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  • richardmitnick 3:10 pm on April 28, 2015 Permalink | Reply
    Tags: , , Cosmic Rays,   

    From Symmetry: “AMS results create cosmic ray puzzle” 

    Symmetry

    April 15, 2015
    Sarah Charley

    1
    Courtesy of NASA

    New results from the Alpha Magnetic Spectrometer experiment defy our current understanding of cosmic rays.

    New results from the Alpha Magnetic Spectrometer experiment disagree with current models that describe the origin and movement of the high-energy particles called cosmic rays.

    These deviations from the predictions might be caused by dark matter, a form of matter that neither emits nor absorbs light. But, according to Mike Capell, a senior researcher at the Massachusetts Institute of Technology working on the AMS experiment, it’s too soon to tell.

    “It’s a real head scratcher,” Capell says. “We cannot say we are seeing dark matter, but we are seeing results that cannot be explained by the conventional wisdom about where cosmic rays come from and how they get here. All we can say right now is that our results are consistently confusing.”

    The AMS experiment is located on the International Space Station and consists of several layers of sensitive detectors that record the type, energy, momentum and charge of cosmic rays. One of AMS’s scientific goals is to search for signs of dark matter.

    Dark matter is almost completely invisible—except for the gravitational pull it exerts on galaxies scattered throughout the visible universe. Scientists suspect that dark matter is about five times as prevalent as regular matter, but so far have observed it only indirectly.

    If dark matter particles collide with one another, they could produce offspring such as protons, electrons, antiprotons and positrons. These new particles would look and act like the cosmic rays that AMS usually detects, but they would appear at higher energies and with different relative abundances than the standard cosmological models forecast.

    “The conventional models predict that at higher energies, the amount of antimatter cosmic rays will decrease faster than the amount of matter cosmic rays,” Capell says. “But because dark matter is its own antiparticle, when two dark matter particles collide, they are just as likely to produce matter particles as they are to produce antimatter particles, so we would see an excess of antiparticles.”

    This new result compares the ratio of antiprotons to protons across a wide energy range and finds that this proportion does not drop down at higher energies as predicted, but stays almost constant. The scientists also found that the momentum-to-charge ratio for protons and helium nuclei is higher than predicted at greater energies.

    “These new results are very exciting,” says CERN theorist John Ellis. “They’re much more precise than previous data and they are really going to enable us to pin down our models of antiproton and proton production in the cosmos.”

    In 2013 and 2014 AMS found a similar result for the proportion of positrons to electrons—with a steep climb in the relative abundance of positrons at about 8 billion electronvolts followed by the possible start of a slow decline around 275 billion electronvolts. Those results could be explained by pulsars spitting out more positrons than expected or accelerating supernovae remnants, Capell says.

    “But antiprotons are so much heavier than positrons and electrons that they can’t be generated in pulsars,” he says. “Likewise, supernova remnants would not propagate antiprotons in the way we are observing.”

    If this antimatter excess is the result of colliding dark matter particles, physicists should see a definitive bump in the relative abundance of antimatter particles with a particular energy followed by a decline back to the predicted value. Thus far, AMS has not collected enough data to see this full picture.

    “This is an important new piece of the puzzle,” Capell says. “It’s like looking at the world with a really good new microscope—if you take a careful look, you might find all sort of things that you don’t expect.”

    Theorists are now left with the task of developing better models that can explain AMS’s unexpected results. “I think AMS’s data is taking the whole analysis of cosmic rays in this energy range to a whole new level,” Ellis says. “It’s revolutionizing the field.”

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 6:56 pm on April 9, 2015 Permalink | Reply
    Tags: , , Cosmic Rays   

    From AMS-02: “New results from the Alpha Magnetic Spectrometer on the International Space Station” 

    AMS-02 Bloc

    AMS-02
    AMS 02 schematic

    Alpha Magnetic Spectrometer

    September 18th, 2014 (Presented in social media today, 4.9.15)

    The new results on energetic cosmic ray electrons and positrons are announced today. They are based on the first 41 billion events measured with the Alpha Magnetic Spectrometer (AMS) on the International Space Station (ISS). These results provide a deeper understanding of the nature of high energy cosmic rays and shed more light on the dark matter existence.

