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  • richardmitnick 10:15 am on May 13, 2016 Permalink | Reply
    Tags: , Brane theory and testing, , physicsworld.com   

    From physicsworld: “Parallel-universe search focuses on neutrons” 

    physicsworld
    physicsworld.com

    May 10, 2016
    Edwin Cartlidge

    1
    No braner: there is no evidence that ILL neutrons venture into an adjacent universe. No image credit.

    The first results* from a detector designed to look for evidence of particles reaching us from a parallel universe have been unveiled by physicists in France and Belgium. Although they drew a blank, the researchers say that their experiment provides a simple, low-cost way of testing theories beyond the Standard Model of particle physics, and that the detector could be made significantly more sensitive in the future.

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

    A number of quantum theories of gravity predict the existence of dimensions beyond the three of space and one of time that we are familiar with. Those theories envisage our universe as a 4D surface or “brane” in a higher-dimensional space–time “bulk”, just as a 2D sheet of paper exists as a surface within our normal three spatial dimensions. The bulk could contain multiple branes separated from one another by a certain distance within the higher dimensions.

    Physicists have found no empirical evidence for the existence of other branes. However, in 2010, Michaël Sarrazin of the University of Namur in Belgium and Fabrice Petit of the Belgian Ceramic Research Centre put forward a model showing that particles normally trapped within one brane should occasionally be able to tunnel quantum mechanically into an adjacent brane. They said that neutrons should be more affected than charged particles because the tunnelling would be hindered by electromagnetic interactions.

    Nearest neighbour

    The researchers have now teamed up with physicists at the University of Grenoble in France and others at the University of Namur to put their model to the test. This involved setting up a helium-3 detector a few metres from the nuclear reactor at the Institut Laue-Langevin (ILL) in Grenoble and then recording how many neutrons it intercepted. The idea is that neutrons emitted by the reactor would exist in a quantum superposition of being in our brane and being in an adjacent brane (leaving aside the effect of more distant branes). The neutrons’ wavefunctions would then collapse into one or other of the two states when colliding with nuclei within the heavy-water moderator that surrounds the reactor core.

    Most neutrons would end up in our brane, but a small fraction would enter the adjacent one. Those neutrons, so the reasoning goes, would – unlike the neutrons in our brane – escape the reactor, because they would interact extremely weakly with the water and concrete shielding around it. However, because a tiny part of those neutrons’ wavefunction would still exist within our brane even after the initial collapse, they could return to our world by colliding with helium nuclei in the detector. In other words, there would be a small but finite chance that some neutrons emitted by the reactor would disappear into another universe before reappearing in our own – so registering events in the detector.

    Sarrazin says that the biggest challenge in carrying out the experiment was minimizing the considerable background flux of neutrons caused by leakage from neighbouring instruments within the reactor hall. He and his colleagues did this by enclosing the detector in a multilayer shield – a 20 cm-thick polyethylene box on the outside to convert fast neutrons into thermal ones and then a boron box on the inside to capture thermal neutrons. This shielding reduced the background by about a factor of a million.

    Stringent upper limit

    Operating their detector over five days in July last year, Sarrazin and colleagues recorded a small but still significant number of events. The fact that these events could be residual background means they do not constitute evidence for hidden neutrons, say the researchers. But they do allow for a new upper limit on the probability that a neutron enters a parallel universe when colliding with a nucleus – one in two billion, which is about 15,000 times more stringent than a limit the researchers had previously arrived at by studying stored ultra-cold neutrons. This new limit, they say, implies that the distance between branes must be more than 87 times the Planck length (about 1.6 × 10–35 m).

    To try and establish whether any of the residual events could indeed be due to hidden neutrons, Sarrazin and colleagues plan to carry out further, and longer, tests at ILL in about a year’s time. Sarrazin points out that because their model doesn’t predict the strength of inter-brane coupling, these tests cannot be used to completely rule out the existence of hidden branes. Conversely, he says, they could provide “clear evidence” in support of branes, which, he adds, could probably not be obtained using the LHC at CERN. “If the brane energy scale corresponds to the Planck energy scale, there is no hope to observe this kind of new physics in a collider,” he says.

    Axel Lindner of DESY, who carries out similar “shining-particles-through-a-wall” experiments (but using photons rather than neutrons), supports the latest research. He believes it is “very important” to probe such “crazy” ideas experimentally, given presently limited indications about what might supersede the Standard Model. “It would be highly desirable to clarify whether the detected neutron signals can really be attributed to background or whether there is something else behind it,” he says.

    The research is described in Physics Letters B.

    *Science paper:
    Search for passing-through-walls neutrons constrains hidden braneworlds

    See the full article here .

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    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.
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  • richardmitnick 12:24 pm on April 30, 2016 Permalink | Reply
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    From physicsworld.com: “Are wormholes or ‘gravastars’ mimicking gravitational-wave signals from black holes?” 

    physicsworld
    physicsworld.com

    Apr 29, 2016
    Tushna Commissariat

    1
    Into a wormhole: characteristic modes are light-ring potential wells. No image credit

    Earlier this year, researchers working on the Advanced Laser Interferometer Gravitational-wave Observatory (aLIGO) made the first ever detection of gravitational waves.

