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  • richardmitnick 1:19 pm on March 14, 2019 Permalink | Reply
    Tags: "The potential of plasma wakefield acceleration", , , , , , , , Symmetry Magazine   

    From Symmetry: “The potential of plasma wakefield acceleration” 

    Symmetry Mag
    From Symmetry

    Daniel Garisto

    Illustration by Sandbox Studio, Chicago with Ana Kova

    Scientists around the world are testing ways to further boost the power of particle accelerators while drastically shrinking their size.

    At least when it comes to particle accelerators, bigger is usually better. The bigger the particle accelerator, the more energetic its particle collisions; the more energetic the collision, the greater the variety of particles produced.

    Before CERN’s Large Hadron Collider, the world’s most powerful accelerator was the Tevatron, a circular collider 4 miles long. Scientists used it to discover the last and most massive of the quarks, the top quark. To discover the Higgs boson, the LHC had to be larger still— almost 17 miles around. Scientists are discussing ideas for even bigger accelerators, such as the proposed Future Circular Collider, which would have a colossal circumference of more than 62 miles.


    CERN map

    CERN LHC Tunnel

    CERN LHC particles

    FNAL Tevatron

    FNAL/Tevatron map

    FNAL/Tevatron DZero detector

    FNAL/Tevatron CDF detector

    [Don’t forget that the U.S. was going to build the Supercoducting Super Collider [SSC], cancelled by our idiot Congress for having “no immediate economic benefit. If we had built the SSC, Higgs would have been found in the U.S., which instead simply ceded High Energy Physics [HEP] to Europe.


    Its planned ring circumference was 87.1 kilometers (54.1 mi) with an energy of 20 TeV per proton and was set to be the world’s largest and most energetic. It would have greatly surpassed the current record held by the Large Hadron Collider which has ring circumference 27 km (17 mi) and energy of 14 TeV per proton. The project’s director was Roy Schwitters, a physicist at the University of Texas at Austin. Dr. Louis Ianniello served as its first Project Director for 15 months. The project was cancelled in 1993 due to budget problems (read:ignorance and stupidity.]

    CERN FCC Future Circular Collider details of proposed 100km-diameter successor to LHC

    Bigger colliders (and the bigger price tags that come with them) have been essential for advances in particle physics. But what if there were a way to scale down their immense size? What if you could accelerate particles to even higher energies in only a few meters?

    This is the alluring potential of an up-and-coming technology called plasma wakefield acceleration.

    Let’s break down the name. “Plasma” is often referred to as the “fourth state of matter.” It’s created when atoms in a gas are stripped of their electrons, often via a laser. This mixture of ions and free floating electrons behaves like a gas, except that it’s extremely sensitive to electric and magnetic fields.

    A “wake” is created when something is quickly pushed through a fluid or gaseous substance, like a boat cutting through water. In this case, the substance is plasma.

    And “acceleration” simply refers to the effect: When a bunch of particles is placed behind a plasma wake, it accelerates, like a wake surfer.

    There are a variety of ways to create plasma wakefield acceleration, or PWFA. Generally, these can be broken down into “laser wakefield acceleration” and “beam wakefield acceleration.” Both rely on plasma as a medium, but to “drive” the wake, one technique uses lasers while the other uses a beam of particles. Current efforts using this beam technique rely on electrons, protons, or positrons.

    This month, PWFA turns 40. The concept was developed in an audacious 1979 paper by scientists Toshiki Tajima and John Dawson [Physical Review Letters], both then at the University of California, Los Angeles. Today, several hundred physicists at institutes around the world study PWFA.

    In the past few years, advances in the field have turned heads in the larger physics community. Studies have corroborated the technique’s ability to accelerate particles and increased its prospects of practical application. But even if PWFA is as promising as its proponents claim, it will be years if not decades before it begins to succeed traditional accelerating technology.

    RF cavities vs. PWFAs

    Conventional accelerators rely on hollow metal chambers called radio-frequency cavities, or RF cavities. An electric field inside an RF cavity accelerates particles that pass through it.

    “In simple terms, it works like a battery,” says Edda Gschwendtner, a particle physicist who heads the AWAKE plasma wakefield accelerator R&D collaboration at CERN.

    CERN AWAKE schematic



    “You have a positive end and a negative end, and then particles … are attracted by the field and get accelerated.”

    This technology is extremely reliable, and used in the nearly 30,000 accelerators around the world. For decades, improvements to the design of RF cavities and larger machines using more and more of them allowed accelerator energy to double about every six years. Recently, however, this trend has been leveling off.

    That’s because RF cavities can sustain electric fields only up to a certain strength—too high and the metal can ionize, releasing electrons that contaminate the vacuum inside the cavities, destroying the RF field inside the cavity.

    Today’s cavities have an acceleration gradient, or increase in energy, of about 10 GeV—10 million electronvolts—per meter. Proposed colliders like the International Linear Collider aim to investigate physics at the Higgs scale—around 125,000 GeV. To reach that energy, electrons and positrons would each have to travel through about 8 miles of cavities. Unless the accelerating technology improves, machines will have to get larger and larger to reach higher energies where physics beyond the Standard Model may be hidden.

    PWFA has the potential to blow these numbers away.

    When he gives talks, physicist Spencer Gessner of the AWAKE team likes to give people an idea of how potent plasma is. “The air in the room that we’re breathing has a particle density of 2.7×1019 particles per cubic centimeter,” Gessner says.

    So what? Well, if you plug that density into an equation that tells you how much acceleration a plasma can support, you get a big number. A really big number, one that puts highly engineered, state-of-the art RF cavities to shame: 500,000 GeV per meter. That’s enough force to produce a Higgs boson in an accelerator the size of a shoe box.

    “We just have to kind of light the air on fire and then drive a wake in that, and you have something a thousand times higher gradient than these finely engineered devices,” Gessner says. It’s a simplification of the process, but his point is clear: Plasma has potential.

    “The beauty of plasma is that it’s basically giving you this enormous acceleration gradient,” Gessner says. “Of course, the complication is harnessing that.”

    And it is certainly easier said than done. The basic principle, though, is easy enough to grasp.

    “Imagine you have a boat which crosses a lake,” Gschwendtner says. “In our case the lake is the plasma, and the boat is what we call the ‘drive beam.’ The drive beam goes into the lake and creates waves, and these are the wakefields.”

    Behind the drive beam sits a “trailing beam,” which in this analogy is like a wake surfer, riding behind a wake.

    “Now what you do is sit electrons onto these wakes, and then they get accelerated,” Gschwendtner says. Why? Wake surfers accelerate because they effectively ride down a watery hill; they’re pulled along by gravity. Electrons or other particles accelerate because they’re pulled by an electric field.

    How do you create an electric field? Plasma is what’s known as “quasi-neutral.” As a whole, the positive charges of its ions are cancelled out by the negative charges of its electrons. But these free-floating electrons are easily pushed around, and a difference smaller than 1 percent in electron density can create a sizeable electric field.

    The strength of the electric field is proportional to the square root of the density; as plasma gets denser, the field can get a bit stronger. A stronger electric field creates more acceleration.

    But how you get that acceleration depends on the type of boat you use.

    Laser wakefield acceleration

    All PWFA experiments require lasers to create a plasma—that’s how they ionize gas. But laser wakefield accelerators also use a laser as a drive beam. The radiation pressure from the laser pushes electrons out of the way. Ions, which are much heavier, remain essentially motionless, while bubbles of electron-free areas propagate forward through the plasma.

    This difference in electron density creates an electric field that accelerates particles placed precisely at the back of a bubble.

    Beam wakefield acceleration

    Beam wakefield acceleration techniques use a beam of particles as a drive beam instead of a laser. Though they’re called “beams,” particle beams aren’t continuous and long like lasers, but instead are short bursts of particles fired in a straight line.

    Plasma wakefield acceleration using electrons

    Using a beam of electrons as the drive beam is similar to using a laser. A bundle of electrons is fired into the plasma; this time it pushes aside other electrons because they are both negatively charged. Again, the ions remain in place so that a positively charged bubble is formed. Particles at the back of the bubble are accelerated because of a strong electric field created by differences in electron density.

    Plasma wakefield acceleration using positrons

    Ideally, physicists would like to be able to use plasma wakefield acceleration to accelerate both electrons and positrons. Because both are fundamental units of matter and matter-antimatter partners, they annihilate cleanly on contact. Compared to the proton-proton collisions of the LHC, electron-positron collisions are incredibly clean and easy to interpret.

    Unfortunately, positrons are trickier to work with. When a bunch of positrons are fired through plasma, they suck in electrons instead of expelling them. Sucking in electrons also creates a similar bubble of mostly electron-free space, but it doesn’t stay electron-free for long—electrons rush down the center to catch up with the positrons. With electrons in the center of the bubble, the electric field can get defocused, so that positrons aren’t accelerated uniformly forward. Physicists have put forward possible solutions that rely on lasers to shape the plasma so that the defocusing effect is mitigated.

