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  • richardmitnick 2:48 pm on February 2, 2016 Permalink | Reply
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    From FNAL: “Quantum Gravity” video with Don Lincoln 

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

    2.2.16
    FNAL Don Lincoln
    Don Lincoln

    While there are many challenges facing modern particle physics, perhaps the ultimate one (and certainly among the most difficult) is to describe the nature of gravity in the quantum realm. Despite a century of effort, scientists have had only the most cursory of success. In this video, Fermilab’s Dr. Don Lincoln talks about the idea of quantum gravity and sketches out the need for this difficult advance.


    Download the mp4 video here .

    Watch, enjoy, learn.

    See the full article here .

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    Fermilab Campus

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

     
  • richardmitnick 7:56 pm on January 15, 2016 Permalink | Reply
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    From FNAL: Don Lincoln on Quantum Field Theory 

    FNAL II photo

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

    The subatomic world has long been known to be truly mind-bending, with particles that are waves and vice versa. Cats are alive and dead and everything is governed by probability.

    While this remains true, science has progressed since the invention of quantum mechanics and scientists currently use an extended form of quantum mechanics called quantum field theory or QFT. QFT teaches us that all particles are waves that interact with one another. If you thought the quantum world was weird before, modern ideas can give you a headache. In this video, Fermilab’s Dr. Don Lincoln tells us all about it.

    Watch, enjoy, learn.

    See the full article here .

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    Fermilab Campus

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

     
  • richardmitnick 5:05 pm on November 25, 2015 Permalink | Reply
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    From Don Lincoln at FNAL: “What good is particle physics?” 

    FNAL II photo

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

    FNAL Don Lincoln
    Don Lincoln

    Most particle physics research is publicly funded, so it is fair that society asks if this is a good use of taxpayers’ money. In this video, Fermilab’s Dr. Don Lincoln explains how this research attempts to answer questions that have bothered humanity since time immemorial. And, for those with a more practical bent, he explains how this research is an excellent investment with a high rate of return for society.

    See the full article here .

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    Fermilab Campus

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

     
  • richardmitnick 11:54 am on November 20, 2015 Permalink | Reply
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    From FNAL- “Frontier Science Result: CMS Lead bottom” 

    FNAL II photo

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

    Nov. 20, 2015
    FNAL Don Lincoln
    Don Lincoln

    1
    Today’s article describes what happens when you collide individual protons into lead nuclei. This result helps understand an exciting new state of matter called a quark gluon plasma. Image: CERN

    The nice thing about the LHC research program is that it allows scientists to investigate many phenomena.

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC

    All are exotic, with some pushing the very frontier of knowledge, while some investigate complex phenomena as a means to understand even more complex phenomena.

    When two heavy atomic nuclei are slammed together at very high energy, a peculiar thing occurs. The temperatures in these collisions are so high that the protons and neutrons in the nuclei literally melt, and the quarks and gluons that are normally inside the protons and neutrons can move around freely. We call this state of matter a quark-gluon plasma.

    In addition, the high collision energy can convert into matter-antimatter pairs, as suggested by Einstein’s equation E=mc2. If you want to study what occurs in the collision, you look for types of matter that don’t exist as ordinary matter. One example of this more exotic type of matter is bottom quarks. Since they don’t generally exist inside the nuclei of atoms, if you see bottom quarks, you know that they were made from the energy of the collision.

    Scientists have lots of experience making bottom quarks by colliding two protons together. This is the way we run the LHC for most of the time, and we have made (although not recorded) many billions of bottom quarks. The process is pretty well-understood.

    We also can make bottom quarks by colliding two lead nuclei together. We do this at the LHC about one month per year. In these collisions, a total of 416 protons and neutrons are smashed together. Naively, you’d expect that all the protons and neutrons can participate in the collision and that the number of bottom quarks that are made can be easily calculated from the well-understood proton-proton scattering process.

    However, we see fewer bottom quarks than we’d expect from lead-lead collisions. The usual explanation is that these bottom quarks have to push their way through the hot quark-gluon plasma. They become tired and slow down, so they don’t escape the collision.

