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  • richardmitnick 5:18 pm on February 19, 2015 Permalink | Reply
    Tags: , , , , Symmetry Magazine   

    From Symmetry: “Physics for the people” 

    Symmetry

    February 19, 2015
    Manuel Gnida and Kathryn Jepsen

    Citizen scientists dive into particle physics and astrophysics research.

    1
    Illustration by Manuel Gnida, SLAC / Images courtesy of CERN, ESA/Hubble & NASA

    Citizen science, scientific work done by the general public, is having a moment.

    In June 2014, the term “citizen science” was added to the Oxford English Dictionary. This month, the American Association for the Advancement of Science—one of the world’s largest general scientific societies—dedicated several sessions at its annual meeting to the topic. A two-day preconference organized by the year-old Citizen Science Association attracted an estimated 700 participants.

    Citizen scientists interested in taking part in particle physics research have few options at the moment, but they may have a new opportunity on the horizon with the Large Synoptic Survey Telescope.

    LSST Exterior
    LSST Interior
    LSST Camera
    LSST

    Hunting the Higgs

    Citizen science projects have helped researchers predict the structure of proteins, transcribe letters from Albert Einstein, and monitor populations of bees and invasive crabs. The citizen science portal “Zooniverse,” launched in 2007, has attracted 1.3 million users from around the world. According to a report by Oxford University astronomer Brooke Simmons, the first Zooniverse project, “Galaxy Zoo,” has so far published 57 scientific papers with the help of citizen scientists.

    Of the 27 projects on the Zooniverse portal, just one allows volunteers to help with the analysis of real data from a particle physics experiment. “Higgs Hunters,” launched in November 2014, invites citizen scientists to help physicists find evidence of strange particle behavior in images of collisions from the Large Hadron Collider.

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC

    When protons collide in the LHC, their energy transfers briefly into matter, forming different types of particles, which then decay into less massive particles and eventually dissipate back into energy. Some particle collisions create Higgs bosons, particles discovered in 2012 at the LHC.

    “We don’t yet know much about how the Higgs boson decays,” says particle physicist Alan Barr at Oxford University in the UK, one of the leads of the Higgs Hunters project. “One hypothesis is that the Higgs decays into new, lighter Higgs particles, which would travel some distance from the center of our detector where LHC’s protons collide. We wouldn’t see these new particles until they decayed themselves into known particles, generating tracks that emerge ‘out of thin air,’ away from the center.”

    So far, almost 5,000 volunteers have participated in the Higgs Hunters project. Over the past three months, they have classified 600,000 particle tracks.

    Why turn to citizen science for this task?

    “It turns out that our current algorithms aren’t trained well enough to identify the tracks we’re interested in,” Barr says. “The human eye can do much better. We hope that we can use the information from our volunteers to train our algorithms and make them better for the second run of LHC.”

    Humans are also good at finding problems an algorithm might miss. Many participants flagged as “weird” an image showing what looked like a shower of particles called muons passing through the detector, Barr says. “When we looked at it in more detail, it turned out that it was a very rare detector artifact, falsely identified as a real event by the algorithms.”

    Volunteers interested in Higgs Hunters have only a couple of months left to participate. Barr estimates that by April, the project will have collected enough data for researchers to proceed with an in-depth analysis.

    Distortions in space

    Armchair astrophysicists can find their own project in the Zooniverse. “SpaceWarps” asks volunteers to look for distortions in images of faraway galaxies—evidence of gravitational lensing.

    Gravitational lensing occurs when the gravitational force of massive galaxies or galaxy clusters bends the space around them so that light rays traveling near them follow curved paths.

    Einstein predicted this effect in his Theory of General Relativity. You can see an approximation of it by looking at a light through the bottom of a wine glass. Gravitational lensing is used to determine distances in the universe—key information in measuring the expansion of the universe and understanding dark energy.

    Recognizing gravitational lensing is a difficult task for a computer program, but a relatively easy one for a human, says Phil Marshall, a scientist at the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University and SLAC National Accelerator Laboratory.

    Marshall, one of three principal investigators for SpaceWarps, says he sees a lot of potential in the interface between humans and machines. “They both have different skills that complement each other.”

    According to the SpaceWarps website, more than 51,000 volunteers have made more than 8 million classifications to date and have discovered dozens of candidates for gravitational lenses that were not detected by algorithms. The project is currently adding new data for people to analyze.

    The Large Synoptic Survey Telescope

    Citizen science may become particularly important for another project Marshall is interested in: the Large Synoptic Survey Telescope, to be built on a mountaintop in Chile.

    Technicians recently completed a giant double mirror for the project, and its groundbreaking will take place this spring. Beginning in 2022, LSST will take a complete image of the entire southern sky every few nights. It is scheduled to run for a decade, collecting 6 million gigabytes of data each year. The information collected may help scientists unravel cosmic mysteries such as dark matter and dark energy.

    “Nobody really knows what citizen science will look like for LSST,” Marshall says. “However, a good approach would be to make use of the fact that humans are very good at understanding confusing things. They could help us inspect images for odd features, potentially spotting new things or pointing out problems with the data.”

    Citizen scientists could also help with the LSST budget.

    Henry Sauermann at the Georgia Institute of Technology and Chiara Franzoni at the Politecnico di Milano in Italy recently studied seven Zooniverse projects started in 2010. They calculated the efforts of unpaid volunteers over just the first 180 days to be worth $1.5 million.

    But the value of citizen science to LSST may depend on whether it can attract a dedicated group of amateur researchers.

    Sauermann and Franzoni’s study showed that 10 percent of contributors to the citizen science projects they studied completed an average of almost 80 percent of all of the work.

    “We also see that with SpaceWarps,” Marshall says. “Most Internet users have a very short attention span.”

