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  • richardmitnick 5:14 pm on October 23, 2014 Permalink | Reply
    Tags: ARC Centre of Excellence for Particle Physics at the Terascale, , Dark Energy/Dark Matter, Grand Sasso National Laboratory   

    From Symmetry: “Australia’s first dark matter experiment” 

    Symmetry

    October 23, 2014
    Glenn Roberts Jr.

    Physicists are hoping to hit pay dirt with a proposed experiment—the first of its kind in the Southern Hemisphere—that would search for traces of dark matter more than a half mile below ground in Victoria, Australia.

    The current plan, now being explored by an international team, is for two new, identical dark matter experiments to be installed and operated in parallel—one at an underground site at Grand Sasso National Laboratory in Italy, and the other at the Stawell Gold Mine in Australia.

    team

    “An experiment of this significance could ultimately lead to the discovery of dark matter,” says Elisabetta Barberio of the ARC Centre of Excellence for Particle Physics at the Terascale (CoEPP) and the University of Melbourne, who is Australian project leader for the proposed experiment.

    The experiment proposal was discussed during a two-day workshop on dark matter in September. Work could begin on the project as soon as 2015 if it gathers enough support. “We’re looking at logistics and funding sources,” Barberio says.

    The experiments would be modeled after the DAMA experiment at Gran Sasso, now called DAMA/LIBRA, which in 1998 found a possible sign of dark matter.

    DAMA/LIBRA looks for seasonal modulation, an ebb and flow in the amount of potential dark matter signals it sees depending on the time of year.

    If the Milky Way is surrounded by a halo of dark matter particles, then the sun is constantly moving through it, as is the Earth. The Earth’s rotation around the sun causes the two to spend half of the year moving in the same direction and the other half moving in opposite directions. During the six months in which the Earth and sun are cooperating, a dark matter detector on the Earth will move faster through the dark matter particles, giving it more opportunities to catch them.

    This seasonal difference appears in the data from DAMA/LIBRA, but no other experiment has been able to confirm this as a sign of dark matter.

    For one thing, the changes in the signal could be caused on other factors that change by the season.

    “There are environmental effects—different characteristics of the atmosphere—in winter and summer that are clearly reversed if you go from the Northern to the Southern hemisphere,” says Antonio Masiero, vice president for the Italian National Institute of Nuclear Physics (INFN) and a member of the Italian delegation collaborating on the proposal, which also includes Gran Sasso Director Stefano Ragazzi. If the results matched up at both sites at the same time of year, that would help to rule out such effects.

    The Australian mine hosting the proposed experiment could also house scientific experiments from different fields.

    “It wouldn’t be limited to particle physics and could include experiments involving biology, geosciences and engineering,” Barberio says. “These could include neutrino detection, nuclear astrophysics, geothermal energy extraction and carbon sequestration, and subsurface imaging and sensing.”

    Preliminary testing has begun at the mine site down to depths of about 880 meters, about 200 meters above the proposed experimental site. Regular mining operations are scheduled to cease at Stawell in the next few years.

    The ARC Centre of Excellence for All-Sky Astrophysics (CAASTRO), the local government in the Victoria area, and the mine operators have joined forces with COEPP and INFN to support the proposal.

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.


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  • richardmitnick 10:39 am on October 15, 2014 Permalink | Reply
    Tags: , , Dark Energy/Dark Matter, ,   

    From FNAL: “From the Center for Particle Astrophysics – Big eyes” 


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

    Wednesday, Oct. 15, 2014

    ch
    Craig Hogan, head of the Center for Particle Astrophysics, wrote this column.

    To create small things you need particles with lots of energy, and to learn about them you need to capture and study lots of particles. So it is not surprising that the worldwide physics community is in the business of building giant accelerators and detectors..

    We also find out about new physics without using accelerators by studying the biggest system of all — the cosmos. Such experiments also need big detectors, in particular, giant cameras to make deep, wide-field maps of cosmic structure. For example, Fermilab’s Dark Energy Camera (DECam) is now collecting data for the Dark Energy Survey, using light from distant galaxies gathered by the 4-meter Blanco telescope on Cerro Tololo in Chile. Designed for depth, speed, sensitivity and scientific precision, it’s a behemoth compared to the camera in your phone. By the time you add up all the parts — the detectors, the lenses, the cooling systems, the electronics and the structure to hold them precisely in place 50 feet up in the telescope beam — you have a machine that weighs about 10 tons. That may not seem very big compared to the Tevatron or the thousand-ton telescope the camera is mounted on, but it’s a lot for a digital camera — the biggest ever built.

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco 4 meter telescope

    DECam
    DECam

    FNALTevatron
    Tevatron

    The giant telescope simulator used to test DECam has recently been removed from the Fermilab building where the camera was put together. In the same space, another giant camera will soon start to take shape. This one will study the cosmic microwave background — the primordial light from the big bang. That light has been cooled by the cosmic expansion to microwave wavelengths, so the camera detectors and even its lenses must be cold to match. About 15,000 advanced superconducting detectors from Argonne National Laboratory will be integrated into a camera system about as big as DECam and then shipped for an experiment to take place under the thin, cold, crystalline skies at the South Pole.