    But there might be other explanations. Maybe the fact that the colliding protons and neutrons are bound in nuclei (rather that floating freely) influences how their component quarks and gluons are distributed inside them.

    To work out this ambiguity, CMS scientists decided to smash together a beam of protons into a beam of lead nuclei.

    CERN CMS Detector
    CMS

    If the lower-than-expected number of bottom quarks in lead-lead collisions was due to the way bottom quarks plow through quark-gluon plasma you’d expect to see no reduction in the production of bottom quarks from these lead-proton collisions, since the quark-gluon plasma is not made in these kinds of collisions. If the effect was due to the moving around of energy inside nuclei, you’d expect to see behavior midway between the proton-proton and lead-lead scattering.

    As it happens, scientists observed no reduction in the production of bottom quarks. This strongly suggests that the reduction seen in collisions between two lead nuclei originates in the bottom quarks trying to punch through the quark gluon plasma. Thus this measurement validates our understanding of the behavior of matter hot enough to melt protons and neutrons.

    See the full article here .

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    Fermilab Campus

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

     
  • richardmitnick 7:43 pm on November 19, 2015 Permalink | Reply
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    From SPACE.com: “Einstein’s Unfinished Dream: Marrying Relativity to the Quantum World” 

    space-dot-com logo

    SPACE.com

    November 18, 2015
    FNAL Don Lincoln
    Don Lincoln, Senior Scientist, Fermi National Accelerator Laboratory; Adjunct Professor of Physics, University of Notre Dame

    1
    This artist’s illustration depicts how the foamy structure of space-time may appear, showing tiny bubbles quadrillions of times smaller than the nucleus of an atom that are constantly fluctuating and last for only infinitesimal fractions of a second. Credit: NASA/CXC/M.Weiss

    This November marks the centennial of Albert Einstein’s theory of general relativity. This theory was the crowning achievement of Einstein’s extraordinary scientific life. It taught us that space itself is malleable, bending and stretching under the influence of matter and energy. His ideas revolutionized humanity’s vision of the universe and added such mind-blowing concepts as black holes and wormholes to our imagination.

    Einstein’s theory of general relativity describes a broad range of phenomena, from nearly the moment of creation to the end of time, and even a journey spiraling from the deepest space down into a ravenous black hole, passing through the point of no return of the event horizon, down, down, down, to nearly the center, where the singularity lurks.

    Deep into a quantum world

    If you were reading that last paragraph carefully, you’ll note that I used the word “nearly” twice. And that wasn’t an accident. Einstein’s theory has been brilliantly demonstrated at large size scales. It deftly explains the behavior of orbiting binary pulsars and the orbit of Mercury. It is a crucial component of the GPS system that helps many of us navigate in our cars every day.

    But the beginning of the universe and the region near the center of a black hole are very different worlds — quantum worlds. The size scales involved in those environments are subatomic. And that’s where the trouble starts.

    Einstein’s heyday coincided with the birth of quantum mechanics, and the stories of his debates with physicist Niels Bohr over the theory’s counterintuitive and probabilistic predictions are legendary. “God does not play dice with the universe,” he is famously reported to have said.

    However, regardless of his disdain for the theory of quantum mechanics, Einstein was well aware of the need to understand the quantum realm. And, in his quest to understand and explain general relativity, he sought to understand how of gravity performed in his epic theory when it was applied to the world of the supersmall. The result can be summarized in three words: It failed badly.


    download the mp4 video here.

    Bridging the quantum world to relativity

    Einstein spent the rest of his life, without success, pursuing ways to integrate his theory of general relativity with quantum mechanics. While it is tempting to describe the history of this attempt, the effort is of interest primarily to historians. After all, he didn’t succeed, nor did anyone in the decades that followed.

    Instead, it is more interesting to get a sense of the fundamental problems associated with wedding these two pivotal theories of the early 20th century. The initial issue was a systemic one: General relativity uses a set of differential equations that describe what mathematicians call a smooth and differentiable space. In layman’s terms, this means that the mathematics of general relativity is smooth, without any sharp edges.

