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  • richardmitnick 3:33 pm on October 7, 2015 Permalink | Reply
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    From Symmetry: “A measurement to watch” 


    October 07, 2015
    Lauren Biron

    Photo by Roy Kaltschmidt, Lawrence Berkeley National Laboratory

    Finding a small discrepancy in measurements of the properties of neutrinos could show us how they fit into the bigger picture.

    Physics, perhaps more so than any other science, relies on measuring the same thing in multiple ways. Different experiments let scientists narrow in on right answers that satisfy all parties—a scientific system of checks and balances.

    That’s why it’s exciting when a difference, even a minute one, appears. It can teach physicists something about their current model – or physics that extends beyond it. It’s possible that just such a discrepancy exists between a certain measurement of neutrinos coming out of accelerator experiments and reactor-based experiments.

    Neutrinos are minuscule, neutral particles that don’t interact with much of anything. They can happily pass through a light-year of lead without a peep. Trillions pass through you every second. In fact, they are the most abundant massive particle in the universe—and something scientists are, naturally, quite keen to understand.

    The ghostly particles come in three flavours: electron, muon and tau [and their antimatter equivalents]. They transition between these three flavours as they travel.

    This means that a muon neutrino leaving an accelerator at Fermi National Accelerator Laboratory in Illinois can show up as an electron neutrino in an underground detector in South Dakota.

    Sanford Underground levels
    Sanford Underground Research Facility

    Not complicated enough for you? These neutrino flavors are made of mixtures of three different “mass states” of neutrinos, masses 1, 2 and 3.

    At the end of the day, neutrinos are weird. They hang out in the quantum realm, a land of probabilities and mixing matrices and other shenanigans. But here’s what you should know. There are lots of different things we can measure about neutrinos—and one of them is a parameter called theta13 (pronounced theta one three). Theta13 relates deeply to how neutrinos mix together, and it’s here that scientists have seen the faintest hint of disagreement from different experiments.

    Accelerators vs. reactors

    There are lots of different ways to learn about neutrinos and things like theta13. Two of the most popular involve particle accelerators and nuclear reactors.

    The best measurements of theta13 come from nuclear reactor experiments such as Double Chooz, RENO and Daya Bay Reactor Neutrino Experiment based in China (which released the best measurement to date a few weeks ago).

    Doube Chooz France
    Double Chooz (France)

    RENO Expderiment South Korea
    RENO (South Korea)

    Daya Bay
    Daya Bay (China)

    Detectors located near nuclear reactors provide such wonderful readings of theta13 because reactors produce an extremely pure fountain of electron antineutrinos, and theta13 is closely tied to how electron neutrinos mix. Researchers can calculate theta13 based on the number of electron antineutrinos that disappear as they travel from a near detector to the far detector, transforming into other types.

    Accelerators, on the other hand, typically start with a beam of muon neutrinos. And while that beam is fairly pure, it can have a bit of contamination in the form of electron neutrinos. Far detectors can look for both muon neutrinos that have disappeared and electron neutrinos that have appeared, but that variety comes with a price.

    “Both the power and the curse of long-baseline neutrino oscillation is that it’s sensitive to all of neutrino oscillation, not just theta13,” says Dan Dwyer, a scientist at Lawrence Berkeley National Laboratory and researcher on Daya Bay.

    With that in mind, we come to the source of the disagreement. The results coming out of accelerator-based experiments, such as the United States-based [FNAL]NOvA and Japan-based T2K, see just a few more electron neutrinos than researchers would predict based on what the reactor experiments are saying.

    FNAL NOvA experiment

    T2K Experiment
    J-PARC T2K (Japan)

    “The theta13 value that fits the beam experiments, that really describes how much electron neutrino you get, is somewhat larger than what Daya Bay, RENO and Double Chooz measure,” says Kate Scholberg, professor of physics at Duke University and researcher on T2K. “So there’s a little bit of tension.”

    Many grains of salt

    Data coming out of the accelerator experiments is still very young compared to the strong readings from reactor experiments, and it is complicated by the nature of the beam. No one is jumping on the discrepancy yet because it can be explained in different ways. Most importantly, the accelerator experiments just don’t have enough information.

    “We have to wait for T2K and NOvA to get sufficient statistics, and that’s going to take a while,” says Stephen Parke, head of the Theoretical Physics Department at Fermilab. Parke, Scholberg and Dwyer all estimated that about five more years of data collection will be required before researchers are able to start saying anything substantial.

    “There’s been a lot of pressure on Daya Bay to try to eke out as precise a measurement as we possibly can,” Dwyer says. “Every bit of increased precision we provide further improves the ability of NOvA and T2K and eventually [proposed neutrino experiment] DUNE to measure the other parameters.”

    FNAL Dune & LBNF

    Finding meaning in neutrinos

    If the accelerator experiments gather more data and if a clear discrepancy emerges—a big if—what does it mean?

    Turns out there are lots of reasons to love theta13. It’s one of the fundamental parameters that can define our universe. From a practical standpoint, it helps design future experiments to better understand neutrinos. And it could help physicists learn something new.

    “We don’t expect things not to agree, but we kind of hope that they won’t,” says André de Gouvêa, professor of physics at Northwestern University. “It means that we’re missing something.”

    That something could be CP violation, evidence that neutrinos and antineutrinos behave differently. CP violation has never been seen in neutrinos before, but if researchers observed it with accelerator experiments, it could help explain why our universe is made of matter rather than equal parts of matter and antimatter.

    Figuring out if CP violation is occurring means nailing down all of the different neutrino mixing parameters, which in turn means building more powerful, next-generation experiments such as Hyper-K in Japan, JUNO in China and the Deep Underground Neutrino Experiment in the United States.


    JUNO Chinese Neutrino Experiment
    JUNO Neutrino detector China

    DUNE will build on oscillation experiments like NOvA but will be able to better separate background noise from neutrino events, see a broader energy spectrum of neutrinos and find other neutrino characteristics.

    DUNE, which will be built in a repurposed gold mine in South Dakota and detect neutrinos passed 800 miles through the Earth from Fermilab in Illinois, will be one of the best ways to see CP violation and rely on expertise gained from smaller neutrino experiments.

    “Developing these types of experiments is very complicated,” de Gouvêa says. One of the major challenges of physics experiments is making sure you are measuring what you think you are measuring. “That’s part of the reason why we have a significant number of neutrino oscillation experiments.”

