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  • richardmitnick 1:19 pm on January 21, 2020 Permalink | Reply
    Tags: , Axions, , , , , ,   

    From Symmetry: “The other dark matter candidate” 

    Symmetry Mag
    From Symmetry<

    01/21/20
    Laura Dattaro

    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

    CERN CAST Axion Solar Telescope

    As technology improves, scientists discover new ways to search for theorized dark matter particles called axions.

    In the early 1970s, physics had a symmetry problem. According to the Standard Model, the guiding framework of particle physics, a symmetry between particles and forces in our universe and a mirror version should be broken.

    Standard Model of Particle Physics

    It was broken by the weak force, a fundamental force involved in processes like radioactive decay.

    This breaking should feed into the interactions mediated by another fundamental force, the strong force. But experiments show that, unlike the weak force, the strong force obeys mirror symmetry perfectly. No one could explain it.

    The problem confounded physicists for years. Then, in 1977, physicists Roberto Peccei and Helen Quinn found a solution: a mechanism that, if it existed, would cause the strong force to obey this symmetry and right the Standard Model.

    Shortly after, Frank Wilczek and Steven Weinberg—both of whom went on to win the Nobel Prize—realized that this mechanism creates an entirely new particle. Wilczek ultimately dubbed this new particle the axion, after a dish detergent with the same name, for its ability to “clean up” the symmetry problem.

    Several years later, the theoretical axion was found not only to solve the symmetry problem, but also to be a possible candidate for dark matter, the missing matter that scientists think makes up 85% of the universe but the true nature of which is unknown.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

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

    Coma cluster via NASA/ESA Hubble

    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

    The LSST, or Large Synoptic Survey Telescope is to be named the Vera C. Rubin Observatory by an act of the U.S. Congress.

    LSST telescope, The Vera Rubin Survey 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.

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

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background [CMB]hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    [caption id="attachment_73741" align="alignnone" width="632"] CMB per ESA/Planck

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    LBNL LZ Dark Matter project at SURF, Lead, SD, USA


    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

    Despite its theoretical promise, though, the axion stayed in relative obscurity, due to a combination of its strange nature and being outshone by another new dark matter candidate, called a WIMP, that seemed even more like a sure thing.

    But today, four decades after they were first theorized, axions are once again enjoying a moment in the sun, and may even be on the verge of detection, poised to solve two major problems in physics at once.

    “I think WIMPs have one last hurrah as these multiton experiments come online,” says MIT physicist Lindley Winslow. “Since they’re not done building those yet, we have to take a deep breath and see if we find something.

    “But if you ask me the thing we need to be ramping up, it’s axions. Because the axion has to be there, or we have other problems.”

    Around the time the axion was proposed, physicists were developing a theory called Supersymmetry, which called for a partner for every known particle.

    Standard Model of Supersymmetry via DESY

    The newly proposed dark matter candidate called a WIMP—or weakly interacting massive particle—fit beautifully with the theory of Supersymmetry, making physicists all but certain they’d both be discovered.

    Even more promising was that both the supersymmetric particles and the theorized WIMPs could be detected at the Large Hadron Collider at CERN.

    LHC

    CERN map


    CERN LHC Maximilien Brice and Julien Marius Ordan


    CERN LHC particles

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    CERN ATLAS Image Claudia Marcelloni CERN/ATLAS

    ALICE

    CERN/ALICE Detector


    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    “People just knew nature was going to deliver supersymmetric particles at the LHC,” says University of Washington physicist Leslie Rosenberg. “The LHC was a machine built to get a Nobel Prize for detecting Supersymmetry.”

    Experiments at the LHC made another Nobel-worthy discovery: the Higgs boson. But evidence of both WIMPS and Supersymmetry has yet to appear.

    Peter Higgs

    CERN CMS Higgs Event May 27, 2012

    CERN ATLAS Higgs Event

    Axions are even trickier than WIMPs. They’re theorized to be extremely light—a millionth of an electronvolt or so, about a trillion times lighter than the already tiny electron—making them next to impossible to produce or study in a traditional particle physics experiment. They even earned the nickname “invisible axion” for the unlikeliness they’d ever be seen.

    But axions don’t need to be made in a detector to be discovered. If axions are dark matter, they were created at the beginning of the universe and exist, free-floating, throughout space. Theorists believe they also should be created inside of stars, and because they’re so light and weakly interacting, they’d be able to escape into space, much like other lightweight particles called neutrinos. That means they exist all around us, as many as 10 trillion per cubic centimeter, waiting to be detected.

    In 1983, newly minted physics professor Pierre Sikivie decided to tackle this problem, taking inspiration from a course he had just taught on electromagnetism. Sikivie discovered that axions have another unusual property: In the presence of an electromagnetic field, they should sometimes spontaneously convert to easily detectable photons.

    “What I found is that it was impossible or extremely difficult to produce and detect axions,” Sikivie says. “But if you ask a less ambitious goal of detecting the axions that are already there, axions already there either as dark matter or as axions emitted by the sun, that actually became feasible.”

    When Rosenberg, then a postdoc working on cosmic rays at the University of Chicago, heard about Sikivie’s breakthrough—what he calls “Pierre’s Great Idea”—he knew he wanted to dedicate his work to the search.

    “Pierre’s paper hit me like a rock in the head,” Rosenberg says. “Suddenly, this thing that was the invisible axion, which I thought was so compelling, is detectable.”

    Rosenberg began work on what’s now called the Axion Dark Matter Experiment, or ADMX. The concept behind the experiment is relatively simple: Use a large magnet to create an electromagnetic field, and wait for the axions to convert to photons, which can then be detected with quantum sensors.

    When work on ADMX began, the technology wasn’t sensitive enough to pick up the extremely light axions. While Rosenberg kept the project moving forward, much of the field has focused on WIMPs, building ever-larger dark matter detectors to find them.

    But neither WIMPs nor supersymmetric particles have been discovered, pushing scientists to think creatively about what happens next.

    “That’s caused a lot of people to re-evaluate what other dark matter models we have,” says University of Michigan theorist Ben Safdi. “And when people have done that re-evaluation, the axion is the natural candidate that’s still floating around. The downfall of the WIMP has been matched exactly by the rise of axions in terms of popularity.”

    See the full article here .


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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 9:14 am on October 17, 2019 Permalink | Reply
    Tags: "Physicists have found quasiparticles that mimic hypothetical dark matter axions", Axions, , If axions exist as fundamental particles they could constitute a hidden form of matter in the cosmos- dark matter., , The axions analogs within the crystal are a type of quasiparticle a disturbance in a material that can mimic fundamental particles like axions., The new study reveals for the first time that the phenomenon has a life beyond mere equations., , Within a crystal a wave of varying density of electromagnetic charge forms. When that wave slides back and forth it is mathematically equivalent to an axion.   