    AMS has analyzed 41 billion primary cosmic ray events. Of these, 10 million have been identified as electrons and positrons. AMS has measured the positron fraction (ratio of the number of positrons to the combined number of positrons and electrons) in the energy range 0.5 to 500 GeV. We have observed that the energy at which the fraction starts to quickly increase is 8 GeV (see Figure 1) indicating the existence of a new source of positrons. Figure 2 shows that the exact rate at which the positron fraction increases with energy has now been accurately determined and the fraction shows no observable sharp structures. The energy at which the positron fraction ceases to increase (corresponding to the turning point energy at which the positron fraction reaches its maximum) has been measured to be 275+32 GeV as shown in Figure 2 (upper plot). This is the first experimental observation of the positron fraction maximum after half a century of cosmic rays experiments. The excess of the positron fraction is isotropic within 3% strongly suggesting the energetic positrons may not be coming from a preferred direction in space.

    The new results from AMS (published today in Physical Review Letters) show that items (1)-(4) have been unambiguously resolved and are observations of a new phenomena. They are consistent with a dark matter particle (neutralino) of mass on the order of 1 TeV. To determine if the observed new phenomena is from dark matter or from astrophysical sources such as pulsars, measurements are underway by AMS to determine the rate of decrease at which the positron fraction falls beyond the turning point, (item 5), as well as the measurement of the anti-proton fraction (anti-proton to proton plus anti-proton ratio). These will be reported in future publications.

    Secondly, AMS reports the precise measurements of the electron flux and the positron flux,i.e. intensities of cosmic ray electrons and positrons. These measurements show that the behavior of electrons and positrons are significantly different from each other both in their magnitude and energy dependence. Figure 3 (upper plot) shows the electron and positron fluxes multiplied by the energy cubed (E3, for the purpose of presentation). The positron flux first increases (0.5 to 10 GeV), then levels out (10 to 30 GeV), and then increases again (30 to 200 GeV). Above 200 GeV, it has a tendency to decrease. This is totally different from the scaled electron flux.

    The behavior of the flux as a function of energy is described by the spectral index and the flux was expected to be proportional to energy E to the power of the spectral index. The result shows that neither flux can be described with a constant spectral index, see Figure 3 (lower plot). In particular, between 20 and 200 GeV, the rate of change of the positron flux is surprisingly higher than the rate for electrons. This is important proof that the excess seen in the positron fraction is due to a relative excess of high energy positrons, as expected from dark matter collisions, and not the loss of high energy electrons. These results are published today in Physical Review Letters in a separate article.

    This new observation of the electron and positron fluxes also demonstrates, as pointed out by Dr. Michael S. Turner, that there is a fundamental difference between matter (electrons) and antimatter (positrons).

    In 1932, Carl Anderson discovered the positron in cosmic rays. Non-magnetic detectors in space and on the ground can measure the flux of the sum of electrons plus positrons. Over the last 50 years, there have been many experiments that measured the combined flux of electrons plus positrons in cosmic rays. These measurements have yielded interesting results and few of them indicated the possible existence of a structure at 300-800 GeV.

    AMS, being a particle physics detector, provides many independent measurements of electrons, positrons, and electrons plus positrons. After collecting 41 billon cosmic ray events, AMS has been able to provide a measurement of the flux of electrons plus positrons, shown in Figure 4 (upper plot).The combined flux is smooth and reveals new and distinct information. Most interesting is the observation that, at high energies and over a wide energy range, the combined flux can be described by a single, constant spectral index (see Figure 4, lower plot).

