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  • richardmitnick 2:12 pm on November 25, 2015 Permalink | Reply
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    From Symmetry: “Revamped LHC goes heavy metal” 


    Sarah Charley

    Physicists will collide lead ions to replicate and study the embryonic universe.

    “In the beginning there was nothing, which exploded.”

    ~ Terry Pratchett, author

    For the next three weeks physicists at the Large Hadron Collider will cook up the oldest form of matter in the universe by switching their subatomic fodder from protons to lead ions.

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

    Lead ions consist of 82 protons and 126 neutrons clumped into tight atomic nuclei. When smashed together at extremely high energies, lead ions transform into the universe’s most perfect super-fluid: the quark gluon plasma. Quark gluon plasma is the oldest form of matter in the universe; it is thought to have formed within microseconds of the big bang.

    “The LHC can bring us back to that time,” says Rene Bellwied, a professor of physics at the University of Houston and a researcher on the ALICE experiment.


    “We can produce a tiny sample of the nascent universe and study how it cooled and coalesced to make everything we see today.”

    Scientists first observed this prehistoric plasma after colliding gold ions in the Relativistic Heavy Ion Collider [RHIC], a nuclear physics research facility located at the US Department of Energy’s Brookhaven National Laboratory.

    BNL RHIC Campus

    “We expected to create matter that would behave like a gas, but it actually has properties that make it more like a liquid,” says Brookhaven physicist Peter Steinberg, who works on both RHIC and the ATLAS heavy ion program at the LHC. “And it’s not just any liquid; it’s a near perfect liquid, with a very uniform flow and almost no internal resistance.”

    The LHC is famous for accelerating and colliding protons at the highest energies on Earth, but once a year physicists tweak its magnets and optimize its parameters for lead-lead or lead-proton collisions.

    The lead ions are accelerated until each proton and neutron inside the nucleus has about 2.51 trillion electronvolts of energy. This might seem small compared to the 6.5 TeV protons that zoomed around the LHC ring during the summer. But because lead ions are so massive, they get a lot more bang for their buck.

    “If protons were bowling balls, lead ions would be wrecking balls,” says Peter Jacobs, a scientist at Lawrence Berkeley National Laboratory working on the ALICE experiment. “When we collide them inside the LHC, the total energy generated is huge; reaching temperatures around 100,000 times hotter than the center of the sun. This is a state of matter we cannot make by just colliding two protons.”

    Compared to the last round of LHC lead-lead collisions at the end of Run I, these collisions are nearly twice as energetic. New additions to the ALICE detector will also give scientists a more encompassing picture of the nascent universe’s behavior and personality.

    “The system will be hotter, so the quark gluon plasma will live longer and expand more,” Bellwied says. “This increases our chances of producing new types of matter and will enable us to study the plasma’s properties more in depth.”

    The Department of Energy, Office of Science, and the National Science Foundation support this research and sponsor the US-led upgrades the LHC detectors.

    Bellwied and his team are particularly interested in studying a heavy and metastable form of matter called strange matter. Strange matter is made up of clumps of quarks, much like the original colliding lead ions, but it contains at least one particularly heavy quark, called the strange quark.

    “There are six quarks that exist in nature, but everything that is stable is made only out of the two lightest ones,” he says. “We want to see what other types of matter are possible. We know that matter containing strange quarks can exist, but how strange can we make it?”

    Examining the composition, mass and stability of ‘strange’ matter could help illuminate how the early universe evolved and what role (if any) heavy quarks and metastable forms of matter played during its development

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 1:07 pm on November 24, 2015 Permalink | Reply
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    From Symmetry: “Charge-parity violation” 


    Photo by Reidar Hahn, Fermilab with Sandbox Studio, Chicago

    Manuel Gnida and Kathryn Jepsen

    Matter and antimatter behave differently. Scientists hope that investigating how might someday explain why we exist.

    One of the great puzzles for scientists is why there is more matter than antimatter in the universe—the reason we exist.

    It turns out that the answer to this question is deeply connected to the breaking of fundamental conservation laws of particle physics. The discovery of these violations has a rich history, dating back to 1956.

    Parity violation

    It all began with a study led by scientist Chien-Shiung Wu of Columbia University. She and her team were studying the decay of cobalt-60, an unstable isotope of the element cobalt. Cobalt-60 decays into another isotope, nickel-60, and in the process, it emits an electron and an electron antineutrino. The nickel-60 isotope then decays into a pair of photons.

    The conservation law being tested was parity conservation, which states that the laws of physics shouldn’t change when all the signs of a particle’s spatial coordinates are flipped. The experiment observed the decay of cobalt-60 in two arrangements that mirrored one another.

    The release of photons in the decay is an electromagnetic process, and electromagnetic processes had been shown to conserve parity. But the release of the electron and electron antineutrino is a radioactive decay process, mediated by the weak force. Such processes had not been tested in this way before.

    Parity conservation dictated that, in this experiment, the electrons should be emitted in the same direction and in the same proportion as the photons.