    From Science News: “Physicists have found quasiparticles that mimic hypothetical dark matter axions” 

    From Science News

    October 15, 2019
    Emily Conover

    1
    Scientists have spotted a solid matter analog to hypothetical subatomic particles called axions. Within a crystal, a wave of varying density of electromagnetic charge forms. When that wave slides back and forth, it is mathematically equivalent to an axion. sesame/DigitalVision Vectors/Getty.

    An elusive hypothetical particle comes in imitation form.

    Lurking within a solid crystal is a phenomenon that is mathematically similar to proposed subatomic particles called axions, physicist Johannes Gooth and colleagues report online October 7 in Nature.

    If axions exist as fundamental particles, they could constitute a hidden form of matter in the cosmos, dark matter. Scientists know dark matter exists thanks to its gravitational pull, but they have yet to identify what it is. Axions are one possibility, but no one has found the particles yet (SN: 4/9/18).

    Enter the imitators. The axions analogs within the crystal are a type of quasiparticle, a disturbance in a material that can mimic fundamental particles like axions. Quasiparticles result from the coordinated jostling of electrons within a solid material. It’s a bit like how birds in a flock seem to take on new forms by syncing up their movements.

    Axions were first proposed in the context of quantum chromodynamics — the theory that explains the behaviors of quarks, tiny particles that are contained, for example, inside protons. Axions and their new doppelgängers “are mathematically similar but physically totally unrelated,” says theoretical physicist Helen Quinn of SLAC National Accelerator Laboratory in Menlo Park, Calif., one of the scientists who formulated the theory behind axions. That means scientists are no closer to solving their dark matter woes.

    Still, the new study reveals for the first time that the phenomenon has a life beyond mere equations, in quasiparticle form. “It’s actually amazing,” says Gooth, of the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany. The idea of axions is “a very mathematical concept, in a sense, but it still exists in reality.”

    In the new study, the researchers started with a material that hosts a type of quasiparticle known as a Weyl fermion, which behaves as if massless (SN: 7/16/15). When the material is cooled, Weyl fermions become locked into place, forming a crystal. That results in the density of electrons varying in a regular pattern across the material, like a stationary wave of electric charge, with peaks in the wave corresponding to more electrons and dips corresponding to fewer electrons.

    Applying parallel electric and magnetic fields to the crystal caused the wave to slosh back and forth. That sloshing is the mathematical equivalent of an axion, the researchers say.

    To confirm that the sloshing was occurring, the team measured the electric current through the crystal. That current grew quickly as the researchers ramped up the electric field’s strength, in a way that is a fingerprint of axion quasiparticles.

    If the scientists changed the direction of the magnetic field so that it no longer aligned with the electric field, the enhanced growth of the electric current was lost, indicating that the axion quasiparticles went away. “This material behaves exactly as you would expect,” Gooth says.

    See the full article here .


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  • richardmitnick 12:36 pm on September 28, 2019 Permalink | Reply
    Tags: Axions, , , , , , ,   

    From Stanford University and SLAC: “Stanford developing a radio that searches for dark matter” 

    Stanford University Name
    From Stanford University

    and

    SLAC National Accelerator Lab

    1
    The dark matter radio is a tabletop device that could explain the mysterious matter that makes up 85 percent of the mass of our universe. (Image credit: Harrison Truong)

    September 25, 2019
    Taylor Kubota

    A team of Stanford University researchers are on a mission to identify dark matter once and for all. But first, they’ll need to build the world’s most sensitive radio.

    “Dark matter is most of the matter in our universe. We don’t know what it is but we know it’s there because we can see its gravitational effects,” explained Peter Graham, an associate professor of physics in Stanford’s School of Humanities and Sciences and one of the leaders of this search for dark matter. “We also know it has to be made out of a totally different particle with different properties than anything we’ve ever found.”

    Graham and Savas Dimopoulos, the Hamamoto Family Professor in physics at Stanford, have developed theories about dark matter that advocate for high-precision experiments focused on finding axions, theorized particles that are among the most likely candidates for dark matter. Their theories – once considered “interesting but out there,” according to Graham – are gaining popularity as other candidates for dark matter get ruled out and new technologies are making their exacting experiments possible. Now the Gordon and Betty Moore Foundation have granted Stanford researchers roughly $2.5 million to prototype a new kind of dark matter sensor.

    Guided by Graham and Dimopoulos’ theories, Kent Irwin, a professor of physics, of particle physics and astrophysics and of photon science at Stanford and SLAC National Accelerator Laboratory, is building the Dark Matter Radio, which will search for the signal of axions the same way a standard AM radio picks up a broadcast. Like an AM radio station, axion dark matter has a precise frequency, but this frequency is unknown. Due to advances in quantum sensors, the radio will be much more sensitive than past dark matter experiments, and able to scan a large swath of the frequencies that are most likely to reveal axions.

    2
    Peter Graham and Kent Irwin are building a tabletop-sized device to detect dark matter. (Image credit: Harrison Truong)

    “This project is a really beautiful example of people with very different expertise coming together to solve a hard problem,” said Risa Wechsler, director of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) and professor of physics and of particle physics and astrophysics.

    3
    Risa Wechsler, professor of physics and of particle physics and astrophysics. (Image credit: Holly Hernandez)

    “Dark matter is 85 percent of the mass in the universe and I think it’s very unlikely that we would exist without it. The exciting thing about this experiment is that it opens up so much discovery space that was previously inaccessible.”

    Even if the researchers don’t find the axion, their work would have the distinction of searching a significant fraction of its possible frequency range. The researchers are also excited to see how their sensor development will contribute to spinoff applications in various fields.

    The Dark Matter Radio

    Dark matter makes up most of the mass in the universe, but each axion is theorized to have such a low mass – falling in the category of ultra-light dark matter – that it might spread out over kilometers. Quantum mechanics, which is the study of behavior of extremely small particles, contends that every particle also behaves like a wave. So, if axions do exist, they’re rippling all around us like a radio signal. The Dark Matter Radio team will scan for the frequency that carries the signal from the wave-like undulations of this ocean of overlapping axions.

    The first trick is to convert axion waves into radio waves – carried out by a strong magnetic field inside the Dark Matter Radio. The Dark Matter Radio is also surrounded by a superconducting shield of niobium that blocks out regular radio signals, but will let axions through.

    Even with all these enhancements, axions will give off a very weak signal. So, the radio’s tuning has to be incredibly sharp – the equivalent of a car radio that can detect stations separated by one one-millionth of a decimal place. As part of achieving this level of sensitivity and precision, Irwin is working with a new type of quantum sensor that is capable of picking up magnetic signals a hundred million trillion times smaller than what is produced by a typical refrigerator magnet.

    “There’s been a breakthrough in the ability to control, create and manipulate quantum states in ways that allow us to take advantage of theory that’s been around for many decades,” said Irwin. “These are some of the same techniques that are being used to develop quantum computers. Instead of using them to compute, we can measure things much more sensitively and precisely than we could before, and the techniques we’re using will have broad applications.”