    Caltech/MIT Advanced aLigo detector in Livingston, Louisiana
    Caltech/MIT Advanced aLigo detector in Livingston, Louisiana

    The waves are believed to have been created by the merger of two binary black holes, in an event dubbed GW150914.

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

    Black holes merging Swinburne Astronomy Productions
    Black holes merging Swinburne Astronomy Productions

    Now, however, new theoretical work done by an international team of researchers suggests that other hypothetical exotic stellar objects – such as wormholes or “gravastars” – could produce a very similar gravitational-wave signal. While it is theoretically possible to differentiate between the different sources, it is impossible to tell whether GW150914 had a more exotic origin than merging black holes because the signal was not strong enough to be resolved.

    The researchers point out that, in the future, the detection of stronger gravitational-wave signals could reveal more information about their sources – especially once the sensitivity of aLIGO is increased to its ultimate design level. In addition, future space-based detectors, such as the European Space Agency’s Evolved Laser Interferometer Space Antenna (eLISA), could reveal tiny discrepancies between detected and predicted signals, if they exist.

    ESA/LISA Pathfinder
    ESA/LISA Pathfinder

    Ringing frequencies

    Einstein’s general theory of relativity provides a very clear theoretical framework for the type of gravitational-wave signal that would be produced during the collision and subsequent merger of massive, compact bodies, such as black holes. Gravitational waves are produced constantly before, during and just after a merger. The waves’ frequencies will vary, telling us when the black holes’ orbit begins to reduce and they begin their slow inward collapse, or “inspiral”. The smaller the initial distance between the two, the more radiation is emitted as the black holes plunge into one another. This produces a characteristic “chirp” waveform, wherein the frequency and the amplitude of the waves increase until they peak at the merger.

    But such a cataclysmic merger initially gives birth to a highly distorted black hole, which rids itself of its deformity almost instantly, by ringing like a bell and producing further gravitational radiation. The system quickly loses energy and the strength of the waves decays exponentially to form a “ringdown” signal, all of which was picked up by aLIGO for GW150914.

    2
    Ringing chirp: the waveform of event GW150914. No image credit.

    The chirp and the ringdown signal are of immense interest as these carry crucial information about the mass and spin of both the initial black holes, and of the newly formed one. “This ringdown phase is very important: just as a Stradivarius violin vibrates in a characteristic way, so too do black holes. Thus, by studying carefully how it rings, you hope to know the black hole itself,” says physicist Vitor Cardoso from the University of Lisbon, Portugal.

    These vibrational modes of a nascent black hole – known as quasinormal modes – must be detected within the signal, to be absolutely certain that the gravitational waves have arisen from coalescing black holes. Our current understanding suggests that these vibrational modes are inherently linked to a black hole’s key feature – its event horizon, or the boundary past which nothing, not even light, can escape from its gravitational pull.

    Light rings

    But new simulations and analysis – carried out by Cardoso together with team members Paolo Pani and Edgardo Franzin – have shown that a virtually indistinguishable ringdown signal can be produced by a “black-hole mimicker”, thereby potentially allowing us to detect these exotic objects. These mimickers are hypothetical objects that could be as compact as black holes but do not have an event horizon. They could be gravastars – celestial objects whose interior is made of dark energy – or wormholes – a tunnel through space–time connecting two distant regions of the universe.

    These exotic objects possess “light rings”, which are yet another artefact of general relativity – a circular photon orbit which is predicted to exist around very compact objects. “A light ring is very different from an event horizon, because signals can escape from regions within the light ring – although they would be highly red-shifted – whereas nothing can escape from the event horizon,” explains Cardoso. All compact objects would in theory possess a light ring. Indeed back holes have one that is associated with the border of their silhouette. These are the so-called “black-hole shadows” that lie just outside of their event horizon. On the other hand, neutron stars, while very compact, are not compact enough to develop a light ring.

    Cardoso and colleagues looked into objects with only light rings and found that “if an object is compact enough to possess a light ring, then the ringdown would be almost identical to that of a black hole. The more compact the object, the more similar the ringdown”. Indeed, the team’s simulations showed that the ringdown signal is mostly associated with the light ring. It is the light ring itself that is vibrating, not the event horizon.
    Mimicking wormholes

    The team’s simulations calculated this explicitly for a wormhole, but Pani told physicsworld.com that the “same result is valid for gravastars and, as we claim, for all ultracompact black-hole mimickers”. But the researchers’ analysis also showed that these mimickers eventually leave an imprint in the gravitational-wave signal in the form of “echoes”, which are reflections of the waves from the surface of these objects. “These echoes may take a long time to reach our detectors, so it is important to scrutinize the data even long after the main pulse has arrived,” says Cardoso. More precisely, the mimicker signal will ultimately deviate from that predicted for a black hole, but only at late times.

    LIGO scientist Amber Stuver, who is based at the LIGO Livingston Observatory in Louisiana, US, is “thrilled” by the possibility that aLIGO may have detected an exotic object, but she confirms that “there is nothing in our observations that is inconsistent with this being a normal stellar mass black-hole system possessing an event horizon. Until we have evidence otherwise, we can’t claim that this was anything but a stellar mass black hole binary merger.” She tells physicsworld.com that “advanced detectors such as aLIGO, aVirgo, and KAGRA will need to increase their sensitivity” to pick up such signals. She also points out that the GW150914 event “was detected with aLIGO at about 30% of its design sensitivity. The potential is real that, if these exotic horizonless objects are out there mimicking black holes, we may very well find them in the near future”.