    Cosmic Background Radiation Planck
    CMB from ESA/Planck

    ESA Planck
    ESA Planck schematic
    ESA/Planck

    This machine — the SPT-3G camera — will also be the largest of its kind ever built. When it is finished, it will be installed on the South Pole Telescope, where it will map the faint ripples of polarization imprinted on the light since it was created almost 14 billion years ago.

    South Pole Telescope
    South Pole Telescope

    The SPT-3G experiment will advance cosmic mapping by an order of magnitude, but it is also a stepping stone along a path to an even larger Stage 4 CMB project in the following decade. That project, endorsed by the P5 report and supported by a nationwide collaboration of labs and university groups now forming, will carry out a comprehensive survey of the primordial radiation over much of the sky and teach us about new physics ranging from neutrino masses to dark energy.

    See the full article here.

    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.

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  • richardmitnick 4:42 pm on October 13, 2014 Permalink | Reply
    Tags: , Dark Energy/Dark Matter, ,   

    From physicsworld: “Dark matter could light up giant mirror” 

    physicsworld
    physicsworld.com

    Oct 13, 2014
    Edwin Cartlidge

    A large metallic mirror previously used as a prototype for a cosmic-ray observatory will be reused by physicists in Germany to hunt for “hidden photons”. These exotic and hitherto unseen cousins of normal photons could account for some dark matter – the mysterious and invisible substance that appears to account for about 85% of the matter in the universe.

    Most dark-matter experiments try to detect weakly interacting massive particles (WIMPs), which are predicted by the theory of supersymmetry and interact with other matter only via the weak nuclear force and gravity. WIMP detectors aim to capture the tiny amounts of energy given off in collisions between the putative particles and atomic nuclei – usually in large detectors deep underground. However, about a quarter of a century has passed since the first such experiment started and not a single WIMP has been unambiguously detected.

    Supersymmetry standard model
    Standard Model of Super Symmetry

    Hidden photons are predicted in some extensions of the Standard Model of particle physics, and unlike WIMPs they would interact electromagnetically with normal matter. Hidden photons also have a very small mass, and are expected to oscillate into normal photons in a process similar to neutrino oscillation. Observing such oscillations relies on detectors that are sensitive to extremely small electromagnetic signals, and a number of these extremely difficult experiments have been built or proposed.

    Many different experiments

    “In the last few years, the interest in hidden photons has been growing,” says Jonathan Feng of the University of California, Irvine – partly because searches for other dark-matter candidates have “come up empty”. Also, physicists have realized that many different kinds of experiment can be built to try and detect hidden photons.

    Now, Babette Döbrich and colleagues at DESY in Hamburg, the Karlsruhe Institute for Technology and other institutes in Europe are using a portion of a spherical, metallic mirror to look for hidden photons. This was suggested in 2012 by physicists in Germany in a paper called Searching for WISPy Cold Dark Matter with a Dish Antenna. The scheme exploits the fact that hidden photons would interact with electrons – albeit feebly – and when they strike a conductor they would set the constituent electrons vibrating. These vibrations would result in normal photons being emitted at right angles to the conductor’s surface.

    A spherical mirror is ideal for detecting such light because the emitted photons would be concentrated at the sphere’s centre, whereas any background light bouncing off the mirror would pass through a focus midway between the sphere’s surface and centre. A receiver placed at the centre could then pick up the dark-matter-generated photons, if tuned to their frequency – which is related to the mass of the incoming hidden photons – with mirror and receiver shielded as much as possible from stray electromagnetic waves.

    Ideal mirror at hand

    mirror
    Reflecting on dark matter: giant mirror will seek dark matter

    Fortunately for the team, an ideal mirror is at hand: a 13 m2 aluminium mirror used in tests during the construction of the Pierre Auger Observatory and located at the Karlsruhe Institute of Technology. Döbrich and co-workers have got together with several researchers from Karlsruhe, and the collaboration is now readying the mirror by adjusting the position of each of its 36 segments to minimize the spot size of the focused waves. They are also measuring background radiation within the shielded room that will house the experiment. As for receivers, the most likely initial option is a set of low-noise photomultiplier tubes for measurements of visible light, which corresponds to hidden-photon masses of about 1 eV/C2. Another obvious choice is a receiver for gigahertz radiation, which corresponds to masses less than 0.001 eV/C2; however, this latter set-up would require more shielding.

    The DESY/Karlsruhe experiment – provisionally named FUNK (Finding U(1)’s of a Novel Kind) – will not be the first to search for hidden photons. The CERN Resonant WISP Search (CROWS) at the CERN laboratory in Geneva, which has been running since 2011, looks for both hidden photons and other low-mass dark-matter particles, such as axions. Also looking is the Axion Dark Matter Experiment at the University of Washington in Seattle. Although, as its name suggests, this facility has been set up mainly to detect axions, it can nevertheless probe the existence of hidden photons down to very low interaction strengths. The advantage of FUNK over its rivals, says Döbrich, is that it will be able to operate across quite a broad range of frequencies – just how broad will depend on the availability of suitable electromagnetic detectors and the performance of the mirror.

    Fritz Caspers of CERN applauds FUNK’s “very nice” design, but has concerns about how difficult it will be in practice to shield the mirror from electromagnetic interference. “The devil is always in the detail,” he says. He also wonders why Döbrich and colleagues did not “go directly” to look for emitted radio-frequency radiation using a radio telescope, with a dish up to perhaps 100 m across, rather than the smaller version they will use. “You could easily find much bigger mirrors in the world,” he says. Döbrich points out that in terms of optical measurements, their mirror is a very good choice.