    The same quantum sensors that the researchers are building into the radio could also enhance the precision of medical scanning techniques that measure the properties of magnetic and electric fields in the human body.

    Beyond the whiteboard

    So far, the researchers have successfully built a soda-can-sized prototype of the dark matter radio that works as an extra-sensitive AM radio. They are currently working on a larger version that will be able to scan all the frequencies of interest with enough sensitivity to measure axion dark matter.

    “Most of the ideas that we theorists have fail before they ever get anywhere, so it was a big deal to see this crazy idea that we had on a whiteboard become a physical thing,” said Graham. “The experimentalists, like Kent, still have a lot of work ahead of them but for me, it feels like the culmination of so many years of work. The Dark Matter Radio is going to be real. It’s going to happen.”

    See the full article here .


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    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

     
  • richardmitnick 1:27 pm on December 19, 2018 Permalink | Reply
    Tags: Axions, , , , ,   

    From WIRED: “Dark Matter Hunters Pivot After Years of Failed Searches” 

    Wired logo

    From WIRED

    12.19.18
    Sophia Chen

    1
    NASA Goddard

    Physicists are remarkably frank: they don’t know what dark matter is made of.

    “We’re all scratching our heads,” says physicist Reina Maruyama of Yale University.

    “The gut feeling is that 80 percent of it is one thing, and 20 percent of it is something else,” says physicist Gray Rybka of the University of Washington. Why does he think this? It’s not because of science. “It’s a folk wisdom,” he says.

    Peering through telescopes, researchers have found a deluge of evidence for dark matter. Galaxies, they’ve observed, rotate far faster than their visible mass allows. The established equations of gravity dictate that those galaxies should fall apart, like pieces of cake batter flinging off a spinning hand mixer. The prevailing thought is that some invisible material—dark matter—must be holding those galaxies together. Observations suggest that dark matter consists of diffuse material “sort of like a cotton ball,” says Maruyama, who co-leads a dark matter research collaboration called COSINE-100.

    2
    Jay Hyun Jo/DM-Ice/KIMS

    Here on Earth, though, clues are scant. Given the speed that galaxies rotate, dark matter should make up 85 percent of the matter in the universe, including on our provincial little home planet. But only one experiment, a detector in Italy named DAMA, has ever registered compelling evidence of the stuff on Earth.

    DAMA-LIBRA at Gran Sasso


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

    “There have been hints in other experiments, but DAMA is the only one with robust signals,” says Maruyama, who is unaffiliated with the experiment. For two decades, DAMA has consistently measured a varying signal that peaks in June and dips in December. The signal suggests that dark matter hits Earth at different rates corresponding to its location in its orbit, which matches theoretical predictions.

    But the search has yielded few other promising signals. This year, several detectors reported null findings. XENON1T, a collaboration whose detector is located in the same Italian lab as DAMA, announced they hadn’t found anything this May.

    XENON1T at Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy

    Panda-X, a China-based experiment, published in July that they also hadn’t found anything.

    PandaX II Dark Matter experiment at Jin-ping Underground Laboratory (CJPL) in Sichuan, China

    Even DAMA’s results have been called into question: In December, Maruyama’s team published that their detector, a South-Korea based DAMA replica made of some 200 pounds of sodium iodide crystal, failed to reproduce its Italian predecessor’s results.

    These experiments are all designed to search for a specific dark matter candidate, a theorized class of particles known as Weakly Interacting Massive Particles, or WIMPs, that should be about a million times heavier than an electron. WIMPs have dominated dark matter research for years, and Miguel Zumalacárregui is tired of them. About a decade ago, when Zumalacárregui was still a PhD student, WIMP researchers were already promising an imminent discovery. “They’re just coming back empty-handed,” says Zumalacárregui, now an astrophysicist at the University of California, Berkeley.

    He’s not the only one with WIMP fatigue. “In some ways, I grew tired of WIMPs long ago,” says Rybka. Rybka is co-leading an experiment that is pursuing another dark matter candidate: a dainty particle called an axion, roughly a billion times lighter than an electron and much lighter than the WIMP. In April, the Axion Dark Matter Experiment collaboration announced that they’d finally tweaked their detector to be sensitive enough to detect axions.

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

    The detector acts sort of like an AM radio, says Rybka. A strong magnet inside the machine would convert incoming axions into radio waves, which the detector would then pick up. “Given that we don’t know the exact mass of the axion, we don’t know which frequency to tune to,” says Rybka. “So we slowly turn the knob while listening, and mostly we hear noise. But someday, hopefully, we’ll tune to the right frequency, and we’ll hear that pure tone.”

    He is betting on axions because they would also resolve a piece of another long-standing puzzle in physics: exactly how quarks bind together to form atomic nuclei. “It seems too good to just be a coincidence, that this theory from nuclear physics happens to make the right amount of dark matter,” says Rybka.

    As Rybka’s team sifts through earthly data for signs of axions, astrophysicists look to the skies for leads. In a paper published in October, Zumalacárregui and a colleague ruled out an old idea that dark matter was mostly made of black holes. They reached this conclusion by looking through two decades of supernovae observations. When a supernova passes behind a black hole, the black hole’s gravity bends the supernova’s light to make it appear brighter. The brighter the light, the more massive the black hole. So by tabulating the brightness of hundreds of supernovae, they calculated that black holes that are at least one-hundredth the size of the sun can account for up to 40 percent of dark matter, and no more.

    “We’re at a point where our best theories seem to be breaking,” says astrophysicist Jamie Farnes of Oxford University. “We clearly need some kind of new idea. There’s something key we’re missing about how the universe is working.”

    Farnes is trying to fill that void. In a paper published in December [Astronomy and Astrophysics], he proposed that dark matter could be a weird fluid that moves toward you if you try to push it away. He created a simplistic simulation of the universe containing this fluid and found that it could potentially also explain why the universe is expanding, another long-standing mystery in physics. He is careful to point out that his ideas are speculative, and it is still unclear whether they are consistent with prior telescope observations and dark matter experiments.

    WIMPs could still be dark matter as well, despite enthusiasm for new approaches. Maruyama’s Korean experiment has ruled out “the canonical, vanilla WIMP that most people talk about,” she says, but lesser-known WIMP cousins are still on the table.

    It’s important to remember, as physicists clutch onto their favorite theories—regardless of how refreshing they are—that they need corroborating data. “The universe doesn’t care what is beautiful or elegant,” says Farnes. Nor does it care about what’s trendy. Guys, the universe might be really uncool.

    See the full article here .