    B S Sathyaprakash from Cardiff University in the UK, who is also a part of the LIGO team, agrees with the theorists’ work, saying that “Our signal is consistent with both the formation of a black hole and a horizonless object – we just can’t tell.” He further explains that, although Einstein’s equations predict how slightly deformed black holes vibrate, our understanding is incomplete when their deformation is large. “That’s why we need a signal in which the post-merger oscillations of the merged object are large, and this can happen if we detect even more massive objects than GW150914, or if GW150914 is at least two to four times closer.” Then, it would be possible to distinguish the signals, he says.

    Cardoso acknowledges that “black-hole mimickers are very exotic objects and by far black holes remain the most natural hypothesis”. But he adds: “It is important to understand whether these exotic objects can be formed (for example in a stellar collapse) and if they are stable. Most importantly, we only focused on the ringdown part, but it is equally relevant to explain the entire gravitational-wave signal, including the inspiral and the merger phases. This would require performing numerical simulations with supercomputers to understand whether this picture is viable or not. We are currently working on this.”

    The research* is published in Physical Review Letters.

    *Science paper:
    Is the Gravitational-Wave Ringdown a Probe of the Event Horizon?

    See the full article here .

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    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.
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  • richardmitnick 12:14 pm on March 11, 2016 Permalink | Reply
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    From physicsworld.com: “Einstein meets the dark sector in a new numerical code that simulates the universe” 

    physicsworld
    physicsworld.com

    Mar 10, 2016
    Keith Cooper

    A powerful numerical code that uses [Albert] Einstein’s general theory of relativity to describe how large-scale structures form in the universe has been created by physicists in Switzerland and South Africa. The program promises to help researchers to better incorporate dark matter and dark energy into huge computer simulations of how the universe has evolved over time.

    At the largest length scales, the dynamics of the universe are dominated by gravity. The force binds galaxies together into giant clusters and, in turn, holds these clusters tight within the grasp of immense haloes of dark matter. The cold dark matter (CDM) model assumes that dark matter comprises slow-moving particles. This means that non-relativistic Newtonian physics should be sufficient to describe the effects of gravity on the assembly of large-scale structure in the universe.

    Universe map  2MASS Extended Source Catalog XSC
    Universe map 2MASS Extended Source Catalog XSC

    However, if dark matter moves at speeds approaching that of light, the Newtonian description breaks down and Einstein’s general theory of relativity must be incorporated into the simulation – something that has proven difficult to do.

    Upcoming galaxy surveys, such as those to be performed by the Large Synoptic Survey Telescope in Chile or the European Space Agency’s Euclid mission, will observe the universe on a wider scale and to a higher level of precision than ever before.

    LSST Camera
    LSST Interior
    LSST Exterior
    The LSST, camera built at SLAC, and the building in Chile which will house the telescope

    ESA Euclid spacecraft
    ESA/Euclid spacecraft

    Computer simulations based on Newtonian assumptions may not be able to reproduce this level of precision, making observational results difficult to interpret. More importantly, we don’t know enough about what dark matter and dark energy are, to be able to conclusively say which treatment of gravity is most appropriate for them.

    Evolving geometry

    Now, Julian Adamek of the Observatoire de Paris and colleagues have developed a numerical code called “gevolution”, which provides a framework for introducing the effects of general relativity into complex simulations of the cosmos. “We wanted to provide a tool that describes the evolution of the geometry of space–time,” Adamek told physicsworld.com.

    General relativity describes gravity as the warp created in space–time by the mass of an object. This gives the cosmos a complex geometry, rather than the linear space described by Newtonian gravity. The gevolution code is able to compute the Friedmann–Lemaítre–Robertson–Walker metric that solves Einstein’s field equations to describe [spacetime’s] complex geometry and how particles move through that geometry. The downside is that it sucks up a lot of resources: 115,000 central-processing-unit (CPU) hours compared to 25,000 CPU hours for a similarly sized Newtonian simulation.

    Other uncertainties

    Not everyone is convinced that the code is urgently required, and Joachim Harnois-Déraps of the Institute for Astronomy at the Royal Observatory in Edinburgh points out that there are other challenges facing physicists running cosmological simulations. “There are many places where things could go wrong in simulations.”

    Harnois-Déraps cites inaccuracies in modelling the nonlinear clustering of matter in the universe, as well as feedback from supermassive black holes in active galaxies blowing matter out from galaxies and redistributing it. A recent study led by Markus Haider of the University of Innsbruck in Austria, for example, showed that jets from black holes could be sufficient to blow gas all the way into the voids within the cosmic web of matter that spans the universe.

    “Central and shining”

    “In my opinion, the bulk of our effort should instead go into improving our knowledge about these dominant sources of uncertainty,” says Harnois-Déraps who, despite his scepticism, hails gevolution as a great achievement in coding. “If suddenly a scenario arises where general relativity is needed, the gevolution numerical code would be central and shining.”

    Indeed, Adamek views the gevolution code as a tool, ready and waiting should it be required. Newtonian physics works surprisingly well for the current standard model of cold dark matter and dark energy as the cosmological constant. However, should dark matter prove to have relativistic properties, or if dark energy is a dynamic, changing field rather than a constant, then Newtonian approximations will have to make way for the more precise predictions of general relativity.