    In contrast, quantum mechanics describes a quantized world, e.g. a world in which matter comes in discrete chunks. This means that there is an object here, but not there. Sharp edges abound.

    The water analogy

    In order to clarify these different mathematical formulations, one need think a bit more deeply than usual about a very familiar substance we know quite well: liquid water. Without knowing it, you already hold two different ideas about water that illustrate the tension between differential equations and discrete mathematics.

    For example, when you think of the familiar experience of running your hand through water, you think of water as a continuous substance. The water near your hand is similar to the water a foot away. That distant water might be hotter or colder or moving at a different speed, but the essence of water is the same. As you consider different volumes of water that get closer and closer to your hand, your experience is the same. Even if you think about two volumes of water separated by just a millimeter or half a millimeter, the space between them consists of more water. In fact, the mathematics of fluid flow and turbulence assumes that there is no smallest, indivisible bit of water. Between any two arbitrarily-close distances, there will be water. The mathematics that describes this situation is differential equations. Digging down to its very essence, you find that differential equations assume that there is no smallest distance.

    But you also know that this isn’t true. You know about water molecules. If you consider distances smaller than about three angstroms (the size of a water molecule), everything changes. You can’t get smaller than that, because when you probe even smaller distances, water is no longer a sensible concept. At that point, you’re beginning to probe the empty space inside atoms, in which electrons swirl around a small and dense nucleus. In fact, quantum mechanics is built around the idea that there are smallest objects and discrete distances and energies. This is the reason that a heated gas emits light at specific wavelengths: the electrons orbit at specific energies, with no orbits between the prescribed few.

    Thus a proper quantum theory of water has to take into account the fact that there are individual molecules. There is a smallest distance for which the idea of “water” has any meaning.

    Thus, at the very core, the mathematics of the two theories (e.g. the differential equations of general relativity and the discrete mathematics of quantum mechanics) are fundamentally at odds.


    download the mp4 video here.

    Can the theories merge?

    This is not, in and of itself, an insurmountable difficulty. After all, parts of quantum mechanics are well described by differential equations. But a related problem is that when one tries to merge the two theories, infinities abound; and when an infinity arises in a calculation, this is a red flag that you have somehow done something wrong.

    As an example, suppose you treat an electron as a classical object with no size and calculate how much energy it takes to bring two electrons together. If you did that, you’d find that the energy is infinite. And infinite to a mathematician is a serious business. That’s more energy than all of the energy emitted by all of the stars in the visible universe. While that energy is mind-boggling in its scale, it isn’t infinite. Imagining the energy of the entire universe concentrated in a single point is just unbelievable, and infinite energy is much more than that.

    Therefore, infinities in real calculations are a clear sign that you’ve pushed your model beyond the realm of applicability and you need to start looking to find some new physical principles that you’ve overlooked in your simplified model.

    In the modern day, scientists have tried to solve the same conundrum that so flummoxed Einstein. And the reason is simple: The goal of science is to explain all of physical reality, from the smallest possible objects to the grand vista of the cosmos.

    The hope is to show that all matter originates from a small number of building blocks (perhaps only one) and a single underlying force from which the forces we currently recognize originates. Of the four known fundamental forces of nature, we have been able to devise quantum theories of three: electromagnetism, the strong nuclear force, and the weak nuclear forces. However, a quantum theory of gravity has eluded us.

    General relativity is no doubt an important advance, but until we can devise a quantum theory of gravity, there is no hope of devising a unified theory of everything. While there is no consensus in the scientific community on the right direction in which to proceed, there have been some ideas that have had limited success.

    Superstring theory

    The best-known theory that can describe gravity in the microworld is called superstring theory. In this theory, the smallest known particles should not be thought of as little balls, but rather tiny strings, kind of like an incredibly small stick of uncooked spaghetti or a micro-miniature Hula-Hoop. The basic idea is that these tiny strings (which are smaller compared to a proton than a proton is compared to you) vibrate, and each vibration presents a different fundamental particle.