    But Wu and her team found just the opposite to be true. This meant that nature was playing favorites. Parity, or P symmetry, had been violated.

    Two theorists, Tsung Dao Lee and Chen Ning Yang, who had suggested testing parity in this way, shared the 1957 Nobel Prize in physics for the discovery.

    Charge-parity violation

    Many scientists were flummoxed by the discovery of parity violation, says Ulrich Nierste, a theoretical physicist at the Karlsruhe Institute of Technology in Germany.

    “Physicists then began to think that they may have been looking at the wrong symmetry all along,” he says.

    The finding had ripple effects. For one, scientists learned that another symmetry they thought was fundamental—charge conjugation, or C symmetry—must be violated as well.

    Charge conjugation is a symmetry between particles and their antiparticles. When applied to particles with a property called spin, like quarks and electrons, the C and P transformations are in conflict with each other.

    Physicists then began to think that they may have been looking at the wrong symmetry all along.

    This means that neither can be a good symmetry if one of them is violated. But, scientists thought, the combination of the two—called CP symmetry—might still be conserved. If that were the case, there would at least be a symmetry between the behavior of particles and their oppositely charged antimatter partners.

    Alas, this also was not meant to be. In 1964, a research group led by James Cronin and Val Fitch discovered in an experiment at Brookhaven National Laboratory that CP is violated, too.

    The team studied the decay of neutral kaons into pions; both are composite particles made of a quark and antiquark. Neutral kaons come in two versions that have different lifetimes: a short-lived one that primarily decays into two pions and a long-lived relative that prefers to leave three pions behind.

    However, Cronin, Fitch and their colleagues found that, rarely, long-lived kaons also decayed into two instead of three pions, which required CP symmetry to be broken.

    The discovery of CP violation was recognized with the 1980 Nobel Prize in physics. And it led to even more discoveries.

    It prompted theorists Makoto Kobayashi and Toshihide Maskawa to predict in 1973 the existence of a new generation of elementary particles. At the time, only two generations were known. Within a few years, experiments at SLAC National Accelerator Laboaratory found the tau particle—the third generation of a group including electrons and muons. Scientists at Fermi National Accelerator Laboratory later discovered a third generation of quarks—bottom and top quarks.
    Digging further into CP violation

    In the late 1990s, scientists at Fermilab and European laboratory CERN found more evidence of CP violation in decays of neutral kaons. And starting in 1999, the BaBar experiment at SLAC and the Belle experiment at KEK in Japan began to look into CP violation in decays of composite particles called B mesons

    By analyzing dozens of different types of B meson decays, scientists on BaBar and Belle revealed small differences in the way B mesons and their antiparticles fall apart. The results matched the predictions of Kobayashi and Maskawa, and in 2008 their work was recognized with one half of the physics Nobel Prize.

    “But checking if the experimental data agree with the theory was only one of our goals,” says BaBar spokesperson Michael Roney of the University of Victoria in Canada. “We also wanted to find out if there is more to CP violation than we know.”

    This is because these experiments are seeking to answer a big question: Why are we here?

    When the universe formed in the big bang 14 billion years ago, it should have generated matter and antimatter in equal amounts. If nature treated both exactly the same way, matter and antimatter would have annihilated each other, leaving nothing behind but energy.

    And yet, our matter-dominated universe exists.

    CP violation is essential to explain this imbalance. However, the amount of CP violation observed in particle physics experiments so far is a million to a billion times too small.

    Current and future studies

    Recently, BaBar and Belle combined their data treasure troves in a joint analysis (1). It revealed for the first time CP violation in a class of B meson decays that each experiment couldn’t have analyzed alone due to limited statistics.

    This and all other studies to date are in full agreement with the standard theory. But researchers are far from giving up hope on finding unexpected behaviors in processes governed by CP violation.

    The future Belle II, currently under construction at KEK, will produce B mesons at a much higher rate than its predecessor, enabling future CP violation studies with higher precision.

    And the LHCb experiment at CERN’s Large Hadron Collider is continuing studies of B mesons, including heavier ones that were only rarely produced in the BaBar and Belle experiments. The experiment will be upgraded in the future to collect data at 10 times the current rate.

    To date, CP violation has been observed only in particles like these ones made of quarks.

    “We know that the types of CP violation already seen using some quark decays cannot explain matter’s dominance in the universe,” says LHCb collaboration member Sheldon Stone of Syracuse University. “So the question is: Where else could we possibly find CP violation?”

    One place for it to hide could be in the decay of the Higgs boson. Another place to look for CP violation is in the behavior of elementary leptons—electrons, muons, taus and their associated neutrinos. It could also appear in different kinds of quark decays.

    “To explain the evolution of the universe, we would need a large amount of extra CP violation,” Nierste says. “It’s possible that this mechanism involves unknown particles so heavy that we’ll never be able to create them on Earth.”

    Such heavyweights would have been produced last in the very early universe and could be related to the lack of antimatter in the universe today. Researchers search for CP violation in much lighter neutrinos, which could give us a glimpse of a possible large violation at high masses.

    The search continues.