    It’s all about how well the researchers design the project, he says.

    “It must be easy to get started and, at the same time, empower the participant enough to make serious contributions to science,” Marshall says. “It’s on us to provide volunteers with interesting things to do.”

    See the full article here.

    I am surprised that the distinguished authors of this essay forgot one of the earliest sets of Citizen Science project, those stemming from the LHC, namely lhc@home, now named Sixtrack@home, and vLHC@home which began life as test4theory@home.

    LHC Sixtrack

    vLHC Logo

    BOINC

    These projects run on software from BOINC at UC Berkeley. BOINC enables the home computer user to participate in a large variety of scientific projects by donating time on their computers running Windows, Mac and Linux software. Dave Anderson and his cohorts at UC Berkeley practically invented Citizen Science. There are many projects of all kinds running on BOINC software. Please visit the BOINC web site and think about helping on some projects. Also, in a related group of projects is World Community Grid (WCG), a section of the Smarter Planet social effort from IBM Corporation. WCG projects also run on BOINC software. Please visit the WCG web site and take a look.

    WCGLarge

    Please help promote STEM in your local schools.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 1:41 pm on February 3, 2015 Permalink | Reply
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    From Symmetry: “Tracking glaciers with accelerators” 

    Symmetry

    February 03, 2015
    Kelen Tuttle

    To predict Earth’s future, geologists use particle accelerators to understand its past.

    3

    Geologists once thought that, until about 18,000 years ago, a mammoth glacier covered the top two-thirds of Ireland. Recently, however, they found evidence that it wasn’t just the top two-thirds: The Irish glacier was much larger, completely engulfing the country and extending far offshore.

    They learned this with the help of a particle accelerator.

    Glaciers are always on the move, advancing or retreating as fast as 30 meters a day or as slow as half a meter a year. During the most recent ice age, huge glaciers spread over much of Earth’s northern climes, extending all the way from the northern tip of Greenland to Cape Cod and across to Chicago, which was buried under a kilometer of ice. It was the same in Europe, with parts of the British Isles, Germany, Poland and Russia all hidden beneath an enormous ice sheet.

    “For the last 2.5 million years of Earth’s history, we’ve had this pattern of alternating ice ages and interglacials,” says Fred Phillips, a professor in New Mexico Tech’s Department of Earth and Environmental Science who, among other things, is an expert at dating the movements of glaciers.

    “Trying to understand these cycles—to understand geographical distribution of climate fluctuations and trying to pin down the chronology—has preoccupied scientists for 200 years now.”

    Over the past 30 years, scientists have begun to use particle accelerators to help them track how these glaciers move.

    The process begins with a globetrotting geologist and some huge rocks. As a glacier recedes, it will sometimes pluck a boulder from its depths and push it into daylight. While trapped beneath the ice, the boulder is shielded from the barrage of cosmic rays that continuously assaults Earth’s surface. But as soon as the boulder is exposed, cosmic rays begin to interact with the atoms inside the rock, rapidly producing rare isotopes called cosmogenic nuclides, such as helium-3, neon-21 or beryllium-10.

    To determine just how long ago the boulder was forced to the surface, geologists like Phillips use a hammer and chisel—or, sometimes, rock saws and small explosive devices—to remove a chunk of rock about the size of a grapefruit. They bring that sample back to the lab, grind it up and extract one specific mineral, such as quartz, that produces cosmogenic nuclides at a known rate.

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    1. Geologists in Antarctica use a hammer and chisel to sample the upper few centimeters of a boulder for cosmogenic nuclide dating.

    2. Bethan Davies samples a boulder for cosmogenic nuclide dating in Greenland.
    Courtesy of: David Roberts and Bethan Davies, http://www.AntarcticGlaciers.org

    After isolating one particular nuclide from that mineral, they send a beam of cesium ions at the sample. That adds an extra electron to atoms within the sample, forming negative elemental or molecular ions. These ions are sent into an accelerator beam and smashed through a thin foil or gas, which strips them of electrons and destroys any remaining molecules. Finally, the ions are sent into a detector that counts the ratio of unstable to stable atoms, revealing the amount of cosmogenic nuclides. The more cosmogenic nuclides in the sample, the more time has elapsed since the glacier ejected the boulder.

    The original idea for this type of geological dating came from none other than Raymond Davis Jr., the Brookhaven National Laboratory nuclear chemist who won a Nobel Prize for detecting neutrinos streaming from the sun. Davis came up with the idea working in collaboration with Oliver Schaeffer, an expert in the environmental production of background radioactivity.

    Although the duo correctly set forth the basic experimental concept for using cosmogenic nuclides to date rock samples in the mid-1950s, it took nearly 30 years for detector technologies to catch up with their ideas. Once possible, the technique took off. “Since the mid-1980s, there have been thousands of scientific papers published on glacial chronologies and other geological dating using this method,” Phillips says.

    Today, Phillips says, significant effort is being made to understand the rise and fall of the West Antarctic Ice Sheet.

    “This is important because it looks like now this ice sheet is in a state of slow collapse, which could raise sea level by about 5 meters,” he says. “Understanding what controls the extent of that ice is critically important.”

    By understanding the past, researchers like Phillips might better understand what’s to come.

    See the full article here.

    Please help promote STEM in your local schools.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 3:45 pm on January 28, 2015 Permalink | Reply
    Tags: , Helen Quinn, , Symmetry Magazine   

    From Symmetry: “Of symmetries, the strong force and Helen Quinn” 

    Symmetry

    January 27, 2015
    Matthew R. Francis

    1

    Scientist Helen Quinn has had a significant impact on the field of theoretical physics.

    Modern theoretical physicists spend much of their time examining the symmetries governing particles and their interactions. Researchers describe these principles mathematically and test them with sophisticated experiments, leading to profound insights about how the universe works.