    The research is described in a preprint on arXiv.

    See the full article here.

    PhysicsWorld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
    IOP Institute of Physics

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  • richardmitnick 7:28 pm on October 6, 2014 Permalink | Reply
    Tags: , Dark Energy/Dark Matter,   

    From Kavli: ” A Warm Dark Matter Search Using XMASS “ 

    KavliFoundation

    The Kavli Foundation

    10/06/2014
    Yoichiro Suzuki
    Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo
    E-mail: yoichiro.suzuki_at_ipmu.jp 

    The XMASS collaboration, led by Yoichiro Suzuki at the Kavli IPMU, has reported its latest results on the search for warm dark matter. Their results rule out the possibility that super-weakly interacting massive bosonic particles (bosonic super-WIMPs) constitute all dark matter in the universe. This result was published in the September 19th issue of the Physical Review Letters as an Editors’ Suggestion.

    xmass
    XMASS DetectorConstruction of XMASS-Ⅰ detector (2010/Feb./25) (C) Kamioka Observatory, ICRR(Institute for Cosmic Ray Research), The University of Tokyo

    The universe is considered to be filled with dark matter, which cannot be observed by ordinary light. Although much evidence supports the existence of dark matter, it has yet to be directly detected and its nature is not understood.

    Various theoretical models have been proposed to explain the nature of dark matter. Some models extend the standard model of particle physics, such as super-symmetry, and suggest that weakly interacting massive particles (WIMPs) are dark matter candidates. These models have motivated most experimental research on dark matter. In discussions on the large-scale structure formation of the universe, these WIMPs fit the cold dark matter (CDM) paradigm.

    Supersymmetry standard model
    Standard Model of Supersymmetry

    On the other hand, some simulations based on the CDM scenario predict a much richer structure of the universe on galactic scales than those observed. Furthermore, high-energy collider experiments have yet to provide evidence of super-symmetric particles. These facts have increased the interest in lighter and further weakly interacting particles such as bosonic super-WIMPs as dark matter. Super-WIMPs with masses greater than a twentieth of an electron (more than 3 keV) do not conflict with the structure formation of the universe.

    “Bosonic super-WIMPs are experimentally attractive since if they are absorbed in ordinary material, they would deposit energy essentially equivalent to the super-WIMP’s rest mass,” Suzuki says. “And only ultra-low background detectors like XMASS can detect the signal.”

    The XMASS experiment was conducted to directly search for such bosonic super-WIMPS, especially in the mass range between a tenth and a third that of an electron (between 40 and 120 keV). XMASS is a cryogenic detector using about 1 ton of liquid xenon as the target material. Using 165.9 days of data, a significant excess above the background is not observed in the fiducial mass of 41 kg. The absence of such a signal excludes the possibility that bosonic super-WIMPs constitute all dark matter in the universe.

    “Light super-WIMPs are a good candidate of dark matter on galactic scales,” Professor Naoki Yoshida, a cosmologist at the School of Science, the University of Tokyo and a Project Professor at the Kavli IPMU says. “The XMASS team derived an important constraint on the possibility of such light dark models for a broad range of particle masses.”

    See the full article here.

    The Kavli Foundation, based in Oxnard, California, is dedicated to the goals of advancing science for the benefit of humanity and promoting increased public understanding and support for scientists and their work.

    The Foundation’s mission is implemented through an international program of research institutes, professorships, and symposia in the fields of astrophysics, nanoscience, neuroscience, and theoretical physics as well as prizes in the fields of astrophysics, nanoscience, and neuroscience.

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  • richardmitnick 3:10 pm on September 18, 2014 Permalink | Reply
    Tags: , , Dark Energy/Dark Matter,   

    From Symmetry: “Pursuit of dark matter progresses at AMS” 

    Symmetry

    September 18, 2014
    Kathryn Jepsen

    A possible sign of dark matter will eventually become clear, according to promising signs from the Alpha Magnetic Spectrometer experiment.

    NASA AMS02 Banner

    NASA AMS02 device
    AMS Device

    New results from the Alpha Magnetic Spectrometer experiment show that a possible sign of dark matter is within scientists’ reach.

    Dark matter is a form of matter that neither emits nor absorbs light. Scientists think it is about five times as prevalent as regular matter, but so far have observed it only indirectly.

    The AMS experiment, which is secured to the side of the International Space Station 250 miles above Earth, studies cosmic rays, high-energy particles in space. A small fraction of these particles may have their origin in the collisions of dark matter particles that permeate our galaxy. Thus it may be possible that dark matter can be detected through measurements of cosmic rays.

    AMS scientists—based at the AMS control center at CERN research center in Europe and at collaborating institutions worldwide—compare the amount of matter and antimatter cosmic rays of different energies their detector picks up in space. AMS has collected information about 54 billion cosmic ray events, of which scientists have analyzed 41 billion.

    Theorists predict that at higher and higher energies, the proportion of antimatter particles called positrons should drop in comparison to the proportion of electrons. AMS found this to be true.

    However, in 2013 it also found that beyond a certain energy—8 billion electronvolts [BeV]—the proportion of positrons begins to climb steeply.