    1.First observation of CP violation in B0->D(*)CP h0 decays by a combined time-dependent analysis of BaBar and Belle data.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 11:34 am on November 18, 2015 Permalink | Reply
    Tags: , Cleanroom, Symmetry Magazine   

    From Symmetry: “Cleanroom is a verb” 


    Chris Patrick


    Although they might be invisible to the naked eye, contaminants less than a micron in size can ruin very sensitive experiments in particle physics.

    Flakes of skin, insect parts and other air-surfing particles—collectively known as dust—force scientists to construct or conduct certain experiments in cleanrooms, special places with regulated contaminant levels. There, scientists use a variety of tactics to keep their experiments dust-free.

    The enemy within

    Cleanrooms are classified by how many particles are found in a cubic foot of space. The fewer the particles, the cleaner the cleanroom.

    To prevent contaminating particles from getting in, everything that enters cleanrooms must be covered or cleaned, including the people. Scratch that: especially the people.

    “People are the dirtiest things in a cleanroom,” says Lisa Kaufman, assistant professor of nuclear physics at Indiana University. “We have to protect experiment detectors from ourselves.”

    Humans are walking landfills as far as a cleanroom is concerned. We shed hair and skin incessantly, both of which form dust. Our body and clothes also carry dust and dirt. Even our fingerprints can be adversaries.

    “Your fingers are terrible. They’re oily and filled with contaminants,” says Aaron Roodman, professor of particle physics and astrophysics at SLAC National Accelerator Laboratory.

    In an experiment detector susceptible to radioactivity, the potassium in one fingerprint can create a flurry of false signals, which could cloud the real signals the experiment seeks.

    As a cleanroom’s greatest enemy, humans must cover up completely to go inside: A zip-up coverall, known as a bunny suit, sequesters shed skin. (Although its name alludes otherwise, the bunny suit lacks floppy ears and a fluffy tail.) Shower-cap-like headgear holds in hair. Booties cover soiled shoes. Gloves are a must-have. In particularly clean cleanrooms, or for scientists sporting burly beards, facemasks may be necessary as well.

    These items keep the number of particles brought into a cleanroom at a minimum.

    “In a normal place, if you have some surface that’s unattended, that you don’t dust, after a few days you’ll see lots and lots of stuff,” Roodman says. “In a cleanroom, you don’t see anything.”

    Getting to nothing, however, can take a lot more work than just covering up.

    Washing up at SNOLAB

    “This one undergrad who worked here put it, ‘Cleanroom is a verb, not a noun.’ Because the way you get a cleanroom clean is by constantly cleaning,” says research scientist Chris Jillings.

    Jillings works at SNOLAB, an underground laboratory studying neutrinos and dark matter. The lab is housed in an active Canadian mine.


    It seems an unlikely place for a cleanroom. And yet the entire 50,000-square-foot lab is considered a class-2000 cleanroom, meaning there are fewer than 2000 particles per cubic foot. Your average indoor space may have as many as 1 million particles per cubic foot.

    SNOLAB’s biggest concern is mine dust, because it contains uranium and thorium. These radioactive elements can upset sensitive detectors in SNOLAB experiments, such as DEAP-3600, which is searching for the faint whisper of dark matter. Uranium and thorium could leave signals in its detector that look like evidence of dark matter.

    DEAP Dark Matter detector
    DEAP-3600 dark matter detector

    Most workplaces can’t guarantee that all of their employees shower before work, but SNOLAB can. Everyone entering SNOLAB must shower on their way in and re-dress in a set of freshly laundered clothes.

    “We’ve sort of made it normal. It doesn’t seem strange to us,” says Jillings, who works on DEAP-3600. “It saves you a few minutes in the morning because you don’t have to shower at home.” More importantly, showering removes mine dust.

    SNOLAB also regularly wipes down every surface and constantly filters the air.

    Clearing the air for EXO

    Endless air filtration is a mainstay of all modern cleanrooms. Willis Whitfield, former physicist at Sandia National Laboratories, invented the modern cleanroom in 1962 by introducing this continuous filtered airflow to flush out particles.

    The filtered, pressurized, dehumidified air can make those who work in cleanrooms thirsty and contact-wearers uncomfortable.

    “You get used to it over time,” says Kaufman, who works in a cleanroom for the SLAC-headed Enriched Xenon Observatory experiment, EXO-200.

    SLAC EXO-200 experiment

    EXO-200 is another testament to particle physicists’ affinity for mines. The experiment hunts for extremely rare double beta decay events at WIPP, a salt mine in New Mexico, in its own class-1000 cleanroom—even cleaner than SNOLAB.

    As with SNOLAB experiments, anything emitting even the faintest amount of radiation is foe to EXO-200. Though those entering EXO-200’s cleanroom don’t have to shower, they do have to wash their arms, ears, face, neck and hands before covering up.

    Ditching the dust for LSST

    SLAC laboratory recently finished building another class-1000 cleanroom, specifically for assembly of the Large Synoptic Survey Telescope [LSST]. LSST, an astronomical camera, will take over four years to build and will be the largest camera ever.