    Ultimately, the neutrino puzzle is still missing many pieces. A variety of experiments are ramping up to fill in the gaps, making it an exciting time to be a neutrino physicist.

    “We have to untangle the mysteries of the neutrino, and it’s not easy,” Parke says. “The neutrino doesn’t give up her secrets very easily.”

    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 1:52 pm on October 2, 2015 Permalink | Reply
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    From Symmetry: “The burgeoning field of neutrino astronomy” 


    October 02, 2015
    Glenn Roberts Jr.

    A new breed of experiments seeks sources of cosmic rays and other astrophysics phenomena.

    Ghostlike subatomic particles called neutrinos could hold clues to some of the greatest scientific questions about our universe: What extragalactic events create ultra-high-energy cosmic rays? What happened in the first seconds following the big bang? What is dark matter made of?

    Scientists are asking these questions in a new and fast-developing field called neutrino astronomy, says JoAnne Hewett, director of Elementary Particle Physics at SLAC National Accelerator Laboratory.

    SLAC Campus

    “When I was a graduate student I never thought we’d be thinking about neutrino astronomy,” she says. “Now not only are we thinking about it, we’re already doing it. At some point it will be a standard technique.”

    Neutrinos, the most abundant massive particles in the universe, are produced in a multitude of different processes. The new neutrino astronomers go after several types of neutrinos: ultra-high-energy neutrinos and neutrinos from supernovae, which they can already detect, and low-energy ones they have only measured indirectly so far.

    “Every time we look for these astrophysical neutrinos, we’re hoping to learn two things,” says André de Gouvêa, a theoretical physicist at Northwestern University: what high-energy neutrinos can tell us about the processes that produced them, and what low-energy neutrinos can tell us about the conditions of the early universe.

    Ultra-high-energy neutrinos

    At the ultra-high-energy end of the spectrum, researchers hope to follow cosmic neutrinos like a trail of bread crumbs back to their sources. They are thought to originate in the universe’s most powerful, natural particle accelerators, such as supermassive black holes.

    “We’re confident we’ve seen neutrinos coming from outside (our galaxy)—astrophysical sources,” says Kara Hoffman, a physics professor at the University of Maryland. She is a member of the international collaboration for IceCube, the largest neutrino telescope on the planet, which uses a cubic kilometer of South Pole ice as a massive, ultrasensitive detector.

    ICECUBE neutrino detector
    IceCube neutrino detector interior
    U Wisconsin/IceCube

    Scientists have been tracking high-energy particles from space for decades. But cosmic neutrinos are different: Because they are neutral particles, they travel in a straight line, unaffected by the magnetic fields of space.

    IceCube collaborators are exploring whether there is a correlation between ultra-high-energy neutrino events and observations of incredibly intense releases of energy known as gamma-ray bursts. Scientists also hope to learn whether there is a correlation between these neutrino events and with theorized phenomena known as gravitational waves.

    Alexander Friedland, a theorist at SLAC, says high-energy neutrinos (which are less energetic than ultra-high-energy neutrinos) can provide a useful window into physics at the earliest stages of supernovae explosions.

    “Neutrinos tell you about the explosion engine, and what happens later when the shock goes through,” Friedland says. “These are very rich conditions that you can never make on Earth. This is an amazing experiment that nature made for us.”

    With modern detectors it may be possible to detect thousands of neutrinos and to reconstruct their energy on a second-by-second basis.

    “Neutrinos basically give you a different eye to look at the universe and a unique probe of new physics,” Friedland says.
    Low-energy neutrinos

    At the low-energy end of the spectrum, researchers hope to find “relic” neutrinos produced at the start of the universe, leftovers from the big bang. Their energy is expected to be more than a quadrillion times lower than the highest-energy neutrinos.

    The lower the energy of the neutrino, however, the harder it is to detect. So for now, the cosmic neutrino background remains somewhat out of reach.

    “We already know a lot about it, even though we’ve never seen it directly,” de Gouvêa says. “If we look at the universe at very large scales, we can only explain things if this background exists. We can safely say: ‘Either this cosmic neutrino background exists, or there is something out there that behaves exactly like neutrinos do.’”

    The European Space Agency’s Planck satellite has helped to shape our understanding of this relic neutrino background, and the planned ground-based Large Synoptic Survey Telescope will provide new data.

    ESA Planck

    LSST Exterior
    LSST Interior
    LSST Camera
    LSST home to be built in Chile, the interior base, and the LSST camera, being built under the direction of LBL

    These surveys provide bounds on the quantity and interaction of these relic neutrinos, and can give us information about neutrino mass.

    As detectors become more sensitive, researchers may also learn whether a theorized particle called a “sterile neutrino” may be a component in dark matter, the invisible stuff we know accounts for most of the mass of the universe.

    Some proposed experiments, such as PTOLEMY at Princeton Plasma Physics Laboratory and the Project 8 collaboration, led by scientists at the Massachusetts Institute of Technology and University of California, Santa Barbara, are working to establish properties of these neutrinos by watching for evidence of their production in a radioactive form of hydrogen called tritium.

    Looking ahead

    There are several upgrades and new projects in the works in the fledgling field of neutrino astronomy.

    A proposal called PINGU would extend the sensitivity of the IceCube array to a broader range of neutrino energies. It could look for neutrinos coming from the center of the sun, a possible sign of dark matter interactions, and could also look for neutrinos produced in Earth’s atmosphere.

    Another project would greatly expand an underwater neutrino observatory in the Mediterranean called Antares. A third project would build a large-scale observatory in a lake in Siberia.

    Scientists also hope to eventually establish the Askaryan Radio Array, a 100-cubic-kilometer neutrino detector in Antarctica.

    The field of neutrino astronomy is young, but it’s constantly growing and improving, Hoffman says.

    “It’s kind of like having a Polaroid that you’re waiting to develop, and you just start to see the shadow of something,” she says. “What the picture’s going to look like we don’t really know.”

    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 11:22 am on September 29, 2015 Permalink | Reply
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    From Symmetry: “New discovery? Or just another bump?” 


    September 29, 2015
    Sarah Charley

    For physicists, seeing is not always believing.