    For example, understanding symmetries in nature allowed physicists to predict the flow of electricity through materials and the shape of protons. Spotting imperfect symmetries led to the discovery of the Higgs boson.

    2
    Possible Higgs event

    One researcher who has used an understanding of symmetry in nature to make great strides in theoretical physics is Helen Quinn. Over the course of her career, she has helped shape the modern Standard Model of particles and interactions— and outlined some of its limitations.

    sm
    The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    With various collaborators, she has worked to establish the deep mathematical connection between the fundamental forces of nature, pondered solutions to the mysterious asymmetry between matter and antimatter in the cosmos and helped describe properties of the particle known as the charm quark before it was discovered experimentally.

    “Helen’s contributions to physics are legendary,” says Stanford University professor of physics Eva Silverstein. Silverstein first met Quinn as an undergraduate in 1989, then became her colleague at SLAC in 1997.

    Quinn’s best-known paper is one she wrote with fellow theorist Roberto Peccei in 1977. In it, they showed how to solve a major problem with the strong force, which governs the structure of protons and other particles. The theory continues to find application across particle physics. “That’s an amazing thing: that an idea you had almost 40 years ago is still alive and well,” says Peccei, now a professor emeritus of physics at the University of California, Los Angeles.

    GUTs, glory, and broken symmetries

    Quinn was born in Australia in 1943 and emigrated with her family to the United States while she was still a university student. For that reason, she says, “I had a funny path through undergraduate school.”

    When she moved to Stanford University, she had already spent two years studying at the University of Melbourne to become a meteorologist with support from the Australian Weather Bureau, and needed to select an academic major that wouldn’t force her to start over again. That program happened to be physics.

    With the longest linear accelerator in the world nearing completion next door at what is now called SLAC National Accelerator Laboratory, Stanford was an auspicious place to study particle physics, so Quinn stayed on to finish her PhD. “Really, the beginning was the fact that particle physics was bubbling at that time at Stanford, and that’s where I got hooked on it,” she says. She entered the graduate program when women comprised only about 2 percent of all physics students in American PhD programs.

    After finishing her PhD, Quinn traveled to Germany for postdoctoral research at the DESY laboratory before returning to the United States. She taught high school in Boston briefly before landing a position at Harvard University. While there, she collaborated with theorist Steven Weinberg and Howard Georgi to work on something known as “grand unified theories,” whimsically nicknamed GUTs. GUT models were attempts to bring together the three forces described by quantum physics: electromagnetism, which holds together atoms, and the weak and strong forces, which govern nuclear structure. (There still is no quantum theory of gravity, the fourth fundamental force.)

    “Her paper with Howard Georgi and Steve Weinberg on grand unified theories was the first paper that made sense of grand unified theories,” Peccei says.

    Quinn returned to SLAC during a leave of absence from Harvard, where she connected with Peccei. The two of them had frequent conversations with Weinberg and Gerard ’t Hooft, both of whom were visiting SLAC at that time. (Both Weinberg and ’t Hooft later won Nobel Prizes for their work on symmetries in particle physics.)

    At that time, many theorists were engaged in understanding the strong force, which governs the structure of particles such as protons, using a theory called quantum chromodynamics, or QCD . (The name “chromodynamics” refers to the “color charge” of quarks, which is analogous to electric charge.)

    The problem: QCD predicted some results at odds with experiment, including an electrical property of neutrons.

    Quinn and Peccei realized that they could make that problem go away if one type of quark had no mass. While that was at odds with reality, it hadn’t always been so, Quinn says: “That led me to think, well, in the very early universe when it’s hot …quarks are massless.”

    By adding a new symmetry once quarks acquired their masses from the Higgs field, they could resolve the problem with QCD. As soon as their paper came out, Weinberg realized the theory also made a prediction that Quinn and Peccei had not noticed: the axion, which might comprise some or all of the mysterious dark matter binding galaxies together. (Independently, Frank Wilczek also found the axion implicit in the Peccei-Quinn theory.) Quinn laughs now over how obvious she says it seems in retrospect.

    Experiments and education

    After her collaboration with Peccei, Quinn worked extensively with experimentalists and other theorists at SLAC to understand the interactions involving the bottom quark. Studying particles containing bottom quarks is one of the best ways to investigate the symmetries built into QCD, which in turn may offer clues as to why there’s a lot more matter than antimatter in the cosmos.

    Along the way, Quinn was elected as member of the National Academy of Sciences, and has received a number of prestigious prizes, including the J.J. Sakurai Prize for theoretical physics and the Dirac Medal from the International Center for Theoretical Physics. She also served as president of the American Physical Society, the premiere professional organization for physicists in the United States.

    Since retiring in 2010, Quinn has turned her attention full-time to one of her long-time passions: science education at the kindergarten through high-school level. As part of the board on science education at the National Academy of Sciences, she headed the committee that produced the document “A Framework for K-12 Science Education” in 2011.

    “The overarching goal is that most students should have the experience of learning and understanding, not just a bunch of disconnected facts,” she says.

    Instead of enduring perpetual tests as required under current policy, she wants students to focus on learning “the way science works: how to think about problems as scientists do and analyze data and evidence and draw conclusions based on evidence.” Peccei calls her “unique among very well-known physicists” for this later work.

    “She’s devoted a tremendous amount of time to physics education, and has been really a champion of that at a national level,” he says.

    On top of that, the Peccei-Quinn model remains a powerful tool for theorists and “a good candidate to solve some of the outstanding problems in particle physics and cosmology,” Silverstein says. Along with dark matter, these include Silverstein’s own research in string theory and early universe inflation.