    Employing a musical metaphor, an electron might be an A-sharp, while a photon could be a D-flat. In the same way that a single violin string can have many overtones, the vibrations of a single superstring can be different particles. The beauty of superstring theory is that it allows for one of the vibrations to be a graviton, which is a particle that has never been discovered but is thought to be the particle that causes gravity.

    It should be noted that superstring theory is not generally accepted, and indeed, some in the scientific community don’t even consider it to be a scientific theory at all. The reason is that, in order for a theory to be scientific, it must be able to be tested, and have the potential to be proven wrong. However, the very small scale of these theoretical strings makes it difficult to imagine any tests that could be done in the foreseeable future. And, some say, if you can’t realistically do a test, it isn’t science.

    Personally, I think that is an extreme opinion, as one can imagine doing such a test when technology advances. But that time will be far in the future.

    Another idea for explaining quantum gravity is called loop quantum gravity. This theory actually quantizes space-time itself. In other words, this model says that there is a smallest bit of space and a shortest time. This provocative idea suggests, among other things, that the speed of light might be different for different wavelengths. However, this effect, if it exists, is small and requires that light travel for great distances before such differences could be observed. Toward that end, scientists are looking at gamma-ray bursts, explosions so bright that they can be seen across billions of light-years — an example of the cosmic helping scientists study the microscopic.

    The simple fact is that we don’t yet have a good and generally accepted theory of quantum gravity. The question is simply just too difficult, for now. The microworld of the quantum and the macroworld of gravity have long resisted a life of wedded bliss and, at least for the moment, they continue to resist. However, scientists continue to find the linkage that blends the two. In the meantime, a theory of quantum gravity remains one of the most ambitious goals of modern science — the hope that we will one day fulfill Einstein’s unfinished dream.

    See the full article here .

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  • richardmitnick 12:00 pm on October 19, 2015 Permalink | Reply
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    From Don Lincoln at FNAL: “What the heck is a Multiverse? ” Video 

    FNAL II photo

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

    10.16.15

    The idea of a multiverse (short for multiple universes) can seem absurd. After all, the definition of universe means everything, so what does it mean to have multiple universes? In this video, Fermilab’s Dr. Don Lincoln lists a couple possible definitions for a multiverse. The reality in which we live might indeed be a very strange place.

    Watch, enjoy, learn.

    See the full article here .

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    Fermilab Campus

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

     
  • richardmitnick 4:18 pm on October 7, 2015 Permalink | Reply
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    From DON Lincoln (FNAL) for NOVA: “Neutrino Physicists win Nobel, but Neutrino Mysteries Remain” 

    PBS NOVA

    NOVA

    07 Oct 2015
    FNAL Don Lincoln
    Don Lincoln

    Neutrinos are the most enigmatic of the subatomic fundamental particles. Ghosts of the quantum world, neutrinos interact so weakly with ordinary matter that it would take a wall of solid lead five light-years deep to stop the neutrinos generated by the sun. In awarding this year’s Nobel Prize in physics to Takaaki Kajita (Super-Kamiokande Collaboration/University of Tokyo) and Arthur McDonald (Sudbury Neutrino Observatory Collaboration/Queen’s University, Canada) for their neutrino research, the Nobel committee affirmed just how much these “ghost particles” can teach us about fundamental physics. And we still have much more to learn about neutrinos.

    Super-Kamiokande experiment Japan
    Super-Kamiokande experiment Japan

    Sudbury Neutrino Observatory
    Sudbury Neutrino Observatory

    1
    View from the bottom of the SNO acrylic vessel and photomultiplier tube array with a fish-eye lens. This photo was taken immediately before the final, bottom-most panel of photomultiplier tubes was installed. Photo courtesy of Ernest Orlando, Lawrence Berkeley National Laboratory.

    Neutrinos are quantum chameleons, able to change their identity between the three known species (called electron-, muon– and tau-neutrinos). It’s as if a duck could change itself into a goose and then a swan and back into a duck again. Takaaki Kajita and Arthur B. McDonald received the Nobel for finding the first conclusive proof of this identity-bending behavior.