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  • richardmitnick 10:55 am on July 24, 2018 Permalink | Reply
    Tags: Axions, Daniel Bowring at FNAL, , , , , ,   

    From Fermilab: “Daniel Bowring receives $2.5 million from DOE to search for axions with quantum sensors” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

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

    July 19, 2018
    Jordan Rice

    1
    Daniel Bowring examines a superconducting qubit mounted in a copper microwave cavity. Photo: Reidar Hahn

    Dark matter makes up nearly 80 percent of all matter in the universe, yet its nature has eluded scientists.

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al


    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    Scientists theorize that it could take the form of a subatomic particle, and one possible candidate comes in the form of a small, theoretical particle called the axion. If it exists, the axion will interact incredibly weakly with matter, so detecting one requires an incredibly sensitive detector.

    Fermilab scientist Daniel Bowring is planning to build just such an instrument. The Department of Energy has selected Bowring for a 2018 Early Career Research Award to build a detector that would ferret out the hypothesized particle. He will receive $2.5 million over five years to build and operate his experiment. The award funds equipment, engineers, technicians and a postdoctoral researcher.

    “We are very motivated to find the axion because it would solve several interesting problems for us in the particle physics community,” Bowring said.

    Not only would the axion’s discovery explain, at least in part, the nature of dark matter, it could also solve the strong CP problem, a long-standing thorn in the side of theoretical physics models.

    The strong CP problem is an inconsistency in particle physics. Particles behave differently from their mirror-reversed, antimatter counterparts — at least, they do under the influence of the electromagnetic force and the weak nuclear force (which governs nuclear decay).

    But under the influence of the strong force (which holds matter together), particles and their mirror-image antiparticles behave similarly. Or, in physics speak, they’re CP-symmetric under the strong force. (CP stands for charge-parity. It’s the property that’s flipped when you take a mirror image of a particle’s antimatter partner.) Why is the strong force the exception?

    One potential answer lies in the existence of the axion. In the math of strong interactions, the addition of the axion enables theoretical models to reflect the reality of strong-force CP symmetry.

    Bowring is following the axion math where it leads — to the construction of a device that can pick up the signal of the fundamental particle, whose mass is predicted to be vanishingly small, between 1 billion and 1 trillion times smaller than an electron.

    One way to look for the axion is to look for light: In the presence of a strong electromagnetic field — Bowring’s experiment will use about 14 Tesla, or roughly 10 times stronger than an MRI magnet — an axion should convert into a single particle of light, called a photon, which is more easily observed.

    “Physicists have gotten pretty good at detecting photons over the years,” Bowring said.

    When an axion enters the detector filled with the electromagnetic field, the particle will spontaneously convert into a photon with a specific frequency. The frequency corresponds to the axion’s mass, so scientists can measure the axion mass indirectly, thanks to the detection of particles of light.

    Much like someone tuning a sensitive AM radio, researchers will scan slowly through the relevant range of photon frequencies until they pick up a signal, which would point to the presence of an axion.

    It’s a subtle business, one that requires being able to detect single photons. While photon detection is an old hat for physicists, discerning a lone photon amid the experimental noise of a particle detector is a job for new technology. Bowring’s experiment will use supersensitive, superconducting quantum bits, or qubits, to pluck the solo photon signal from the noise and thus accurately count the number of detected photons.

    Bowring’s experiment will be an opportunity to bridge the gap between particle physics and the science behind quantum computing.

    Quantum computing – IBM

    “Daniel’s proposed experiment will demonstrate how qubits, the essential elements of quantum computing, can be used to detect a range of axion masses,” said Fermilab scientist Keith Gollwitzer. “Quantum computing may be the next large step in computing power and particle physics experiments.”

    In that respect, the application of technologies in their infancy to century-old problems is a reflection of the larger scientific field.

    “Fermilab’s mission is doing particle physics, and qubits are just a way for us to meet the requirements of that mission,” Bowring says. “It is a way for us to build new experiments that address the problems of particle physics at the forefront of where the field is.”

    See the full article here .


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    FNAL Icon

    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.


    FNAL/MINERvA

    FNAL DAMIC

    FNAL Muon g-2 studio

    FNAL Short-Baseline Near Detector under construction

    FNAL Mu2e solenoid

    Dark Energy Camera [DECam], built at FNAL

    FNAL DUNE Argon tank at SURF

    FNAL/MicrobooNE

    FNAL Don Lincoln

    FNAL/MINOS

    FNAL Cryomodule Testing Facility

    FNAL Minos Far Detector

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

    FNAL/NOvA experiment map

    FNAL NOvA Near Detector

    FNAL ICARUS

    FNAL Holometer

     
  • richardmitnick 1:52 pm on May 14, 2018 Permalink | Reply
    Tags: Axion Cold Dark Matter experiment, Axions, , , , , , Planckian interacting dark matter, Superfluid models of dark matter,   

    From Physics- “Meetings: WIMP Alternatives Come Out of the Shadows” 

    Physics LogoAbout Physics

    Physics Logo 2

    From Physics

    May 14, 2018

    At an annual physics meeting in the Alps, WIMPs appeared to lose their foothold as the favored dark matter candidate, making room for a slew of new ideas.

    The Rencontres de Moriond (Moriond Conferences) have been a fixture of European high-energy physics for over half a century. These meetings—typically held at an Alpine ski resort—have been the site of many big announcements, such as the first public talk on the top quark discovery in 1995 and important Higgs updates in 2013. One day, perhaps, a dark matter detection will headline at Moriond. For now, physicists wait. But they’ve gotten a bit anxious, as their shoo-in candidate, the WIMP, has yet to make an appearance—despite several ongoing searches.

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    Lux Dark Matter 2 at SURF, Lead, SD, USA

    DARWIN Dark Matter experiment. A design study for a next-generation, multi-ton dark matter detector in Europe at the University of Zurich

    At this year’s Moriond, held this past March in La Thuile, Italy, some of the limelight passed to other dark matter candidates, such as axions, black holes, superfluids, and more.

    1
    T. Tait/University of California, Irvine

    WIMPs, or weakly interacting massive particles, have been a popular topic over the years at Moriond, according to meeting organizer Jacques Dumarchez from the Laboratory of Nuclear Physics and High Energy (LPNHE) in France. The reason for this enthusiasm is that WIMPs fall out of theory without much tweaking. Extensions of the standard model, like supersymmetry, predict a host of particles with weak interactions and a mass in the 1 to 100GeV∕c2 range. If WIMPs like this were created in the big bang, then, according to simple thermodynamic arguments, their density would match the expectations for dark matter based on astronomical observations. This seemingly effortless matching has been called the WIMP miracle.