    The precision measurements of the positron fraction, the individual fluxes and the combined flux are complementary to one to another. Together they will provide a deeper understanding of the origin of high energy cosmic rays and shed more light on the existence of dark matter.

    4
    Figure 1. The positron fraction measured by AMS (red circles) compared with the expectation from the collision of ordinary cosmic rays showing that above 8 billion electron volts (8 GeV) the positron fraction begins to quickly increase. This increase indicates the existence new sources of positrons.

    5
    Figure 2. Upper plot shows the slope of positron fraction measured by AMS (red circles) and a straight line fit at the highest energies (blue line). The data show that at 275±32 GeV the slope crosses zero. Lower plot shows the measured positron fraction as function of energy as well as the location of the maximum. No sharp structures are observed.

    6
    Figure 3. The upper plot highlights the difference between the electron flux (blue dots, left scale) and the positron flux (red dots, right scale). The lower plot shows the spectral indices of the electron flux and of the positron flux as functions of energy.

    7
    Figure 4. (Upper plot) The combined flux of electrons plus positrons measured by AMS multiplied by E3 together with the results from earlier experiments [1-7]. (Lower plot) The combined flux of e± multiplied by E3 versus energy and the result of a single power law fit.

    [1] S. Torii et al., Astrophys. J. 559, 973 (2001); [2] M. A. DuVernois et al., Astrophys. J. 559, 296 (2001); [3] J. Chang et al., Nature (London) 456, 362 (2008); [4] K. Yoshida et al., Adv. in Space Res. 42, 1670 (2008); [5] F. Aharonian et al., Phys. Rev. Lett. 101, 261104 (2008); [6] F. Aharonian et al., Astron. Astrophys. 508, 561 (2009); [7] M. Ackermann et al., Phys. Rev. D 82, 092004 (2010).

    Background of AMS

    AMS was assembled and tested at the European Organization for Nuclear Research, CERN, Geneva, Switzerland. Detector components were constructed at universities and research institutes around the world. Fifteen countries from Europe, Asia, and America participated in the construction of AMS (Finland, France, Germany, Netherlands, Italy, Portugal, Spain, Switzerland, Turkey, China, Korea, Taiwan, Russia, Mexico and the United States). The Principal Investigator of AMS is Prof. Samuel Ting of MIT and CERN. AMS is a U.S. Department of Energy sponsored particle physics experiment on the ISS under a DOE-NASA Implementing Arrangement. The Collaboration works closely with the NASA AMS Project Management team from Johnson Space Center as it has throughout the entire process. AMS was launched by NASA to the ISS as the primary payload onboard the final mission of space shuttle Endeavour (STS-134) on May 16, 2011. Once installed on the ISS, AMS was powered up and immediately began collecting data from primary sources in space and these were transmitted to the AMS Payload Operations Control Center (POCC). The POCC is located at CERN, Geneva, Switzerland.

    After 40 months of operations in space, AMS has collected 54 billion cosmic ray events. To date 41 billion have been analyzed. The data is analyzed at the AMS Science Operations Center (SOC) located at CERN as well as AMS universities around the world. Over the lifetime of the Space Station, AMS is expected to measure hundreds of billions of primary cosmic rays. Among the physics objectives of AMS is the search for antimatter, dark matter, and the origin of cosmic rays. The Collaboration will also conduct precision measurements on topics such as the boron to carbon ratio, nuclei and antimatter nuclei, and antiprotons, precision measurements of helium flux, proton flux and photons as well as the search for new physics and astrophysics phenomena such as strangelets.

    It is important to note that, in the search for an understanding of dark matter, there are three distinct approaches:

    Production experiments, such as those being carried at the LHC with the ATLAS and CMS experiments, use particle collisions to produce dark matter particles and detect their decay products. This is similar to experiments at the Brookhaven, Fermilab, CERN-SPS and CERN-LHC which led to the discovery of CP violation, the J particle, Z and W bosons, the b and t quarks, and the Higgs boson.