    In 1970, chemist Ray Davis built a large experiment designed to detect neutrinos from the sun. This detector was made up of a 100,000-gallon tank filled with a chlorine-containing compound. When a neutrino hit a chlorine nucleus, it would convert it into argon. In spite of a flux of about 100,000 trillion solar neutrinos per second, neutrinos interact so rarely that he expected to see only about a couple dozen argon atoms after a week’s running.

    But the experiment found even fewer argon atoms than predicted, and Davis concluded that the flux of electron-type neutrinos hitting his detector was only about a third of that emitted by the sun. This was an incredible scientific achievement and, for it, Davis was awarded a part of the 2002 Nobel Prize in physics.

    Explaining how these neutrinos got “lost” in their journey to Earth would take nearly three decades. The correct answer was put forth by the Italian-born physicist Bruno Pontecorvo, who hypothesized that the electron-type neutrinos emitted by the sun were morphing, or “oscillating,” into muon-type neutrinos. (Note that the tau-type neutrino was postulated in 1975 and observed in 2000; Pontecorvo was unaware of its existence.) This also meant that neutrinos must have mass—a surprise, since even in the Standard Model of particle physics, our most modern theory of the behavior of subatomic particles, neutrinos are treated as massless.

    3
    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.

    So, if neutrinos could really oscillate, we would know that our current theory is wrong, at least in part.

    In 1998, a team of physicists led by Takaaki Kajita was using the Super Kamiokande (SuperK) experiment in Japan to study neutrinos created when cosmic rays from space hit the Earth’s atmosphere. SuperK was an enormous cavern, filled with 50,000 tons of water and surrounded by 11,000 light-detecting devices called phototubes. When a neutrino collided with a water molecule, the resulting debris from the interaction would fly off in the direction that the incident neutrino was traveling. This debris would emit a form of light called Cerenkov radiation and scientists could therefore determine the direction the neutrino was traveling.

    4
    Cherenkov radiation glowing in the core of the Advanced Test Reactor [Idaho National Laboratory].

    By comparing the neutrinos created overhead, about 12 miles from the detector, to those created on the other side of the Earth, about 8,000 miles away, the researchers were able to demonstrate that muon-type neutrinos created in the atmosphere were disappearing, and that the rate of disappearance was related to the distance that the neutrinos traveled before being detected. This was clear evidence for neutrino oscillations.

    Just a few years later, in 2001, the Sudbury Neutrino Observatory (SNO) experiment, led by Arthur B. McDonald, was looking at neutrinos originating in the sun. Unlike previous experiments, the SNO could identify all three neutrino species, thanks to its giant tank of heavy water (i.e. D2O, two deuterium atoms combined with oxygen). SNO first used ordinary water to measure the flux of electron-type neutrinos and then heavy water to observe all three types. The SNO team was able to demonstrate that the neutrino flux of all three types of neutrinos agreed exactly with those emitted by the sun, but that the flux of electron-type was lower than would be expected in a no-oscillation scenario. This experiment was a definitive demonstration of the oscillation of solar neutrinos.

    With the achievements of both the SuperK and SNO experiments, it is entirely fitting that Kajita and McDonald share the 2015 Nobel Prize in physics. They demonstrated that neutrinos oscillate and, therefore, that neutrinos have mass. This is a clear crack in the impressive façade of the Standard Model of particle physics and may well lead to a better and more complete theory.

    The neutrino story didn’t end there, though. To understand the phenomenon in greater detail, physicists are now generating beams of neutrinos at many sites over the world, including Fermilab, Brookhaven, CERN and the KEK laboratory in Japan. Combined with studies of neutrinos emitted by nuclear reactors, significant progress has been made in understanding the nature of neutrino oscillation.

    Real mysteries remain. Our measurements have shown that the mass of each neutrino species is different. That’s why we know that some must have mass: if they are different, they can’t all be zero. However, we don’t know the absolute mass of the neutrino species—just the mass differences. We don’t even know which species is the heaviest and which is the lightest.