    “The Newtonian approach works well in some cases,” says Adamek, “But there might be other situations where we’re better off using the correct gravitational field.”

    The research is described in Nature Physics.

    See the full article here .

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    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.
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  • richardmitnick 8:58 pm on February 19, 2016 Permalink | Reply
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    From physicsworld.com: “How LIGO will change our view of the universe” 

    physicsworld
    physicsworld.com

    Feb 19, 2016
    Tushna Commissariat

    Gravitational waves
    Gravitational waves, Werner Benger, Zuse-Institut Berlin and Max-Planck-Institut für Gravitationsphysik

    Results and data from the Advanced Laser Interferometer Gravitational-wave Observatory (aLIGO) collaboration – which revealed last week that it had observed a gravitational wave for the first time – are already providing astronomers and cosmologists the world over with previously unknown information about our universe. While the current results have posed intriguing questions for astronomers regarding binary black-hole systems, gravitational-wave astronomy will also revolutionize our understanding of the universe during its infancy, according to cosmologist and Perimeter Institute director Neil Turok.

    Many scientists, such as LIGO veteran Kip Thorne, have pointed out that the collaboration’s results have opened a new window onto the universe. Each time that this has happened in the past, unexpected phenomena have come to light – for example, the advent of radio astronomy revealed the universe’s most luminous objects in the form of quasars and pulsars.

    NRAO VLA
    NRAO/ Very Large Array

    Pristine objects

    Turok told physicsworld.com that black holes – some of the most prolific producers of these ripples – are some of the simplest objects in the universe. He points out that when it comes to these “perfectly pristine objects”, there are “not too many parameters that need to be determined” because a black hole’s dynamics are mainly determined by its mass. Turok also points out that gravitational waves will provide even deeper insights, as they involve the fundamental force of gravity, which itself is still something of a puzzle.

    Indeed, for Turok, this is what is most exciting about aLIGO’s discovery, which he says “may mark a bit of a transition as gravitational-wave observatories become the high-energy colliders of the future as we probe gravity and other extremely basic physics”. Gravitational waves can go to a time/place that, currently, we have very little information about – the early universe, which is opaque to all electromagnetic radiation.

    Looking back in time

    Thankfully, gravitational waves can travel freely through the hot plasma of the early universe and could be used “to look back to a trillionth of a second after the Big Bang”, according to Turok. For him, the discovery is very timely, as he is currently working with colleagues on a new theoretical proposal for “shockwaves” produced a millionth of a second after the Big Bang, which would have been present across all scales in the early universe. If these shockwaves exist, they would have an effect on the measured density variation that is seen in the cosmic microwave background, and could only be detected by gravitational radiation. Once they have a more complete theoretical description, Turok is convinced that LIGO and its successors such as the LISA Pathfinder and other space-based experiments could pick up the shockwave signal, if it exists.

    ESA LISA Pathfinder
    ESA\LISA Pathfinder

    Ultimately, Turok is delighted by LIGO’s discovery, and although he says that it is “much more important than any prize”, he is sure that it will win not only a Nobel prize, but also a slew of others, such as the Breakthrough prize.

    A preprint of Turok’s paper on shockwaves is available on the arXiv server.

    See the full article here .

    Please help promote STEM in your local schools.

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    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.
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  • richardmitnick 9:38 pm on December 29, 2015 Permalink | Reply
    Tags: , , , physicsworld.com, The world of physics in 2016   

    From physicsworld.com: “The world of physics in 2016” 

    physicsworld
    physicsworld.com

    Dec 17, 2015
    Matin Durrani

    As another year draws to a close, it’s time for me to peer into my crystal ball and predict the key events in physics that could take place in 2016. I always find it simpler and easier to say what’s coming up in “big science” – dominated as it is by massive projects in particle physics, astronomy and cosmology that are planned years in advance. And next year is no exception.

    1
    Fresh direction: CERN’s new boss Fabiola Gianotti

    So let’s start at CERN, where physicists at the Large Hadron Collider (LHC) will spend 2016 continuing to smash protons together at an energy of 13 TeV as part of “Run II”, which began last year.

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

    Fabiola Gianotti, who takes the reins from Rolf-Dieter Heuer next month as CERN’s 15th director-general, will be keen to ensure the lab gathers as many top-quality data as possible, even if the LHC’s unlikely to reach its planned collision energy of 14 TeV or get “new physics” beyond the Standard Model in 2016.

    7
    Rolf-Dieter Heuer

    8
    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    Indeed, a presentation at CERN just before Christmas of the first Run II data from the ATLAS and CMS experiments already appears to limit the possibility of “supersymmetric” particles to yet higher energies.

    CERN ATLAS New
    CERN ATLAS Higgs Event
    ATLAS and a Higgs event in ATLAS.

    CERN CMS Detector
    CERN CMS Event
    CMS and a Higgs event in CMS

    Supersymmetry standard model
    Standard Model of Supersymmetry

    Up in space, NASA’s Juno mission is set to enter the orbit of Jupiter on 4 July, handily timed for a watching US public. After a five-year journey, Juno will be the first craft to visit Jupiter since Galileo in 1995.