    Scattering experiments utilize the fact that dark matter can penetrate deep underground and that it can be detected by recoil nuclei from the scattering of dark matter with pure liquid or solid targets. This is similar to electron-proton scattering experiments performed at SLAC leading to the discovery of partons and the electro-weak effects.

    Annihilation experiments for dark matter are done in space and are based on the fact that dark matter collisions can produce excesses of positrons and anti-protons. These are the main goals of AMS. On the ground, annihilation experiments are done in electron-positron colliders (SPEAR, PETRA, LEP, BaBar, TRISTAN) leading to the discovery of the psi particle, the heavy electron (tau) and gluons, precision measurements of CP violation effects and the properties of Z and W bosons.

    The scattering experiments, the production experiments, and the annihilation experiments each produce unique physics discoveries. The absence of a dark matter signal from one of these three ways does not exclude its discovery by the other two.

    The U.S. participation in AMS involves MIT, Yale (Professor Jack Sandweiss), the University of Hawaii (Professors Veronica Bindi and Philip von Doetinchem), the University of Maryland (Professor Roald Sagdeev and Professor Eun Suk SEO) and NASA’s Johnson Space Center (Mr. Trent Martin and Mr. Ken Bollweg). The AMS project is coordinated by the Laboratory for Nuclear Science at MIT under the leadership of Professor Richard Milner. The major responsibility for space operations and data analysis is carried by Drs. U. J. Becker, J. Burger, X.D. Cai, M. Capell, V. Choutko, F.J. Eppling, P. Fisher, A. Kounine,V. Koutsenko, A. Lebedev, Z.Weng, and P. Zuccon of MIT.

    Germany made a major contribution to the detector construction and data analysis under the leadership of Professors Dr. Stefan Schael, Henning Gast, and Iris Gebauer. Germany’s participation is supported by DLR and RWTH Aachen.

    Italy made a major contribution to the detector construction and presently to the data analysis, under the leadership of Professors Roberto Battiston, Deputy PI and currently President of ASI, Bruna Bertucci, Italian Coordinator, Franco Cervelli, Andrea Contin, Giovanni Ambrosi, Marco Incagli, Giuliano Laurenti, Federico Palmonari, and Pier-Giorgio Rancoita. Italy’s participation is supported by ASI and INFN.

    Spain made a major contribution to the detector construction and presently to the data analysis under the leadership of Manuel Aguilar, Javier Berdugo, Jorge Casaus, Carlos Delgado and Carlos Mana. Spain’s participation is supported by CIEMAT and CDTI.

    France has made major contributions to the detector construction and to the data analysis both from LPSC, Grenoble and LAPP, Annecy under the leadership of Professors Laurent Derome, Sylvie Rosier-Lees, and Jean-Pierre Vialle. France’s participation is supported by IN2P3 and CNES.

    Taiwan made a major contribution to the detector construction and presently to the data analysis, under the leadership of Academician Shih-Chang Lee and Profs. Y.H. Chang and S. Haino. Taiwan’s participation is supported by Academia Sinica, National Science Council and CSIST. Taiwan also maintains the AMS Asia POCC.

    From China, Shandong University made a major contribution to the detector construction and to the data analysis under the leadership of Professor Cheng Lin. The Institute of High Energy Physics in Beijing has made major contributions to the detector construction and data analysis under the leadership of Academician Hesheng Chen. Southeast University in Nanjing has made major contributions to the detector construction and data analysis under the leadership of Professor Hong Yi and J. Z. Luo. Beihang University under the leadership of Academician Wei Li, Professor Zhi-Ming Zheng and Dr. Baosong Shan made important contributions to the data analysis. Sun Yat-Sen University in Guangzhou has made major contributions to the detector construction and data analysis under the leadership of Professor N.S. Xu. Shanghai Jiaotong University in Shanghai has made important contributions to the detector construction. The Institute of Electrical Engineering under Q. L. Wang and the Chinese Academy of Launch Vehicle Technology were responsible for the AMS permanent magnet.