    “This means there’s something new there,” says AMS leader and Nobel Laureate Sam Ting of the Massachusetts Institute of Technology and CERN. “It’s totally unexpected.”

    The excess was a clear sign of an additional source of positrons. That source might be an astronomical object we already know about, such as a pulsar. But the positrons could also be produced in collisions of particles of dark matter.

    Today, Ting announced AMS had discovered the other end of this uptick in positrons—an indication that the experiment will eventually be able to discern what likely caused it.

    “Scientists have been measuring this ratio since 1964,” says Jim Siegrist, associate director of the US Department of Energy’s Office of High-Energy Physics, which funded the construction of AMS. “This is the first time anyone has observed this turning point.”

    The AMS experiment found that the proportion of positrons begins to drop off again at around 275 billion electronvolts.

    The energy that comes out of a particle collision must be equal to the amount that goes into it, and mass is related to energy. The energies of positrons made in dark matter particle collisions would therefore be limited by the mass of dark matter particles. If dark matter particles of a certain mass are responsible for the excess positrons, those extra positrons should drop off rather suddenly at an energy corresponding to the dark matter particle mass.

    If the numbers of positrons at higher energies do decrease suddenly, the rate at which they do it can give scientists more clues as to what kind of particles caused the increase in the first place. “Different particles give you different curves,” Ting says. “With more statistics in a few years, we will know how quickly it goes down.”

    If they decrease gradually instead, it is more likely they were produced by something else, such as pulsars.

    To gain a clearer picture, AMS scientists have begun to collect data about another matter-antimatter pair—protons and antiprotons—which pulsars do not produce.

    p
    The quark structure of the proton. The color assignment of individual quarks is arbitrary, but all three colors must be present. Forces between quarks are mediated by gluons.

    ap
    The quark structure of the antiproton.

    The 7.5-ton AMS experiment was able to make these unprecedented measurements due to its location on the International Space Station, above the interference of Earth’s atmosphere.

    “It’s really profound to me, the fact that we’re getting this fundamental data,” says NASA Chief Scientist Ellen Stofan, who recently visited the AMS control center. “Once we understand it, it could change how we see the universe.”

    AMS scientists also announced today that the way that the positrons increased within the area of interest, between 8 and 257 GeV, was steady, with no sudden peaks. Such jolts could have indicated the cause of the positron proliferation were sources other than, or in addition to, dark matter.

    In addition, AMS discovered that positrons and electrons act very differently at different energies, but that, when combined, the fluxes of the two together unexpectedly seem to fit into a single, straight slope.

    “This just shows how little we know about space,” Ting says.

    Fifteen countries from Europe, Asia and America participated in the construction of AMS. The collaboration works closely with a management team at NASA’s Johnson Space Center. NASA carried AMS to the International Space Station on the final mission of the space shuttle Endeavour in 2011.

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.


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  • richardmitnick 7:02 am on September 9, 2014 Permalink | Reply
    Tags: , , , , Dark Energy/Dark Matter,   

    From The Royal Astronomical Society: “Interactive dark matter could explain Milky Way’s missing satellite galaxies” 

    Royal Astronomical Society

    Royal Astronomical Society

    Tuesday, 09 September 2014
    Media contacts

    Durham University Media Relations Team
    Tel: +44 (0)191 334 6075
    media.relations@durham.ac.uk

    Dr Robert Massey
    Royal Astronomical Society
    Tel: +44 (0)20 7734 3307 x214
    Mob: +44 (0)794 124 8035
    rm@ras.org.uk

    Science contacts

    All the contacts are available for interview on Monday 8 and Tuesday 9 September.

    Professor Carlton Baugh
    Institute for Computational Cosmology
    Durham University
    Tel: +44 (0)191 33 43542
    c.m.baugh@durham.ac.uk

    Ryan Wilkinson
    Institute for Computational Cosmology
    Durham University
    Tel: +44 (0)191 33 45753
    ryan.wilkinson@durham.ac.uk

    Jascha Schewtschenko
    Institute for Computational Cosmology
    Durham University
    Tel: +44 (0)191 33 43710
    j.a.schewtschenko@durham.ac.uk

    Scientists believe they have found a way to explain why there are not as many galaxies orbiting the Milky Way as expected. Computer simulations of the formation of our galaxy suggest that there should be many more small galaxies around the Milky Way than are observed through telescopes.

    This has thrown doubt on the generally accepted theory of cold dark matter, an invisible and mysterious substance that scientists predict should allow for more galaxy formation around the Milky Way than is seen.

    sim
    The simulated distribution of dark matter in a Milky Way-like galaxy for standard, non-interacting dark matter (top left), warm dark matter (top right) and the new dark matter model that interacts with the photon background (bottom). Smaller structures are erased up to the point where, in the most extreme model (bottom right), the galaxy is completely sterilised. Credit: Durham University. Now cosmologists and particle physicists at the Institute for Computational Cosmology and the Institute for Particle Physics Phenomenology, at Durham University, working with colleagues at LAPTh College & University in France, think they have found a potential solution to the problem.

    Writing in the journal Monthly Notices of the Royal Astronomical Society, the scientists suggest that dark matter particles, as well as feeling the force of gravity, could have interacted with photons and neutrinos in the young Universe, causing the dark matter to scatter.