    As with her efforts on behalf of education, the impact of Quinn’s physics research is in how it lays the foundation for others to build on. There’s a certain symmetry in that.

    See the full article here.

    Please help promote STEM in your local schools.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 2:08 pm on January 22, 2015 Permalink | Reply
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    From Symmetry: “DECam’s nearby discoveries” 

    Symmetry

    January 22, 2015
    Liz Kruesi

    The Dark Energy Camera does more than its name would lead you to believe.

    DECam
    DECam, built at FNAL

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco 4m Telescope which houses the DECam

    The Dark Energy Camera, or DECam, peers deep into space from its mount on the 4-meter Victor Blanco Telescope high in the Chilean Andes.

    Thirty percent of the camera’s observing time—about 105 nights per year—go to the team that built it: scientists working on the Dark Energy Survey.

    Another small percentage of the year is spent on maintenance and upgrades to the telescope. So who else gets to use DECam? Dozens of other projects share its remaining time.

    Many of them study objects far across the cosmos, but five of them investigate ones closer to home.

    Overall, these five groups take up just 20 percent of the available time, but they’ve already taught us some interesting things about our planetary neighborhood and promise to tell us more in the future.

    Far-out asteroids

    Stony Brook University’s Aren Heinze and the University of Western Ontario’s Stanimir Metchev used DECam for four nights in early 2014 to search for unknown members of our solar system’s main asteroid belt, which sits between Mars and Jupiter.

    To detect such faint objects, one needs to take a long exposure. However, the paths of these asteroids lie close enough to Earth that taking an exposure longer than a few minutes results in blurred images. Heinze and Metchev’s fix was to stack more than 100 images taken in less than two minutes each.

    With this method, the team expects to measure the positions, motions and brightnesses of hundreds of main belt asteroids not seen before. They plan to release their survey results in late 2015, and an early partial analysis indicates they’ve already found hundreds of asteroids in a region smaller than DECam’s field of view—about 20 times the area of the full moon.
    Whole new worlds

    Scott Sheppard of the Carnegie Institution for Science in Washington DC and Chad Trujillo of Gemini Observatory in Hilo, Hawaii, use DECam to look for distant denizens of our solar system. The scientists have imaged the sky for two five-night stretches every year since November 2012.

    Every night, the DECam’s sensitive 570-megapixel eye captures images of an area of sky totaling about 200 to 250 times the area of the full moon, returning to each field of view three times. Sheppard and Trujillo run the images from each night through software that tags everything that moves.

    “We have to verify everything by eye,” Sheppard says. So they look through about 60 images a night, or 300 total from a perfect five-night observing run, a process that gives them a few dozen objects to study at Carnegie’s Magellan Telescope.

    The scientists want to find worlds beyond Pluto and its brethren—a region called the Kuiper Belt, which lies some 30 to 50 astronomical units from the sun (compared to the Earth’s 1). On their first observing run, they caught one.

    2
    Kuiper Belt

    This new world, with the catalog name of 2012 VP113, comes as close as 80 astronomical units from the sun and journeys as far as 450. Along with Sedna, a minor planet discovered a decade ago, it is one of just two objects found in what was once thought of as a complete no man’s land.

    4
    The discovery images of 2012 VP113, as made by the Cerro Tololo Inter-American Observatory [read DECam at Blanco]. The image is a merger of three images with three colored dots pinpointing the image of 2012 VP113. The three images were taken 2 hours apart each. The red dot represents 2012 VP113’s location on the first image, the second represents its location on the second image, and the blue dot representing its location on the third.

    Sheppard and Trujillo also have discovered another dwarf planet that is one of the top 10 brightest objects beyond Neptune, a new comet, and an asteroid that occasionally sprouts an unexpected tail of dust.

    Mythical creatures

    Northern Arizona University’s David Trilling and colleagues used the DECam for three nights in 2014 to look for “centaurs”—so called because they have characteristics of both asteroids and comets. Astronomers believe centaurs could be lost Kuiper Belt objects that now lie between Jupiter and Neptune.

    Trilling’s team expects to find about 50 centaurs in a wide range of sizes. Because centaurs are nearer to the sun than Kuiper Belt objects, they are brighter and thus easier to observe. The scientists hope to learn more about the size distribution of Kuiper Belt objects by studying the sizes of centaurs. The group recently completed its observations and plan to report them later in 2015.


    Next-door neighbors

    Lori Allen of the National Optical Astronomy Observatory outside Tucson, Arizona, and her colleagues are looking for objects closer than 1.3 astronomical units from the sun. These near-Earth objects have orbits that can cross Earth’s—creating the potential for collision.

    Allen’s team specializes in some of the least-studied NEOs: ones smaller than 50 meters across.

    Even small NEOs can be destructive, as demonstrated by the February 2013 NEO that exploded above Chelyabinsk, Russia. The space rock was just 20 meters wide, but the shockwave from its blast shattered windows, which caused injuries to more than 1000 people.

    In 2014, Allen’s team used the DECam for 10 nights. They have 20 more nights to use in 2015 and 2016.

    They have yet to release specific findings from the survey’s first year, but the researchers say they have a handle of the distribution of NEOs down to just 10 meters wide. They also expect to discover about 100 NEOs the size of the one that exploded above Chelyabinsk.

    Space waste

    Most surveys looking for “space junk”—inactive satellites, parts of spacecraft and the like in orbit around the Earth—can see only pieces larger than about 20 centimeters. But there’s a lot more material out there.

    How much is a question Patrick Seitzer of the University of Michigan and colleagues hope to answer. They used DECam to hunt for debris smaller than 10 centimeters, or the size of a smartphone, in geosynchronous orbit.

    The astronomers need to capture at least four images of each piece of debris to determine its position, motion and brightness. This can tell them about the risk from small debris to satellites in geosynchronous orbit. Their results are scheduled for release in mid-2015.