    Switzerland has made a major contribution to the detector construction and the data analysis, both from ETH/Zurich and the University of Geneva under the leadership of Professors Maurice Bourquin, Catherine Leluc, and Martin Pohl of the University of Geneva.

    Collaborating Insititutes on the two Physical Review Letters:

    I. Physics Institute and JARA-FAME, RWTH Aachen University, D-52056 Aachen, Germany

    Department of Physics, Middle East Technical University, METU, 06800 Ankara, Turkey

    Laboratoire d’Annecy-Le-Vieux de Physique des Particules, LAPP, IN2P3/CNRS and Universite de Savoie, F-74941 Annecy-le-Vieux, France

    Beihang University, BUAA, Beijing, 100191, China

    Institute of Electrical Engineering, IEE, Chinese Academy of Sciences, Beijing, 100080, China

    Institute of High Energy Physics, IHEP, Chinese Academy of Sciences, Beijing, 100039, China

    INFN-Sezione di Bologna, I-40126 Bologna, Italy

    Universita di Bologna, I-40126 Bologna, Italy

    Massachusetts Institute of Technology, MIT, Cambridge, Massachusetts 02139, USA

    National Central University, NCU, Chung-Li, Tao Yuan 32054, Taiwan

    East-West Center for Space Science, University of Maryland, College Park, Maryland 20742, USA

    IPST, University of Maryland, College Park, Maryland 20742, USA

    CHEP, Kyungpook National University, 702-701 Daegu, Korea

    CNR-IROE, I-50125 Firenze, Italy

    European Organization for Nuclear Research, CERN, CH-1211 Geneva 23, Switzerland

    DPNC, Universite de Geneve, CH-1211 Geneve 4, Switzerland

    Laboratoire de Physique subatomique et de cosmologie, LPSC, Universite Grenoble-Alpes, CNRS/IN2P3, F-38026 Grenoble, France

    Sun Yat-Sen University, SYSU, Guangzhou, 510275, China

    University of Hawaii, Physics and Astronomy Department, 2505 Correa Road, WAT 432; Honolulu, Hawaii 96822, USA

    Julich Supercomputing Centre and JARA-FAME, Research Centre Julich, D-52425 Julich, Germany

    NASA, National Aeronautics and Space Administration, Johnson Space Center, JSC, and Jacobs-Sverdrup, Houston, TX 77058, USA

    Institut fur Experimentelle Kernphysik, Karlsruhe Institute of Technology, KIT, D-76128 Karlsruhe, Germany

    Instituto de Astrofisica de Canarias, IAC, E-38205, La Laguna, Tenerife, Spain

    Laboratorio de Instrumentacao e Fisica Experimental de Particulas, LIP, P-1000 Lisboa, Portugal

    National Chung-Shan Institute of Science and Technology, NCSIST, Longtan, Tao Yuan 325, Taiwan

    Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas, CIEMAT, E-28040 Madrid, Spain

    Instituto de Fisica, Universidad Nacional Autonoma de Mexico, UNAM, Mexico, D. F., 01000 Mexico

    INFN-Sezione di Milano and Universita di Milano, I-20090 Milano, Italy

    INFN-Sezione di Milano-Bicocca, I-20126 Milano, Italy

    Universita di Milano-Bicocca, I-20126 Milano, Italy

    Laboratoire Univers et Particules de Montpellier, LUPM, IN2P3/CNRS and Universite de Montpellier II, F-34095 Montpellier, France