    The biggest question in neutrino oscillation physics, though, is whether neutrinos and antimatter neutrinos oscillate the same way. If they don’t, this could explain why our universe is composed solely of matter even while we believe that matter and antimatter existed in equal quantities right after the Big Bang.

    Accordingly, Fermilab, America’s premier particle physics laboratory, has launched a multi-decade effort to build the world’s most intense beam of neutrinos, aimed at a distant detector located 800 miles away in South Dakota.

    Sanford Underground Research Facility Interior
    Sanford Underground Research Facility

    Named the Deep Underground Neutrino Experiment (DUNE), it will dominate the neutrino frontier for the foreseeable future.
    FNAL DUNE
    FNAL Dune & LBNF
    LBNF/DUNE

    This year’s Nobel Prize acknowledged a great step forward in our understanding of these ghostly, subatomic chameleons, but their entire story hasn’t been told. The next few decades will be a very interesting time.

    See the full article here .

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    NOVA is the highest rated science series on television and the most watched documentary series on public television. It is also one of television’s most acclaimed series, having won every major television award, most of them many times over.

     
  • richardmitnick 2:02 pm on October 6, 2015 Permalink | Reply
    Tags: , Don Lincoln, , , , Sterile neutrinos   

    From NOVA: “Sterile Neutrinos: The Ghost Particle’s Ghost” July 2014. Old, but Worth It for the Details 

    PBS NOVA

    NOVA

    11 Jul 2014

    FNAL Don Lincoln
    Don Lincoln, FNAL

    What do you call the ghost of a ghost?

    If you’re a particle physicist, you might call it a sterile neutrino. Neutrinos, known more colorfully as “ghost particles,” can pass through (almost) anything. If you surrounded the Sun with five light years’ worth of solid lead, a full half of the Sun’s neutrinos would slip right on through. Neutrinos have this amazing penetrating capability because they do not interact by the electromagnetic force, nor do they feel the strong nuclear force. The only forces they feel are the weak nuclear force and the even feebler tug of gravity.

    2
    The Perseus galaxy cluster, one of 73 clusters from which mysterious x-rays, possible produced by sterile neutrinos, were observed. Credit: Chandra: NASA/CXC/SAO/E.Bulbul, et al.; XMM-Newton: ESA

    NASA Chandra Telescope
    NASA/Chandra

    ESA XMM Newton
    ESA/XMM-Newton

    When Wolfgang Pauli first postulated neutrinos in 1930, he thought that his proposed particles could never be detected. In fact, it took more than 25 years for physicists to confirm that neutrinos—Italian for “little neutral ones”—were real. Now, physicists are hunting for something even harder to spot: a hypothetical ghostlier breed of neutrinos called sterile neutrinos.

    Today, we know of three different “flavors” of neutrinos: electron neutrinos, muon neutrinos and tau neutrinos (and their antimatter equivalents). In the the late 1960s, studies of the electron-type neutrinos emitted by the Sun led scientists to suspect that they were somehow disappearing or morphing into other forms. Measurements made in 1998 by the Super Kamiokande experiment strongly supported this hypothesis, and in 2001, the Sudbury Neutrino Observatory clinched it.

    Super-Kamiokande Detector
    Super-Kamiokande Detector

    Sudbury Neutrino Observatory
    Sudbury Neutrino Observatory

    One of the limitations of studying neutrinos from the Sun and other cosmic sources is that experimenters don’t have control over them. However, scientists can make beams of neutrinos in particle accelerators and also study neutrinos emitted by man-made nuclear reactors. When physicists studied neutrinos from these sources, a mystery presented itself. It looked like there weren’t three kinds of neutrinos, but rather four or perhaps more.

    Ordinarily, this wouldn’t be cause for alarm, as the history of particle physics is full of the discovery of new particles. However, in 1990, researchers using the LEP accelerator demonstrated convincingly that there were exactly three kinds of ordinary neutrinos. Physicists were faced with a serious puzzle.