    W boson

    Higgs Boson
    Possible Higgs event

    In the 1960s physicists at the University of California, Berkeley, saw evidence of new, unexpected particles popping up in data from their bubble chamber experiments.

    A bubble chamber

    But before throwing a party, the scientists did another experiment. They repeated their analysis, but instead of using the real data from the bubble chamber, they used fake data generated by a computer program, which assumed there were no new particles.

    The scientists performed a statistical analysis on both sets of data, printed the histograms, pinned them to the wall of the physics lounge, and asked visitors to identify which plots showed the new particles and which plots were fakes.

    Karl Pearson: To roughly assess the probability distribution of a given variable by depicting the frequencies of observations occurring in certain ranges of values

    No one could tell the difference. The fake plots had just as many impressive deviations from the theoretical predictions as the real plots.

    Eventually, the scientists determined that some of the unexpected bumps in the real data were the fingerprints of new composite particles. But the bumps in the fake data remained the result of random statistical fluctuations.

    So how do scientists differentiate between random statistical fluctuations and real discoveries?

    Just like a baseball analyst can’t judge if a rookie is the next Babe Ruth after nine innings of play, physicists won’t claim a discovery until they know that their little bump-on-a-graph is the real deal.

    After the histogram “social experiment” at Berkeley, scientists developed a one-size-fits-all rule to separate the “Hall of Fame” discoveries from the “few good games” anomalies: the five-sigma threshold.

    “Five sigma is a measure of probability,” says Kyle Cranmer, a physicist from New York University working on the ATLAS experiment.

    ATLAS in the LHC at CERN

    “It means that if a bump in the data is the result of random statistical fluctuation and not the consequence of some new property of nature, then we could expect to see a bump at least this big again only if we repeated our experiment a few million more times.”

    Bump plot points. No image credit.

    To put it another way, five sigma means that there is only a 0.00003 percent chance scientists would see this result due to statistical fluctuations alone—a good indication that there’s probably something hiding under that bump.

    But the five-sigma threshold is more of a guideline than a golden rule, and it does not tell physicists whether they have made a discovery, according to Cousins.

    “A few years ago scientists posted a paper claiming that they had seen faster-than-light neutrinos,” Cousins says. But few people seemed to believe it—even though the result was six sigma. (A six-sigma result is a couple of hundred times stronger than a five-sigma result.)

    The five-sigma rule is typically used as the standard for discovery in high-energy physics, but it does not incorporate another equally important scientific mantra: The more extraordinary the claim, the more evidence you need to convince the community.

    “No one was arguing about the statistics behind the faster-than-light neutrinos observation,” Cranmer says. “But hardly anyone believed they got that result because the neutrinos were actually going faster than light.”

    Within minutes of the announcement, physicists started dissecting every detail of the experiment to unearth an explanation. Anticlimactically, it turned out to be a loose fiber optic cable.

    The “extraordinary claims, extraordinary evidence” philosophy also holds true for the inverse of the statement: If you see something you expected, then you don’t need as much evidence to claim a discovery. Physicists will sometime relax their stringent statistical standards if they are verifying processes predicted by the Standard Model of particle physics—a thoroughly vetted description of the microscopic world.

    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.

    “But if you don’t have a well-defined hypothesis that you are testing, you increase your chances of finding something that looks impressive just because you are looking everywhere,” Cousins says. “If you perform 800 broad searches across huge mass ranges for new particles, you’re likely to see at least one impressive three-sigma bump that isn’t anything at all.”

    In the end, there is no one-size-fits-all rule that separates discoveries from fluctuations. Two scientists could look at the same data, make the same histograms and still come to completely different conclusions.

    So which results windup in textbooks and which results are buried in the archive?

    “This decision comes down to two personal questions: What was your prior belief, and what is the cost of making an error?” Cousins says. “With the Higgs discovery, we waited until we had overwhelming evidence of a Higgs-like particle before announcing the discovery, because if we made an error it could weaken people’s confidence in the LHC research program.”

    Experimental physicists have another way of verifying their results before making a discovery claim: comparable studies from independent experiments.

    “If one experiment sees something but another experiment with similar capabilities doesn’t, the first thing we would do is find out why,” Cranmer says. “People won’t fully believe a discovery claim without a solid cross check.”

    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 2:09 pm on September 27, 2015 Permalink | Reply
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    From Symmetry: “Scientists below the surface” 


    September 03, 2015

    Photo by Steve Babbitt, Black Hills State University

    Lauren Biron

    Getting into the Majorana Demonstrator clean room is an adventure. Unless you have to do it every day for work, in which case, it’s probably a chore.

    Majorano Demonstrator Experiment
    U Washington Majorana Demonstrator

    It all starts in Lead, South Dakota, a town once built around and seemingly forever linked to the underground. It’s 10 miles from Sturgis, which celebrated its 75th annual motorcycle rally in August by welcoming almost 1 million bikers. It’s three miles from Deadwood, the 1870s, Wild West version of which is the setting for the eponymous HBO show (though it’s filmed in California).

    Lead, pronounced so that it rhymes with reed and not red, is home to a former goldmine turned science lab. A mile below the surface, it hosts an immaculate clean room where scientists are assembling a detector to find what could be one of the rarest processes in nature, if it occurs at all. Their laboratory is 3230 square feet of scrubbed floor and filtered air, filled with glove boxes, a chemistry lab, hand-machined parts and a big shield made of lead bricks that looked like a pizza oven before it was wrapped in a few additional layers of insulation.

    It’s a unique environment with a bizarre commute. The road to Sanford Lab winds past old brick and timber buildings and the modern Sanford Lab Visitors Center before climbing a steep hill to Summit Avenue. An abrupt left takes scientists through the gate to the set of brick administration buildings and the gateway to the Yates shaft, a tall, white beacon in the Black Hills.

    Sanford Underground levels
    Sanford Underground Research Facility

    After descending a few creaky flights of stairs with bright yellow handrails, scientists gear up. Those who didn’t arrive in dark coveralls with reflective yellow bands slide them on, along with a hard hat, lamp, wraparound safety glasses, a belt or backpack with a rescue breather, and (often) steel-toe boots. Backpacks, lunches, laptops and other gear are placed in thick plastic bags to protect them on the trip down the shaft. Scientists take one of their metal tags from the “Out” board and place it in their pocket, while the twin tag goes on the “In” board, a record of those living the mole lifestyle for the day.

