WIMP-argon collisions is as large as the diversity of WIMP masses, it is finite – by ruling out different masses of WIMPs, Giampa and the DEAP team are honing in on the mass of the WIMP that may interact with an argon nucleus.

    Finding such a particle would be a boon for the field of particle physics. While WIMPS were chosen because they fit snugly into current theoretical models as potential dark matter particles, their discovery would have vast ramifications that extend beyond our current understanding of particle physics. Our entire concept of the universe would undergo a dramatic, tectonic shift.

    With this lofty goal as their north star, the DEAP team (including TRIUMF scientists Pierre-Andre Amadruz, Ben Smith, Thomas Lidner, and TRIUMF team leader Fabrice Retiere) will continue their search, re-calibrating and tuning into different bandwidths of potential collisions. Further data-taking has been ongoing since August 2016, and it’s possible that more results will surface soon.

    “We’re very excited to have proven the precision and sensitivity of the detector apparatus. While we’re but one of the many experiments around the world investigating the identity of dark matter, we can’t help but think that we are now one step closer to making this remarkable discovery.” – Dr. Pietro Giampa

    To keep tabs on the DEAP team or to learn more about the experiment, visit: http://deap3600.ca/

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition
    Triumf Campus
    Triumf Campus
    World Class Science at Triumf Lab, British Columbia, Canada
    Canada’s national laboratory for particle and nuclear physics
    Member Universities:
    University of Alberta, University of British Columbia, Carleton University, University of Guelph, University of Manitoba, Université de Montréal, Simon Fraser University,
    Queen’s University, University of Toronto, University of Victoria, York University. Not too shabby, eh?

    Associate Members:
    University of Calgary, McMaster University, University of Northern British Columbia, University of Regina, Saint Mary’s University, University of Winnipeg, How bad is that !!

     
  • richardmitnick 3:28 pm on February 28, 2017 Permalink | Reply
    Tags: , , PICO collaboration, SNOLAB   

    From FNAL: “New world-leading limit on dark matter search from PICO experiment” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    February 27, 2017
    Andre Salles
    Fermilab Office of Communication
    asalles@fnal.gov
    630-840-6733

    Editor’s note: The PICO-60 detector was originally called “COUPP-60,” with COUPP standing for “Chicagoland Observatory for Underground Particle Physics.” It was designed and built by Fermilab in collaboration with the University of Chicago and Indiana University, South Bend. Work began at Fermilab in 2005, and, after extensive testing, the detector was moved to SNOLAB in 2012.

    1
    A team of Fermilab scientists installs the PICO-60 dark matter detector at SNOLAB. Photo: Fermilab

    “We’ve been working on this for a long time,” said Fermilab’s project manager Andrew Sonnenschein of the below result. “This is by far our most satisfying result yet, because the techniques we used to reject background events from sources other than dark matter worked flawlessly. Bubble chambers are finally living up to their full potential as dark matter detectors. Now the dark matter just needs to show up.”

    Read the original SNOLAB press release on the SNOLAB website.

    The PICO Collaboration is excited to announce that the PICO-60 dark matter bubble chamber experiment has produced a new dark matter limit after analysis of data from the most recent run. This new result is a factor of 17 improvement in the limit for spin-dependent WIMP-proton cross-section over the already world-leading limits from PICO-2L run-2 and PICO-60 CF3I run-1 in 2016.

    The PICO-60 experiment is currently the world’s largest bubble chamber in operation; it is filled with 45 Liters of C3F8 (octafluoropropane) and is taking data in the ladder lab area of SNOLAB. The detector uses the target fluid in a superheated state such that a dark matter particle interaction with a fluorine nucleus causes the fluid to boil and creates a tell tale bubble in the chamber.

    The PICO experiment uses digital cameras to see the bubbles and acoustic pickups to improve the ability to distinguish between dark matter particles and other sources when analysing the data.

    The superheated detector technology has been at the forefront of spin-dependent (SD) searches, using various refrigerant targets including CF3I, C4F10 and C2ClF5, and two primary types of detectors: bubble chambers and droplet detectors. PICO is the leading experiment in the direct detection of dark matter for spin-dependent couplings and is developing a much larger version of the experiment with up to 500 kg of active mass.

    2
    Inside the PICO-60 detector, installed at SNOLAB in Sudbury, Ontario. Photo: SNOLAB

    About PICO

    17 participating institutions: University of Alberta; University of Chicago; Czech Technical University; Fermilab; Indiana University South Bend; Kavli Institute for Cosmological Physics; Laurentian University; Université de Montréal; Northeastern Illinois University (NEIU); Northwestern University; Universidad Nacional Autonoma de Mexico; Pacific Northwest National Laboratory; Queen’s University at Kingston; Saha Institute of Nuclear Physics, India; SNOLAB; Universitat Politecnica de Valencia; Virginia Tech.

    The PICO Collaboration (formed from the merger of two existing groups, PICASSO and COUPP) uses bubble chambers and superheated fluid to search for dark matter. The PICO-60 detector consists of a fused-silica jar sealed to flexible, stainless steel bellows, all immersed in a pressure vessel filled with hydraulic fluid. Eight lead zirconate (PZT) piezoelectric acoustic transducers mounted to the exterior of the bell jar record the acoustic emissions from bubble nucleation and four 2-megapixel resolution fast CMOS cameras are used to photograph the chamber. The PICO-60 detector was built at Fermilab in Batavia, IL and installed underground at SNOLAB in 2012.

    The PICO bubble chambers are made insensitive to electromagnetic interactions by tuning the operating temperatures of the experiment, while the alpha decays are discriminated from dark matter interactions by their sound signal, making these detectors very powerful tools in the search for dark matter.

    PICO is operating two detectors deep underground at SNOLAB: PICO-60, a bubble chamber with 52 kg of C3F8 and PICO-2L, another bubble chamber with 2.9 kg of C3F8.

    The paper is available on the arXiv.

    About SNOLAB

    SNOLAB is Canada’s leading edge astroparticle physics research facility located 2 km (6800 ft) underground in the Vale Creighton Mine. The SNOLAB facility was created by an expansion of the underground research areas next to the highly successful Sudbury Neutrino Observatory (SNO) experiment. The entire laboratory is operated as an ultra-clean space to limit local radioactivity. With greater depth and cleanliness than any other international laboratory, it has the lowest background from cosmic rays providing an ideal location for measurements of rare processes that would be otherwise unobservable.

    Learn more

    PICO website

    SNOLAB

    For more information, please contact:
    Samantha Kuula
    Communications officer, SNOLAB
    Phone: 705-692-7000 ext. 2222
    Email: Samantha.Kuula@snolab.ca
    Website: http://www.snolab.ca

    French language contact:
    Guillaume Giroux
    Postdoctoral fellow, Queen’s University
    Email: ggiroux@owl.phy.queensu.ca
    Phone: 613-533-6000 ext. 79203

    U.S. contact:
    Andrew Sonnenschein
    Project manager, PICO-60
    Fermi National Accelerator Laboratory
    Email: sonnensn@fnal.gov
    Phone: 630-840-2883

    See the full article here .

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
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