    Still, physicists have had some success with positrons, accelerating them to 5000 GeV in about a meter.

    Plasma wakefield acceleration using protons

    Like positrons, protons have a positive charge, which makes them tricky to work with, because they don’t create completely electron-free bubbles. So why work with them? Their energy.

    “The way we accelerate is that we take energy from whatever beam we put in. We give it to the plasma, and the plasma gives it to the charge that we accelerate,” says Diana Amorim, a physicist at Stony Brook University.

    While a bunch of electrons or a laser might hit the plasma with 60 joules of energy, a more massive bunch of protons can have 20,000 joules. Here, it’s again helpful to use the boat and wake surfer analogy.

    “A laser beam or electron beam has little petrol stored. So in these beams, the boat stops on the lake. You cannot accelerate particles for a very long distance,” Gschwendtner says.

    Each joule is about 6 trillion GeV, but most of the energy is inefficiently lost. If scientists could extract the massive energy stored in the bunches of protons, their boat could go for dozens of meters, allowing the particles in their wake to accelerate all along the way.

    Last year, AWAKE successfully used a drive beam of protons to accelerate electrons to 2000 GeV.

    Type of acceleration Experiments
    Laser wakefield acceleration BELLA, TREX, CLF, LUX
    Plasma wakefield acceleration FACET, FACET II, DESY FLASHForward
    using electrons
    Plasma wakefield acceleration FACET, FACET II
    using positrons
    Plasma wakefield acceleration AWAKE
    using protons

    Future questions

    Each of these PWFA techniques has pros and cons, but they’re all still in development and all need to answer one question, Gessner says: Can you have high efficiency, high quality acceleration at the same time?

    High efficiency means that particles in the wake actually get the energy from the drive beam, so it’s not wasted. High quality refers to features of a beam, like the energy spread among the particles in a beam—physicists want all of their accelerated particles to have about the same energy.

    Physicists at FACET accelerator facility at SLAC National Accelerator Laboratory, for example, have already created high efficiency, low quality beams. But getting both features is tricky, because higher energy beams want to misbehave more—they’re more likely to wiggle up or down instead of simply going straight.

    SLAC FACET-II upgrading its Facility for Advanced Accelerator Experimental Tests (FACET) – a test bed for new technologies that could revolutionize the way we build particle accelerators


    To someday replace existing accelerator technology, achieving both is a must for PWFA.

    With experiments at DESY in Germany, CERN in France and Switzerland, and SLAC, Argonne National Laboratory and Lawrence Berkeley National Laboratory in the United States, physicists studying PWFA are confident they’ll continue to take steps toward that goal the next few years.

    “It was easy for the community to be skeptical when you have not shown any results,” Gschwendtner says. “Of course, they are now more convinced because we’ve shown these results.”

    “The amazing thing about plasma accelerators is that the naysayers have been coming up with why things wouldn’t work at every stage of the program,” says Chan Joshi, a particle physicist at UCLA who helped found the field of PWFA.

    In the beginning, he says, naysayers doubted plasma accelerator researchers could reach the high gradient they predicted they could reach, a thousand times larger than the conventional cavity.

    “Well that turned out to be not the case,” he says.

    After that, the doubters thought plasma accelerator researchers would never achieve a narrow-energy-spread beam.

    “Well that turned out not to be the case,” he says.

    Challenges remain, but scientists around the world continue to push the technology forward in the hopes of showing that, while bigger has historically been better, in the future smaller can be best.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 12:41 pm on February 26, 2019 Permalink | Reply
    Tags: "10 words that mean something different to physicists", , , , , , , , Symmetry Magazine   

    From Symmetry: “10 words that mean something different to physicists” 

    Symmetry Mag
    From Symmetry

    Illustration by Sandbox Studio, Chicago with Corinne Mucha

    Lauren Biron

    Some of this science sounds awfully familiar.

    Given the popularity of our first article about physics concepts with deceptively common names, Symmetry is back with 10 more seemingly normal words that mean something different in a science context. Get ready to talk science:

    Illustration by Sandbox Studio, Chicago with Corinne Mucha


    In particle physics, flavor has nothing to do with your taste buds. Instead, the term signifies different kinds of particles. There are six “flavors,” or varieties, of quark: up, down, top, bottom, strange and charm. There are also six flavors of leptons: the electron, muon and tau, and their corresponding neutrinos (the electron, muon and tau neutrinos).

    Illustration by Sandbox Studio, Chicago with Corinne Mucha


    Put away your box of crayons. Color, much like flavor, is another way of differentiating subatomic particles, but it isn’t based on hue. Quarks can be designated as red, green or blue, but the colorful naming scheme represents an abstract characteristic of the particles’ charge related to the strong (instead of electric) force rather than an actual color. In fact, there’s a whole field of physics dedicated to QCD: quantum chromo (or color) dynamics.

    Illustration by Sandbox Studio, Chicago with Corinne Mucha


    Physical fields can be dotted with crops or laden with grass and flowers. Fields in physics, however, are more monotone, and usually extend to infinity. They permeate the universe, becoming apparent only when they encounter something that can interact with them. Electrically charged particles can interact with the electromagnetic field; particles with mass can interact with the gravitational field, and part of what gives those particles mass is the Higgs field.

    Illustration by Sandbox Studio, Chicago with Corinne Mucha


    This is your captain speaking: In particle physics, jets are unrelated to airplanes. Jets are showers of hadrons (particles made of quarks and gluons) that often emerge from high-energy collisions in places like the Large Hadron Collider. They’re caused when an energetic quark or gluon starts to head off on its own. Quarks and gluons don’t like to appear solo, so the energetic particle pulls some friends out of the vacuum, creating a shower of particles headed in roughly the same direction. A jet is born!

    Illustration by Sandbox Studio, Chicago with Corinne Mucha


    We typically think of a trigger as a device that sets something off. In particle physics experiments, a trigger is the system that tells a computer in a split second to capture the data from a certain collision. It’s a way of focusing on just the most interesting and relevant particle interactions at experiments that produce far more data than can be reasonably recorded, stored and analyzed.

    Illustration by Sandbox Studio, Chicago with Corinne Mucha


    Backgrounds aren’t just for paintings and photographs. In physics experiments, the background refers to all of the extra signals that a detector may pick up while it is searching for something unique. For example, a detector built to study a beam of neutrinos produced at an accelerator might also detect particles coming from space. Sorting the desired signal from the background is a crucial part of particle physics experiments.

    Illustration by Sandbox Studio, Chicago with Corinne Mucha


    While “wimp” is an insult used to imply someone lacks courage or is weak, a “WIMP” is a strong candidate for dark matter. WIMP is an acronym for “weakly interacting massive particle,” a hypothetical particle that would be massive enough to explain mysterious gravitational effects cosmologists see in the universe but that would interact with other matter rarely enough to explain why it has yet to be observed. They’re one of several ideas for what makes up dark matter, the invisible substance that is thought to vastly outnumber regular matter in our universe.



    Inflation probably makes you think of a balloon blowing up or currency going down in value. But it could also inspire thoughts of the beginning of our universe. Physicists refer to inflation as the period just after the Big Bang when space expanded exponentially in all directions, causing small quantum variations to expand to a cosmic scale. This ultimately led to the large-scale structure of matter in the universe that we see today in things like galaxy clusters.


    Alan Guth, from Highland Park High School and M.I.T., who first proposed cosmic inflation

    HPHS Owls

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    Alan Guth’s notes:

    Illustration by Sandbox Studio, Chicago with Corinne Mucha


    When most of us deal with something entangled, it’s usually something like the cables of a pair of headphones. But for particle physicists, entanglement refers to what Einstein called “spooky action at a distance”: the way that two particles can be separated by great distances but “connected” in such a way that influencing one seems to affect the other instantaneously.

    Illustration by Sandbox Studio, Chicago with Corinne Mucha


    Your standard candle is probably made of wax and has a wick. An astrophysicist’s standard candle is an astronomical object with a known brightness (or luminosity) that can be used to measure distances on an enormous scale. Examples of standard candles include X-ray bursts and different types of stars, such as Cepheid variable stars or supernovae (exploding stars). Measuring the speed of the expansion of the universe over time using standard candles, scientists made the startling discovery that the universe is growing at an accelerating rate.