    Then it’s through a series of heavy sliding doors to the staging area where everyone boards the cage—tall people toward the back, shorties in the front. The cage operator talks to the hoist operator, who frees the box and sends it smoothly down through the rock and timber supports.

    It’s a damp yet delightful ride, strangely reminiscent of the Haunted Mansion at Disneyland. For 10 minutes, slabs of wet wood stream past, many with colorful numbers or letters marking repair work or the level of descent. The dizzying streaks are punctuated by black holes, drifts once mined for gold that now disappear into the earth. And for the entire ride, water splatters in, kissing faces and climbing up any coverall leg long and foolish enough to touch the floor.

    One can only imagine how it was for miners descending at three times the speed.

    Photo by: Matt Kapust, Sanford Lab

    A mile below, the cage slows and gently settles near a spot called The Big X, where pathways split and run deep into the darkness or toward the well-lit lab areas. Researchers—and engineers, construction workers, guides and other myriad folk who pass through—run their feet through a boot wash before heading toward the scientific portion of the underground. Then it’s a quick stripping of the coveralls, a helmet exchange, a slip of two pairs of booties around the shoes, and the debagging process—complete with a brief alcohol swipe for object exteriors.

    Another set of doors reveals the shiny brown hallway leading to the experiments. Thin tables run along their exterior in the hallway, the home for researchers working on laptops when not completing the day’s other tasks. A morning meeting to discuss the day’s plan, and then it’s on to the next costume change.

    The machinist and his assistant often head in first. Randy Hughes is the sole machinist underground at Majorana (and perhaps the only machinist working a mile underground anywhere in the world, let alone at a scientific experiment), and he has a tight schedule for creating parts out of special copper electroformed underground, away from radiation.

    Then the scientists get changed. The clean room is not so different from those on the surface—it has special air filtration and is kept free of particulate matter through special procedures and handy yet unexpected items like clean room paper and clean room pens.

    The Majorana lab is a class 100-400 clean room, meaning there can be only 100 to 400 particles larger than half a micron per cubic foot (by comparison, a human hair is 100 microns). Typically, the room has only 100 to 200 particles. Humans are by far the dirtiest things that enter, causing the particle count to spike even with all the precautions.

    First, scientists step through plastic sheeting into a space barely large enough to fit a full-size bed. Sticky blue sheets on the ground pull any dirt off the booties, but scientists still pull off the outer pair and replace them with a fresh set. Helmets come off and are swabbed with alcohol, and hairnets go on.

    Facemasks slide over the nose and mouth. Because the wraparound safety glasses are still required in the lab, many people opt to tape the upper portion of the facemask down around their nose and cheeks, preventing hot air from rising up the channel and fogging their glasses. Over that goes a full head hood, leaving an oval of space for the glasses to pop out. The hood tucks into a clean pair of white coveralls that zip up. White booties slide up over the legs, the elastic holding them around mid calf, a wrap-around string at the ankles making them vaguely shoe-like.

    Then it’s two pairs of white gloves on each hand. The coverall sleeves have button snaps and are taped to the inner pair of gloves. Scientists replace the outer ones fairly often throughout the day.

    Finally, the helmet goes back on, and everything that will enter the clean room is attacked with alcohol-soaked pads. Fabrics aren’t friends of the clean room, so most of what goes in is plastic or metal—cameras and what must be the cleanest laptops in South Dakota seem the most common.

    And then that’s it. Through the doors onto more blue sticky tape, and the scientists are finally ready for work. That might mean cleaning copper components, assembling detectors in a glove box, calibrating modules, testing cryostats, working on wiring or vacuum systems, or a hundred other things. It’s not the easiest outfit to work in. It’s a little warm, a little hard to breathe, a little like working through a fog. Most agree that the best part of the day is the sweet freedom when they remove their layers, ripping off the face mask and tape like a scientific Bioré pore strip.

    Some—like Randy—aren’t real fans of the cumbersome procedures, while others don’t mind all that much. But everyone agrees that there is one cardinal rule to working in a clean room: Go to the bathroom before you head in.

    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 3:41 pm on September 23, 2015 Permalink | Reply
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    From Symmetry: “Muon g-2 magnet successfully cooled down and powered up” 


    September 23, 2015
    Andre Salles

    Photo by Reidar Hahn, Fermilab

    It survived a month-long journey over 3200 miles, and now the delicate and complex electromagnet is well on its way to exploring the unknown.

    Two years ago, scientists on the Muon g-2 experiment successfully brought a fragile, expensive and complex 17-ton electromagnet on a 3200-mile land and sea trek from Brookhaven National Laboratory in New York to Fermilab in Illinois. But that was just the start of its journey.

    Now, the magnet is one step closer to serving its purpose as the centerpiece of an experiment to probe the mysteries of the universe with subatomic particles called muons. This week, the ring—now installed in a new, specially designed building at Fermilab—was successfully cooled down to operating temperature (minus 450 degrees Fahrenheit) and powered up, proving that even after a decade of inactivity, it remains a vital and viable scientific instrument.

    Getting the electromagnet to this point took a team of dedicated people more than a year, and the results have that team breathing a collective sigh of relief. The magnet was built at Brookhaven in the 1990s for a similar muon experiment, and before the move to Fermilab, it spent more than 10 years sitting in a building, inactive.

    “There were some questions about whether it would still work,” says Kelly Hardin, lead technician on the Muon g-2 experiment. “We didn’t know what to expect, so to see that it actually does work is very rewarding.”

    Moving the ring from New York to Illinois cost roughly 10 times less than building a new one. But it was a tricky proposition—the 52-foot-wide, 17-ton magnet, essentially three rings of aluminum with superconducting coils inside, could not be taken apart, nor twisted more than a few degrees without causing irreparable damage.

    Scientists sent the ring on a fantastic voyage, using a barge to bring it south around Florida and up a series of rivers to Illinois. A specially designed truck gently drove it the rest of the way to Fermilab.

    The Muon g-2 experiment plans to use the magnet to build on the Brookhaven experiment but with a much more powerful particle beam. The experiment will trap muons in the magnetic field and use them to detect theoretical phantom particles that might be present, impacting the properties of the muons. But to do that, the team had to find out whether the machine could generate the needed magnetic field.