    CERN LEP
    LEP at CERN

    There were some caveats to the LEP measurement. It was only capable of finding neutrinos if they were low mass and interacted via the weak nuclear force. This led scientists to hypothesize that perhaps the fourth (and fifth and…) forms of neutrinos were sterile, a word coined by Russian physicist Bruno Pontecorvo to describe a form of neutrino that didn’t feel the weak nuclear force.

    Searching for sterile neutrinos is a vibrant experimental program and a confusing one. Researchers pursuing some experiments, such as the LSND and MiniBoone, have published measurements consistent with the existence of these hypothetical particles, while others, like the Fermilab MINOS team, have ruled out sterile neutrinos with the same properties. Inconsistencies abound in the experimental world, leading to great consternation among scientists.

    LSND Experiment
    LANL/LSND Experiment

    FNAL MiniBoone
    FNAL/MiniBoone

    FNAL Minos Far Detector
    FNAL/MINOS

    In addition, theoretical physicists have been busy. There are many different ways to imagine a particle that doesn’t experience the strong, weak, or electromagnetic forces (and is therefore very difficult to make and detect); proposals for a variety of different kinds of sterile neutrinos have proliferated wildly, and sterile neutrinos are even a credible candidate for dark matter.

    Perhaps the only general statement we can make about sterile neutrinos is that they are spin ½ fermions, just like neutrinos, but unlike “regular” neutrinos, they don’t experience the weak nuclear force. Beyond that, the various theoretical ideas diverge. Some predict that sterile neutrinos have right-handed spin, in contrast to ordinary neutrinos, which have only left-handed spin. Some theories predict that sterile neutrinos will be very light, while others have them quite massive. If they are massive, that could explain why ordinary neutrinos have such a small mass: perhaps the mathematical product of the masses of these two species of neutrinos equals a constant, say proponents of what scientists call the “see-saw mechanism”; as one mass goes up, the other must go down, resulting in low-mass ordinary neutrinos and high-mass sterile ones.

    Now, some astronomers have proposed sterile neutrinos could be the source of a mysterious excess of x-rays coming from certain clusters of galaxies. Both NASA’s Chandra satellite and the European Space Agency’s XMM-Newton have spotted an excess of x-ray emission at 3.5 keV. It is brighter than could immediately be accounted for by known x-ray sources, but it could be explained by sterile neutrinos decaying into photons and regular neutrinos. However, one should be cautious. There are tons of atomic emission lines in this part of the x-ray spectrum. One such line, an argon emission line, happens to be at 3.62 keV. In fact, if the authors allow a little more of this line than predicted, the possible sterile neutrino becomes far less convincing.

    Thus the signal is a bit sketchy and could easily disappear with a better understanding of more prosaic sources of x-ray emission. This is not a criticism of the teams who have made the announcement, but an acknowledgement of the difficulty of the measurement. Many familiar elements emit x-rays in the 3.5 keV energy range, and though the researchers attempted to remove those expected signals, they may find that a fuller accounting negates the “neutrino” signal. Still, the excess was seen by more than one facility and in more than one cluster of galaxies, and the people involved are smart and competent, so it must be regarded as a possible discovery.

    It is an incredible long shot that the excess of 3.5 keV x-ray from galaxy clusters is a sterile neutrino but, if it is, it will be a really big deal. The first order of business is a more detailed understanding of more ordinary emission lines. Unfortunately, only time will tell if we’ve truly seen a ghost.

    See the full article here .

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    NOVA is the highest rated science series on television and the most watched documentary series on public television. It is also one of television’s most acclaimed series, having won every major television award, most of them many times over.

     
  • richardmitnick 2:23 pm on September 8, 2015 Permalink | Reply
    Tags: , Don Lincoln, , Special Relativity   

    From Don Lincoln at FNAL 

    FNAL II photo

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

    FNAL Don Lincoln
    Don Lincoln

    Published on Sep 8, 2015

    One of the most non-intuitive physics theories ever devised is [Albert] Einstein’s Theory of Special Relativity, which claim such crazy-sounding things as two people disagreeing on such familiar concepts as length and time. In this video, Fermilab’s Dr. Don Lincoln shows that every single day particle physicists prove that moving clocks tick more slowly than stationary ones. He uses an easy to understand example of particles that move for far longer distances than you would expect from combining their velocity and stationary lifetime.