    Scientists think clumps of dark matter – or haloes – that emerged from the early Universe, trapped the intergalactic gas needed to form stars and galaxies. Scattering the dark matter particles wipes out the structures that can trap gas, stopping more galaxies from forming around the Milky Way and reducing the number that should exist.

    Lead author Dr Celine Boehm, in the Institute for Particle Physics Phenomenology at Durham University, said: “We don’t know how strong these interactions should be, so this is where our simulations come in.”

    “By tuning the strength of the scattering of particles, we change the number of small galaxies, which lets us learn more about the physics of dark matter and how it might interact with other particles in the Universe.”

    “This is an example of how a cosmological measurement, in this case the number of galaxies orbiting the Milky Way, is affected by the microscopic scales of particle physics.”

    There are several theories about why there are not more galaxies orbiting the Milky Way, which include the idea that heat from the Universe’s first stars sterilised the gas needed to form stars. The researchers say their current findings offer an alternative theory and could provide a novel technique to probe interactions between other particles and cold dark matter.

    two
    Two models of the dark matter distribution in the halo of a galaxy like the Milky Way, separated by the white line. The colours represent the density of dark matter, with red indicating high-density and blue indicating low-density. On the left is a simulation of how non-interacting cold dark matter produces an abundance of smaller satellite galaxies. On the right the simulation shows the situation when the interaction of dark matter with other particles reduces the number of satellite galaxies we expect to observe around the Milky Way. Credit: Durham University.

    Co-author Professor Carlton Baugh said: “Astronomers have long since reached the conclusion that most of the matter in the Universe consists of elementary particles known as dark matter.”

    “This model can explain how most of the Universe looks, except in our own backyard where it fails miserably.”

    “The model predicts that there should be many more small satellite galaxies around our Milky Way than we can observe.”

    “However, by using computer simulations to allow the dark matter to become a little more interactive with the rest of the material in the Universe, such as photons, we can give our cosmic neighbourhood a makeover and we see a remarkable reduction in the number of galaxies around us compared with what we originally thought.”

    The calculations were carried out using the COSMA supercomputer at Durham University, which is part of the UK-wide DiRAC super-computing framework.

    The work was funded by the Science and Technology Facilities Council and the European Union.

    See the full article here.

    The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science.

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  • richardmitnick 2:32 pm on August 26, 2014 Permalink | Reply
    Tags: , , , CERN CAST, , Dark Energy/Dark Matter, International Axion Observatory (IAXO)   

    From CERN Courier: “IAXO: the International Axion Observatory” 

    CERN Courier

    Aug 26, 2014

    Igor G Irastorza, Universidad de Zaragoza, Michael Pivovaroff, Lawrence Livermore National Laboratory, and Herman Ten Kate, CERN, on behalf of the IAXO collaboration.

    A large superconducting magnet could open a new window on the dark universe.

    The recent discovery of a Higgs boson at CERN appears to represent the summit in the successful experimental verification of the Standard Model of particle physics.

    sm
    The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    However, although essentially all of the data from particle accelerators are so far in perfect agreement with the model’s predictions, a number of important theoretical and observational considerations point to the necessity of physics beyond the Standard Model. An especially powerful argument comes from cosmology. The currently accepted cosmological model invokes two exotic ingredients – dark matter and dark energy – which pervade the universe. In particular, the observational evidence for dark matter (via its gravitational effects on visible matter) is now overwhelming, even though the particle-physics nature of both dark matter and dark energy remains a mystery.

    At the same time, the theoretical foundations of the Standard Model have shortcomings that prompt theorists to propose and explore hypothetical ways to extend it. Supersymmetry is one such hypothesis, which also naturally provides particles as candidates for dark matter, known as weakly interacting massive particles (WIMPs).

    Supersymmetry standard model

    Other extensions to the Standard Model predict particles that could lie hidden at the low-energy frontier, of which the axion is the prototype. The fact that supersymmetry has not yet been observed at the LHC, and that no clear signal of WIMPs has appeared in dark-matter experiments, has increased the community’s interest in searching for axions. However, there are independent and powerful motivations for axions, and dark matter composed of both WIMPs and axions is viable, implying that they should not be considered as alternative, exclusive solutions to the same problem.

    Axions appear in Standard Model extensions that include the Peccei–Quinn mechanism, which provides the most promising solution so far to one of the problems of the Standard Model: why do strong interactions seem not to violate charge–parity symmetry, while according to QCD, the standard theory of strong interactions, they should do? Unlike many particles predicted by theories that go beyond the Standard Model, axions should be light, and it might seem that they should have been detected already. Nevertheless, they could exist and remain unnoticed because they naturally couple only weakly with Standard Model particles.

    A generic property of axions is that they couple with photons in a way that axion–photon conversion (and vice versa) can occur in the presence of strong magnetic or electric fields. This phenomenon is the basis of axion production in the stars, as well as of most strategies for detecting axions. Magnets are therefore at the core of any axion experiment, as is the case for axion helioscopes, which look for axions from the Sun. This is the strategy followed by the CERN Axion Solar Telescope (CAST), which uses a decommissioned LHC test magnet (CERN Courier April 2010 p22). After more than a decade of searching for solar axions, CAST has put the strongest limits yet on axion–photon coupling across a range of axion masses, surpassing previous astrophysical limits for the first time and probing relevant axion models of sub-electron-volt mass. However, to improve these results and go deep into unexplored axion parameter space requires a completely new experiment.