    NASA Juno
    NASA/Juno

    NASA Galileo
    NASA/Galileo 1

    The Japanese Space Agency (JAXA) is set for a busy year, too. Its Akatsuki spacecraft entered orbit around Venus last month, and mission scientists expect to receive its first data in April.

    JAXA AKATSUKI
    JAXA/AKATSUKI

    JAXA also plans to launch the ASTRO-H X-ray telescope into low Earth orbit this year, to study everything from the large-scale structure of the universe,

    2MASS LSS chart-NEW Nasa
    2MASS LSS chart large-scale structure of the universe

    to the distribution of dark matter in galaxy clusters.

    Meanwhile, the European Space Agency will release the first data early next year from its Gaia mission, which seeks to create a 3D catalogue of about a billion astronomical objects.

    ESA Gaia satellite
    ESA/Gaia

    March will see the European Space Agency’s Lisa Pathfinder craft begin work to test the technology for a future space-based gravitational-wave observatory.

    ESA LISA Pathfinder
    ESA/Pathfinder 1

    Another tantalizing prospect for 2016 will be the Event Horizon Telescope imaging a black hole for the first time.

    Event Horizon Telescope map
    Event Horizon Telescope
    Event Horizon telescope and map

    Astroparticle physicists, meanwhile, are set to start work in 2016 on a $14m upgrade to the Pierre Auger Observatory – the world’s largest cosmic-ray observatory – in Argentina.

    Pierre Augur Observatory
    Pierre Auger Observatory

    The AugerPrime upgrade will involve installing scintillation detectors alongside the 1660 existing water Cherenkov detectors, allowing researchers to more efficiently separate the electrons and muons that are created in the cascade of secondary particles created when a comic ray hits the Earth’s atmosphere. This, in turn, should make it easier to identify cosmic rays that are high-energy protons.

    Ups and downs

    All is not entirely rosy in astronomy, though. Hawaii’s Supreme court recently ruled that the construction permit for the $1.4bn Thirty Meter Telescope (TMT) on top of Mauna Kea mountain is invalid.

    TMT
    The more than proposed TMT

    The ruling will force the telescope’s backers to restart the entire permit process, delaying the project and adding further uncertainty. Construction of the TMT has already been on hold since last April following protests by native Hawaiians, who see its construction on Mauna Kea as desecration of their spiritual and cultural pinnacle.

    In nuclear physics, the ITER tokomak fusion reactor, which is being built in Cadarache in southern France, faces another turbulent year.

    ITER Tokamak
    ITER tokamak

    After last November’s ITER council meeting, rumours surfaced that the project’s completion could slip by six years, from 2019 to 2025. The council will now carry out its own review to see if there is scope for tightening the timeline and cutting costs, with a new plan, or “baseline”, due out in June. On a related note, the Wendelstein 7-X stellerator in Greifswald, Germany, which switched on last week, is set to be put through its paces next year as researchers test this type of fusion device.

    Wendelstein 7-AS
    Wendelstein 7-X stellerator

    Quantum frontiers

    Predicting what will happen across the rest of physics and in physics-based industry is harder, where progress is vital but fragmented across myriad groups, sectors and businesses. My tip is seeing “Li-Fi” – a light-based alternative to radio-frequency Wi-Fi – gaining commercial traction. Work on graphene and other 2D materials will continue, with the focus on layering a few 2D materials to make novel “designer” heterostructures using, say, graphene layers as electrodes and boron nitride as insulators.

    6
    Graphene. The ideal crystalline structure of graphene is a hexagonal grid.

    Applications of physics are crucial, and it is thanks to them – and through the advocacy of organizations like the Institute of Physics (IOP), which publishes Physics World – that science funding in the UK survived cuts in the country’s recent Comprehensive Spending Review. There will be further positive developments for UK science in 2016, with the opening of the massive new £650m Francis Crick Institute in London. Named after the co-discoverer of the structure of DNA, the institute will be the country’s flagship biomedical-science lab, with as many as a fifth of the 1250 staff being physicists, chemists, mathematicians and engineers. Remember that biosciences and the environment dominate Altmetric’s list of the top 100 most popular scientific papers of 2015, as judged by how much they were shared and discussed in mainstream and social media.

    7
    Future tech: quantum physics will continue to throw up surprises

    The beauty of physics, however, is that even the most esoteric research can unleash unforeseen benefits – as the winners of the Physics World 2015 Breakthrough of the Year will concur. We picked Jian-Wei Pan and Chaoyang Lu of the University of Science and Technology of China in Hefei, for being the first to achieve the simultaneous quantum teleportation of two inherent properties of a fundamental particle – the photon. The researchers are already talking about applications, such as “long-distance quantum communications that provide unbreakable security, ultrafast quantum computers and quantum networks”. We can also look forward to further developments in 2016 from the UK’s ambitious £270m National Quantum Technologies Programme, which seeks to stimulate applications of quantum physics.