    But these days, the miracle has less of a halo around it. At this year’s Moriond, updates from direct and indirect searches for WIMPs sounded almost apologetic. Alessandro Manfredini of the Weizmann Institute of Science in Israel told his listeners to “keep calm… and fingers crossed,” as he gave the latest news from Xenon 1T, a one-ton dark matter detector at Italy’s Gran Sasso laboratory. He showed that the experiment has now reached record-breaking sensitivity, so that if a 50GeV∕c2 WIMP exists, the next data release could reveal ten events. But, like other WIMP searches, the current results rule the particles out—by putting tighter limits on their properties—rather than rule them in. The hunt will continue for years to come, but the WIMP paradigm has “started to look less as the obvious solution to the dark matter problem,” Dumarchez said.

    XENON1T at Gran Sasso


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

    When did WIMP confidence start to deflate? Tim Tait from the University of California, Irvine, described the change as gradual. “It is hard to say exactly when it began, but I think it was becoming noticeable around 2014 or so,” Tait said. That’s when the null results from dark matter searches began closing the favored parameter space for the WIMP model. “Of course, there is still a good opportunity for those searches to discover WIMPs,” he said.

    At Moriond, Tait gave an overview of dark matter candidates, in which he discussed WIMPs but devoted much of his time to the dazzling variety of other dark matter theories. Chief among these is the axion.

    CERN CAST Axion Solar Telescope

    U Washington ADMX Axion Dark Matter Experiment

    AXION DME experiment at U Washington

    Like the WIMP, it is well-motivated from particle physics theory, as it may explain why strong interactions do not violate CP symmetry, while weak interactions do. The axion is also the target of several dedicated searches, such as ADMX. Other familiar “dark horse” candidates discussed at Moriond were neutrinos and black holes—with the latter seeing a boost in popularity after recent gravitational-wave observations.

    But at the conference, the doors seemed open to all comers, with several new dark matter ideas taking the stage. One of the talks was by Justin Khoury from the University of Pennsylvania in Philadelphia, who advocates a superfluid model of dark matter. The main assumption here is that dark matter has strong self-interactions that cause it to cool and condense in the centers of galaxies. The resulting superfluid could help explain certain anomalies in observed galactic velocity profiles.

    Martin Sloth from the University of Southern Denmark takes a very different approach. Rather than having strong interactions, his so-called Planckian interacting dark matter has zero interactions beyond gravity, but it makes up for its lack of interactions with an enormous mass (around 1028eV∕c2). At the opposite end of the mass spectrum is fuzzy dark matter, weighing in at 10−22eV∕c2. These ethereal particles could explain an apparent lack of small galaxies. But they could also run into constraints from observed absorption in the intergalactic medium, explained Eric Armengaud from France’s Atomic Energy Commission (CEA) in Saclay.

    Although WIMPs continue to be the odds-on favorite, the field has certainly expanded—with light and heavy masses, weak and strong interactions, and seemingly everything in between. Sloth compared the current situation without a WIMP detection to a Wimbledon tournament without Roger Federer: “Everybody is signing up, thinking that they now have a chance.”

    But can theorists make compelling arguments for these alternatives, as they did for WIMPs? David Kaplan from Johns Hopkins University, Maryland, believes that theoretical backing will not be a problem. In fact, he commented that the community has been too fixated on WIMPs (and the miracle) for the last 30 years. He warned his compatriots to not make the same mistake again: “I don’t want the next 30 years to be just axions.”

    See the full article here .

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    • mpc755 11:18 am on May 15, 2018 Permalink | Reply

      There is evidence of dark matter every time a double-slit experiment is performed, as it is the medium that waves.

      Like

      • richardmitnick 11:25 am on May 15, 2018 Permalink | Reply

        Thanks for reading and commenting. It is much appreciated.

        Like

        • mpc755 12:08 pm on May 15, 2018 Permalink | Reply

          Dark matter is a supersolid that fills ’empty’ space and is displaced by visible matter. What is referred to geometrically as curved spacetime physically exists in nature as the state of displacement of the dark matter. The state of displacement of the dark matter is gravity.

          Dark matter ripples when galaxy clusters collide and waves in a double-slit experiment, relating general relativity and quantum mechanics.

          Thanks for the response.

          Like

  • richardmitnick 4:40 pm on May 6, 2018 Permalink | Reply
    Tags: , Axions, , , , , ,   

    From Symmetry: “The origins of dark matter” 

    Symmetry Mag
    From Symmetry

    11/08/16 [Just brought forward in social media]
    Matthew R. Francis

    1
    Artwork by Sandbox Studio, Chicago with Corinne Mucha

    [Because this article is well over a year old, I have updated it with Dark Matter experiments and also included a section on the origins of Dark Matter research by Vera Rubin and Fritz Zicky.]

    Dark Matter Research

    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    Milky Way Dark Matter Halo Credit ESO L. Calçada


    Dark matter halo. Image credit: Virgo consortium / A. Amblard / ESA

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    LUX/Dark matter experiment at SURF

    Edelweiss Dark Matter Experiment, located at the Modane Underground Laboratory in France

    Transitions are everywhere we look. Water freezes, melts, or boils; chemical bonds break and form to make new substances out of different arrangements of atoms. The universe itself went through major transitions in early times. New particles were created and destroyed continually until things cooled enough to let them survive. Those particles include ones we know about, such as the Higgs boson or the top quark. But they could also include dark matter, invisible particles which we presently know only because of their gravitational effects. In cosmic terms, dark matter particles could be a “thermal relic,” forged in the hot early universe and then left behind during the transitions to more moderate later eras. One of these transitions, known as “freeze-out,” changed the nature of the whole universe.

    The hot cosmic freezer

    On average, today’s universe is a pretty boring place. If you pick a random spot in the cosmos, it’s far more likely to be in intergalactic space than, say, the heart of a star or even inside an alien solar system. That spot is probably cold, dark and quiet. The same wasn’t true for a random spot shortly after the Big Bang. “The universe was so hot that particles were being produced from photons smashing into other photons, of photons hitting electrons, and electrons hitting positrons and producing these very heavy particles,” says Matthew Buckley of Rutgers University. The entire cosmos was a particle-smashing party, but parties aren’t meant to last. This one lasted only a trillionth of a second. After that came the cosmic freeze-out. During the freeze-out, the universe expanded and cooled enough for particles to collide far less frequently and catastrophically. “One of these massive particles floating through the universe is finding fewer and fewer antimatter versions of itself to collide with and annihilate,” Buckley says. “Eventually the universe would get large enough and cold enough that the rate of production and the rate of annihilation basically goes to zero, and you just a relic abundance, these few particles that are floating out there lonely in space.” Many physicists think dark matter is a thermal relic, created in huge numbers in before the cosmos was a half-second old and lingering today because it barely interacts with any other particle.

    A WIMPy miracle

    One reason to think of dark matter as a thermal relic is an interesting coincidence known as the “WIMP miracle.” WIMP stands for “weakly-interacting massive particle,” and WIMPs are the most widely accepted candidates for dark matter. Theory says WIMPs are likely heavier than protons and interact via the weak force, or at least interactions related to the weak force. The last bit is important, because freeze-out for a specific particle depends on what forces affect it and the mass of the particle. Thermal relics made by the weak force were born early in the universe’s history because particles need to be jammed in tight for the weak force, which only works across short distances, to be a factor.