    CERN CAST Axion Solar Telescope
    CERN CAST

    The International Axion Observatory (IAXO) aims for a signal-to-noise ratio 105 better than CAST. Such an improvement is possible only by building a large magnet, together with optics and detectors that optimize the axion helioscope’s figure of merit, while building on experience and concepts of the pioneering CAST project.

    cast
    Schematic view of IAXO

    The central component of IAXO is a superconducting toroid magnet. The detector relies on a high magnetic field distributed across a large volume to convert solar axions to detectable X-ray photons. The magnet’s figure of merit is proportional to the square of the product of magnetic field and length, multiplied by the cross-sectional area filled with the magnetic field. This consideration leads to a 25-m-long and 5.2-m-diameter toroid assembled from eight coils, generating 2.5 T in eight bores of 600 mm diameter, thereby having a figure of merit that is 300 times better than the CAST magnet. The toroid’s stored energy is 500 MJ.

    The design is inspired by the barrel and endcap toroids of the ATLAS experiment at the LHC, which has the largest superconducting toroids ever built and currently in operation at CERN. The superconductor used is a NbTi/Cu-based Rutherford cable co-extruded with aluminum – a successful technology common to most modern detector magnets. The IAXO detector needs to track the Sun for the longest possible period, so to allow rotation around the two axes, the 250-tonne magnet is supported at its centre of mass by a system used for large telescopes (figure 1). The necessary services for vacuum, helium supply, current and controls rotate together with the magnet.

    Each of the eight magnet bores will be equipped with X-ray focusing optics that rely on the fact that at X-ray energies the index of refraction is less than unity for most materials. By working at shallow (or grazing) incident angles, it is possible to make mirrors with high reflectivity. Mirrors are commonly used at synchrotrons and free-electron lasers to condition or focus the intense X-ray beams for user experiments, but IAXO requires optics with much larger apertures. For nearly 50 years, the X-ray astronomy and astrophysics community has been building telescopes following the design principle of Hans Wolter, employing two conic-shaped mirrors to provide true-imaging optics. This class of optics allows “nesting” – that is, placing concentric co-focal X-ray mirrors inside one another to achieve high throughput.

    The IAXO collaboration envisions using optics similar to those used on NASA’s NuSTAR – an X-ray astrophysics satellite with two focusing telescopes that operate in the 3–79 keV band. NuSTAR’s optics consist of thousands of thermally formed glass substrates deposited with multilayer coatings to enhance the reflectivity above 10 keV (figure 2). For IAXO, the multilayer coatings will be designed to match the softer 1–10 keV solar-axion spectrum.

    NASA NuSTAR
    NASA/Nu-STAR

    At the focal plane in each of the optics, IAXO will have small time-projection chambers read by pixelized planes of Micromegas. These detectors (figure 2) have been developed extensively within the CAST collaboration and show promise for detecting X-rays with a record background level of 10–8–10–7 counts/keV/cm2/s. This is achieved by the use of radiopure detector components, appropriate shielding, and offline discrimination algorithms on the 3D event topology in the gas registered by the pixelized read-out.

    Beyond the baseline described above, additional enhancements are being considered to explore extensions of the physics case for IAXO. Because a high magnetic field in a large volume is an essential component in any axion experiment, IAXO could evolve into a generic “axion facility” and facilitate various detection techniques. Most intriguing is the possibility of hosting microwave cavities and antennas to search for dark-matter axions in mass ranges that are complementary to those in previous searches.

    The growing IAXO collaboration has recently finished the conceptual design of the experiment, and last year a Letter of Intent was submitted to the SPS and PS Experiments Committee of CERN. The committee acknowledged the physics goals of IAXO and recommended proceeding with the next stage – the creation of the Technical Design Report. These are the first steps towards the realization of the most ambitious axion experiment so far.

    After more than three decades, the axion hypothesis remains one of the most compelling portals to new physics beyond the Standard Model, and must be considered seriously. IAXO will use CERN’s expertise efficiently to venture deep into unexplored axion parameter space. Complementing the successful high-energy frontier at the LHC, the IAXO facility would open a new window on the dark universe.

    See the full article here.

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  • richardmitnick 3:41 pm on August 18, 2014 Permalink | Reply
    Tags: , , , , , Dark Energy/Dark Matter   

    From Symmetry: “Dark Energy Survey kicks off second season” 

    Symmetry

    August 18, 2014
    No Writer Credit

    On August 15, with its successful first season behind it, the Dark Energy Survey collaboration began its second year of mapping the southern sky in unprecedented detail. Using the Dark Energy Camera, a 570-megapixel imaging device built by the collaboration and mounted on the Victor M. Blanco Telescope in Chile, the survey’s five-year mission is to unravel the fundamental mystery of dark energy and its impact on our universe.

    CTIO Victor M Blanco 4m Telescope
    Victor M Blanco 4m Telescope

    Dark Energy Camera
    Dark Energy Camera

    Along the way, the survey will take some of the most breathtaking pictures of the cosmos ever captured. The survey team has announced two ways the public can see the images from the first year.