    Standard Candles to measure age and distance of the universe NASA

    Cosmic distance ladder

    Standard Candles – Philosophy of Cosmology

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 3:58 pm on February 19, 2019 Permalink | Reply
    Tags: A simplified version of that interface will make some of that data accessible to the public, , , , , Every 40 seconds LSST’s camera will snap a new image of the sky, Hundreds of computer cores at NCSA will be dedicated to this task, International data highways, LSST Data Journey, , National Center for Supercomputing Applications at the University of Illinois Urbana-Champaign, NCSA will be the central node of LSST’s data network, , Symmetry Magazine, The two data centers NCSA and IN2P3 will provide petascale computing power corresponding to several million billion computing operations per second, They are also developing machine learning algorithms to help classify the different objects LSST finds in the sky   

    From Symmetry: “An astronomical data challenge” 

    Symmetry Mag
    From Symmetry

    Illustration by Sandbox Studio, Chicago with Ana Kova

    Manuel Gnida

    The Large Synoptic Survey Telescope will manage unprecedented volumes of data produced each night.


    LSST Camera, built at SLAC

    LSST telescope, currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    The Large Synoptic Survey Telescope—scheduled to come online in the early 2020s—will use a 3.2-gigapixel camera to photograph a giant swath of the heavens. It’ll keep it up for 10 years, every night with a clear sky, creating the world’s largest astronomical stop-motion movie.

    The results will give scientists both an unprecedented big-picture look at the motions of billions of celestial objects over time, and an ongoing stream of millions of real-time updates each night about changes in the sky.

    Illustration by Sandbox Studio, Chicago with Ana Kova

    Accomplishing both of these tasks will require dealing with a lot of data, more than 20 terabytes each day for a decade. Collecting and storing the enormous volume of raw data, turning it into processed data that scientists can use, distributing it among institutions all over the globe, and doing all of this reliably and fast requires elaborate data management and technology.

    International data highways

    This type of data stream can be handled only with high-performance computing, the kind available at the National Center for Supercomputing Applications at the University of Illinois, Urbana-Champaign.

    NCSA U Illinois Urbana-Champaign Blue Waters Cray Linux XE/XK hybrid machine supercomputer

    Unfortunately, the U of I is a long way from Cerro Pachón, the remote Chilean mountaintop where the telescope will actually sit.

    But a network of dedicated data highways will make it feel like the two are right next door.

    LSST Data Journey,Illustration by Sandbox Studio, Chicago with Ana Kova

    Every 40 seconds, LSST’s camera will snap a new image of the sky. The camera’s data acquisition system will read out the data, and, after some initial corrections, send them hurtling down the mountain through newly installed high-speed optical fibers. These fibers have a bandwidth of up to 400 gigabits per second, thousands of times larger than the bandwidth of your typical home internet.

    Within a second, the data will arrive at the LSST base site in La Serena, Chile, which will store a copy before sending them to Chile’s capital, Santiago.

    From there, the data will take one of two routes across the ocean.

    The main route will lead them to São Paolo, Brazil, then fire them through cables across the ocean floor to Florida, which will pass them to Chicago, where they will finally be rerouted to the NCSA facility at the University of Illinois.

    If the primary path is interrupted, the data will take an alternative route through the Republic of Panama instead of Brazil. Either way, the entire trip—covering a distance of about 5000 miles—will take no more than 5 seconds.

    Curating LSST data for the world

    NCSA will be the central node of LSST’s data network. It will archive a second copy of the raw data and maintain key connections to two US-based facilities, the LSST headquarters in Tucson, which will manage science operations, and SLAC National Accelerator Laboratory in Menlo Park, California, which will provide support for the camera. But NCSA will also serve as the main data processing center, getting raw data ready for astrophysics research.

    NCSA will prepare the data at two speeds: quickly, for use in nightly alerts about changes to the sky, and at a more leisurely pace, for release as part of the annual catalogs of LSST data.

    Illustration by Sandbox Studio, Chicago with Ana Kova

    Alert production has to be quick, to give scientists at LSST and other instruments time to respond to transient events, such as a sudden flare from an active galaxy or dying star, or the discovery of a new asteroid streaking across the firmament. LSST will send out about 10 million of these alerts per night, each within a minute after the event.

    Hundreds of computer cores at NCSA will be dedicated to this task. With the help of event brokers—software that facilitates the interaction with the alert stream—everyone in the world will be able to subscribe to all or a subset of these alerts.

    NCSA will share the task of processing data for the annual data releases with IN2P3, the French National Institution of Nuclear and Particle Physics, which will also archive a copy of the raw data.


    The two data centers will provide petascale computing power, corresponding to several million billion computing operations per second.

    Illustration by Sandbox Studio, Chicago with Ana Kova

    The releases will be curated catalogs of billions of objects containing calibrated images and measurements of object properties, such as positions, shapes and the power of their light emissions. To pull these details from the data, LSST’s data experts are creating advanced software for image processing and analysis. They are also developing machine learning algorithms to help classify the different objects LSST finds in the sky.

    Annual data releases will be made available to scientists in the US and Chile and institutions supporting LSST operations.

    Last but not least, LSST’s data management team is working on an interface that will make it easy for scientists to use the data LSST collects. What’s even better: A simplified version of that interface will make some of that data accessible to the public.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 4:10 pm on January 30, 2019 Permalink | Reply
    Tags: , , , , Retired equipment lives on in new physics experiments, Symmetry Magazine   

    From Symmetry: “Retired equipment lives on in new physics experiments” 

    Symmetry Mag
    From Symmetry

    Emily Ayshford

    Courtesy of CERN

    Physicists often find thrifty, ingenious ways to reuse equipment and resources.

    What do you do with 800 square feet of scintillator from an old physics experiment? Cut it up and give it to high schools to make cosmic ray detectors, of course.

    And what about an 800-ton magnet originally used to discover new particles? Send it off on a months-long journey via truck, train and ship halfway across the world to detect oscillating particles called neutrinos.

    FNAL G-2 magnet from Brookhaven Lab finds a new home in the FNAL Muon G-2 experiment

    It’s all part of the vast recycling network of the physics community, where decommissioned experimental equipment and data are reused, re-analyzed and repurposed, giving expensive materials and old tapes of data second or even third lives—often in settings vastly different from their original homes.

    For physicists whose experiments can easily cost millions or even billions of dollars, such reuse is not just thrifty, it’s essential for building next-generation experiments.

    When experiments are shut down, “the vultures come knocking at your door,” jokes Jonathan Lewis, deputy head of the particle physics division at Department of Energy’s Fermi National Accelerator Laboratory. He was in charge of decommissioning the Collider Detector at Fermilab (CDF) experiment in 2011.

    FNAL/Tevatron CDF detector

    “You try to get the word out, but people in the community know what experiments are being shut down. They start to look to see what’s available.”

    Shipping magnets around the world

    Take, for example, the UA1 experiment magnet.

    UA1 magnet sets off for a second new life – CERN

    Originally built in 1979, it was part of a particle detector at CERN that discovered the W and Z bosons. After that experiment shut down in 1990, it was used in the NOMAD neutrino experiment from 1995 to 1998.

    The NOMAD Detector

    But then it sat outside at CERN, rusting a bit and waiting for its next home, which would ultimately be the T2K neutrino experiment in Japan.

    T2K map, T2K Experiment, Tokai to Kamioka, Japan

    T2K Experiment, Tokai to Kamioka, Japan

    “Even with the amount of work needed to refurbish it, and the cost of transporting it, it was still worthwhile to reuse it,” says Chang Kee Jung, US principal investigator for the experiment and professor at Stony Brook University. “Usually when you are using old equipment, it’s like driving a used car. The parts aren’t new, so it will break down more often, and you will have more maintenance costs. But magnets generally have much longer lifetimes than other devices, since they are rather simple equipment.”

    In 2009, the magnet was dismantled, cleaned and polished. Most of it was then loaded up into 35 containers, which traveled by train to Antwerp before being loaded onto container ships bound for Japan. The magnet eventually reached the J-PARC facility north of Tokyo and became part of the T2K neutrino oscillation experiment.

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

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

    Magnet reuse is common—even magnets from MRI scanners have been reused in physics experiments—but their special transportation often makes headlines. In 1979, Argonne National Laboratory sent a 107-ton superconducting magnet to what is now called SLAC National Accelerator Laboratory. Jung recalls stories about local news stations reporting on its 20-day journey via a special tractor-trailer, which took up two lanes of interstate highway while traveling 25 miles per hour. The Muon g-2 experiment at Fermi National Accelerator Laboratory in Illinois uses a giant magnet transported 3200 miles by land and sea from its original home at Brookhaven National Accelerator Laboratory in New York [above]. (That trip even had its own hashtag: #bigmove.)

    But magnets prove their worth. Even as the UA1 magnet nears its fifth decade, Jung imagines it still has a good decade worth of life left. “Second lives for equipment in physics are not unusual, but to have a third life like this is unusual,” he says. “This is probably the longest-used magnet.”