    See the full article here.

    Please help promote STEM in your local schools.

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    Fermilab Campus

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

     
  • richardmitnick 12:05 pm on September 6, 2015 Permalink | Reply
    Tags: , , Don Lincoln, ,   

    From CNN: “Has Stephen Hawking solved the mystery of black holes?” 

    1
    CNN

    September 4, 2015
    FNAL Don Lincoln
    Don Lincoln, FNAL

    Black holes have a way of capturing our imagination. That’s why when Stephen Hawking recently talked about them the media went wild.

    Stephen Hawking
    Stephen Hawking

    But what was he really saying? Was it a breakthrough moment?

    At the Hawking Radiation Conference organized by Laura Mersini-Houghton, a professor of physics at the University of North Carolina, 32 eminent physicists gathered to discuss outstanding issues involved with apparent contradictions in our current understanding of the theories of [General] relativity and quantum mechanics. The convergence of the two take us to the inner workings of black holes.

    Black holes are ravenous monsters of the cosmos, constantly reaching out and gobbling nearby mass as they grow larger and larger. The poster child of [Albert] Einstein’s theory of relativity, black holes exert such a strong gravitational force that not even light can escape, and they are able to distort the very fabric of space and slow the passage of time. These are very real objects.

    And yet they embody a very significant mystery. Black holes are said to absorb matter and never let it go. The matter simply disappears inside the black hole. But matter is more than, well, matter. It is information. For instance, if I have a single atom of hydrogen, I have a proton and electron. That’s matter. But there is also information in how they are connected. Are they near one another, or far apart?

    The information component is even more important in, say, a piece of fruit. While I might tell you just how many protons, neutrons and electrons exist in an apple, without the information that tells you how they arranged, it wouldn’t have the apple’s tart taste. In fact, it wouldn’t be an apple at all. Ultimately, it is information that is at the heart of the mystery.

    According to the rules of quantum mechanics, information should never be lost, not even if it gets sucked inside the black hole. This is because of two premises: causality and reversibility. Taken together, it means that effects have causes, and those causes can be undone.

    For example, you can break a glass and then find all the pieces and glue it back together. Yet, these two premises don’t hold for a classical black hole, in which the information is permanently and irreversibly lost as it enters the black hole.

    Note that information being lost isn’t the same as matter being lost. In the 1970s, Hawking postulated what is now called Hawking radiation, which in principle, cause black holes eventually to evaporate as the radiation carries away energy. However, Hawking radiation should be completely independent of the matter absorbed by a black hole. So, information really does appear to be lost, in complete contradiction of quantum theory.

    This is where Hawking’s announcement comes in. He is saying that he can solve the conundrum.

    He is countering the claim that the black hole gobbles and destroys the information by positing that the information never actually falls into the black hole. Instead, the information is held on the black hole’s surface — the event horizon.

    This is an intriguing thought and is analogous to how holograms are made. Holograms are two-dimensional sheets of, for example, plastic that can make three-dimensional images. All of the information of three dimensions is encoded in the two dimensional plastic. (By the way, there are some who hypothesize that our entire universe is a hologram!)

    It is difficult to properly evaluate Hawking’s announcement. The claim as it has been described is not very precise. There is no paper published on the idea, nor has the idea passed peer review. In fact, scientists who attended the conference are still trying to absorb the idea and to cast it in a mathematical language so that the implication can be assessed.

    Hawking developed this concept in collaboration with Malcolm Perry of Cambridge University and Andrew Strominger of Harvard University. They plan to submit a paper in a month or so. That’s when the real evaluation of the proposal can begin.

    While everyone would much prefer to hear about a definitive advancement in science, the actual process of developing scientific ideas can be both intellectually stimulating and thoroughly messy.

    Stephen Hawking’s new ideas are certainly interesting and may point us in the right direction. But we will have to wait a bit longer to solve the enigma of what happens when information confronts a black hole. Sit tight, we’re on a very long journey.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
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