    LSST Exterior
    LSST Interior
    LSST Camera
    LSST camera, being built at SLAC, with the exterior and interior of the telescope building which will house it in Chile

    While SNOLAB and the EXO-200 cleanroom are mostly concerned with the radioactivity in particles containing uranium, thorium or potassium, LSST is wary of even the physical presence of particles.

    “If you’ve got parts that have to fit together really precisely, even a little dust particle can cause problems,” Roodman says. Dust can block or absorb light in various parts of the LSST camera.

    LSST’s parts are also vulnerable to static electricity. Built-up static electricity can wreck camera parts in a sudden zap known as an electrostatic discharge event.

    To reduce the chance of a zap, the LSST cleanroom features static-dissipating floors and all of its benches and tables are grounded. Once again, humans prove to be the worst offenders.

    “Most electrostatic discharge events are generated from humans,” says Jeff Tice, LSST cleanroom manager. “Your body is a capacitor and able to store a charge.”

    Scientists assembling the camera will wear static-reducing garments as well as antistatic wrist straps that ground them to the floor and prevent the buildup of static electricity.

    From static electricity to mine dust to fingerprints, every cleanroom is threatened by its own set of unseen enemies. But they all have one visible enemy in common: us.

    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 6:35 am on November 8, 2015 Permalink | Reply
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    From Symmetry: “The light side of dark matter” 


    Glenn Roberts Jr.

    New technology and new thinking are pushing the dark matter hunt to lower and lower masses.


    It’s a seemingly paradoxical but important question in particle physics: Can dark matter be light?

    Light in this case refers to the mass of the as-yet undiscovered particle or group of particles that may make up dark matter, the unseen stuff that accounts for about 85 percent of all matter in the universe.

    Ever-more-sensitive particle detectors, experimental hints and evolving theories about the makeup of dark matter are driving this expanding search for lighter and lighter particles—even below the mass of a single proton—with several experiments giving chase.

    An alternative to WIMPs?

    Theorized weakly interacting massive particles, or WIMPs, are counted among the leading candidates for dark matter particles. They most tidily fit some of the leading models.

    Many scientists expected WIMPs might have a mass of around 100 billion electronvolts—about 100 times the mass of a proton. The fact that they haven’t definitively showed up in searches covering a range from about 10 billion electronvolts to 1 trillion electronvolts has cracked the door to alternative theories about WIMPs and other candidate dark matter particles.

    Possible low-energy signals measured at underground dark matter experiments CoGeNT in Minnesota and DAMA/LIBRA in Italy, along with earlier hints of dark matter particles in space observations of our galaxy’s center by the Fermi Gamma-ray Space Telescope, excited interest in a mass range below about 11 billion electronvolts—roughly 11 times the mass of a proton.

    CoGeNT experiment

    DAMA LIBRA Dark Matter Experiment

    NASA Fermi Telescope

    Such low-energy particles could be thought of as lighter, “wimpier” WIMPs, or they could be a different kind of particles: light dark matter.

    SuperCDMS, an WIMP-hunting experiment in the Soudan Underground Laboratory in Minnesota, created a special search mode, called CDMSlite, to make its detectors sensitive to particles with mass reaching below 5 billion electronvolts. With planned upgrades, CDMSlite should eventually be able to stretch down to detect particles with a mass about 50 times less than this.


    In September, the CDMS collaboration released results that narrow the parameters used to search for light WIMPs in a mass range of 1.6 billion to 5.5 billion electronvolts.

    Also in September, collaborators with the CRESST experiment (pictured above) at Gran Sasso laboratory in Italy released results that explored for the first time masses down to 0.5 billion electronvolts.

    Other underground experiments, such as LUX at the Sanford Underground Research Facility in South Dakota, Edelweiss at Modane Underground Laboratory in France, and DAMIC at SNOLAB in Canada, are also working to detect light dark matter particles. Many more experiments, including Earth- and space-based telescopes and CERN’s Large Hadron Collider, are playing a role in the dark matter hunt as well.

    LUX Dark matter


    Edelweiss Dark Matter Experiment

    This hunt has broadened in many directions, says David Kaplan, a physics professor at Johns Hopkins University.

    “Incredible progress has been made—scientists literally gained over 10 orders of magnitude in sensitivity from the beginning of really dedicated WIMP experiments until now,” he says. “In a sense, the WIMP is the most boring possibility. And if the WIMP is ruled out, it’s an extremely interesting time.”

    Peter Graham, an assistant professor of physics at Stanford University, says the light dark matter search is especially intriguing because any discovery in the light dark matter range would fly in the face of classical physics theories. “If we find it, it won’t be in the Standard Model,” he says.

    Coming attractions

    The experiments searching for light dark matter are working together to see through the background particles that can obscure their searches, says Dan Bauer, spokesman for the SuperCDMS collaboration and group leader for the effort at Fermilab..

    “In this whole field, it’s competitive but it’s also collaborative,” he says. “We all share information.”

    The next few months will bring new results from the CDMSlite experiment and for CRESST.