    Absorbing an old experiment into a new one

    Sometimes, entire detectors are absorbed from one experiment to another. That was the case with ICARUS, the first large-scale time projection liquid-argon neutrino detector. It started out at the Laboratori Nazionali del Gran Sasso in Italy to look for neutrino oscillations over a long baseline, then was transported to CERN for refurbishment and then to Fermilab in 2017. There, it will join the lab’s program to search for sterile neutrinos, which could help solve questions about the origin of our universe. The detector survived a complex journey, traveling thousands of miles via truck and barge. (Hashtag: #IcarusTrip.)

    INFN Gran Sasso ICARUS, since moved to FNAL

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


    Reusing mines, battleships

    Physics experiments don’t just reuse their own equipment—they also often give second lives to non-scientific facilities and resources. Old mines, with their hollowed-out underground sites shielded from cosmic rays, have been the sites of countless physics experiments. The Homestake Mine in South Dakota houses several experiments, including the Majorana Demonstrator, LUX dark matter experiment, and the upcoming Deep Underground Neutrino Experiment.

    U Washington Majorana Demonstrator Experiment at SURF

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

    Being replaced with

    LBNL LZ project at SURF, Lead, SD, USA

    The Mozumi Mine in Japan has been home to many experiments, including the Super-Kamiokande, and a set of experiments (KamiokaNDE, KamLAND, and KamLAND-Zen) that have all re-used the same neutrino detector.

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

    Hyper-Kamiokande, a neutrino physics laboratory located underground in the Mozumi Mine of the Kamioka Mining and Smelting Co. near the Kamioka section of the city of Hida in Gifu Prefecture, Japan.

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

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

    KamLAND-Zen detector, an electron antineutrino detector at the Kamioka Observatory, an underground neutrino detection facility near Toyama, Japan

    Other resources have found new life in physics experiments: the Sudbury Neutrino Observatory in Canada, for example, once borrowed 1000 tons of heavy water from Canadian nuclear reactors to use in a neutrino detector.

    Sudbury Neutrino Observatory, , no longer operating

    And the CDF experiment, which studied high energy proton-antiproton collisions at Fermilab’s Tevatron collider, was partially constructed using steel from decommissioned battleships.

    FNAL/Tevatron map

    FNAL/Tevatron CDF detector

    That experiment ultimately paid it forward by disassembling and sharing a long list of experimental equipment after it was shut down in 2011. Lewis can cite where everything went: phototubes to India, electronics to Italy, computer servers to South Korea. Here in the United States, Brookhaven National Laboratory and Jefferson Lab got hundreds of phototubes for nuclear physics experiments, and 1000 tons of the old battleship steel will be used as shielding for the Long-Baseline Neutrino Facility target.

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

    The 800 square feet of scintillator was sent to QuarkNet, an educational program, to be used as cosmic ray detectors for high schools.

    “All that’s left is the magnet and a few detector pieces that are on display,” he says. “And a legacy of over 700 papers and lots of memories. In fact, people are still doing analysis on the data.”

    Revisiting old data anew

    Data can be analyzed and looked at anew for years to come.

    That’s the case for DZero, the other experiment on the Tevatron at Fermilab that ran from 1992 to 2011.

    FNAL/Tevatron DZero

    In its heyday, the experiment revealed particles like the top quark. Though it shut down soon after the start of the Large Hadron Collider, scientists have data from about 10 billion events that still have a story to tell. Dozens of papers from that data have been published in the last six years.

    “They are probably not Nobel Prize-winning measurements, but they are very important for understanding specific areas in particle physics,” says Dmitri Denisov, a distinguished scientist at Fermilab and spokesperson for the DZero experiment. For example, the data has been important in searching for exotic particles, a field that did not become popular until after the Tevatron shut down.

    From experiment to education

    Perhaps one of the most inspirational ways for experiments to live second lives is as educational displays. The DZero experiment was left mostly intact, and now thousands of visitors per year can stand right next to a four-story particle detector Fermilab scientists used to discover the top quark.

    Denisov sometimes leads tours of high school students through the control room, where computer screens still look as though they are taking data. “You can see how excited the students are,” he says. “It shows them the joy of complex particle physics experiments. That’s probably the best second life that none of us expected.”

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 1:25 pm on December 17, 2018 Permalink | Reply
    Tags: Anode plane assemblies, , Components from three continents, DUNE-Deep Underground Neutrino Experiment, , , , , , Short-Baseline Neutrino Detector, Sterile neutrino?, Symmetry Magazine   

    From Symmetry: “First critical components arrive for SBND” 

    Symmetry Mag
    From Symmetry

    Jim Daley

    International collaborators are delivering parts to be used in Fermilab’s Short-Baseline Neutrino program.

    Photo by Reidar Hahn, Fermilab

    Major components for a new neutrino experiment at the US Department of Energy’s Fermi National Accelerator Laboratory are arriving at the lab from around the world. The components will be used in the upcoming Short-Baseline Near Detector, an important piece of the laboratory’s neutrino program. The first of four anode plane assemblies, highly sensitive electronic components, came to Fermilab in October. More are on their way.

    SBND is one of three particle detectors that make up the Short-Baseline Neutrino program at Fermilab. Neutrinos, renegade particles that are famously difficult to study, could provide scientists with clues about the evolution of the universe.

    The Short-Baseline Neutrino program, or SBN, focuses its search on a particular type of neutrino, called the sterile neutrino, which could be the explanation for unexpected results seen in several past neutrino experiments. The particle’s existence has been teased but never clearly confirmed.

    SBND will also be a testing ground for some of the technologies, including the anode plane assemblies, that will be used in the international Deep Underground Neutrino Experiment, known as DUNE, a megascience experiment hosted by Fermilab that is currently under construction in South Dakota.

    Fermilab’s three Short-Baseline Neutrino detectors will be positioned at various distances along the path of a neutrino beam generated by Fermilab’s particle accelerators.

    “The reason you have three detectors is that you want to sample the neutrino beam along the beamline at different distances,” says Ornella Palamara, SBND co-spokesperson and neutrino scientist at Fermilab.

    Of the three, SBND will be the nearest to the beam source at a distance of 110 meters. The other two, MicroBooNE and ICARUS, are 470 meters and 600 meters from the source, respectively. MicroBooNE has been taking data since 2015. ICARUS, installed earlier this year, is expected to begin taking data in 2019.

    FNAL Short-Baseline Near Detector



    As neutrinos pass through one detector after the other, some of them leave behind traces in the detectors. SBN scientists will analyze this information to search for firm evidence of the hypothesized but never seen member of the neutrino family.

    Making a (dis)appearance

    Neutrinos come in one of three lepton flavors, or types, which correspond to three other particles: electron, muon and tau. They change from one flavor into another as they travel through space, a behavior called oscillation. Neutrinos are known to oscillate in and out of the three flavors, but only further evidence will help scientists determine whether they also oscillate into a fourth type—a sterile neutrino.

    SBN scientists will look for signs of neutrinos oscillating into the new type.

    “The overall goal of the SBN program is to perform a definitive measurement that tests the possibility of sterile neutrino oscillations,” Palamara says.

    Sterile neutrinos are hypothetical particles that don’t interact with matter at all. (The neutrinos we’re familiar with do interact, but only rarely.) In 1995, results from the LSND experiment at Los Alamos National Laboratory hinted at the possibility of the sterile neutrino’s existence, but so far, no one has confirmed it. Results from the MiniBooNE experiment at Fermilab also indicate that something is going on with neutrinos that we don’t yet fully understand.


    SBND, as the first detector in the beam, will record the number of electron and muon neutrinos that pass through it before oscillation can occur. The vast majority of them—about 99.5 percent—will be muon neutrinos. By the time of their arrival at the far detectors, MicroBooNE and ICARUS, a few out of every thousand muon neutrinos may have converted into electron neutrinos.

    “The SBN program is powerful because you can measure this oscillation by looking at two different effects,” Palamara says.

    One is that the far detectors see more electron neutrinos than expected. This could be evidence that sterile neutrinos are also present: The neutrinos could be converting into and out of sterile neutrino states in a way that produces an excess of electron neutrinos.

    The other is that the far detectors see fewer muon neutrinos than expected—the muon neutrinos spotted in SBND “disappear”—because they converted into sterile neutrinos.

    Either effect could indicate the existence of the new particle.

    “Having a single experiment where we can see electron neutrino appearance and muon neutrino disappearance simultaneously and make sure their magnitudes are compatible with one another is enormously powerful for trying to discover sterile neutrino oscillations,” says David Schmitz, SBND co-spokesperson and assistant professor at the University of Chicago. “The near detector substantially improves our ability to do so.”

    Components from three continents

    SBND will be a 4-by-4-by-5-meter tank—the size of a large bedroom—filled with liquid argon. Its active liquid-argon mass—the volume monitored by the anode plane assemblies, or APAs—comes to 112 tons. The APAs, situated inside the detector, are huge frames covered with thousands of delicate sense wires. An electric field lies between the wire planes and a cathode plane.