    The magnet was moved into its own building on the Fermilab site. Over the past year, workers took on the painstaking task of reassembling the steel base. Two dozen 26-ton pieces of steel—and a dozen 11-ton pieces—had to be maneuvered into place with tremendous precision.

    “It was like building a 750-ton Swiss watch,” says Chris Polly, project manager for the experiment.

    While that assembly was taking place, other members of the team had to completely replace the control system for the magnet, redesigning it from scratch. Del Allspach, the project engineer, and Hogan Nguyen, one of the primary managers of the ring, oversaw much of this effort, as well as the construction of the infrastructure (helium lines, power conduits) needed before the ring could be cooled and powered.

    “That work was very challenging,” Nguyen says. “We had to stay within very strict tolerances for the alignment of the equipment.”

    The tightest of those tolerances was 10 microns. For comparison, the width of a human hair is 75 microns. A red blood cell is about 5 microns across.

    While assembling the components around the ring, the team also tracked down and sealed a significant helium leak, one that had been previously documented at Brookhaven. Hardin says that the team was relieved to discover that the leak was in an area that could be accessed and fixed. The successful cool-down proved that the leak had been plugged.

    “That’s where the big relief comes in,” says Hardin. “We had a good team, and we worked together well.”

    Bringing the ring down to its operating temperature of minus 450 degrees Fahrenheit required cooling it with a helium refrigeration system and liquid nitrogen for more than two weeks. Polly noted that this was a tricky process, since the magnet as a whole shrank by at least an inch as it cooled down. This could have damaged the delicate coils inside if it was not done slowly.

    Once cooling was complete, the ring had to be powered with 5300 amps of current to produce the magnetic field. This was another slow process, with technicians easing the ring up by fewer than two amps per second and stopping every 1000 amps to check the system.

    “It proves we started with a good magnet,” Allspach says. “It had been off for more than a decade, then moved across the country, installed, cooled and powered. I’m very happy to be at this point. It’s a big success for all of us.”

    The next step for the magnet is a long process of “shimming,” or adjusting the magnetic field to within extraordinarily small tolerances. Fermilab is in the process of constructing a beamline that will provide muons to the magnet, and scientists expect to start measuring those muons in 2017.

    For Nguyen, that step—handing the magnet off to early-career scientists, who will help carry out the experiment—is exciting. One of the thrills of the process, he says, was watching these younger members of the team learn and grow as the experiment took shape.

    “I can’t wait to see these younger people get to control this beautiful magnet,” he says.

    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 12:14 pm on September 22, 2015 Permalink | Reply
    Tags: , , Proton Decay (?), Symmetry Magazine   

    From Symmetry: “Do protons decay?” 



    September 22, 2015
    Matthew R. Francis

    The stuff of daily existence is made of atoms, and all those atoms are made of the same three things: electrons, protons and neutrons.

    Protons and neutrons are very similar particles in most respects. They’re made of the same quarks, which are even smaller particles, and they have almost exactly the same mass.

    Yet neutrons appear to be different from protons in an important way: They aren’t stable. A neutron outside of an atomic nucleus decays in a matter of minutes into other particles.

    What about protons?

    A free proton is a pretty common sight in the cosmos. Much of the ordinary matter (as opposed to dark matter) in galaxies and beyond comes in the form of hydrogen plasma, a hot gas made of unattached protons and electrons. If protons were as unstable as neutrons, that plasma would eventually vanish.

    But that isn’t happening. Protons—whether inside atoms or drifting free in space—appear to be remarkably stable. We’ve never seen one decay.

    However, nothing essential in physics forbids a proton from decaying. In fact, a stable proton would be exceptional in the world of particle physics, and several theories demand that protons decay.

    If protons are not immortal, what happens to them when they die, and what does that mean for the stability of atoms?

    Following the rules

    Fundamental physics relies on conservation laws: certain quantities that are preserved, such as energy, momentum and electric charge. The conservation of energy—combined with the famous equation E=mc2—means that lower-mass particles can’t change into higher-mass ones without an infusion of energy. Combining conservation of energy with conservation of electric charge tells us that electrons are probably stable forever: No lower-mass particle with a negative electric charge exists, to the best of our knowledge.

    Protons aren’t constrained the same way: They are more massive than a number of other particles, and the fact that they are made of quarks allows for several possible ways for them to die.

    For comparison, a neutron decays into a proton, an electron and a neutrino. Both energy and electric charge are preserved in the decay: A neutron is a wee bit heftier than a proton and electron combined, and the positively-charged proton balances out the negatively-charged electron to make sure the total electric charge is zero both before and after the decay. (The neutrino—or technically an antineutrino, the antimatter version—is necessary to balance other things, but that’s a story for another day.)

    Because atoms are stable and we’ve never seen a proton die, perhaps protons are intrinsically stable. However, as Kaladi Babu of Oklahoma State University points out, there’s no “proton conservation law” like charge conservation to preserve a proton.

    “You ask this question: What if the proton decays?” he says. “Does it violate any fundamental principle of physics? And the answer is no.”

    No GUTs, no glory

    So if there’s no rule against proton decay, is there a reason scientists expect to see it? Yes. Proton decay is the strongest testable prediction of several grand unified theories, or GUTs.

    GUTs unify three of the four fundamental forces of nature: electromagnetism, the weak force and the strong force. (Gravity isn’t included because we don’t have a quantum theory for it yet.)

    The first GUT, proposed in the 1970s, failed. Among other things, it predicted a proton lifetime short enough that experiments should have seen decays when they didn’t. However, the idea of grand unification was still valuable enough that particle physicists kept looking for it. (You might say they had a GUT feeling. Or you might not.)

    “The idea of grand unification is really beautiful and explains many things that seem like bizarre coincidences,” says theorist Jonathan Feng, a physicist at the University of California, Irvine.

    Feng is particularly interested in a GUT that involves Supersymmetry, a brand of particle physics that potentially could explain a wide variety of phenomena, including the invisible dark matter that binds galaxies together.

    Supersymmetry standard model
    Standard Model of Supersymmetry

    Supersymmetric GUTs predict some new interactions that, as a pleasant side effect, result in a longer lifetime for protons, yet still leave proton decay within the realm of experimental detection. Because of the differences between supersymmetric and non-supersymmetric GUTs, Feng says the proton decay rate could be the first real sign of Supersymmetry in the lab.