    Southeast University, SEU, Nanjing, 210096, China

    Physics Department, Yale University, New Haven, Connecticut 06520, USA

    INFN-Sezione di Perugia, I-06100 Perugia, Italy

    Universita di Perugia, I-06100 Perugia, Italy

    INFN-Sezione di Pisa, I-56100 Pisa, Italy

    Universita di Pisa, I-56100 Pisa, Italy

    INFN-TIFPA and Universita di Trento, I-38123 Povo, Trento, Italy

    INFN-Sezione di Roma 1, I-00185 Roma, Italy

    Universita di Roma La Sapienza, I-00185 Roma, Italy

    Department of Physics, Ewha Womans University, Seoul, 120-750, Korea

    Shandong University, SDU, Jinan, Shandong, 250100, China

    Shanghai Jiaotong University, SJTU, Shanghai, 200030, China

    Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan

    Space Research Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland

    See the full article here.

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    AMS-02 Mission Control at CERN
    AMS-02 Mission Control at CERN in Prevessin, France

    The Alpha Magnetic Spectrometer (AMS-02) is a state-of-the-art particle physics detector designed to operate as an external module on the International Space Station. It will use the unique environment of space to study the universe and its origin by searching for antimatter, dark matter while performing precision measurements of cosmic rays composition and flux. The AMS-02 observations will help answer fundamental questions, such as “What makes up the universe’s invisible mass?” or “What happened to the primordial antimatter?”

     
    • richardmitnick 10:10 pm on April 9, 2015 Permalink | Reply

      This is a truly massive project, many many people and organizations involved. But, we have the right as tax payers to ask, why are we just now in April 2015 getting news from September 2014?

      Like

  • richardmitnick 12:37 pm on November 18, 2014 Permalink | Reply
    Tags: , , , Cosmic Rays, , Pierre Auger collaboration   

    From Symmetry: “Auger reveals subtlety in cosmic rays” 

    Symmetry

    November 18, 2014

    FNAL Leah Hesla
    Leah Hesla

    Scientists home in on the make-up of cosmic rays, which are more nuanced than previously thought.

    Unlike the twinkling little star of nursery rhyme, the cosmic ray is not the subject of any well-known song about an astronomical wonder. And yet while we know all about the make-up of stars, after decades of study scientists still wonder what cosmic rays are.

    cr
    Courtesy of ASPERA/Novapix/L. Bret

    Thanks to an abundance of data collected over eight years, researchers in the Pierre Auger collaboration are closer to finding out what cosmic rays—in particular ultrahigh-energy cosmic rays [UHECRs]—are made of. Their composition would tell us more about where they come from: perhaps a black hole, a cosmic explosion or colliding galaxies.

    pa
    Pierre Auger installation

    Auger’s latest research has knocked out two possibilities put forward by the prevailing wisdom: that UHECRs are dominated by either lightweight protons or heavier nuclei such as iron. According to Auger, one or more middleweight components, such as helium or nitrogen nuclei, must make up a significant part of the cosmic-ray mix.

    “Ten years ago, people couldn’t posit that ultrahigh-energy cosmic rays would be made of something in between protons and iron,” says Fermilab scientist and Auger collaborator Eun-Joo Ahn, who led the analysis. “The idea would have garnered sidelong glances.”

    Cosmic rays are particles that rip through outer space at incredibly high energies. UHECRs, upwards of 1018 electronvolts, are rarely observed, and no one knows exactly where they originate.

    One way physicists reach back to a cosmic ray’s origins is by looking to the descendants of its collisions. The collision of one of these breakneck particles with the Earth’s upper atmosphere sets off a domino effect, generating more particles that in turn collide with air and produce still more. These ramifying descendants form an air shower, spreading out like the branches of a tree reaching toward the Earth. Twenty-seven telescopes at the Argentina-based Auger Observatory look for ultraviolet light resulting from the cosmic rays, and 1600 detectors, distributed over a swath of land the size of Rhode Island, record the showers’ signals.

    Scientists measure how deep into the atmosphere—how close to Earth—the air shower is when it maxes out. The closer to the Earth, the more lightweight the original cosmic ray particle is likely to be. A proton, for example, would penetrate the atmosphere more deeply before setting off an air shower than would an iron nucleus.