    See the full article here.

    Please help promote STEM in your local schools.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 8:01 pm on January 13, 2015 Permalink | Reply
    Tags: , , Symmetry Magazine   

    From Symmetry: “Dark horse of the dark matter hunt” 

    Symmetry

    January 13, 2015
    Matthew R. Francis

    Dark matter might be made up of a type of particle not many scientists are looking for: the axion.

    The ADMX experiment seems to be an exercise in contradictions.

    a

    Dark matter, the substance making up 85 percent of all the mass in the universe, is invisible. The goal of ADMX is to detect it by turning it into photons, particles of light. Dark matter was forged in the early universe, under conditions of extreme heat. ADMX, on the other hand, operates in extreme cold. Dark matter comprises most of the mass of a galaxy. To find it, ADMX will use sophisticated devices microscopic in size.

    Scientists on ADMX—short for the Axion Dark Matter eXperiment—are searching for hypothetical particles called axions. The axion is a dark matter candidate that is also a bit of a dark horse, even as this esoteric branch of physics goes.

    4
    UW physicists Leslie Rosenberg (left) and Gray Rybka examine the Axion Dark Matter Experiment

    Unlike most dark matter candidate possibilities, axions are very low in mass and interact very weakly with particles of ordinary matter and so are difficult to detect. However, according to theory, axions can turn into photons, which are much more interactive and easier to detect.

    In July 2014, the US Department of Energy picked three dark matter experiments as most promising for continued support, including ADMX. The other two—the Large Underground Xenon (LUX) detector and the Cryogenic Dark Matter Search (CDMS) [today, SuperCDMS at Soudan in Minnesota]—are both designed to hunt for another dark matter candidate, weakly interacting massive particles, or WIMPs.

    With the upgrade funded by the Department of Energy, the ADMX team has added a liquid helium-cooled refrigerator to chill its sensitive detectors, known as superconducting quantum interference devices (SQUIDs). The ADMX experiment uses its powerful magnetic field to turn dark matter axions into microwave photons, which a SQUID can detect when operating at a specific frequency corresponding to the mass that of the axion.

    Axions may be as puny as one trillionth of the mass of an electron. Compare that to WIMPs, which are predicted to be hundreds of thousands of times more massive than electrons, making them heavier than protons and neutrons.

    The other two DOE-boosted experiments, CDMS and LUX, have plenty of competition around the world in their search for WIMPs. But ADMX stands nearly alone as a large-scale hunter for axions. Leslie Rosenberg, University of Washington physicist and a leader of the ADMX project, sees this as a call to work quickly before others catch up. “People are getting nervous about WIMP dark matter,” he says. So the pressure is on to “do a definitive experiment, and either detect this [axion] or reject the hypothesis.”
    The answer to a problem

    Axions are hypothetical particles proposed in the late 1970s, originally to fix a problem entirely unrelated to dark matter.

    As physicists developed the theory of the strong nuclear force, which binds quarks together inside protons and neutrons, they noticed something wrong. Interactions inside neutrons should have made them electrically asymmetrical, so that they would flip when subjected to an electric field. However, experiments show no such thing, so something must have been missing in the theory.

    “If you could just impose the symmetry, maybe that would be an answer, but you cannot,” says retired Stanford University physicist Helen Quinn. Instead, in 1977 she and Roberto Peccei, who was also at Stanford at that time, proposed a simple modification to the mathematics describing the strong force. The Peccei-Quinn model, as it is now known, both removed the neutron asymmetry and instead predicted a new particle: the axion.

    Axions are appealing from a conceptual point of view, Rosenberg says. “I learned about axions when I was a graduate student, and it really hit a resonance with me then. Stuff that wasn’t making sense suddenly made sense because of the axion.”

    A dark matter candidate

    Unlike the Higgs boson, axions lie outside the Standard Model of particle physics and are not governed by the same forces. If they exist, axions are transparent to light, don’t interact directly with ordinary matter except in very tenuous ways, and could have been produced in sufficient amounts in the early universe to make up the 85 percent of mass we call dark matter.

    “Provided axions exist, they’re almost certain to be some fraction of dark matter,” says Oxford University theoretical physicist Joseph Conlon.

    “Axions are an explanation that fits in with everything we know about physics and all the ideas of how you might extend physics,” he says. “I think axions are one particle that almost all particle theorists would probably bet rather large amounts of money on that they do exist, even if they are very, very hard to detect.”

    Even if, like Conlon, we’re willing to wager that axions exist, it’s another matter to say they exist in such quantities and at the proper mass range to show up in our detectors.

    Rosenberg trusts that ADMX will work, and after that, it’s up to nature to reveal its hand: “What I can say is we’ll likely have an experiment that at least over a broad mass range will either detect this axion or reject the hypothesis at high confidence.”

    Finding any axion detection would be a vindication of the theory developed by Quinn, Peccei and others. Finding many axions could finally solve the dark matter problem and would make this dark horse particle a champion.

    See the full article here.

    Please help promote STEM in your local schools.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 7:08 pm on January 12, 2015 Permalink | Reply
    Tags: , , , Symmetry Magazine   

    From Symmetry: “Mirror, mirror” 

    Symmetry

    January 12, 2015
    Kathryn Jepsen

    After more than six years of grinding and polishing, the first-ever dual-surface mirror for a major telescope is complete.

    In March 2008, a group of people gathered around a giant, red oven in a six-story workshop space beneath the bleachers of the University of Arizona football stadium.

    The oven was about 10 meters wide and 2 meters tall, big enough to live in, really. But that day it was rendered less than hospitable by its extreme internal temperature—2200 degrees Fahrenheit—and its persistent spinning at 35 miles per hour. Also, it was full of 22 tons of molten glass.