    Speaking of which, surely 2016 will be the year when Anton Zeilinger – the doyen of quantum communication, computation and information – will finally win a long-overdue Nobel Prize for Physics? I’ve backed the Austrian quantum guru for Nobel glory for a long time, and 2016 has to be his year, possibly with Alain Aspect and John Clauser for their Bell’s inequality experiments. The Nobel Committee for Physics take note.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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

     
  • richardmitnick 11:27 am on November 17, 2015 Permalink | Reply
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    From physicsworld.com: “Astronomers gaze upon the oldest stars in the galaxy” 

    physicsworld
    physicsworld.com

    Nov 13, 2015
    Tushna Commissariat

    Temp 1
    Dark heart: the dusty heart of the Milky Way galaxy

    The oldest stars in our Milky Way galaxy have been discovered by an international team of researchers. These ancient stars could contain vital clues about how the first stars in the early universe died, and their discovery marks the first time that extremely metal-poor stars have been observed in the central region of the galaxy. The location of the stars suggests that they formed when the Milky Way underwent rapid chemical changes during the first 1–2 billion years of the universe.

    After the Big Bang, only elements such as hydrogen, helium and some trace amounts of lithium existed in the universe. Heavier elements such as oxygen, nitrogen, carbon and iron – referred to as “metals” by astronomers – were forged in the extremely high-pressure centres of the first massive stars, which are predicted to have formed within 200 million years after the Big Bang. The metals were scattered across the cosmos when these first stars, known as “population III” stars, quickly burned out and exploded in supernovae. These explosions seeded the universe with the metals to form “population II” stars, which are still “metal-poor” compared with “population I” stars like the Sun.

    Not the stars we are looking for?

    A true first population-III star has not yet been discovered, although the best evidence for them was found earlier this year in an extremely bright and distant galaxy in the early universe. Astronomers believe that old metal-poor stars would have formed in the central regions or the “bulges” of galaxies, where the effects of gravity were the strongest. The Milky Way bulge underwent a rapid chemical enrichment in the early universe, and this should have created a host of metal-poor stars – indeed, we should find them there even today. However, metal-poor stars have only been found in the outer regions or the “halo” of the Milky Way and not at its centre.

    Now, Louise Howes of the Australian National University in Canberra and an international team have used the SkyMapper telescope to identify nearly 500 extremely metal-poor stars in the Milky Way bulge.

    ANU Skymapper telescope
    ANU Skymapper telescope interior
    SkyMapper telescope

    The team also confirmed that most of these old stars are in tight orbits around the galactic centre, rather than being halo stars passing through the bulge. The researchers also found that the chemical compositions of these stars are, for the most part, similar to typical halo stars of the same metal content (or metallicity). However, some unexpected differences exist when it comes to the amount of carbon in such stars.

    Stars with a low metal content look slightly bluer than others, so the team could sift through the millions of stars at the centre and whittle the observations down to 14,000 promising candidates. From those, the researchers identified 500 stars that had less than 100th the amount of iron in the Sun, making it the first extensive catalogue of metal-poor stars in the bulge. Of these, Howse and colleagues focused on 23 candidates that were the most metal-poor, and from these data, they homed in on nine stars with a metal content less than 1000th of the amount seen in the Sun. This includes one star with an iron abundance 10,000 times lower than that of the Sun – now the record-breaker for the most metal-poor star in the centre of the galaxy.

    To and fro

    To ensure that these stars were truly old – and not those that had formed much later in other parts of the galaxy that were not as dense and are now merely passing through the centre – the researchers used precise measurements and computer simulations to plot the stars’ movement in the sky. This allowed them to predict where the stars came from and where they were moving to. The team found that while some stars were indeed just passing through, seven of them were formed in the bulge and had remained there since.

    “These pristine stars are among the oldest surviving stars in the universe, and certainly the oldest stars we have ever seen,” says Howes. “These stars formed before the Milky Way, and the galaxy formed around them.” While it is currently not possible to directly determine the ages of these ancient stars, the researchers say that it could be inferred from data collected by the extended Kepler mission or its successors.

    The team’s discovery also challenges current theories about the environment of the early universe from which these stars formed. “The stars have surprisingly low levels of carbon, iron and other heavy elements, which suggests the first stars might not have exploded as normal supernovae,” says Howes. “Perhaps they ended their lives as hypernovae – poorly understood explosions of probably rapidly rotating stars, producing 10 times as much energy as normal supernovae.” If true, such hypernovae would be one of the most energetic things in the universe, and very different from the kinds of stellar explosions that we see today.

    The research is published in Nature.

    See the full article here .

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  • richardmitnick 11:40 am on November 12, 2015 Permalink | Reply
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    From physicsworld.com: “Gran Sasso steps up the hunt for missing particles” 

    physicsworld
    physicsworld.com

    Nov 11, 2015
    Edwin Cartlidge

    XENON1T
    XENON1T

    Physicists working at the Gran Sasso National Laboratory in central Italy, located 1400 m under the mountain of the same name, are soon to start taking data from two new experiments.

    INFN Gran Sasso ICARUS
    Gran Sasso

    Each facility will target a different kind of missing matter: one will search for dark matter while the other will try and detect absent neutrinos to prove that neutrinos are their own antiparticle.

    Dark flash

    The hunt for dark matter – the mysterious substance believed to make up about 80% of all matter in the universe but not yet detected directly – will be carried out using XENON1T. This experiment, which was inaugurated at an event at Gran Sasso today, consists of 3.5 tonnes of liquid xenon. It is designed to measure very faint flashes of light that are given off whenever particles from the dark matter halo of the Milky Way collide with the xenon nuclei. The xenon will be stored at a temperature of about –100 °C in a cryostat and surrounded by a tank containing some 700 tonnes of purified water to minimize background radioactivity.