    When a neutrino collides with the nucleus of an argon atom, charged particles are produced. These particles stream through the liquid volume, ionizing argon atoms as they pass by. The ionization produces thousands of free electrons, which “drift” under the influence of the electric field toward the APAs, where they are detected. By collecting these clouds of electrons on the wires, scientists create detailed images of the tracks of the particles emerging from a collision, which give information about the original neutrino that triggered the interaction.

    The construction of the wire planes is a collaboration between a group of universities in the United Kingdom funded by the Science and Technology Facilities Council, part of UK Research and Innovation, and another group of universities in the United States funded by a grant from the National Science Foundation. The US effort to build the wire planes was a collaboration between Syracuse University, the University of Chicago and Yale University. In the United Kingdom, Lancaster University, Manchester University and the University of Sheffield contributed to the effort.

    The APA technology will also be an integral part of DUNE, which will be the world’s largest liquid-argon neutrino detector when complete. The National Science Foundation recently funded a planning grant for DUNE’s anode plane assemblies; the NSF has a long history of pioneering investments in major particle physics experiments, including several neutrino experiments.

    Institutions in Europe, South America and the United States are helping build SBND’s various components. In all, more than 20 institutions on three continents are involved in the effort. Another dozen are collaborating on software tools to analyze data once the detector is operational, Schmitz says.

    “Being part of an international collaboration is great,” Palamara says. “Of course, there are challenges, but it’s fantastic to see people coming from all around the world to work on the program. Having pieces of the detector built in different places and then seeing everything come together is exciting.”

    Assembly of SBND is expected to finish in fall 2019, after which the detector will be installed in its building along the accelerator-generated neutrino beam. SBND is scheduled to be commissioned and begin receiving beam in June 2020.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 3:37 pm on November 30, 2018 Permalink | Reply
    Tags: A small and specialized team that studies what happens when the LHC stops colliding protons and instead smashes together heavy atomic nuclei like lead, , , , , Heavy-ion researchers seize their moment, , , Symmetry Magazine   

    From Symmetry: “Heavy-ion researchers seize their moment” 

    Symmetry Mag
    From Symmetry

    Sarah Charley


    During the short heavy-ion run at the Large Hadron Collider at CERN, every moment counts.

    When physicist Marta Verweij arrived at CERN in early November, one of the first things she did was pull an all-nighter in the control center for the CMS experiment.

    CERN/CMS Detector

    “We didn’t get to sleep until 2 p.m. the following day,” she says.

    Verweij and her colleagues were trouble-shooting an issue with the CMS trigger system, which was letting too much data through and flooding their computing farm.

    “Once we identified the problem, it was obvious,” says Verweij, who is a physics professor with a joint appointment at Vanderbilt University and the RIKEN group at the US Department of Energy’s Brookhaven National Laboratory. “But we had to look through 700 settings before we found it.”

    Normally when the detector encounters a problem in the middle of the night, the shifters inside the control room alert the on-call expert, who looks into it while the rest of the collaboration sleeps. But when Verweij and her team smelled trouble, they ordered pizza and prepared to settle in for the night. That’s because Verweij is part of a small and specialized team that studies what happens when the LHC stops colliding protons and instead smashes together heavy atomic nuclei, like lead. And according to Verweij, every minute counts.

    “We have four weeks to collect all the data we will use for the next three years,” she says. “During this run we work seven days a week and whatever hours needed. When the machine has no beam, like when the accelerator physicists are refilling the ion source, we can sometimes get some sleep.”

    Scientists will use this data to study the properties of a very hot and dense subatomic material called the quark-gluon plasma. When two lead nuclei collide, their 414 protons and neutrons are liquefied and melt into an ultra-hot soup of quarks and gluons. Cosmologists suspect that the entire universe was filled with a quark-gluon plasma moments after the Big Bang, and astronomers theorize that this primordial material might still live in the hearts of neutron stars. For the last 20 years, experiments at CERN and Brookhaven have produced and studied this quark-gluon plasma, but because it is so short-lived, much remains to be discovered.


    “We still don’t understand how it evolves over time and what its internal structure looks like,” Verweij says. “We know that it’s not homogenous, but we don’t know how quarks move through it.”

    During this heavy-ion run at CERN, scientists are collecting more data than ever before and will be able to thoroughly investigate these tiny droplets of the early universe. As the run approaches its final few days, Verweij and her team are digging in and planning to finish strong, she says.

    “Now it’s really about squeezing the last bits of data from the detector so that the real fun can start: looking for new signatures of this dense plasma and exploring uncharted territories.”

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 1:39 pm on November 13, 2018 Permalink | Reply
    Tags: , , , , , , , Symmetry Magazine   

    From Symmetry: “Gravitational lenses” 

    Symmetry Mag
    From Symmetry

    Jim Daley

    Gravitational Lensing NASA/ESA

    Illustration by Sandbox Studio, Chicago with Ana Kova [Could not pass this one up.]

    Predicted by Einstein and discovered in 1979, gravitational lensing helps astrophysicists understand the evolving shape of the universe.

    On March 29, 1979, high in the Quinlan Mountains in the Tohono O’odham Nation in southwestern Arizona, a team of astronomers at Kitt Peak National Observatory was scanning the night sky when they saw something curious in the constellation Ursa Major: two massive celestial objects called quasars with remarkably similar characteristics, burning unusually close to one another.

    Kitt Peak National Observatory of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O’odham Nation, 88 kilometers 55 mi west-southwest of Tucson, Arizona, Altitude 2,096 m (6,877 ft)

    The astronomers—Dennis Walsh, Bob Carswell and Ray Weymann—looked again on subsequent nights and checked whether the sight was an anomaly caused by interference from a neighboring object. It wasn’t. Spectroscopic analysis confirmed the twin images were actually both light from a single quasar 8.7 billion light-years from Earth. It appeared to telescopes on Kitt Peak to be two bodies because its light was distorted by a massive galaxy between the quasar and Earth. The team had made the first discovery of a gravitational lens.

    Since then, gravitational lenses have given us remarkable images of the cosmos and granted cosmologists a powerful means to unravel its mysteries.

    “Lensing is one of the primary tools we use to learn about the evolution of the universe,” says Mandeep Gill, an astrophysicist at Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), Stanford. By observing the gravitational lensing and redshift of galaxy clusters, he explains, cosmologists can determine both the matter content of the universe and the speed at which the universe is expanding.

    Gravitational lensing was predicted by Einstein’s theory of general relativity. General relativity posited that massive objects like the sun actually bend the fabric of spacetime around them. Like a billiard ball sinking into a stretched-out rubber sheet, a massive object creates a depression around it; it’s called a “gravity well.” Light passing through a gravity well bends with its curves.

    When an object is really immense—such as a galaxy or galaxy cluster—it can bend the path of passing light dramatically. Astronomers call this “strong lensing.”

    Strong lensing can have remarkable effects. A distant light source arranged in a straight line with a massive body and Earth—a configuration called a syzygy—can appear as a halo around the lensing body, an effect known as an “Einstein ring.” And light from one quasar in the constellation Pegasus bends so much by the time it reaches Earth that it looks like four quasars instead. Astronomers call this phenomenon a “quad lens,” and they’ve named the quasar in Pegasus “the Einstein Cross.”

    Most gravitational lensing events are not so dramatic. Any mass will curve the spacetime around it, causing slight distortions to passing light. While this weak lensing is not apparent from a single observation, taking an average from many light sources allows observers to detect weak lensing effects as well.

    Weak gravitational lensing NASA/ESA Hubble

    The overall distribution of matter in the universe has a lensing effect on light from distant galaxies, a phenomenon known as “cosmic shear.”

    “A cosmic shear measurement is incredibly meticulous as the effect is so small, but it holds a wealth of information about how the structure in the universe has evolved with time,” says Alexandra Amon, an observational cosmologist at KIPAC who specializes in weak lensing.

    Strong and weak gravitational lensing are both important tools in the study of dark matter and dark energy, the invisible stuff that together make up 96 percent of the universe. There is not enough visible mass in the universe to cause all of the gravitational lensing that astronomers see; scientists think most of it is caused by invisible dark matter.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    But most of the real work was done by Vera Rubin a Woman in STEM

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)

    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)

    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    And how all of that matter moves and changes over time is thought to be affected by a mysterious “force” (scientists aren’t really sure what it is) pushing our universe to expand at an accelerating pace: dark energy.

    Studying gravitational lensing can help astrophysicists track the universe’s growth.

    “Strong gravitational lensing can give you a lot of cosmology—from time delays,” Gill says. “From a very far away quasar, you can get multiple images that have followed different light paths. Because they’ve followed different paths, they will get to you at different times. And that time delay depends on the geometry of the universe.”