    This was the “high-fire event,” the day the glass reached its melting point, freeing it to flow into a honeycomb-patterned mold on its way to becoming one of the largest telescope mirrors in the world.

    Now, after months of cooling and more than six years of grinding and polishing, the mirror is complete.

    On Saturday, a new group gathered in the Steward Observatory Mirror Labhttp://mirrorlab.as.arizona.edu/
    —still located under the bleachers—to admire the finished product.

    2
    s
    Steward Observatory Mirror Lab

    It is the first completed piece of the Large Synoptic Survey Telescope, which will eventually be located on Cerro Pachón, a mountain in Chile. In 2022, the massive mirror will enable LSST scientists to begin the most thorough survey ever of the Southern sky.
    Making a movie of the universe

    The mirror goes by the name M1M3, and it’s actually two mirrors in one. The outer ring serves as the first mirror, M1, and another, more steeply curved mirror, M3, has been carved out of the center.

    LSST will capture and focus images of the night sky by bouncing them through a series of three mirrors. Light will shine onto M1, which will reflect it up to another mirror, the 3.4-meter M2, which will reflect it down to M3, which will reflect it up into the lens of a 3.2-gigapixel camera.

    The three-mirror optical system, unique among large telescopes, will allow LSST to take in nearly 10 square degrees of sky with each image—a field of view large enough to fit 40 full moons.

    The combined dual-surface mirror, also unique among large telescopes, will allow scientists to align LSST just as quickly as they could a two-mirror telescope. This will help make LSST nimble enough to scan across the entire Southern sky once every three nights.

    LSST’s frequent sweeps across the same areas of sky will allow scientists to monitor changes to our galaxy and others in a way that has never before been possible.

    They will create time-lapse videos of asteroids, supernovae, variable stars, the effects of dark matter and dark energy—as LSST Director Steve Kahn puts it, “anything that can go bump in the night.” In the end, they hope the survey will lead to a new understanding of our universe.

    The multi-year mirror

    The LSST project has already met a major milestone with the completion of M1M3, although it only recently received federal funding for its construction start.

    In August 2014 the National Science Foundation authorized $473 million for the project. And just this month the US Department of Energy approved $165 million for construction of the LSST camera.

    LSST Camera
    LSST Camera

    The early development of LSST was supported by the LSST Corporation, a non-profit consortium of 40 universities and other research institutions. Building M1M3 and getting started on M2 have been supported by private funding: $20 million from the Charles and Lisa Simonyi Fund for Arts and Sciences; $10 million from Microsoft founder Bill Gates; and more contributions from Interface Inc. founder and chair Richard Caris; the WM Keck Foundation; Wayne Rosing and Dorothy Largay; Eric and Wendy Schmidt; and Edgar Smith.

    For its part, the Tucson-based Research Corporation for Science Advancement contributed $400,000 toward the purchase of the glass.

    This was no ordinary glass; it was high-quality glass made by a specialty company in Japan. It came in chunks weighing a couple of pounds each—light enough for technicians kneeling on a ramp suspended over the mold to pick them up and gently nestle them into place.

    4
    Courtesy of: LSST

    Once the mold was filled, technicians heated it in the oven, which rotated to encourage the glass to travel up the sides and form a shallow bowl shape. The honeycomb design in the mold formed 1600 air pockets in the back of the mirror to reduce its mass and increase temperature-regulating airflow.

    To avoid cracking the mirror, technicians cooled it down slowly over 90 days.

    Scientist Chuck Claver, who has been a part of LSST since it was no more than an interesting idea, was one of the few people in the room when the oven was finally opened.

    “It’s like a cake cover,” he says. “They lift it off with a crane and then there it is… You walk up to this thing and your jaw just drops.”

    Claver keeps a picture of himself and a few other scientists standing in the center of the freshly baked M1M3. “Glass is actually pretty strong stuff. You can take your shoes off and walk on it in socks,” he says.

    “I hate it when they do that,” says LSST Project Manager Victor Krabbendam.

    Once the baking was done, the grinding and polishing began. A special machine shaved and sanded away layers of glass—including several tons from the center to form M2—in a process that removed millimeters and then nanometers at a time.

    “The shape of this mirror has to be good to small fractions of the diameter of a human hair across the whole surface,” Krabbendam says.

    Soon the mirror began to take on a dull shine, like an ice-skating rink after a Zamboni polish. Today, it’s crystal clear.

    After enduring a series of tests, M1M3 will go into storage in a hangar at Tucson International Airport. In a couple of years, scientists will apply a reflective surface and load it on a truck to start its journey to its mountaintop home in Chile.

    5
    Courtesy of: LSST

    See the full article here.

    Please help promote STEM in your local schools.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 3:39 pm on January 8, 2015 Permalink | Reply
    Tags: , Symmetry Magazine, Transition Edge Sensors   

    From Symmetry: “Transition edge sensors” 

    Symmetry

    January 08, 2014
    Kathryn Jepsen

    An update to technology more than a century old might be key to making the next big discovery in particle physics.

    This wiring diagram, drawn in 1994, is an early sketch of a concept that might help scientists detect dark matter or discover what happened just after the big bang. It was drawn by physicist Kent Irwin of Stanford University and SLAC National Accelerator Laboratory, about a year into his development of the transition edge sensor.

    dwg
    Courtesy of: Blas Cabrera, Stanford University
    Drawn by physicist Kent Irwin of Stanford University and SLAC National Accelerator Laboratory

    1
    Optical image of four tungsten transition edge sensors for near-infrared single-photon detection. Image credit: NIST.

    The TES makes use of a centuries-old concept in particle detection. The cooler a metal is, the better it is at conducting electricity. A particle that hits a metal will give itself away by producing heat and changing the metal’s conductivity.