    Auger scientists compared their data with three different simulation models to narrow the possible compositions of cosmic rays.

    Auger’s favoring a compositional middle ground between protons and iron nuclei is based on a granular take on their data, a first for cosmic-ray research. In earlier studies, scientists distilled measurements of shower depths to two values: the average and standard deviation of all shower depths in a given cosmic-ray energy range. Their latest study, however, made no such generalization. Instead, it used the full distribution of data on air shower depth. If researchers measured 1000 different air shower depths for a specific UHECR energy, all 1000 data points—not just the average—went into Auger’s simulation models.

    The result was a more nuanced picture of cosmic ray composition. The analysis also gave researchers greater insight into their simulations. For one model, the data and predictions could not be matched no matter the composition of the cosmic ray, giving scientists a starting point for constraining the model further.

    “Just getting the distribution itself was exciting,” Ahn says.

    Auger will continue to study cosmic rays at even higher energies, gathering more statistics to answer the question: What exactly are cosmic rays made of?

    See the full article here.

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  • richardmitnick 3:18 pm on September 24, 2014 Permalink | Reply
    Tags: , , , Cosmic Rays, , Physics arXiv Blog   

    From Xb: “How Astrophysicists Are Turning The Entire Moon Into A Cosmic Ray Detector” 

    Xb Physics Archive Blog
    The Physics arXiv Blog

    The $1.5 billion plan breaks ground in 2018 and should be complete by 2025

    One of the great mysteries in astrophysics surrounds the origin of the highest energy particles ever observed. These particles, called ultra-high energy cosmic rays, come from space and smash into the Earth with so much energy that physicists have struggled to believe, let alone explain, it.

    An ultra-high energy cosmic ray can have an energy of 10^20 electron volts. To put that in context, that’s a single proton with the same energy as a baseball flying at 100 kilometres per hour.

    It might come as some relief to know that these particles are extremely rare. Physicists detect them on Earth at a rate of less than one particle per square kilometre per century. And that makes them difficult to study.

    So physicists want to study more of these particles to work out where they come from and how they might form. The obvious approach is to build bigger detectors. The largest on Earth is the Pierre Auger Observatory in Argentina that covers an area of 3000 square kilometres, about the size of Rhode Island or Luxembourg.

    Clearly, finding a significantly larger area of the Earth for a bigger detector is no easy task. So scientists are turning their attention to the heavens.

    moon
    Their idea is to exploit an exotic physical effect that turns the entire Moon into a detector for ultra-high energy cosmic rays. Today, Justin Bray at the University of Southampton and a few pals outline the plan.

    This is no pie in the sky project. Their plans are already drawn up and the €1.5 billion budget is in place. They plan to start construction of the necessary equipment in 2018 and be in full operation by 2025.

    So what’s the big deal about ultra-high energy cosmic rays? The biggest mystery is how a single particle can have such high energy.

    Physicists think there are essentially two possible mechanisms. The first is that the particles are accelerated in an electric or magnetic field. But nobody is sure where such extreme fields exist or how they might trap a particle long enough to accelerate it to these energies.

    The second possibility is that the ultrahigh energy particles are created by the decay of a hypothetical supermassive exotic particle, perhaps dark matter or perhaps produced by topological defects early in the universe.

    One way to pinpoint this mechanism is to discover the source of these particles, by finding where in the sky they come from. That is easier said than done because cosmic rays are charged and are therefore bent by magnetic fields as they travel. So the direction of arrival does not necessarily indicate the source.

    Having said that, there is another effect that ought to prevent the highest energy cosmic rays reaching us at all. High-energy particles should interact with the cosmic microwave background radiation as they travel through space and this should cause them to lose energy. That suggests the highest energy particles were probably created within our galaxy since they could not have travelled intergalactic distances and remained so energetic.