    An upgrade, now in progress, will push the lower limits of the CRESST detectors to about 0.1 billion to 0.2 billion electronvolts, says Federica Petricca, a researcher at the Max Planck Institute for Physics and spokesperson for the CRESST experiment.

    “The community has learned to be a bit more open and not to focus on a specific region of the mass range of the dark matter particle,” Petricca says. “I think this is interesting simply because there are motivated theories behind this, and there is no reason to limit the search to some specific model.”

    Researchers are also looking out for future results from an experiment called DAMIC. DAMIC searches for signs of dark matter using an array of specialized charge-coupled devices, similar to the light-sensitive sensors found in today’s smartphone cameras.

    DAMIC already can search for particles with a mass below 6 billion electronvolts. The experiment’s next iteration, known as DAMIC100, should be able to take measurements below 0.3 billion electronvolts after it starts up in 2016, says DAMIC spokesperson Juan Estrada of Fermilab.

    “I think it is very valuable to have several experiments that are looking in the same region,” Estrada says, “because it doesn’t look like any single experiment will be able to confirm a dark matter signal—we will need to have many experiments.

    “There is still a lot of room for innovation.”

    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 7:09 am on November 5, 2015 Permalink | Reply
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    From Symmetry: “The particle physics of you” 


    Ali Sundermier

    Artwork by Sandbox Studio, Chicago with Ana Kova

    Not only are we made of fundamental particles, we also produce them and are constantly bombarded by them throughout the day.

    Fourteen billion years ago, when the hot, dense speck that was our universe quickly expanded, all of the matter and antimatter that existed should have annihilated and left us nothing but energy. And yet, a small amount of matter survived.

    We ended up with a world filled with particles. And not just any particles—particles whose masses and charges were just precise enough to allow human life. Here are a few facts about the particle physics of you that will get your electrons jumping.


    The particles we’re made of

    About 99 percent of your body is made up of atoms of hydrogen, carbon, nitrogen and oxygen. You also contain much smaller amounts of the other elements that are essential for life.

    While most of the cells in your body regenerate every seven to 15 years, many of the particles that make up those cells have actually existed for millions of millennia. The hydrogen atoms in you were produced in the big bang, and the carbon, nitrogen and oxygen atoms were made in burning stars. The very heavy elements in you were made in exploding stars.

    The size of an atom is governed by the average location of its electrons. Nuclei are around 100,000 times smaller than the atoms they’re housed in. If the nucleus were the size of a peanut, the atom would be about the size of a baseball stadium. If we lost all the dead space inside our atoms, we would each be able to fit into a particle of lead dust, and the entire human race would fit into the volume of a sugar cube.

    As you might guess, these spaced-out particles make up only a tiny portion of your mass. The protons and neutrons inside of an atom’s nucleus are each made up of three quarks. The mass of the quarks, which comes from their interaction with the Higgs field, accounts for just a few percent of the mass of a proton or neutron. Gluons, carriers of the strong nuclear force that holds these quarks together, are completely massless.

    If your mass doesn’t come from the masses of these particles, where does it come from? Energy. Scientists believe that almost all of your body’s mass comes from the kinetic energy of the quarks and the binding energy of the gluons.


    The particles we make

    Your body is a small-scale mine of radioactive particles. You receive an annual 40-millirem dose from the natural radioactivity originating inside of you. That’s the same amount of radiation you’d be exposed to from having four chest X-rays. Your radiation dose level can go up by one or two millirem for every eight hours you spend sleeping next to your similarly radioactive loved one.

    You emit radiation because many of the foods you eat, the beverages you drink and even the air you breathe contain radionuclides such as Potassium-40 and Carbon-14. They are incorporated into your molecules and eventually decay and produce radiation in your body.

    When Potassium-40 decays, it releases a positron, the electron’s antimatter twin, so you also contain a small amount of antimatter. The average human produces more than 4000 positrons per day, about 180 per hour. But it’s not long before these positrons bump into your electrons and annihilate into radiation in the form of gamma rays.


    The particles we meet

    The radioactivity born inside your body is only a fraction of the radiation you naturally (and harmlessly) come in contact with on an everyday basis. The average American receives a radiation dose of about 620 millirem every year. The food you eat, the house you live in and the rocks and soil you walk on all expose you to low levels of radioactivity. Just eating a Brazil nut or going to the dentist can up your radiation dose level by a few millirem. Smoking cigarettes can increase it up to 16,000 millirem.

    Cosmic rays, high-energy radiation from outer space, constantly smack into our atmosphere. There, they collide with other nuclei and produce mesons, many of which decay into particles such as muons and neutrinos. All of these shower down on the surface of the Earth and pass through you at a rate of about 10 per second. They add about 27 millirem to your yearly dose of radiation. These cosmic particles can sometimes disrupt our genetics, causing subtle mutations, and may be a contributing factor in evolution.

    In addition to bombarding us with photons that dictate the way we see the world around us, our sun also releases an onslaught of particles called neutrinos. Neutrinos are constant visitors in your body, zipping through at a rate of nearly 100 trillion every second. Aside from the sun, neutrinos stream out from other sources, including nuclear reactions in other stars and on our own planet.