    The Dark Energy Survey is one of several experiments using gravitational lensing to study dark matter and dark energy. DES scientists are using the Cerro Tololo Inter-American Observatory in Chile to perform a 5000-square-degree survey of the southern sky. Along with other measurements, DES is searching for weak lensing and cosmic shear effects of dark matter on distant objects.

    Dark Energy Survey

    Dark Energy Camera [DECam], built at FNAL

    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    The Large Synoptic Survey Telescope, currently under construction in Chile, will also assess how dark matter is distributed in the universe by looking for gravitational lenses, among other things.

    “The LSST will see first light in the next couple of years,” Amon says. “As this telescope charts the southern sky every few nights, it’s going to bombard us with data—literally too much to handle—so a lot of the work right now is building pipelines that can analyze it.”

    Astronomers expect LSST to find 100 times more galaxy-scale strong gravitational lens systems than are currently known.


    LSST Camera, built at SLAC

    LSST telescope, currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    “The ongoing lensing surveys—that is, the Kilo-Degree Survey, Hyper Suprime-Cam and Dark Energy Survey—are doing high-precision and high-quality analyses, but they are really training grounds compared to what we will be able to do with LSST,” Amon says. “We are stepping up from measuring the shapes of tens of millions of galaxies to a billion galaxies, building the largest, deepest map of the Southern sky over 10 years.”

    Surprisingly, these enormous studies of cosmic distortions may bring the make-up of our universe into focus.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 3:56 pm on November 6, 2018 Permalink | Reply
    Tags: “Cosmic Bell” experiment at the Roque de Los Muchachos Observatory in the Canary Islands, , Symmetry Magazine   

    From Symmetry: “The quest to test quantum entanglement” 

    Symmetry Mag
    From Symmetry

    Laura Dattaro

    Quantum entanglement, doubted by Einstein, has passed increasingly stringent tests.

    Quantum entanglement and spatial distribution Credit Nakagawa et al

    Quantum entanglement By Ishdasrox (Own work) [CC BY-SA 4.0 (via Wikimedia Commons)]

    Over 12 billion years ago, speeding particles of light left an extremely luminous celestial object called a quasar and began a long journey toward a planet that did not yet exist. More than 4 billion years later, more photons left another quasar for a similar trek. As Earth and its solar system formed, life evolved, and humans began to study physics, the particles continued on their way. Ultimately, they landed in the Canary Island of La Palma in a pair of telescopes set up for an experiment testing the very nature of reality.

    Schematic of the 2018 “Cosmic Bell” experiment at the Roque de Los Muchachos Observatory in the Canary Islands, where two large telescopes observed the fluctuating color of light from distant quasars (red and blue galaxies). The green beams indicate polarization-entangled photons sent through the open air between stations separated by about one kilometer. Credit: Andrew S. Friedman and Dominik Rauch

    The experiment was designed to study quantum entanglement, a phenomenon that connects quantum systems in ways that are impossible in our macro-sized, classical world. When two particles, like a pair of electrons, are entangled, it’s impossible to measure one without learning something about the other. Their properties, like momentum and position, are inextricably linked.

    “Quantum entanglement means that you can’t describe your joint quantum system in terms of just local descriptions, one for each system,” says Michael Hall, a theoretical physicist at the Australian National University.

    Entanglement first arose in a thought experiment worked out by none other than Albert Einstein. In a 1935 paper, Einstein and two colleagues showed that if quantum mechanics fully described reality, then conducting a measurement on one part of an entangled system would instantaneously affect our knowledge about future measurements on the other part, seemingly sending information faster than the speed of light, which is impossible according to all known physics. Einstein called this effect “spooky action at a distance,” implying something fundamentally wrong with the budding science of quantum mechanics.

    Decades later, quantum entanglement has been experimentally confirmed time and again. While physicists have learned to control and study quantum entanglement, they’ve yet to find a mechanism to explain it or to reach consensus on what it means about the nature of reality.

    “Entanglement itself has been verified over many, many decades,” says Andrew Friedman, an astrophysicist at University of California, San Diego, who worked on the quasar experiment, also known as a “cosmic Bell test.” “The real challenge is that even though we know it’s an experimental reality, we don’t have a compelling story of how it actually works.”

    Bell’s assumptions

    The world of quantum mechanics—the physics that governs the behavior of the universe at the very smallest scales—is often described as exceedingly weird. According to its laws, nature’s building blocks are simultaneously waves and particles, with no definite location in space. It takes an outside system observing or measuring them to push them to “choose” a definitive state. And entangled particles seem to affect one another’s “choices” instantaneously, no matter how far apart they are.

    Einstein was so dissatisfied with these ideas that he postulated classical “hidden variables,” outside our understanding of quantum mechanics, that, if we understood them, would make entanglement not so spooky. In the 1960s, physicist John Bell devised a test for models with such hidden variables, known as “Bell’s inequality.”

    Bell outlined three assumptions about the world, each with a corresponding mathematical statement: realism, which says objects have properties they maintain whether they are being observed or not; locality, which says nothing can influence something far enough away that a signal between them would need to travel faster than light; and freedom of choice, which says physicists can make measurements freely and without influence from hidden variables. Probing entanglement is the key to testing these assumptions. If experiments show that nature obeys these assumptions, then we live in a world we can understand classically, and hidden variables are only creating the illusion of quantum entanglement. If experiments show that the world does not follow them, then quantum entanglement is real and the subatomic world is truly as strange as it seems.

    “What Bell showed is that if the world obeys these assumptions, there’s an upper limit to how correlated entangled particle measurements can be,” Friedman says.

    Physicists can measure properties of particles, such as their spin, momentum or polarization. Experiments have shown that when particles are entangled, the outcome of these measurements are more statistically correlated than would be expected in a classical system, violating Bell’s inequalities.

    In one type of Bell test, scientists send two entangled photons to detectors far apart from one another. Whether the photons reach the detectors depends on their polarization; if they are perfectly aligned, they will pass through, but otherwise, there is some probability they will be blocked, depending on the angle of alignment. Scientists look to see whether the entangled particles wind up with the same polarization more often than could be explained by classical statistics. If they do, at least one of Bell’s assumptions can’t be true in nature. If the world does not obey realism, then properties of particles aren’t well defined before measurements. If the particles could influence one another instantaneously, then they would somehow be communicating to one another faster than the speed of light, violating locality and Einstein’s theory of special relativity.

    Scientists have long speculated that previous experimental results can be explained best if the world does not obey one or both of the first two of Bell’s assumptions—realism and locality. But recent work has shown that the culprit could be his third assumption—the freedom of choice. Perhaps the scientists’ decision about the angle at which to let the photons in is not as free and random as they thought.

    The quasar experiment was the latest to test the freedom of choice assumption. The scientists determined the angle at which they would allow photons into their detectors based on the wavelength of the light they detected from the two distant quasars, something determined 7.8 and 12.2 billion years ago, respectively. The long-traveling photons took the place of physicists or conventional random number generators in the decision, eliminating earthbound influences on the experiment, human or otherwise.

    At the end of the test, the team found far higher correlations among the entangled photons than Bell’s theorem would predict if the world were classical.

    That means that, if some hidden classical variable were actually determining the outcomes of the experiment, in the most extreme scenario, the choice of measurement would have to have been laid out long before human existence—implying that quantum “weirdness” is really the result of a universe where everything is predetermined.

    “That’s unsatisfactory to a lot of people,” Hall says. “They’re really saying, if it was set up that long ago, you would have to try and explain quantum correlations with predetermined choices. Life would lose all meaning, and we’d stop doing physics.”

    Of course, physics marches on, and entanglement retains many mysteries to be probed. In addition to lacking a causal explanation for entanglement, physicists don’t understand how measuring an entangled system suddenly reverts it to a classical, unentangled state, or whether entangled particles are actually communicating in some way, mysteries that they continue to explore with new experiments.

    “No information can go from here to there instantaneously, but different interpretations of quantum mechanics will agree or disagree that there’s some hidden influence,” says Gabriela Barreto Lemos, a postdoctoral researcher at the International Institute of Physics in Brazil. “But something we all agree upon is this definition in terms of correlation and statistics.”

    Looking for something strange

    Developing a deeper understanding of entanglement can help solve problems both practical and fundamental. Quantum computers rely on entanglement. Quantum encryption, a theoretical security measure that is predicted to be impossible to break, also requires a full understanding of quantum entanglement. If hidden variables are valid, quantum encryption might actually be hackable.

    And entanglement may hold the key to some of the most fundamental questions in physics. Some researchers have been studying materials with large numbers of particles entangled, rather than simply pairs. When this many-body entanglement happens, physicists observe new states of matter beyond the familiar solid, liquid and gas, as well as new patterns of entanglement not seen anywhere else.