    However, Supersymmetry is not necessary for GUTs. Babu is fond of a GUT that shares many of the advantages of the supersymmetric versions. This GUT’s technical name is SO(10), named because its mathematical structure involves rotations in 10 imaginary dimensions. The theory includes important features absent from the Standard Model such as neutrino masses, and might explain why there is more matter than antimatter in the cosmos. Naturally, it predicts proton decay.

    The search for proton decay

    Much rests on the existence of proton decay, and yet we’ve never seen a proton die. The reason may simply be that protons rarely decay, a hypothesis borne out by both experiment and theory. Experiments say the proton lifetime has to be greater than about 1034 years: That’s a 1 followed by 34 zeroes.

    For reference, the universe is only 13.8 billion years old, which is roughly a 1 followed by 10 zeros. Protons on average will outlast every star, galaxy and planet, even the ones not yet born.

    The key phrase in that last sentence is “on average.” As Feng says, it’s not like “every single proton will last for 1034 years and then at 1034 years they all boom! poof! in a puff of smoke, they all disappear.”

    Because of quantum physics, the time any given proton decays is random, so a tiny fraction will decay long before that 1034-year lifetime. So, “what you need to do is to get a whole bunch of protons together,” he says. Increasing the number of protons increases the chance that one of them will decay while you’re watching.

    The second essential step is to isolate the experiment from particles that could mimic proton decay, so any realistic proton decay experiment must be located deep underground to isolate it from random particle passers-by. That’s the strategy pursued by the currently operating Super-Kamiokande experiment in Japan, which consists of a huge tank with 50,000 tons of water in a mine.

    Super-Kamiokande experiment Japan
    Super-Kamiokande experiment

    The upcoming Deep Underground Neutrino Experiment, to be located in a former gold mine in South Dakota, will consist of 40,000 tons of liquid argon.

    FNAL Dune & LBNF
    DUNE, managed by FNAL

    Because the two experiments are based on different types of atoms, they are sensitive to different ways protons might decay, which will reveal which GUT is correct … if any of the current models is right. Both Super-Kamiokande and DUNE are neutrino experiments first, Feng says, “but we’re just as interested in the proton decay possibilities of these experiments as in the neutrino aspects.”

    After all, proton decay follows from profound concepts of how the cosmos fundamentally operates. If protons do decay, it’s so rare that human bodies would be unaffected, but not our understanding. The impact of that knowledge would be immense, and worth a tiny bit of instability.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 11:25 am on September 17, 2015 Permalink | Reply
    Tags: , , , Symmetry Magazine   

    From Symmetry: “Hitting the neutrino floor” 


    September 17, 2015
    Laura Dattaro

    Artwork by Sandbox Studio, Chicago with Ana Kova

    Dark matter experiments are becoming so sensitive, even the ghostliest of particles will soon get in the way.

    The scientist who first detected the neutrino called the strange new particle “the most tiny quantity of reality ever imagined by a human being.” They are so absurdly small and interact with other matter so weakly that about 100 trillion of them pass unnoticed through your body every second, most of them streaming down on us from the sun.

    And yet, new experiments to hunt for dark matter are becoming so sensitive that these ephemeral particles will soon show up as background. It’s a phenomenon some physicists are calling the “neutrino floor,” and we may reach it in as little as five years.

    The neutrino floor applies only to direct detection experiments, which search for the scattering of a dark matter particle off of a nucleus. Many of these experiments look for WIMPs, or weakly interacting massive particles. If dark matter is indeed made of WIMPs, it will interact in the detector in nearly the same way as solar neutrinos.

    We don’t know what dark matter is made of. Experiments around the world are working toward detecting a wide range of particles.

    “What’s amazing is now the experimenters are trying to measure dark matter interactions that are at the same strength or even smaller than the strength of neutrino interactions,” says Thomas Rizzo, a theoretical physicist at SLAC National Accelerator Laboratory. “Neutrinos hardly interact at all, and yet we’re trying to measure something even weaker than that in the hunt for dark matter.”

    This isn’t the first time the hunt for dark matter has been linked to the detection of solar neutrinos. In the 1980s, physicists stumped by what appeared to be missing solar neutrinos envisioned massive detectors that could fix the discrepancy. They eventually solved the solar neutrino problem using different methods (discovering that the neutrinos weren’t missing; they were just changing as they traveled to the Earth), and instead put the technology to work hunting dark matter.

    In recent years, as the dark matter program has grown in size and scope, scientists realized the neutrino floor was no longer an abstract problem for future researchers to handle. In 2009, Louis Strigari, an astrophysicist at Texas A&M University, published the first specific predictions of when detectors would reach the floor. His work was widely discussed at a 2013 planning meeting for the US particle physics community, turning the neutrino floor into an active dilemma for dark matter physicists.

    “At some point these things are going to appear,” Strigari says, “and the question is, how big do these detectors have to be in order for the solar neutrinos to show up?”

    Strigari predicts that the first experiment to hit the floor will be the SuperCDMS experiment, which will hunt for WIMPs from SNOLAB in the Vale Inco Mine in Canada.

    LBL SuperCDMS
    LBL SuperCDMS


    While hitting the floor complicates some aspects of the dark matter hunt, Rupak Mahapatra, a principal investigator for SuperCDMS at Texas A&M, says he hopes they reach it sooner rather than later—a know-thy-enemy kind of thing.

    “It is extremely important to know the neutrino floor very precisely,” Mahapatra says. “Once you hit it first, that’s a benchmark. You understand what exactly that number should be, and it helps you build a next-generation experiment.”

    Much of the work of untangling a dark matter signal from neutrino background will come during data analysis. One strategy involves taking advantage of the natural ebbs and flows in the amount of dark matter and neutrinos hitting Earth. Dark matter’s natural flux, which arises from the motion of the sun through the Milky Way, peaks in June and reaches its lowest point in December. Solar neutrinos, on the other hand, peak in January, when the Earth is closest to the sun.

    “That could help you disentangle how much is signal and how much is background,” Rizzo says.

    There’s also the possibility that dark matter is not, in fact, a WIMP. Another potentially viable candidate is the axion, a hypothetical particle that solves a lingering mystery of the strong nuclear force. While WIMP and neutrino interactions look very similar, axion interactions would appear differently in a detector, making the neutrino floor a non-issue.