    Many neutrinos have been around since the first few seconds of the early universe, outdating even your own atoms. But these particles are so weakly interacting that they pass right through you, leaving no sign of their visit.

    You are also likely facing a constant shower of particles of dark matter. Dark matter doesn’t emit, reflect or absorb light, making it quite hard to detect, yet scientists think it makes up about 80 percent of the matter in the universe.

    Looking at the density of dark matter throughout the universe, scientists calculate that hundreds of thousands of these particles might be passing through you every second, colliding with your atoms about once a minute. But dark matter doesn’t interact very strongly with the matter you’re made of, so they are unlikely to have any noticeable effects on your body.

    The next time you’re wondering how particle physics applies to your life, just take a look inside yourself.

    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 4:22 pm on October 31, 2015 Permalink | Reply
    Tags: , , , Symmetry Magazine   

    From Symmetry: “Gravitational waves and where to find them” 


    Matthew R. Francis

    Caltech/MIT/LIGO Lab

    Advanced LIGO has just begun its search for gravitational waves.

    For thousands of years, astronomy was the province of visible light, that narrow band of colors the human eye can see.

    In the 20th century, astronomers pushed into other kinds of light, from radio waves to infrared light to gamma rays. Researchers built neutrino detectors and cosmic ray observatories to study the universe using particles instead. Most recently, another branch of lightless astronomy has been making strides: gravitational wave astronomy.

    It’s easy to make gravitational waves: Just flap your arms. Earth’s orbit produces more powerful gravitational waves, but even these are too small to have a measurable effect. This is a good thing: Gravitational waves carry energy, and losing too much energy would cause Earth to spiral into the sun.

    Gravitational waves are an important prediction of [Albert] Einstein’s general theory of relativity. According to that theory, a variety of astronomical objects—such as supernova explosions, pairs of black holes and other mutually orbiting objects with strong gravity—give off energy as disturbances in the structure of space-time that propagate outward at the speed of light.

    Even though these waves are ubiquitous and often carry enormous amounts of energy, gravity is so weak that they barely nudge other objects as they pass.

    But sufficiently sensitive detectors could measure these waves.

    Detecting gravitational waves

    Scientists have already measured gravitational waves indirectly. They first saw evidence of their existence in the Hulse-Taylor binary pulsar.

    Pulsars are the remnants of stars more massive than the sun. They compress the mass of a star into an object the diameter of an Earth city. Their small size means they can orbit very close to each other, emitting gravitational waves and causing one another to speed up as they lose energy and get closer together.

    Astronomers have monitored the Hulse-Taylor binary pulsar since the 1970s, and the amount of speed-up they see is exactly the predicted effect of gravitational waves.

    Today’s gravitational wave observatories are based on a different concept. One of these is LIGO, the Laser Interferometer Gravitational-wave Observatory, a powerful instrument that recently began collecting data after a major upgrade.

    LIGO consists of two detectors, located in Louisiana and Washington in the United States. With the upgrade came an increase in sensitivity, enabling LIGO to look for gravitational waves produced by supernovae, colliding pulsars and other cataclysmic astronomical events hundreds of millions of light-years away.

    LIGO has two Ls

    Unlike tall observatory buildings and big radio telescope dishes scientists often use to study the cosmos, LIGO hugs the ground. Each detector forms a large L-shape, with arms made of concrete tubes 4 kilometers (2.5 miles) long. The inside of each tube is held at high vacuum. The experiment works by shining a powerful laser down the arms, where the beam bounces off a movable mirror at the far end.

    When a gravitational wave passes, it nudges the mirror, slightly shifting the position of the crests and troughs of the laser beam. By comparing the beams between the two arms, LIGO staff can spot the gravitational wave’s effect—and possibly identify what made the wave in the first place.

    Gravitational wave detectors must be smaller in size than the source of the waves, but smaller detectors are less sensitive. LIGO is designed to be the right size to see waves from binary pulsars or black holes right as they collide, at which point they are separated by mere kilometers. (For more stable systems, like the Hulse-Taylor binary pulsar, we will need a LIGO-type observatory larger than Earth. That’s the idea behind the proposed Laser Interferometer Space Antenna, or LISA, which would consist of three spacecraft orbiting the sun.)


    LIGO also needs to be sensitive. This is because gravity is by far the weakest force in the universe; even very powerful gravitational waves from supernovas or other cataclysms will barely push a thing. As a result, LIGO is capable of measuring nudges to its mirror of about 10-20 meters, or about one ten-thousandth of the width of an atomic nucleus.

    That sensitivity is greater than any other experiment in existence, but it comes at a big price. Lots of things can shake the mirror, from earthquakes to trucks to high winds buffeting the buildings in which LIGO sits. That’s part of the reason for having two LIGO antennas, separated by 3000 kilometers. Whatever’s causing noise in one detector will be unrelated to the noise in the other—though earthquakes will typically show up in both, thanks to how well they travel through Earth’s crust.