    “If dark matter is a thermal relic, you can calculate how big the interaction [between dark matter particles] needs to be,” Buckley says. Both the primordial light known as the cosmic microwave background [CMB] and the behavior of galaxies tell us that most dark matter must be slow-moving (“cold” in the language of physics).

    COBE CMB


    NASA/COBE 1989 to 1993.


    Cosmic Microwave Background NASA/WMAP


    NASA/WMAP 2001 to 2010


    CMB per ESA/Planck


    ESA/Planck 2009 to 2013

    That means interactions between dark matter particles must be low in strength. “Through what is perhaps a very deep fact about the universe,” Buckley says, “that interaction turns out to be the strength of what we know as the weak nuclear force.” That’s the WIMP miracle: The numbers are perfect to make just the right amount of WIMPy matter. The big catch, though, is that experiments haven’t found any WIMPs yet.

    It’s too soon to say WIMPs don’t exist, but it does rule out some of the simpler theoretical predictions about them.

    Ultimately, the WIMP miracle could just be a coincidence. Instead of the weak force, dark matter could involve a new force of nature that doesn’t affect ordinary matter strongly enough to detect. In that scenario, says Jessie Shelton of the University of Illinois at Urbana-Champaign, “you could have thermal freeze-out, but the freeze-out is of dark matter to some other dark field instead of [something in] the Standard Model.” In that scenario, dark matter would still be a thermal relic but not a WIMP. For Shelton, Buckley, and many other physicists, the dark matter search is still full of possibilities. “We have really compelling reasons to look for thermal WIMPs,” Shelton says. “It’s worth remembering that this is only one tiny corner of a much broader space of possibilities.”

    Well, what about AXIONS?

    CERN CAST Axion Solar Telescope


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

    Origins of Dark Matter Research

    Vera Rubin measuring spectra (Emilio Segre Visual Archives AIP SPL)

    Vera Florence Cooper Rubin was an American astronomer who pioneered work on galaxy rotation rates. She uncovered the discrepancy between the predicted angular motion of galaxies and the observed motion, by studying galactic rotation curves. This phenomenon became known as the galaxy rotation problem, and was evidence of the existence of dark matter. Although initially met with skepticism, Rubin’s results were confirmed over subsequent decades. Her legacy was described by The New York Times as “ushering in a Copernican-scale change” in cosmological theory.

    Fritz Zwicky, the Father of Dark Matter research.No image credit after long search

    Fritz Zwicky, a Swiss astronomer. He worked most of his life at the California Institute of Technology in the United States of America, where he made many important contributions in theoretical and observational astronomy. In 1933, Zwicky was the first to use the virial theorem to infer the existence of unseen dark matter, describing it as “dunkle Materie

    There was no Nobel award for either Rubin or Zwicky.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 12:43 pm on April 11, 2018 Permalink | Reply
    Tags: Axions, , , ,   

    From U Washington via UC Berkeley: “Start of most sensitive search yet for dark matter axion” 

    U Washington

    University of Washington

    UC Berkeley

    UC Berkeley

    April 9, 2018
    Robert Sanders
    rlsanders@berkeley.edu

    1
    The SQUID-based amplifier, which is about a millimeter square, is supercooled to be sensitive to faint signals from axions, should they convert into a microwave photon in the ADMX detector. Sean O’Kelley image

    Thanks to low-noise superconducting quantum amplifiers invented at UC Berkeley, physicists are now embarking on the most sensitive search yet for axions, one of today’s top candidates for dark matter.

    The Axion Dark Matter Experiment (ADMX) reported results today showing that it is the world’s first and only experiment to have achieved the necessary sensitivity to “hear” the telltale signs of dark matter axions.

    The milestone is the result of more than 30 years of research and development, with the latest piece of the puzzle coming in the form of a quantum device that allows ADMX to listen for axions more closely than any experiment ever built.

    John Clarke, a professor of physics in the graduate school at UC Berkeley and a pioneer in the development of sensitive magnetic detectors called SQUIDs (superconducting quantum interference devices), developed the amplifier two decades ago. ADMX scientists, with Clarke’s input, have now incorporated it into the ADMX detector at the University of Washington, Seattle, and are ready to roll.

    “ADMX is a complicated and quite expensive piece of machinery, so it took a while to build a suitable detector so that they could put the SQUID amplifier on it and demonstrate that it worked as advertised. Which it did,” Clarke said.

    The ADMX team published their results online today in the journal Physical Review Letters.

    “This result signals the start of the true hunt for axions,” said Andrew Sonnenschein at the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois, the operations manager for ADMX. “If dark matter axions exist within the frequency band we will be probing for the next few years, then it’s only a matter of time before we find them.”

    Dark matter: MACHOs, WIMPs or axions?

    U Washington ADMX cutaway rendering of the ADMX detector

    Dark matter is the missing 84 percent of matter in the universe, and physicists have looked extensively for many possible candidates, most prominently massive compact halo objects, or MACHOs, and weakly interacting massive particles, or WIMPs. Despite decades of searching for MACHOs and WIMPs, scientists have struck out; they can see the effects of dark matter in the universe, in how galaxies and stars within galaxies move, but they can’t see dark matter itself.

    Axions are becoming the favored alternative, in part because their existence would also solve problems with the standard model of particle physics today, including the fact that the neutron should have an electric dipole moment, but doesn’t.

    Like other dark-matter candidates, axions are everywhere but difficult to detect. Because they interact with ordinary matter so rarely, they stream through space, even passing through the Earth, without “touching” ordinary matter. ADMX employs a strong magnetic field and a tuned, reflective box to encourage axions to convert to microwave-frequency photons, and uses the quantum amplifier to “listen” for them. All this is done at the lowest possible temperature to reduce background noise.

    Clarke learned of a key stumbling block for ADMX in 1994, when meeting with physicist Leslie Rosenberg, now a professor at the University of Washington and chief scientist for ADMX, and Karl van Bibber, now chair of UC Berkeley’s Department of Nuclear Engineering. Because the axion signal would be very faint, any detector would have to be very cold and “quiet.” Noise from heat, or thermal radiation, is easy to eliminate by cooling the detector down to 0.1 Kelvin, or roughly 460 degrees below zero Fahrenheit. But eliminating the noise from standard semiconductor transistor amplifiers proved difficult.

    They asked Clarke, would SQUID amplifiers solve this problem?

    Supercold amplifiers lower noise to absolute limit

    Though he had built SQUID amplifiers that worked up to 100 MHz frequencies, none worked at the gigahertz frequencies needed, so he set to work to build one. By 1998, he and his collaborators had solved the problem, thanks in large part to initial funding from the National Science Foundation and subsequent funding from the Department of Energy (DOE) through Lawrence Berkeley National Laboratory. The amplifiers on ADMX were funded by DOE through the University of Washington.