    “One thing it tells you is that the universe is richer than you previously suspected,” says Brian Swingle, a University of Maryland physicist researching such materials. “Just because you have a collection of electrons does not mean that the resulting state of matter has to be electron-like.”

    Such interesting properties are emerging from these materials that physicists are starting to realize that entanglement may actually stitch together space-time itself—a somewhat ironic twist, as Einstein, who first connected space and time in his relativity theory, disliked quantum mechanics so much. But if the theory proves correct, entanglement could help physicists finally reach one of their ultimate goals: achieving a theory of quantum gravity that unites Einstein’s relativistic world with the enigmatic and seemingly contradictory quantum world.

    “It’s important to do these experiments even if we don’t believe we’re going to find anything strange,” Lemos says. “In physics, the revolution comes when we think we’re not going to find something strange, and then we do. So you have to do it.”

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 11:56 am on October 25, 2018 Permalink | Reply
    Tags: , , , Symmetry Magazine   

    From Symmetry: “Already beyond the Standard Model” 

    Symmetry Mag
    From Symmetry

    Matthew R. Francis

    We already know neutrinos break the mold of the Standard Model. The question is: By how much?

    Tested and verified with ever increasing precision, the Standard Model of particle physics is a remarkably elegant way of understanding the relationships between particles and their interactions.

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

    Standard Model of Particle Physics from Symmetry Magazine

    But physicists know it’s not the whole story: It provides no answer to some puzzling questions, such as the identity of the invisible dark matter that constitutes most of the mass in the universe.

    As a result, in the search for physics beyond the Standard Model, one area of notably keen interest continues to be neutrinos.

    In the Standard Model, neutrinos come in three kinds, or flavors: electron neutrinos, muon neutrinos and tau neutrinos. This mirrors the other matter particles in the Standard Model, which each can be organized into three groups. But some experiments have shown hints for a new type of neutrino, one that doesn’t fit neatly into this simple picture.

    “Behind the scenes, there’s grumbling noisiness that maybe there’s something else out there,” says Kate Scholberg, a neutrino physicist at Duke University. “It could be nothing, or it could be something very exciting.”

    This extra neutrino—suggested by results from the Liquid Scintillator Neutrino Detector and the MiniBooNE experiment—wouldn’t match up with the generations of particles in the Standard Model. It would be “sterile,” meaning it likely wouldn’t interact directly with any Standard Model particles. It might even be a form of dark matter.

    LSND experiment at Los Alamos National Laboratory and Virginia Tech


    Whether or not extra neutrino flavors exist, neutrinos have already shown us that they sit beyond the bounds of ordinary physics in other ways.

    According to the Standard Model, neutrinos should be massless. But they aren’t; they have strangely small masses that don’t seem to fit in with the masses of the rest of the fundamental particles.

    This fact could possibly be accounted for by a tweak in the theory. Or it could have deep implications for our understanding of the universe.

    “It’s a picture we’ve gotten used to, so it doesn’t seem very exotic anymore,” says Scholberg, who has been involved in many neutrino experiments over the years. “But it’s certainly not part of the original Standard Model.”

    Changing flavors

    The fact that neutrinos have mass gives scientists a powerful way to test whether certain types of sterile neutrinos exist in the first place.

    Before physicists were sure neutrinos had mass, they realized that even a tiny amount of mass would cause the particles to “oscillate,” or change from one flavor to another. Observing neutrino oscillations in action solved the mystery of why earlier experiments detected only about one-third the expected number of neutrinos from the sun.

    Scientists discovered neutrino oscillations about 20 years ago, and many experiments since then have confirmed the surprising results. Some experiments investigated the behavior of neutrinos from the sun and produced in Earth’s atmosphere (SuperK and SNO). Other experiments studied neutrinos produced by a nuclear reactor (Daya Bay, Double Chooz and RENO) or by a particle accelerator (MINOS, NOvA, Super-K and T2K), measuring neutrinos just after they are born and then determining how many neutrinos of a given flavor show up in a detector some distance away.

    Daya Bay, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China

    Double-Chooz – Two identical detectors are to be installed near the Chooz nuclear power plant, in the French Ardennes, at different distances from the reactors

    RENO Experiment. a short baseline reactor neutrino oscillation experiment in South Korea

    The Liquid Scintillator Neutrino Detector was designed to look for neutrino oscillations at a time before they had been fully established by experiment, measuring the appearance of electron neutrinos in a muon neutrino beam at the US Department of Energy’s Los Alamos National Laboratory during the 1990s.

    “[LSND] saw a relatively large number of electron-flavored neutrinos, much more than you’d expect,” says theorist Joachim Kopp of Johannes Gutenberg University in Mainz. “That’s their signal that’s been around ever since, and for which no one has a convincing explanation.”

    Subsequent experiments have reported mixed results. The MiniBooNE experiment at Fermi National Accelerator Laboratory was designed in part to explain the LSND anomaly, and also found an excess of electron neutrinos.

    “Just LSND and MiniBooNE taken in isolation could be fit perfectly under the hypothesis that there is a fourth neutrino flavor in nature,” says Kopp, whose work compares the results of multiple neutrino experiments. “The problem is, LSND and MiniBooNE are not isolated.”

    Other experiments, such as MINOS and IceCube, have published results that are difficult to reconcile with the sterile neutrinos seen by LSND.


    FNAL Minos map

    U Wisconsin IceCube experiment at the South Pole

    U Wisconsin ICECUBE neutrino detector at the South Pole

    IceCube neutrino detector interior

    When Kopp and his colleagues looked for evidence for a fourth neutrino flavor, the numbers just didn’t work. Kopp doesn’t think this rules out sterile neutrinos yet: “It’s certainly not impossible that a more complicated scenario with extra neutrinos could fit the data.”

    The neutrino tooth fairy

    Neutrinos with mass need extra ingredients not found in the Standard Model. One of the simplest additions would be extra neutrinos with a huge mass—far larger than anything that could be made in a particle collider. Those particles would give the normal neutrinos mass, but not participate in oscillations. In some models, these extra neutrinos come with intriguing bonus predictions, including lower-mass sterile neutrinos.

    “The most basic neutrino mass mechanism gives you a sterile neutrino for free,” says Kevork Abazajian of the University of California, Irvine. “In some ways it’s the simplest beyond-the-Standard Model for both neutrino mass and dark matter.”

    Those bonus sterile neutrinos could participate in neutrino oscillations, explaining the LSND and MiniBooNE results.

    The problem, as Abazajian explains, is that sterile neutrinos of the proper mass to explain the LSND anomaly are inconsistent with many results in cosmology. That includes the observed arrangement of galaxies known as the large-scale structure of the universe. To make everything work requires rethinking some other theories—and that might be a deal breaker for those particles.

    “You have to have multiple tooth fairies in a way,” he says. “You’d have to have these sterile neutrinos plus something else to get them to be consistent with large-scale structure.”

    Like Kopp, Abazajian isn’t ruling sterile neutrinos out yet. “I wouldn’t make conclusions based solely on cosmology,” he says. “It really has to be answered from the laboratory, not just from cosmology.”

    Thankfully, several upcoming experiments are designed to investigate the LSND/MiniBooNE anomaly, particularly the Short-Baseline Neutrino program at Fermilab, which will use three detectors: MicroBooNE, ICARUS and the Short-Baseline Near Detector. Others are looking for sterile neutrinos in other types of detectors. As a result, we should find out in the coming years whether we need a fourth neutrino flavor to explain oscillation results.



    FNAL Short-Baseline Near Detector

    “We’re living in exciting times in neutrino physics,” says Kopp. “I would be super excited if these anomalies were confirmed, and the good thing is, there’s a chance to actually test them.”

    Meanwhile, other oscillation experiments will continue to understand what gave neutrinos their mass in the first place—one of the first hints we have had of physics beyond the Standard Model. The question remains: How far beyond known physics will these mysterious particles take us—and what new mysteries will they require us to solve?

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 12:41 pm on October 23, 2018 Permalink | Reply
    Tags: , , , , High-Luminosity LHC (HL-LHC) at CERN, , LBNL/DESI Dark Energy Spectroscopic Instrument for the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory near Tucson Ariz USA, SLAC Large Synoptic Survey Telescope at Cerro Pachon Chile, , Symmetry Magazine   

    From Symmetry: “The building boom” 

    Symmetry Mag
    From Symmetry

    By Diana Kwon

    Illustration by Sandbox Studio, Chicago with Ana Kova

    These international projects, selected during the process to plan the future of US particle physics, are all set to come online within the next 10 years.

    A mile below the surface at Sanford Underground Research Facility in South Dakota, crews are preparing to excavate more than 800,000 tons of rock. Once the massive caverns they’re creating are complete, they will install four modules that make up a giant particle detector for the Deep Underground Neutrino Experiment. DUNE, hosted by the US Department of Energy’s Fermi National Accelerator Laboratory, is an ambitious, international effort to study neutrinos—the tiny, elusive and yet most abundant matter particles in the universe.