    But that doesn’t mean physicists can abandon the WIMP search in favor of axions, says JoAnne Hewett, a theoretical physicist at SLAC. “WIMPs are still favored for many reasons. The neutrino floor just makes it more difficult to detect. It doesn’t make it less likely to exist.”

    Physicists are confident that they’ll eventually be able to separate a dark matter signal from neutrino noise. Next-generation experiments might even be able to distinguish the direction a particle is coming from when it hits the detector, something the detectors being built today just can’t do. If an interaction seemed to come from the direction of the sun, that would be a clear indication that it was likely a solar neutrino.

    “There’s certainly avenues to go here,” Strigari says. “It’s not game over, we don’t think, for dark matter direct detection.”

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 3:31 pm on September 16, 2015 Permalink | Reply
    Tags: , , MiniCLEAN, Symmetry Magazine   

    From Symmetry: “A light in the dark” 


    September 16, 2015
    Diana Kwon

    Courtesy of the MiniCLEAN collaboration

    Getting to an experimental cavern 6800 feet below the surface in Sudbury, Ontario, requires an unusual commute. The Cage, an elevator that takes people into the SNOLAB facility, descends twice every morning at 6 a.m. and 8 a.m. Before entering the lab, individuals shower and change so they don’t contaminate the experimental areas.


    A thick layer of natural rock shields the clean laboratory where air quality, humidity and temperature are highly regulated. These conditions allow scientists to carry out extremely sensitive searches for elusive particles such as dark matter and neutrinos.

    The Cage returns to the surface at 3:45 p.m. each day. During the winter months, researchers go underground before the sun rises and emerge as it sets. Steve Linden, a postdoctoral researcher from Boston University, makes the trek every morning to work on MiniCLEAN, which scientists will use to test a novel technique for directly detecting dark matter.

    “It’s a long day,” Linden says.

    Scientists and engineers have spent the past eight years designing and building the MiniCLEAN detector. Today that task is complete; they have begun commissioning and cooling the detector to fill it with liquid argon to start its search for dark matter.

    Though dark matter is much more abundant than the visible matter that makes up planets, stars and everything we can see, no one has ever identified it. Dark matter particles are chargeless, don’t absorb or emit light, and interact very weakly with matter, making them incredibly difficult to detect.

    Spotting the WIMPs

    MiniCLEAN (CLEAN stands for Cryogenic Low-Energy Astrophysics with Nobles) aims to detect weakly interacting massive particles, or WIMPs, the current favorite dark matter candidate. Scientists will search for these rare particles by observing their interactions with atoms in the detector.

    To make this possible, the detector will be filled with over 500 kilograms of very cold, dense, ultra-pure materials—argon at first, and later neon. If a WIMP passes through and collides with an atom’s nucleus, it will produce a pulse of light with a unique signature. Scientists can collect and analyze this light to determine whether what they saw was a dark matter particle or some other background event.

    The use of both argon and neon will allow MiniCLEAN to double-check any possible signals. Argon is more sensitive than neon, so a true dark matter signal would disappear when liquid argon is replaced with liquid neon. Only an intrinsic background signal from the detector would persist. Scientists would like to eventually scale this experiment up to a larger version called CLEAN.

    Overcoming obstacles

    MiniCLEAN is a small experiment, with about 15 members in the collaboration and the project lead at Pacific Northwest National Laboratory.. While working on this experiment underground with few hands to spare, the team has run into some unexpected roadblocks.

    MiniCLEAN detector

    One such obstacle appeared while transporting the inner vessel, a detector component that will contain the liquid argon or neon.

    “Last November, as we finished assembling the inner vessel and were getting ready to move it to where it needed to end up, we realized it wouldn’t fit between the doors into the hallway we had to wheel it down,” Linden explains.

    When this happened, the team was faced with two options: somehow reduce the size of the vessel, or cut away a part of the door—not a simple thing to do in a clean lab. Fortunately, temporarily replacing some of the vessel’s parts reduced the size enough to make it fit. They got it through the doorway with about an eighth of an inch clearance on each side.

    “What gives me the energy to persist on this project is that the CLEAN approach is unique, and there isn’t another approach to dark matter that is like it,” says Pacific Northwest National Laboratory scientist Andrew Hime, MiniCLEAN spokesperson and principal investigator. “It’s been eight years since we starting pushing hard on this program, and finally getting real data from the detector will be a breath of fresh air.”

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 12:04 pm on September 10, 2015 Permalink | Reply
    Tags: , , Symmetry Magazine, XMASS   

    From Symmetry: “XMASS continues dark matter debate” 


    September 10, 2015
    Kathryn Jepsen

    Courtesy of Kamioka Observatory, ICRR, The University of Tokyo

    XMASS is the latest of multiple experiments to contradict a previous dark matter discovery claim, but the conversation isn’t over yet.

    Since 1998, scientists on the DAMA-LIBRA experiment at Gran Sasso National Laboratory in Italy have claimed the discovery of an increasingly statistically significant sign of dark matter.

    DAMA-LIBRA at Gran Sasso

    This week, the XMASS experiment in Japan joined the LUX, Xenon100 and CDMS experiments in reporting results that seem to contradict that claim.

    LUX Dark matter

    XENON Dark Matter Experiment


    Scientists look for dark matter in many ways. Both this result from the XMASS experiment and the results from DAMA-LIBRA look for something called annual modulation, a sign that the Earth is constantly moving through a halo of dark matter particles.

    As the sun rotates around the center of the Milky Way, the Earth moves around the sun, completing one revolution per year. During the first half of the year, the Earth moves in the same direction as the sun; during the second half, the Earth completes its circle, moving in the opposite direction.

    When the sun and Earth are moving in the same direction, the Earth should move through slightly more dark matter than when the sun and Earth are moving in opposite directions. So scientists should see a few more dark matter particles hit their detectors during that part of the year.

    Experiments other than DAMA-LIBRA have seen hints of an annual modulation, but only the CoGeNT experiment has ever provided support for DAMA-LIBRA’s claim that this modulation comes from dark matter.

    CoGeNT experiment

    The effect could be caused by other annual changes. Pressure and temperature could affect an experiment. Atmospheric changes with the seasons could affect the number of cosmic rays that reach the experiment. Background radiation from radon gas has been known to change seasonally for underground experiments because of its interaction with the water table in the rock, says Fermilab scientist Dan Bauer of the CDMS experiment.