    Today, the Dark Energy Survey relaunched its photo blog, Dark Energy Detectives. Once every two weeks during the survey’s second season, a new image or video will be posted to http://www.darkenergydetectives.org with an explanation provided by a scientist. During its first year, Dark Energy Detectives drew thousands of readers and followers, including more than 46,000 followers on its Tumblr site.

    Starting on September 1, the one-year anniversary of the start of the survey, the data collected by DES in its first season will become freely available to researchers worldwide. The data will be hosted by the National Optical Astronomy Observatory. The Blanco Telescope is hosted at the National Science Foundation’s Cerro Tololo Inter-American Observatory, the southern branch of NOAO.

    In addition, the hundreds of thousands of individual images of the sky taken during the first season are being analyzed by thousands of computers at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, Fermi National Accelerator Laboratory and Lawrence Berkeley National Laboratory. The processed data will also be released in coming months.

    Scientists on the survey will use these images to unravel the secrets of dark energy, the mysterious substance that makes up 70 percent of the mass and energy of the universe. Scientists have theorized that dark energy works in opposition to gravity and is responsible for the accelerating expansion of the universe.

    “The first season was a resounding success, and we’ve already captured reams of data that will improve our understanding of the cosmos,” says DES Director Josh Frieman of Fermilab and the University of Chicago. “We’re very excited to get the second season under way and continue to probe the mystery of dark energy.”

    While results on the survey’s probe of dark energy are still more than a year away, a number of scientific results have already been published based on data collected with the Dark Energy Camera.

    The first scientific paper based on Dark Energy Survey data was published in May by a team led by Ohio State University’s Peter Melchior. Using data that the survey team acquired while putting the Dark Energy Camera through its paces, they used a technique called gravitational lensing to determine the masses of clusters of galaxies.

    In June, Dark Energy Survey researchers from the University of Portsmouth and their colleagues discovered a rare superluminous supernova in a galaxy 7.8 billion light years away. A group of students from the University of Michigan discovered five new objects in the Kuiper Belt, a region in the outer reaches of our solar system, including one that takes over a thousand years to orbit the Sun.

    kuiper
    Kuiper Belt

    In February, Dark Energy Survey scientists used the camera to track a potentially hazardous asteroid that approached Earth. The data was used to show that the newly discovered Apollo-class asteroid 2014 BE63 would pose no risk.

    Several more results are expected in the coming months, says Gary Bernstein of the University of Pennsylvania, project scientist for the Dark Energy Survey.

    The Dark Energy Camera was built and tested at Fermilab. The camera can see light from more than 100,000 galaxies up to 8 billion light-years away in each crystal-clear digital snapshot.

    “The Dark Energy Camera has proven to be a tremendous tool, not only for the Dark Energy Survey, but also for other important observations conducted year-round,” says Tom Diehl of Fermilab, operations scientist for the Dark Energy Survey. “The data collected during the survey’s first year—and its next four—will greatly improve our understanding of the way our universe works.”

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.


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  • richardmitnick 4:30 pm on August 14, 2014 Permalink | Reply
    Tags: , , , , Dark Energy/Dark Matter,   

    From SPACE.com: ” Could Mystery Signal be First Detection of Dark Matter?” 

    space-dot-com logo

    SPACE.com

    August 14, 2014
    Ian O’Neill

    Through the analysis of light from distant galactic clusters, astronomers have detected a mysterious signal that they’re having a hard time explaining. Although the signal is weak, could it be the much sought-after direct evidence for dark matter?

    Dark matter pervades the entire universe and makes up for the bulk of its mass, but what is it? We know it’s out there and oodles of indirect evidence for its presence, but seeing a direct signal has so far proven elusive.

    When observing a galactic cluster, for example, we can gauge how much mass it contains by how much light is bent around the cluster. The greater the effect on passing light beams, the greater the space-time warping, the greater the cluster’s mass. When astronomers estimate the cluster’s mass, they tally up all the visible matter (i.e. stars), but the amount of visible mass comes way short of the cluster’s space-time-warping mass. There’s therefore mass locked up in “invisible” matter called, simply, “dark matter.”

    The bulk of dark matter is thought to be composed of non-baryonic matter. As opposed to baryonic matter — matter that we know and love like protons, neutrons and all the quarks in between — non-baryonic matter does not interact with electromagnetic radiation. In other words, we can’t directly see it. It does, however, interact gravitationally with normal matter, hence why we can see its gravitational effects on galactic clusters.

    But in a newly published study, astronomers analyzing X-ray radiation from distant galactic clusters have spotted a signal, with a specific energy, that doesn’t seem to be associated with any known element or chemical reaction.

    Galactic Clusters = Dark Matter Hunting Grounds

    Galaxies can become gravitationally bound, creating clusters of galaxies. Our Milky Way, for example, is one member of the aptly-named “Local Group” of galaxies, which also includes the neighboring heavyweight Andromeda. Though the Local Group contains around three dozen other galaxies, as far as galactic clusters go, it’s actually quite dinky. Many clusters contain thousands of galaxies that have immense gravitational dominance over their surroundings.

    Local Group
    Local Group

    ANALYSIS: Is Earth Surrounded by Dark Matter?

    It is therefore believed that these massive gravitational islands “pool” dark matter, causing the clusters to pack on the pounds, making them prime focal points for the search for direct evidence of dark matter.