    In the late 1800s, American astronomer Samuel Langley created a bolometer, a device that used delicately balanced metals to detect the smallest changes in heat. By 1880, it was sensitive enough to detect the thermal radiation from a cow standing in a field more than a quarter of a mile away. Today, technology based on Langley’s bolometer is used in many experiments, including the Planck satellite, which studies patterns in light from the early universe.

    b
    JPL Spiderweb Bolometer
    Spiderweb bolometer for measurements of the cosmic microwave background radiation. Image credit: NASA/JPL-Caltech.

    Cosmic Microwave Background  Planck
    cosmic microwave background per Planck

    ESA Planck
    ESA/Planck

    Before the TES, scientists spent decades trying to figure out how to build bolometers out of superconducting metal. They did this because every superconductor has a temperature above which its ability to conduct electricity rapidly worsens. Right at this transition temperature, a superconducting metal becomes a superbly sensitive thermometer, making it ideal for use in a bolometer.

    However, bolometers operating at this transition temperature also tend to become unstable.

    Irwin was working with physicist Blas Cabrera, also of Stanford University, on a new idea for a dark matter detector when he thought of a way to overcome this weakness. Instead of putting a current through the superconductor and measuring the change in voltage, he would put a voltage across the superconductor and measure the change in current. In his detector, when the temperature rose, the metal’s resistance would go up, causing the current to drop. This would lower the temperature, making the operation stable.

    Today, large arrays of transition edge sensors are essential to a variety of experiments, such as the Cryogenic Dark Matter Experiment, the BICEP2 experiment, the South Pole Telescope and the Atacama Cosmology Telescope—all of which are striving to make the next big discovery.

    See the full article here.

    Please help promote STEM in your local schools.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 1:44 pm on January 7, 2015 Permalink | Reply
    Tags: , , Symmetry Magazine   

    From Symmetry: “Shh! DEAP is hunting dark matter” 

    Symmetry

    January 07, 2015
    Troy Rummler

    How far will scientists go to cut through the noise in search of a subtle signal?

    Two kilometers below ground in Canada, scientists deployed a specially designed sanding robot into the DEAP-3600 dark matter detector.

    DEAP Dark Matter detector
    DEAP

    After entering through a long, airtight neck into the interior cavity, which is about 2 meters wide, the robot extended two arms and shaved half of a millimeter off the entire interior surface.

    The robot’s purpose was to remove any radon the sphere might have absorbed during 18 months of underground assembly at SNOLAB near Sudbury, Ontario. Radon, an element that comes from the radioactive decay of uranium in soil, rock and water, would contribute to background noise—particle interactions that can obscure the phenomenon researchers are hunting for.

    The resurfacer was just one piece of DEAP experimenters’ aggressive agenda to eliminate interference in what will be the world’s most sensitive dark matter detector for high-mass, weakly interacting dark matter particles when it begins taking data in March 2015.

    Discriminating pulses

    When the DEAP experiment starts, researchers will watch 565 imperial gallons (680 US gallons) of liquid argon contained within a detector for flashes that could mean the first direct detection of dark matter.

    Scientists think dark matter is made up of invisible particles that neither absorb nor emit light. Because dark matter interacts very weakly with other matter, it is likely passing through us all of the time. But every once and a while, a dark matter particle might run into something—and scientists hope that thing is inside a dark matter detector.

    In theory, a collision with a dark matter particle should send an argon nucleus recoiling. In the DEAP-3600 detector, some of that energy should be released as a flash of ultraviolet light.

    “What fundamentally makes the experiment difficult is trying to filter out billions and billions of background interactions from maybe one or a handful of dark matter interactions,” says Mark Boulay, DEAP’s project director and a professor at Queen’s University in Ontario.

    The DEAP collaboration is taking the typical experimental precautions to block extraneous particles from cosmic rays, radon and neutrons. They sealed DEAP-3600 in a steel shell, submerged the entire assembly in water and will conduct the experiment deep underground. But that couldn’t block two particularly distracting particles from the outside: electrons and gamma rays.

    Boulay studied the way electrons and gamma rays interacted with the argon and developed a non-physical filter. A true nuclear recoil, he found, takes the energetic blow quickly and releases a sharp spike of light in return. But the pulse of light resulting from an electron or a gamma ray is more diffuse, especially in argon. Researchers are using that distinction, which Boulay calls pulse shape discrimination, as a keystone in DEAP’s ability to eliminate background.

    Reducing radiation

    Another major source of background comes from neutrons and alpha particles from radioactive decay Consequently, the DEAP collaboration has made a point to remove even mildly radioactive materials from their detector—hence the robotic radon-remover.

    But that was only the final step in a series of measures designed to keep radon at bay. Chris Jillings, a SNOLAB researcher and adjunct professor at Laurentian University, played a key role in ensuring that radon exposure was controlled during the entire manufacturing process of plastic acrylic components closest to the liquid argon: the detector’s inner shell and light guides.

    Jillings spent weeks traveling back and forth from Canada to Thailand as part of a team studying their supplier’s acrylic production techniques and quality control protocols. He visited where the acrylic was formed, surveyed the petrochemical plant that made the raw materials, and even inspected the delivery trucks.

    “We did a detailed radon budget of how much exposure to radon the acrylic had at each step in the manufacturing process,” Jillings says.

    “With close cooperation with our vendor—and time and effort—we were able to make sure that the radon load in the acrylic was very small.”

    DEAP-3600 will take data for three years. Researchers hope they have eliminated enough background to find the signal that has eluded everyone so far.

    “[Dark matter] outweighs normal matter by five to one, it makes up most of the stuff out there, and we’ve never seen it,” Boulay says “And it’s exciting to me that we’re just on the verge of possibly seeing this for the first time.”