    “Nobody’s been able to put their finger on what’s causing the DAMA modulation,” he says. “We can’t find the smoking gun.”

    The XMASS experiment in Kamioka, Japan, looks for signs that dark matter particles have bounced off the nuclei in their 832-kilogram container of liquid Xenon. The experiment has sensitivity to two types of possible dark matter interactions, says scientist Yoichiro Suzuki, principal investigator for XMASS at the Tokyo-based Kavli Institute for the Physics and Mathematics of the Universe, in an email.

    After taking data for about 16 months, the XMASS experiment disagreed with the DAMA-LIBRA claim, if one assumes dark matter particles scatter like billiard balls when they collide with nuclei. XMASS did find a low level of annual modulation, though, and that could be a hint of dark matter interacting with normal matter in a different way.

    However, XMASS scientists deduced from their signal some characteristics that the dark matter particles causing the modulation would need to have: their masses and their rates of interaction with normal matter. And experiments that search for dark matter directly have already ruled out those masses and interaction rates.

    But scientists still don’t know for sure what dark matter particles are like. Until they do, or until they identify the source of the annual modulation signals, they might have a hard time dissuading scientists on DAMA-LIBRA.

    The XMASS experiment continues to take data, Suzuki says. XMASS scientists hope eventually to build a 5-ton version of the experiment.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 2:22 pm on September 9, 2015 Permalink | Reply
    Tags: , , , , Symmetry Magazine   

    From Symmetry: “The birth of a black hole, live” 


    September 09, 2015
    Lauren Biron

    Simulation of gravitational lensing by a black hole, which distorts the image of a galaxy in the background

    Black holes fascinate us. We easily conjure up images of them swallowing spaceships, but we know very little about these strange objects. In fact, we’ve never even seen a black hole form. Scientists on neutrino experiments such as the upcoming Deep Underground Neutrino Experiment hope to change that.

    FNAL Dune & LBNF

    “You’ve got to be a bit lucky,” says Mark Thomson, DUNE co-spokesperson. “But it would be one of the major discoveries in science. It would be absolutely incredible.”

    Black holes are sometimes born when a massive star, typically more than eight times the mass of our own sun, collapses. But there are a lot of questions about what exactly happens during the process: How often do these collapsing stars give rise to black holes? When in the collapse does the black hole actually develop?

    What scientists do know is that deep in the dense core of the star, protons and electrons are squeezed together to form neutrons, sending ghostly particles called neutrinos streaming out. Matter falls inward. In the textbook case, matter rebounds and erupts, leaving a neutron star. But sometimes, the supernova fails, and there’s no explosion; instead, a black hole is born.

    DUNE’s gigantic detectors, filled with liquid argon, will sit a mile below the surface in a repurposed goldmine. While much of their time will be spent looking for neutrinos sent from Fermi National Accelerator Laboratory 800 miles away, the detectors will also have the rare ability to pick up a core collapse in our Milky Way galaxy – whether or not that leads to a new black hole.

    The only supernova ever recorded by neutrino detectors occurred in in 1987, when scientists saw a total of 19 neutrinos.

    Remnant of SN 1987A seen in light overlays of different spectra. ALMA data (radio, in red) shows newly formed dust in the center of the remnant. Hubble (visible, in green) and Chandra (X-ray, in blue) data show the expanding shock wave.

    ALMA Array

    NASA Hubble Telescope
    NASA/ESA Hubble

    NASA Chandra Telescope

    Scientists still don’t know if that supernova formed a black hole or a neutron star—there simply wasn’t enough data. Thomson says that if a supernova goes off nearby, DUNE could see up to 10,000 neutrinos.

    DUNE will look for a particular signature in the neutrinos picked up by the detector. It’s predicted that a black hole will form relatively early in a supernova. Neutrinos will be able to leave the collapse in great numbers until the black hole emerges, trapping everything—including light and neutrinos—in its grasp. In data terms, that means you’d get a big burst of neutrinos with a sudden cutoff.

    Neutrinos come in three types, called flavors: electron, muon and tau. When a star explodes, it emits all the various types of neutrinos, as well as their antiparticles.

    They’re hard to catch. These neutrinos arrive with 100 times less energy than those arriving from an accelerator for experiments, which makes them less likely to interact in a detector.

    Most of the currently running, large particle detectors capable of seeing supernova neutrinos are best at detecting electron antineutrinos—and not great at detecting their matter equivalents, electron neutrinos.

    “It would be a tragedy to not be ready to detect the neutrinos in full enough detail to answer key questions,” says John Beacom, director of the Center for Cosmology and Astroparticle Physics at The Ohio State University.

    Luckily, DUNE is unique. “The only one that is sensitive to a huge slug of electron neutrinos is DUNE, and that’s a function of using argon [as the detector fluid],” says Kate Scholberg, professor of physics at Duke University.

    It will take more than just DUNE to get the whole picture, though. Getting an entire suite of large, powerful detectors of different types up and running is the best way to figure out the lives of black holes, Beacom says.

    There is a big scintillator detector, JUNO, in the works in China, and plans for a huge water-based detector, Hyper-K, in Japan. Gravitational wave detectors such as LIGO could pick up additional information about the density of matter and what’s happening in the collapse.

    JUNO Chinese Neutrino Experiment
    JUNO Neutrino detector China


    Caltech LIGO
    Caltech LIGO

    “My dream is to have a supernova with JUNO, Hyper-K and DUNE all online,” Scholberg says. “It would certainly make my decade.”

    The rate at which neutrinos arrive after a supernova will tell scientists about what’s happening at the center of a core collapse—but it will also provide information about the mysterious neutrino, including how they interact with each other and potential insights as to how much the tiny particles actually weigh.

    Within the next three years, the rapidly growing DUNE collaboration will build and begin testing a prototype of the 40,000-ton liquid argon detector. This 400-ton version will be the second-largest liquid-argon experiment ever built to date. It is scheduled for testing at CERN starting in 2018.

    DUNE is scheduled to start installing the first of its four detectors in the Sanford Underground Research Facility in 2021.

    See the full article here .

    Please help promote STEM in your local schools.

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    Symmetry is a joint Fermilab/SLAC publication.

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