    In these clusters, the space between the galaxies is not empty, it’s actually filled with hot gases that have accumulated from billions of years of supernova explosions. These gases generate X-rays that can be readily studied by space-based X-ray telescopes. The elements oxygen, neon, magnesium, silicon, sulfur, argon, calcium, iron, nickel, chromium and manganese have all been identified via their X-ray signals, but Harvard-Smithsonian Center for Astrophysics astronomers have found an X-ray signal detected by the European XMM-Newton space observatory that doesn’t fit in.

    ESA XMM Newton
    ESA/XMM-Newton

    Although more work is needed to tease the signal from the background noise, after analysis of 73 clusters, the same signal keeps appearing in observational data. A few of the clusters have also been studied by NASA’s Chandra X-ray observatory, which has also identified the signal at varying strengths. One explanation could be that they have detected the specific X-ray emission from the decay of the hypothesized “sterile neutrino” — a type of non-baryonic particle that could be a significant dark matter candidate.

    NASA Chandra Telescope
    NASA/Chandra

    The researchers urge caution over the detection of this X-ray signal — that is centered around an energy of 3.56 keV — however. Although the signal has been detected across a large sample of clusters and it appears to be real, its statistical significance is well below the threshold that can be considered to be a “discovery.” Better resolution of this emission line is required, something that may be attainable with the launch of the Japanese Astro-H X-ray observatory in 2015.

    The jury may still be out as to whether this mystery X-ray signal is indeed caused by the decay process of sterile neutrinos, but it’s exciting to think that we may be on the verge of finally uncovering a direct dark matter signal at last.

    See the full article here.

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  • richardmitnick 8:39 am on August 11, 2014 Permalink | Reply
    Tags: , , Dark Energy/Dark Matter,   

    From Brookhaven Lab: “Dark Interactions Workshop Brings Global Physicists to Brookhaven” 

    Brookhaven Lab

    August 11, 2014
    Chelsea Whyte

    people
    Nearly 80 physicists — representing experiments from laboratories including Thomas Jefferson National Accelrator Facility, the Large Hadron Collider, the Mainz Microtron, SLAC National Accelerator Laboratory, KEK, and universities involved in other dark particle detector experiments — attended the Dark Interactions Workshop at Brookhaven National Laboratory in June 2014.

    For three days in June, physicists from around the world came together at the U.S. Department of Energy’s Brookhaven National Laboratory for the inaugural physics workshop “Dark Interactions: Perspectives from Theory and Experiment,” chaired by Brookhaven physicist Ketevi Assamagan. He jointly organized the workshop with Brookhaven physicist Hooman Davoudiasl and Stony Brook University assistant professor of physics Rouven Essig.

    The goal of the workshop was to review and discuss the theoretical context as well as the status and future of the searches for dark sector particles, such as dark vector bosons, and the implications for dark matter.

    “We hope to continue this meeting in the years to come. We gain a lot by sharing ideas between theorists and experimentalists,” Assamagan said. Nearly 80 physicists attended the workshop to hear presentations that covered a range of topics on the frontier of new physics: the theories and experiments trying to track down dark matter, the mysterious substance that neither emits nor absorbs light, but is theorized to comprise nearly 27% of the cosmos.

    So far, despite the tremendous amount of evidence for the existence of dark matter, nobody knows its identity; but if anyone is going to devise a way to determine its makeup, it could be one of the physicists in attendance at the workshop. Over the course of several days, they discussed theoretical motivations for the search for dark matter, and several experiments already looking for the mystery matter, including:

    The DarkLight, HPS, and APEX experiments at Thomas Jefferson National Accelerator Facility;
    The CMS, ATLAS, ALICE and LHCb experiments at the Large Hadron Collider in Geneva, Switzerland;
    The A1 collaboration at the Mainz Microtron;
    Dark photon and low-mass Higgs searches at the BaBar detector at the SLAC National Accelerator Laboratory;
    The Belle Collaboration at KEK
    The PHENIX experiment at Brookhaven National Laboratory
    The Muon g-2 experiment [at Fermilab]
    The Axion Dark Matter Experiment at the University of Washington
    LHC experiments, namely ATLAS, CMS, ALICE and LHCb also contribute to the searches for Dark Matter. Ketevi Assamagan (BNL) and Oliver Keith Baker (Yale University) are working on some of the ATLAS analyses that may provide clues into the nature of Dark Matter.

    “It’s hard to believe dark matter is an idea that’s 80 years old,” said Professor David Brown of the University of Louisville. “Of course, we still don’t know what dark matter is. But colliders let us search for dark particles.”

    “Understanding the nature of dark matter poses one of the most urgent problems for our fundamental description of the Universe,” Davoudiasl said. “Interactive meetings, like DI2014, allow us to share various points of view on the scope of theoretical and experimental opportunities, as well as challenges, that lie ahead in the quest to uncover the properties of dark matter.”

    The attendees shared results from experiments all over the world, with tantalizing hints at the nature of dark matter. And as they continue this search, coordination across disciplines and national borders remains key to collaboration.

    “An enormous amount of progress has been made over the last few years in the search for dark matter and dark forces,” Essig said. “All of us hope that the current generation of experiments will be successful at finding new physics.”

    See the full article here.

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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