    “Large earthquakes anywhere in the world or smaller earthquakes anywhere in north America or central America can [temporarily] knock us out,” says Sheila Dwyer, a gravitational wave researcher based at Caltech who works at the LIGO facility in eastern Washington.

    Significant rumblings like that can happen about once a day, knocking LIGO out of commission for a few hours. Despite that, both detectors are operating about 12 hours out of 24, a substantial amount of time for hunting gravitational wave signals.

    Part of Dwyer’s job is to keep the instruments all working together at the right sensitivity, a task that feels as much like engineering as science. In truth, much of gravitational wave astronomy has that hybrid feel. The objects of study—black holes, supernovae, neutron stars—are in the realm of ordinary astronomy. But the scope of the experiments is more akin to particle physics.

    The project has drawn together experts in a broad range of fields, from theoretical gravitation research to optical engineers to experts in computer algorithms. LIGO papers have hundreds of authors, showing how many people are needed to make everything work.
    Waiting for Godot?

    But the real proof of success of any experiment is in the quality of data it produces. The current phase of operation is known as Advanced LIGO, which began observing in September. Dwyer notes that at this sensitivity, the detector could spot a neutron-star collision as far as 260 million light-years away, more than 100 times the distance to the Andromeda Galaxy, our nearest galactic neighbor. But the work isn’t done yet: Once everything is fully operational within the next two years, that range will extend to 650 million light-years, encompassing a large fraction of the nearby universe.

    It’s up to the universe to do the rest.

    “We’ve been staring at the sky for 400 years with telescopes,” says Shane Larson, a gravitational wave astronomer at Northwestern University.

    Those centuries of observations give scientists a start on estimating how many gravitational wave events LIGO might spot, which conservative guesses estimate to be about 10 per year.

    On the other hand, if we don’t see gravitational waves right away at LIGO, it’s not because they aren’t there—the Hulse-Taylor binary and other systems show that they are—it’s because our theories are overestimating how many we should see. As Larson says, “The true answer is what LIGO’s gonna tell us.”

    The real excitement lies in what we don’t yet understand, including supernovae. With LIGO, “we will be able to ‘see’ inside a star as it collapses,” says researcher Amber Stuver of Caltech, who works at the LIGO facility in Livingston, Louisiana. “There is no other way to observe how that mass moves inside without detecting gravitational waves.”

    And just as X-ray and radio astronomy led to the discovery of surprising new things such as pulsars, gravitational wave astronomy is bound to turn up something entirely new. “Every time humans have observed the universe in a new way, they discovered something they didn’t expect to find,” Stuver says. “I’m here to find the unexpected.”

    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 12:22 am on October 30, 2015 Permalink | Reply
    Tags: , , , , , , Symmetry Magazine   

    From Symmetry: “Next up: A turbocharged LHC” 


    Sarah Charley

    Maximilien Brice, CERN

    Even though the Large Hadron Collider is at the peak of its performance, currently smashing protons at a record-breaking energy, physicists are already planning for its next iteration, which will make its debut in 2025.

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

    Today, scientists and engineers from more than a dozen institutions around the world met in Geneva to discuss the beginning of construction for the High-Luminosity LHC.


    “About halfway through the construction of the LHC, scientists in the United States started developing new magnet and accelerator technologies for the HL-LHC,” says Peter Wanderer, head of the Superconducting Magnet Division at Brookhaven National Laboratory. “This meeting gives us the chance to integrate our work and progress with the efforts at CERN and other organizations involved in the luminosity upgrade.”

    Luminosity describes the rate of particle collisions. By increasing the number and density of protons in the LHC, and by manipulating the orientation of the proton bunches when they collide, physicists can maximize the number of proton collisions per second.

    “The LHC already delivers proton collisions at the highest energy and the highest luminosity ever achieved by an accelerator,” says Director General of CERN, Rolf Heuer. “Yet the LHC has only delivered 1 percent of the total planned number of collisions.”

    Currently, the LHC collides 600 million protons every second. The planned upgrades will increase this rate by at least a factor of five.

    The amount of data the HL-LHC will be able to generate in just a few years would take two decades to collect with the existing LHC, says Roger Rusack of the University of Minnesota, who works on the CMS experiment at the LHC. “It’s an exciting, challenging and interesting project for the US and the global physics community.”

    CERN CMS Detector

    More data will allow scientist to continue to push the limits of human knowledge and search for physics beyond the Standard Model—the best model physicists have to describe the fundamental particles and forces that make up everything around us.

    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.

    Many scientists hope that this new data will shed light on dark matter or help them look for evidence of Supersymmetry.

    The High-Luminosity LHC will also enable physicists to study the Higgs boson in more detail.

    CERN ATLAS Higgs Event
    Higgs Event at ATLAS


    Higgs bosons are produced roughly once in every 10 billion collisions in the LHC. That equals about one Higgs every 17 seconds. Between 2011 and 2012, the LHC generated 1.2 million Higgs bosons. With these upgrades, the LHC will produce 15 million Higgs bosons every year.