    Listening for dark matter: How ADMX employs cold cavities and SQUID amplifiers to find the elusive axion. Courtesy of University of Washington, Seattle.

    Clarke and his group showed that, cooled to temperatures of tens of milliKelvin above absolute zero, the Microstrip SQUID Amplifier (MSA) could achieve a noise that was quantum limited, that is, limited only by Heisenberg’s Uncertainty Principle.

    “You can’t do better than that,” Clarke said.

    This much quieter technology, combined with the refrigeration unit, reduced the noise by a factor of about 30 at 600 MHz so that a signal from the axion, if there is one, should come through loud and clear. The MSA currently in operation on ADMX was fabricated by Gene Hilton at the National Institute of Standards and Technology in Boulder, Colorado, and tested, calibrated and packaged by Sean O’Kelley, a graduate student in Clarke’s research group at UC Berkeley.

    The ADMX team plans to slowly tune through millions of frequencies in hopes of hearing a clear tone from photons produced by axion decay.

    “This result plants a flag,” said Rosenberg. “It tells the world that we have the sensitivity, and have a very good shot at finding the axion. No new technology is needed. We don’t need a miracle anymore, we just need the time.”

    Clarke noted too that the high-frequency, low-noise quantum SQUID amplifiers he invented for ADMX have since been employed in another hot area of physics, to read out the superconducting quantum bits, or qubits, for quantum computers of the future.

    See the full article here .

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    So what defines us — the students, faculty and community members at the University of Washington? Above all, it’s our belief in possibility and our unshakable optimism. It’s a connection to others, both near and far. It’s a hunger that pushes us to tackle challenges and pursue progress. It’s the conviction that together we can create a world of good. Join us on the journey.

     
  • richardmitnick 3:41 pm on January 22, 2018 Permalink | Reply
    Tags: , , Axions, , , , , ,   

    From CfA: “A New Bound on Axions” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    January 19, 2018

    1
    A composite image of M87 in the X-ray from Chandra (blue) and in radio emission from the Very Large Array (red-orange). Astronomers used the X-ray emission from M87 to constrain the properties of axions, putative particles suggested as dark matter candidates. X-ray NASA/CXC/KIPAC/N. Werner, E. Million et al.; Radio NRAO/AUI/NSF/F. Owen.

    NASA/Chandra Telescope

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    An axion is a hypothetical elementary particle whose existence was postulated in order to explain why certain subatomic reactions appear to violate basic symmetry constraints, in particular symmetry in time. The 1980 Nobel Prize in Physics went for the discovery of time-asymmetric reactions. Meanwhile, during the following decades, astronomers studying the motions of galaxies and the character of the cosmic microwave background [CMB] radiation came to realize that most of the matter in the universe was not visible.

    CMB per ESA/Planck

    Cosmic Background Radiation per Planck

    ESA/Planck

    It was dubbed dark matter, and today’s best measurements find that about 84% of matter in the cosmos is dark. This component is dark not only because it does not emit light — it is not composed of atoms or their usual constituents, like electrons and protons, and its nature is mysterious. Axions have been suggested as one possible solution. Particle physicists, however, have so far not been able to detect directly axions, leaving their existence in doubt and reinvigorating the puzzles they were supposed to resolve.

    CfA astronomer Paul Nulsen and his colleagues used a novel method to investigate the nature of axions. Quantum mechanics constrain axions, if they exist, to interact with light in the presence of a magnetic field. As they propagate along a strong field, axions and photons should transmute from one to the other other in an oscillatory manner. Because the strength of any possible effect depends in part on the energy of the photons, the astronomers used the Chandra X-ray Observatory to monitor bright X-ray emission from galaxies. They observed X-rays from the nucleus of the galaxy Messier 87, which is known to have strong magnetic fields, and which (at a distance of only fifty-three million light-years) is close enough to enable precise measurements of variations in the X-ray flux. Moreover, Me3ssier 87 lies in a cluster of galaxies, the Virgo cluster, which should insure the magnetic fields extend over very large scales and also facilitate the interpretation. Not least, Messier 87 has been carefully studied for decades and its properties are relatively well known.

    The search did not find the signature of axions. It does, however, set an important new limit on the strength of the coupling between axions and photons, and is able to rule out a substantial fraction of the possible future experiments that might be undertaken to detect axions. The scientists note that their research highlights the power of X-ray astronomy to probe some basic issues in particle physics, and point to complementary research activities that can be undertaken on other bright X-ray emitting galaxies.

    Science paper:
    A New Bound on Axion-Like Particles, Journal of Cosmology and Astroparticle Physics.

    See the full article here .

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  • richardmitnick 2:20 pm on October 8, 2017 Permalink | Reply
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    From Quanta: Women in STEM: “Mining Black Hole Collisions for New Physics” Asimina Arvanitaki 

    Quanta Magazine
    Quanta Magazine

    July 21, 2016
    Joshua Sokol

    The physicist Asimina Arvanitaki is thinking up ways to search gravitational wave data for evidence of dark matter particles orbiting black holes.

    1
    Asimina Arvanitaki during a July visit to the CERN particle physics laboratory in Geneva, Switzerland.
    Samuel Rubio for Quanta Magazine

    When physicists announced in February that they had detected gravitational waves firsthand, the foundations of physics scarcely rattled.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    ESA/eLISA the future of gravitational wave research

    1
    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    The signal exactly matched the expectations physicists had arrived at after a century of tinkering with Einstein’s theory of general relativity. “There is a question: Can you do fundamental physics with it? Can you do things beyond the standard model with it?” said Savas Dimopoulos, a theoretical physicist at Stanford University. “And most people think the answer to that is no.”

    Asimina Arvanitaki is not one of those people. A theoretical physicist at Ontario’s Perimeter Institute of Theoretical Physics,


    Perimeter Institute in Waterloo, Canada

    Arvanitaki has been dreaming up ways to use black holes to explore nature’s fundamental particles and forces since 2010, when she published a paper with Dimopoulos, her mentor from graduate school, and others. Together, they sketched out a “string axiverse,” a pantheon of as yet undiscovered, weakly interacting particles. Axions such as these have long been a favored candidate to explain dark matter and other mysteries.

    In the intervening years, Arvanitaki and her colleagues have developed the idea through successive papers. But February’s announcement marked a turning point, where it all started to seem possible to test these ideas. Studying gravitational waves from the newfound population of merging black holes would allow physicists to search for those axions, since the axions would bind to black holes in what Arvanitaki describes as a “black hole atom.”

    “When it came up, we were like, ‘Oh my god, we’re going to do it now, we’re going to look for this,’” she said. “It’s a whole different ball game if you actually have data.”