    1
    Student Connor Stone fits a photomultiplier tube into a PMT-mount.
    Courtesy of: SNOLAB

    See the full article here.

    Please help promote STEM in your local schools.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 1:30 pm on December 17, 2014 Permalink | Reply
    Tags: , , , Symmetry Magazine   

    From Symmetry: “LHC filled with liquid helium” 

    Symmetry

    December 17, 2014
    Sarah Charley

    The Large Hadron Collider is now cooled to nearly its operational temperature.

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    The Large Hadron Collider isn’t just a cool particle accelerator. It’s the coldest.

    Last week the cryogenics team at CERN finished filling the eight curved sections of the LHC with liquid helium. The LHC ring is now cooled to below 4 kelvin (minus 452 degrees Fahrenheit).

    ice
    Photo by Maximilien Brice, CERN

    This cool-down is an important milestone in preparing the LHC for its spring 2015 restart, after which physicists plan to use it to produce the highest-energy particle collisions ever achieved on Earth.

    “We are delighted that the LHC is now cold again,” says Beate Heinemann, the deputy leader of the ATLAS experiment and a physicist with the University of California, Berkeley, and Lawrence Berkeley National Laboratory. “We are getting very excited about the high-energy run starting in spring next year, which will open the possibility of finding new particles which were just out of reach.”

    The LHC uses more than 1000 superconducting dipole magnets to bend high-energy particles around its circumference. These superconducting magnets are made from a special material that, when cooled close to absolute zero (minus 460 degrees Fahrenheit), can maintain a high electrical current with zero electrical resistance.

    “These magnets have to produce an extremely strong magnetic field to bend the particles, which are moving at very close to the speed of light,” says Mike Lamont, the head of LHC operations. “The magnets are powered with high electrical currents whenever beam is circulating. Room-temperature electromagnets would be unable to support the currents required.”

    To get the 16 miles of LHC magnets close to absolute zero, engineers slowly inject helium into a special cryogenic system surrounding the magnets and gradually reduce the temperature over the course of several months at a rate of one sector cooled per month. As the temperature drops, the helium becomes liquid and acts as a cold shell to keep the magnets at their operational temperature.

    “Helium is a special element because it only becomes a liquid below 5 kelvin,” says Laurent Tavian, the group leader of the CERN cryogenics team. “It is also the only element which is not solid at very low temperature, and it is naturally inert—meaning we can easily store it and never have to worry about it becoming flammable.”

    The first sector cool-down started in May 2014. Engineers first pre-cooled the helium using 9000 metric tons of liquid nitrogen. After the pre-cooling, engineers injected the helium into the accelerator.

    “Filling the entire accelerator requires 130 metric tons of helium, which we received from our supplier at a rate of around one truckload every week,” Tavian says.

    In January CERN engineers plan to have the entire accelerator cooled to its nominal operating temperature of 1.9 kelvin (minus 456 degrees Fahrenheit), colder than outer space.

    See the full article here.

    Please help promote STEM in your local schools.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 1:29 pm on December 11, 2014 Permalink | Reply
    Tags: , INFN Gran Sasso, , Symmetry Magazine   

    From Symmetry: “ICARUS hits the road” 

    Symmetry

    December 11, 2014
    Kathryn Jepsen

    A giant neutrino detector is traveling by truck from the Italian Gran Sasso laboratories to CERN to get ready for a new life.

    On Tuesday night a 600-metric-tonne particle detector became the world’s largest neutrino experiment currently on an international road trip.

    The ICARUS T600 neutrino detector—the world’s largest liquid-argon neutrino experiment—is on its way from the INFN Gran Sasso laboratories in Italy to European research center CERN on the border of France and Switzerland. Once it arrives at CERN, it will undergo upgrades to prepare it for a second life.

    INFN Gran Sasso ICARUS
    INFN Gran Sasso ICARUS T600
    INFN Gran Sasso ICARUS T600

    “ICARUS is presently the state-of-the-art technology,” says Nobel Laureate Carlo Rubbia, the leader of the ICARUS experiment. “Its success has demonstrated the enormous potentials of this detector technique… Most of the ICARUS developments have become part of the liquid-argon technology that is now being used is most of the other, more recent projects.”

    Since 2010, the ICARUS experiment has studied neutrinos streaming about 450 miles straight through the Earth from CERN to Gran Sasso. Neutrinos come in three types, called flavors, and they switch flavors as they travel. The ICARUS experiment was set up to study those flavor oscillations. Its detector, which works like a huge, three-dimensional camera that visualizes subatomic events, has recorded several thousand neutrino interactions.

    Scientists see more experiments in the detector’s future, possibly using a powerful beam of neutrinos already in operation at Fermi National Accelerator Laboratory near Chicago.

    The detector is 6 meters wide, 18 meters long and 4 meters high. When in operation, it is filled with ultra-pure liquid argon and about 52,000 wires, which collect signals from particles and can reconstruct 3-D images of a what happens when a neutrino knocks an electron off of an atom of argon.

    To prepare the sensitive detector for transport, workers moved its inner chamber on sleds into a shipping container, says Chiara Zarra, the ICARUS movement and transportation coordinator. But getting the experiment out of its home was a challenge, she says. The laboratory layout had changed since ICARUS was first installed, and there were multiple other experiments to maneuver through. A team from CERN helped with planning by creating 3-D simulations of the operation.

    t
    Over the course of about a week, the detector will travel on a special equipment transporter through Rome, Genoa and Turin. After that it will cross the Alps through the Mont Blanc tunnel on its way to Geneva.
    Courtesy of: INFN

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

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    Symmetry is a joint Fermilab/SLAC publication.


     
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