    Run by an international collaboration of 120 students and scientists from more than 2 institutions, XENON1T is expected to be about 100 times more sensitive than its 160 kg predecessor experiment and around 40 times better than the world’s current leading dark-matter detector – the 370 kg Large Underground Xenon experiment in South Dakota, US.

    LUX Dark matter
    LUX

    Due to start taking data by the end of March next year, XENON1T will either detect dark matter or place severe constraints on the properties of theoretically-favoured weakly interacting massive particles (WIMPs), says collaboration spokesperson Elena Aprile of Columbia University in New York.

    Dark heart

    The other new experiment at Gran Sasso is the Cryogenic Underground Observatory for Rare Events (CUORE), which will look for an extremely rare nuclear process known as neutrinoless double beta decay.

    CUORE experiment
    CUORE

    That decay, if it exists, would involve two neutrons in certain nuclei decaying simultaneously into two protons while emitting two electrons but no antineutrinos (unlike normal beta decay), implying that the neutrino is its own antiparticle. Due to turn on early next year, CUORE will measure the energy spectrum of electrons emitted by 741 kg of tellurium dioxide surrounded by radioactively inert lead blocks recovered from a Roman ship that sank 2000 years ago.

    Meanwhile, towards the end of 2016 another group of scientists at Gran Sasso should take delivery of about a kilogram of cerium oxide powder, which they will place several metres below the Borexino neutrino detector.

    Borexino Solar Neutrino detector
    Borexino

    The Short Distance Neutrino Oscillations with BoreXino (SOX) experiment will look for a sinusoidal-like variation in the number of interactions generated within the detector by neutrinos from the radioactive cerium. SOX leader Marco Pallavicini of the University of Genoa says that such a variation would be a sure sign of “sterile” neutrinos – hypothetical particles outside the Standard Model of particle physics that would “oscillate” into ordinary neutrinos but would not interact with any other kind of matter.

    See the full article here .

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    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.
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  • richardmitnick 8:40 am on September 26, 2015 Permalink | Reply
    Tags: , physicsworld.com, Underground laboratories   

    From physicsworld: “Why do physicists do experiments deep underground?” 

    physicsworld
    physicsworld.com

    Sep 23, 2015

    To those who crave natural daylight, the idea of spending large chunks of time deep underground may seem like hell. But to particle physicists, this subterranean lifestyle is a price worth paying for the excellent radiation shielding provided by the overlying rock.

    Art McDonald, who was a long-standing director of the Sudbury Neutrino Observatory (SNO), explains how these underground science labs are designed to detect the interesting particles that can make it through the layers of overlying rock.

    Sudbury Neutrino Observatory

    An example is the neutrinos produced in the core of the Sun, whose properties can help to verify solar dynamics models. “We also make the surrounding areas really clean, avoiding the radioactivity contained in any mine dust that would potentially get into our experiments,” McDonald adds.

    SNO has now expanded into SNOLAB, which covers a more diverse range of research. This includes the search for dark-matter particles and the hunt for a rare form of decay called neutrinoless double beta decay – a process that could help explain why the universe has significantly more matter than antimatter.

    To find out more about subterranean physics, check out this feature article from the May 2015 issue of Physics World that looks at how deep underground laboratories of the world are no longer the scientific realm of astroparticle physics alone.

    Access the video explaining Why Physicists Do Experiments Deep Underground in the full article.

    See the full article here .

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    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.
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  • richardmitnick 10:25 am on April 8, 2015 Permalink | Reply
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    From physicsworld.com: “Mysterious baryon resonance is a subatomic molecule, say physicists” 

    physicsworld
    physicsworld.com

    Apr 7, 2015
    Hamish Johnston

    1
    Does Λ(1405) comprise an anti-kaon and a nucleon?

    Physicists in Australia have produced further evidence that an excited state of the lambda baryon is a “subatomic molecule” – a meson and a nucleon that are bound together. While the physicists are not the first to suggest this exotic structure, they have done new computer simulations and calculations that they say “strongly suggest” that the lambda baryon can exist in this exotic configuration.

    The lambda baryon (Λ) has no electrical charge and comprises three quarks (up, down and strange). Its discovery in 1950 by physicists at the University of Melbourne played an important role in the development of the quark model of matter and ultimately quantum chromodynamics (QCD), which is the theory of the strong interaction that binds quarks together in baryons and mesons.

    Λ is a composite particle, and therefore it exists in a number of different energy states, much like an atom. Λ is the lowest-energy state and Λ(1405), which was discovered in 1961, is the lowest-lying excited state or resonance. As physicists developed the quark model in the 1960s, it became apparent that there was something not quite right about Λ(1405). In particular, the energy difference between Λ and Λ(1405) is much lower than expected, if Λ(1405) is assumed to be a “single particle” containing just three quarks.

    Growing evidence

    In the 1960s the Australian physicist Richard Dalitz and colleagues suggested that that Λ(1405) could comprise an anti-kaon meson bound to a nucleon (proton or neutron). This can occur in two ways: a negatively charged anti-kaon bound to a proton, or a neutral anti-kaon bound to a neutron. Working out the structure of Λ(1405) – or any baryon resonance for that matter – is extremely difficult because of the nonlinear nature of the strong interaction. However, over the past two decades theoretical support for molecular Λ(1405) has grown, with calculations done by several groups of physicists backing up the idea.