    That’s Arvanitaki’s knack: matching what she calls “well-motivated,” field-hopping theoretical ideas with the precise experiment that could probe them. “By thinking away from what people are used to thinking about, you see that there is low-hanging fruit that lie in the interfaces,” she said. At the end of April, she was named the Stavros Niarchos Foundation’s Aristarchus Chair at the Perimeter Institute, the first woman to hold a research chair there.

    It’s a long way to come for someone raised in the small Grecian village of Koklas, where the graduating class at her high school — at which both of her parents taught — consisted of nine students. Quanta Magazine spoke with Arvanitaki about her plan to use black holes as particle detectors. An edited and condensed version of those discussions follows.

    QUANTA MAGZINE: When did you start to think that black holes might be good places to look for axions?

    ASIMINA ARVANITAKI: When we were writing the axiverse paper, Nemanja Kaloper, a physicist who is very good in general relativity, came and told us, “Hey, did you know there is this effect in general relativity called superradiance?” And we’re like, “No, this cannot be, I don’t think this happens. This cannot happen for a realistic system. You must be wrong.” And then he eventually convinced us that this could be possible, and then we spent like a year figuring out the dynamics.
    What is superradiance, and how does it work?

    An astrophysical black hole can rotate. There is a region around it called the “ergo region” where even light has to rotate. Imagine I take a piece of matter and throw it in a trajectory that goes through the ergo region. Now imagine you have some explosives in the matter, and it breaks apart into pieces. Part of it falls into the black hole and part escapes into infinity. The piece that is coming out has more total energy than the piece that went in the black hole.

    You can perform the same experiment by scattering radiation from a black hole. Take an electromagnetic wave pulse, scatter it from the black hole, and you see that the pulse you got back has a higher amplitude.

    So you can send a pulse of light near a black hole in such a way that it would take some energy and angular momentum from the black hole’s spin?

    This is old news, by the way, this is very old news. In ’72 Press and Teukolsky wrote a Nature paper that suggested the following cute thing. Let’s imagine you performed the same experiment as the light, but now imagine that you have the black hole surrounded by a giant mirror. What will happen in that case is the light will bounce on the mirror many times, the amplitude [of the light] grows exponentially, and the mirror eventually explodes due to radiation pressure. They called it the black hole bomb.

    The property that allows light to do this is that light is made of photons, and photons are bosons — particles that can sit in the same space at the same time with the same wave function. Now imagine that you have another boson that has a mass. It can [orbit] the black hole. The particle’s mass acts like a mirror, because it confines the particle in the vicinity of the black hole.

    In this way, axions might get stuck around a black hole?

    This process requires that the size of the particle is comparable to the black hole size. Turns out that [axion] mass can be anywhere from Hubble scale — with a quantum wavelength as big as the universe — or you could have a particle that’s tiny in size.

    So if they exist, axions can bind to black holes with a similar size and mass. What’s next?

    What happens is the number of particles in this bound orbit starts growing exponentially. At the same time the black hole spins down. If you solve for the wave functions of the bound orbits, what you find is that they look like hydrogen wave functions. Instead of electromagnetism binding your atom, what’s binding it is gravity. There are three quantum numbers you can describe, just the same. You can use the exact terminology that you can use in the hydrogen atom.

    How could we check to see if any of the black holes LIGO finds have axion clouds orbiting around black hole nuclei?

    This is a process that extracts energy and angular momentum from the black hole. If you were to measure spin versus mass of black holes, you should see that in a certain mass range for black holes you see no quickly rotating black holes.

    This is where Advanced LIGO comes in. You saw the event they saw. [Their measurements] allowed them to measure the masses of the merging objects, the mass of the final object, the spin of the final object, and to have some information about the spins of the initial objects.

    If I were to take the spins of the black holes before they merged, they could have been affected by superradiance. Now imagine a graph of black hole spin versus mass. Advanced LIGO could maybe get, if the things that we hear are correct, a thousand events per year. Now you have a thousand data points on this plot. So you may trace out the region that is affected by this particle just by those measurements.

    That would be supercool.

    That’s of course indirect. So the other cool thing is that it turns out there are signatures that have to do with the cloud of particles themselves. And essentially what they do is turn the black hole into a gravitational wave laser.

    Awesome. OK, what does that mean?

    2
    Samuel Rubio for Quanta Magazine

    Yeah, what that means is important. Just like you have transitions of electrons in an excited atom, you can have transitions of particles in the gravitational wave atom. The rate of emission of gravitational waves from these transitions is enhanced by the 1080 particles that you have. It would look like a very monochromatic line. It wouldn’t look like a transient. Imagine something now that emits a signal at a very fixed frequency.

    Where could LIGO expect to see signals like this?

    In Advanced LIGO, you actually see the birth of a black hole. You know when and where a black hole was born with a certain mass and a certain spin. So if you know the particle masses that you’re looking for, you can predict when the black hole will start growing the [axion] cloud around it. It could be that you see a merger in that day, and one or 10 years down the line, they go back to the same position and they see this laser turning on, they see this monochromatic line coming out from the cloud.

    You can also do a blind search. Because you have black holes that are roaming the universe by themselves, and they could still have some leftover cloud around them, you can do a blind search for monochromatic gravitational waves.

    Were you surprised to find out that axions and black holes could combine to produce such a dramatic effect?

    Oh my god yes. What are you talking about? We had panic attacks. You know how many panic attacks we had saying that this effect, no, this cannot be true, this is too good to be true? So yes, it was a surprise.

    The experiments you suggest draw from a lot of different theoretical ideas — like how we could look for high-frequency gravitational waves with tabletop sensors, or test whether dark matter oscillates using atomic clocks. When you’re thinking about making risky bets on physics beyond the standard model, what sorts of theories seem worth the effort?

    What is well motivated? Things that are not: “What if you had this?” People imagine: “What if dark matter was this thing? What if dark matter was the other thing?” For example, supersymmetry makes predictions about what types of dark matter should be there. String theory makes predictions about what types of particles you should have. There is always an underlying reason why these particles are there; it’s not just the endless theoretical possibilities that we have.

    And axions fit that definition?

    This is a particle that was proposed 30 years ago to explain the smallness of the observed electric dipole moment of the neutron. There are several experiments around the world looking for it already, at different wavelengths. So this particle, we’ve been looking for it for 30 years. This can be the dark matter. That particle solves an outstanding problem of the standard model, so that makes it a good particle to look for.

    Now, whether or not the particle is there I cannot answer for nature. Nature will have to answer.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    Formerly known as Simons Science News, Quanta Magazine is an editorially independent online publication launched by the Simons Foundation to enhance public understanding of science. Why Quanta? Albert Einstein called photons “quanta of light.” Our goal is to “illuminate science.” At Quanta Magazine, scientific accuracy is every bit as important as telling a good story. All of our articles are meticulously researched, reported, edited, copy-edited and fact-checked.

     
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