    Among the upgrades are stronger beam-squeezing magnets and new superconducting radio-frequency cavities, which will flip the orientation of groups of protons to ensure the greatest number of collisions possible.

    “We’ve had to innovate in many fields, inventing brand new technology for the magnets, the optics of the accelerator, superconducting radio-frequency and the superconducting links,” says Lucio Rossi, head of the High-Luminosity LHC project.

    Scientists on LHC experiments are also designing and building new detector components that will optimize their experiments for future runs of the LHC.

    The University of Minnesota, for example, is working with many other US groups on a new calorimeter to record the energy, direction and time of particles produced during collisions in the CMS detector, Rusack says. “Time is short and we still have a lot to do before these new systems are ready for the huge influx of collisions in 2025.”

    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 12:23 pm on October 13, 2015 Permalink | Reply
    Tags: , , , Symmetry Magazine   

    From Symmetry: “Xenon, xenon everywhere” 


    Artwork by Sandbox Studio, Chicago with Ana Kova

    October 13, 2015
    Glenn Roberts Jr.

    It’s in the air we breathe, but it’s not so easy to get ahold of 10 metric tons of xenon in its liquid form.

    So, you want to buy some xenon to try to detect dark matter deep underground. Not a problem. There’s a market for that, with a few large-scale suppliers.

    Wait, what’s that you say? You need 10 metric tons of incredibly pure, liquid xenon for the LUX-ZEPLIN dark matter experiment? That’s a bit trickier.

    LUX Dark matter
    LUX-ZEPLIN dark matter experiment

    Looking for large amounts of xenon is a bit like searching for dark matter: It’s all around us, but it’s colorless, odorless and hard to separate from everything else. Xenon is in the air that we breathe, but it’s also one of the rarest elements on Earth.

    There is about 1 part xenon in every 11.5 million parts of air. The global industry that extracts liquid xenon produces a total of about 40 tons of xenon per year, so 10 tons is a very tall order.

    “Buying several tons per year won’t perturb the market too much,” says Thomas Shutt, a SLAC physicist who, along with physicist Daniel Akerib, left Case Western Reserve University in Ohio last year to join SLAC National Accelerator Laboratory. “If you buy 10 tons in a year that’s a quarter of the market.”

    Akerib and Shutt are heading up SLAC’s effort in the planned LUX-ZEPLIN, or LZ, experiment, one of the largest-scale efforts to find dark matter particles. Like its smaller predecessor experiment, called LUX (for Large Underground Xenon), LZ will be filled with supercooled liquid xenon.

    Xenon, like several other rare gases, can emit flashes of light and electrons when its atoms are hit by other particles. The LZ detector will sit 1 mile underground in a South Dakota mine [SURF], shielded from most other particles, and wait to see signals from dark matter particles.

    Sanford Underground Research Facility Interior
    Sanford Underground levels
    Sanford Underground Research Facility [SURF], in South Dakota

    “Xenon has really good stopping power,” Akerib says. Its liquid form is so dense that aluminum can float on it. It is particularly sensitive to passing particles.

    Xenon is used in more than just dark matter experiments. It is also in demand as a component in halogen lights such as the bluish headlights in some vehicles, in the bulbs for other specialized lighting such as flash lamps that drive lasers, and as a propellant for satellites and other spacecraft. It is also used in semiconductor manufacturing and medical imaging, and it has been used as an anesthetic.

    Xenon is a by-product of the steel-making process, which uses liquid oxygen to wash away contaminants on the surface of molten iron. Russia, South Africa and Saudi Arabia are among the major producers of xenon. Russia became a major player in this market during the era of the Soviet Union, when steel-making was largely centralized.

    Industrially produced xenon isn’t nearly pure enough for the exacting requirements of LZ, though.

    Shutt says extracting its own xenon from air was not an option. “If we had to start from scratch in refining xenon, it would be vastly more expensive,” he says.

    The LZ team plans to acquire xenon over the next 3 to 4 years.

    There is no expiration date on xenon, Shutt said; it just needs to be tightly contained so no venting occurs. “The xenon we use we can put back on the market or put to other scientific uses after the LZ experiment is complete,” he says. “It’s around forever.”

    To ensure that the dark matter detector is ultrasensitive, the LZ team is building a purification system at SLAC National Accelerator Laboratory to remove krypton, another rare gas that can get mixed in with liquid xenon. LUX started with xenon that had 100 parts of krypton per billion and purified it down to four parts per trillion, and LZ needs xenon purified to a standard of 0.015 parts krypton per trillion—a factor of 300 purer.

    Shutt jokes that, while LZ is all about particle physics, “we have become armchair chemical engineers” in the process of putting the experiment together.

    The current plan is to purify the xenon in 2018, and to run each batch through the purification process twice. The process is expected to take several months in total. LZ is scheduled to start running in 2019.

    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 3:33 pm on October 7, 2015 Permalink | Reply
    Tags: , , Symmetry Magazine   

    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
    Tags: , , , Symmetry Magazine   

    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.

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