    Now, Ross Young and colleagues at the University of Adelaide and the Australian National University have used lattice QCD to gain further insights into the nature of Λ(1405). The team used a lattice QCD simulation that was first developed by the Japan-based PACS-CS collaboration. The most important result of the team’s calculation is that the strange quark appears to make no contribution to the magnetic moment of Λ(1405). This is expected if the strange quark is confined within an anti-kaon with zero spin and is consistent with a molecular model of Λ(1405).

    Energy levels

    The team also analysed the energy levels calculated by lattice QCD and concluded that the Λ(1405) resonance is dominated by the anti-kaon nucleon molecule with a much smaller contribution from the single-particle three-quark state (up, down, strange).

    José Antonio Oller of the University of Murcia in Spain calls the calculation of the strange quark’s magnetic contribution a “remarkable result”. However, he points out that while this zero magnetic contribution is a necessary condition for molecular Λ(1405), it is not sufficient to confirm the molecular nature of the resonance. He added that further calculations of the properties of Λ(1405) using other techniques are needed before the issue can be settled.

    The calculations are described in Physical Review Letters.

    See the full article here.

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  • richardmitnick 4:56 pm on November 28, 2014 Permalink | Reply
    Tags: , , , physicsworld.com   

    From physicsworld.com: “Medical-isotope breakthrough made at Canadian lab” 

    physicsworld
    physicsworld.com

    Nov 28, 2014
    Andrew Williams

    The first commercial shipment of medical isotopes produced using a new particle-accelerator-based technique has been made by scientists at the Canadian Light Source (CLS). Molybdenum-99 (Mo-99) decays to create technetium-99m (Tc-99m), which is used to tag radiopharmaceuticals and plays a unique and vital role in medical imaging. Unlike nuclear reactors, which currently make most of the world’s Mo-99, the system is small enough to be deployed within a large hospital and could thereby improve the supply of the short-lived isotopes.

    Canadian Light Source
    cls
    Canadian Light Source

    The material is made at the Medical Isotope Project (MIP) facility at the CLS, which is located at the University of Saskatchewan in Saskatoon. According to Mark de Jong, director of accelerators at the CLS, the facility is the first of its kind anywhere in the world, and uses a small high-power industrial electron linear accelerator to produce a flux of high-energy X-rays through bremsstrahlung radiation. The X-rays strike a target made of enriched Mo-100, in the process “knocking out” a neutron from the nuclei of some of the target atoms to produce Mo-99.

    m
    Isotope maker: Mark de Jong at MIP

    No fission required

    “The main advantage of this method is the complete avoidance of any use of uranium or fission, with all the problems that arise from both volatile short-lived isotopes, as well as disposing of the long-lived radioactive waste,” says De Jong.

    After several days of irradiation at the CLS facility, the target is shipped 800 km to the Winnipeg Health Sciences Centre’s Radio-Pharmacy Department, where it is dissolved and the Tc-99m is extracted. Transport across long distances is possible because Mo-100 has a half-life of 66 hours, but significant losses do occur. The half-life of Tc-99m is just 6 hours, so it must be produced as near as possible to where it will be used.

    De Jong says that future implementations will not necessarily require such long-distance shipping. “The electron linear accelerator is small enough to be located close to where the Mo-99 is required, possibly even within major hospitals, reducing the losses caused by decay in shipping Mo-99. In the present fission-based production, more than 80% of the Mo-99 produced has decayed before it reaches the hospitals,” he adds.

    Reactor shutdowns

    The MIP was created in the wake of serious Mo-99 shortages in 2007 and 2009, which were both related to two unscheduled shutdowns of the ageing NRU nuclear reactor at Atomic Energy of Canada’s Chalk River Laboratories. NRU provides most of Mo-99 for North America, and isotope production is an important industry in Canada. In 2010, fearful of damage to the industry, the Canadian government launched a call under its Non-nuclear-reactor-based Isotope Supply Program (NISP) to encourage alternative isotope production using either photo-neutron production of Mo-99, or direct production of Tc-99m using proton cyclotrons. The CLS proposal was one of two photo-neutron production projects funded, the other being run by Winnipeg-based Prairie Isotope Production Enterprise (PIPE).

    “Once the work to approve the processes involved – Mo-99 production, target dissolution and Tc-99m extraction – is completed by Health Canada, the facility should produce enough for the hospitals serving a population of more than two million people. The health approvals are the next phase that we are working on with our colleagues at PIPE. We hope to have the New Drug Application (NDA) submitted to the authorities by the end of 2015, with routine clinical use possible by the end of 2016,” says De Jong.
    Other options

    In 2012 scientists at the Vancouver-based TRIUMF national laboratory for particle and nuclear physics pioneered two methods for producing Tc-99m using Mo-100 targets and medical cyclotron-based accelerator technology. Cyclotrons are particle accelerators that rely on electricity and magnets to create isotopes by accelerating ions and bombarding non-radioactive materials.

    “Our process is suitable for large population bases, using medical cyclotrons already installed and operational in our major hospitals throughout the country. We have demonstrated that cyclotrons in Vancouver, London and Hamilton have sufficient capacity to supply their respective hospital catchments with Tc-99m,” says TRIUMF’s Melissa Baluk.

    See the full article here.

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    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.
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