    DUNE is one of several particle physics and astrophysics projects with US participation currently under some stage of construction. These include large-scale projects, such as the construction of Mu2e, the muon-to-electron conversion experiment at Fermilab, and upgrades to the Large Hadron Collider at CERN. And they include smaller ones, such as the assembly of the LZ and SuperCDMS dark matter experiments. Together, these scientific endeavors will investigate a wide range of important concepts, including neutrino mass, the nature of dark matter and cosmic acceleration.

    “In the last 10 years, there have been many facilities in the US that wound down,” says Saul Gonzalez, a program director at the National Science Foundation. “But right now we’re definitely going through a boom—it’s a very exciting time.”

    A community effort

    Members of the US particle physics community identified these projects through a regularly occurring study of the field called the Snowmass planning process, named after the Colorado village where some of the first such dialogs took place in the early 1980s.

    After the most recent Snowmass meeting in Minneapolis in 2013, the 25-member Particle Physics Project Prioritization Panel, or P5, gathered to pinpoint the most important scientific problems in particle physics and propose a 10-year plan to take them on. “Snowmass enabled us to get the questions out there as a field,” says Steven Ritz, the University of California, Santa Cruz physicist who led the P5 panel. “But we’re also aware that budgets are constrained—so P5’s job was to prioritize them.”

    P5’s report, which was published in May 2014 [PDF], outlined five key areas of study: the Higgs boson; neutrinos; dark matter; dark energy and cosmic inflation; and undiscovered particles, interactions and physical principles.

    Shorter-term efforts to address questions in these areas, such as the Mu2e experiment and the Large Synoptic Survey Telescope in Chile, both already under construction, have projected start-up dates around 2020. Longer-term plans, such as DUNE and the high-luminosity upgrade to the LHC, are expected be ready for physics in the mid to latter part of the 2020s.

    “If you look at the timeline, we don’t build everything at once, because of budget and resource constraints,” says Young-Kee Kim, a physicist at the University of Chicago and a former member of the High Energy Physics Advisory Panel, the advisory group that P5 reports to.

    Another consideration was the importance of maintaining a continual stream of data, Ritz says. “We didn’t want to have a building boom where there was no new data for 5 or 10 years.”

    Having multiple experiments at various stages of completion is important for junior scientists. “If you’re a grad student or a postdoc and you’re working on something that’s not going to have physics data until 2024, that’s kind of a problem,” says Kate Scholberg, a physicist at Duke University who was on the P5 panel.

    A staggered timeline gives junior scientists the option of working on a project like DUNE, where they can contribute to research and development, then switch to another experiment where data is available for analysis.

    “Being in a construction phase does have some short-term challenges, but it’s really important as an investment for the future,” Scholberg says. “Because if you stop constructing, then eventually you’re not going to have any more data.”

    Global contributions

    The United States is not undertaking these experiments alone. “Every experiment is really an international collaboration,” Gonzalez says.

    The DUNE collaboration, for example, already includes more than 1100 scientists from 32 countries and counting. And although the Long-Baseline Neutrino Facility, the future home of DUNE, will be in the US, researchers are currently building prototype detectors for the project at the CERN research center in Europe.

    More than 1700 US scientists participate in research at the LHC at CERN; many of them are currently working on future upgrades to the accelerator and its experiments. Although LSST will operate on a mountaintop in Chile, its gigantic digital camera is being assembled at SLAC National Accelerator Laboratory using parts from institutions elsewhere in the United States and in France, Germany and the UK.

    Smaller experiments also have a global presence. Dark matter experiment SuperCDMS, a 23-institution collaboration led by SLAC, will be located at SNOLAB underground laboratory in Ontario and has members in Canada, France and India.

    People with specialized expertise are needed to build the apparatus for these experiments. For example, Fermilab’s Proton Improvement Plan-II, a project to upgrade the lab’s particle accelerator complex to provide protons beams for DUNE, requires individuals with expertise in superconducting radio-frequency technology. “We’re tapping into the SRF expertise around the world to build this,” says Michael Procario, the Director of the Facilities Division in the Office of High Energy Physics within DOE’s Office of Science.

    These DOE-supported endeavors—and the theory and data analysis that go along with them—will likely keep scientists busy until 2035 and beyond. “All the experiments are going to give us definitive answers. Even a null result will give us important information,” Ritz says. “I think it’s a great time for physics.”

    The experiments:

    Muon g-2

    FNAL Muon g-2 studio

    This experiment will measure the magnetic moment of a muon, a subatomic particle 200 times more massive than an electron, in an attempt to identify physics beyond the Standard Model.

    Location: Fermilab, Illinois, United States
    Lead institution: Fermilab
    Currently running

    Axion Dark Matter Experiment (ADMX-Gen 2)

    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington

    U Washington ADMX

    Physicists are probing for signs of axions, hypothetical low-mass dark matter particles at the University of Washington-based ADMX detector.

    Location: University of Washington, United States
    Lead institution: University of Washington
    Currently running

    Physicists will use Mu2e to search for the never-observed direct conversion of a muon into an electron, a process predicted by theories beyond the Standard Model.

    FNAL Mu2e facility under construction

    FNAL Mu2e solenoid

    Location: Fermilab, Illinois, United States
    Lead institution: Fermilab
    Scheduled start-up: 2020


    LBNL LZ project at SURF, Lead, SD, USA

    LZ Dark Matter Experiment at SURF lab

    A liquified xenon detector surrounded by 70,000 gallons of water will be located more than 4000 feet underground at the Sanford Underground Research Facility, where researchers will hunt for interactions between matter and dark matter.

    Location: Sanford Lab, South Dakota, United States
    Lead institution: Berkeley Lab
    Scheduled start-up: 2020

    Dark Energy Spectroscopic Instrument (DESI)

    LBNL/DESI Dark Energy Spectroscopic Instrument for the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory near Tucson, Ariz, USA

    NOAO/Mayall 4 m telescope at Kitt Peak, Arizona, USA, Altitude 2,120 m (6,960 ft)

    Scientists will measure the effect of dark energy on cosmic expansion at the 4-meter Mayall Telescope at Kitt Peak National Observatory in Arizona.

    Location: Kitt Peak National Observatory, Arizona, United States
    Lead institution: Berkeley Lab
    Scheduled start-up: 2021

    Super Cyogenic Dark Matter Search (SuperCDMS)

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

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

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

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

    Physicists will hunt for dark matter particles with a cryogenic germanium detector located deep underground at SNOLAB in Canada.

    Location: SNOLAB, Ontario, Canada
    Lead institution: SLAC
    Scheduled start-up: Early 2020s

    Large Synoptic Survey Telescope (LSST)


    LSST Camera, built at SLAC

    LSST telescope, currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    The 8-meter Large Synoptic Survey Telescope, situated in northern Chile, will observe the whole accessible sky hundreds of times over 10 years to produce the deepest, widest image of the universe to date. This will allow physicists to probe questions about dark energy, dark matter, galaxy formation and more.

    Location: Cerro Pachon, Chile
    Lead institution: SLAC
    Scheduled start-up: Early 2020s

    Proton Improvement Pla-II (PIP-II)

    Upgrades to the Fermilab accelerator complex, including the construction of a 175-meter-long superconducting linear particle accelerator, will create the high-intensity proton beam that will produce beams of neutrinos for DUNE.

    Location: Fermilab, Illinois, United States
    Lead institution: Fermilab
    Scheduled start-up: mid-2020s

    Deep Underground Neutrino Experiment (DUNE)

    CERN Proto DUNE Maximillian Brice

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

    SURF DUNE LBNF Caverns at Sanford Lab

    Scientists will send the world’s most powerful beam of neutrinos through two sets of detectors separated by 800 miles—one at the source of the beam at Fermilab in Illinois and the other at Sanford Underground Research Facility in South Dakota—to help scientists address fundamental concepts in particle physics, such as neutrino mass, matter-antimatter asymmetry, proton decay and black hole formation.

    Location: Fermilab, Illinois and Sanford Lab, South Dakota, United States
    Lead institution: Fermilab
    Scheduled partial start-up (with two detector modules): 2026

    High-Luminosity LHC (HL-LHC)


    CERN map

    CERN LHC Tunnel

    CERN LHC particles

    An upgrade to CERN’s Large Hadron Collider will increase its luminosity—the number of collisions it can achieve—by a factor of 10. More collisions means more data and a higher probability of spotting rare events. The LHC experiments will receive upgrades to manage the higher collision frequency.

    Location: CERN, near Geneva, Switzerland
    Lead institution: CERN
    Scheduled start-up: 2026

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

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