    So where does the Moon come into all this? On Earth, physicists detect these high-energy particles when they smash into the upper atmosphere triggering a cascade of other particles that rain down on the surface. This is how the Pierre Auger Observatory works— by detecting the daughter particles created in the cascade.

    grpah
    These cascades also generate another signal. The rapid acceleration and deceleration of charged particles produces radio waves. So another signature of the impact of an ultra-high energy cosmic ray is a brief burst of radio waves, known as the Askaryan effect after Gurgen Askaryan the Soviet-American physicist who proposed it in the early 1960s.

    It is this signal that astronomers hope to pick up from the Moon. The idea is that ultrahigh energy cosmic rays should smash into the lunar surface generating a cascade of other particles and a short burst of radio waves less than a nanosecond long.

    This effect is complicated by the fact that radio pulses are projected forward in a cone and cannot travel far through the lunar surface before being absorbed.

    That means that astronomers will only be able to see the radio pulses from ultrahigh energy cosmic rays that graze the edge of the Moon coming our way.

    So the gear they need to detect the signal is a highly sensitive radio telescope on Earth. These signals are so short and faint that the current generation of radio telescopes cannot pick them up.

    But astronomers are about to start work on a much bigger and more sensitive radio telescope called the Square Kilometre Array, which will be built in South Africa and Australia at a cost of about €1.5 billion. This will give them access to more data about ultrahigh energy cosmic rays than they have ever had.

    array
    Unnamed portion of SKA

    Although there are limitations on the lunar detector, it is still sizeable. Bray and co estimate that it will be equivalent to a ground array of 33,0000 square kilometres or about the size of Maryland or Belgium. That is more than 10 times larger than the Pierre Auger Observatory. And they say the Array should detect around 165 ultra-high energy cosmic rays a year from the Moon compared to the 15-a-year currently observed.

    That suggests an exciting time ahead for radio astronomers and for the astrophysicists attempting to understand the origin of these mysterious particles. With any luck, they should soon be able to tease apart the extraordinary events that somehow create the most energetic particles ever observed.

    Ref: arxiv.org/abs/1408.6069 : Lunar Detection Of Ultra-High-Energy Cosmic Rays And Neutrinos

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  • richardmitnick 2:28 pm on July 16, 2014 Permalink | Reply
    Tags: , , , Cosmic Rays, , Telescope Array Project   

    From The Christian Science Monitor: “Where do cosmic rays come from? The answer could be in the Big Dipper.” 

    ChristianScienceMonitor

    July 9, 2014
    Nola Taylor Redd, Space.com

    Researchers discovered a hotspot of high-energy particles that could offer clues about origin of cosmic rays.

    A hotspot of powerful, ultrahigh-energy particles streams toward Earth from beneath the handle of the Big Dipper constellation. This collection of cosmic rays may help scientists nail down the origin point of the powerful particles, a century-old mystery.

    “This puts us closer to finding out the sources — but no cigar yet,” Gordon Thomson, of the University of Utah, said in a statement. Thomson is the co-principle investigator for the Telescope Array cosmic ray observatory in southern Utah, which discovered the hotspot, and one of the 125 researchers on the project.

    ta

    “All we see is a blob in the sky, and inside this blob there is all sorts of stuff — various types of objects — that could be the source,” he added. “Now we know where to look.”

    A hundred-year-old mystery

    Gordon worked with an international team of scientists to capture 72 ultrahigh-energy cosmic rays with the Telescope Array over a period of five years. If powerful cosmic ray sources spread evenly across the sky, the resulting waves should also be evenly distributed. Instead, 19 of the detected signals came from a 40-degree circle that makes up only six percent of the sky. The hot spot lies in the constellation Ursa Major, home of the Big Dipper.

    “We have a quarter of our events in that circle instead of 6 percent,” collaborator Charlie Jui, also from the University of Utah, said in the same statement.

    Jui describes the hotspot’s location as “a couple of hand widths below the Big Dipper’s handle.” The region would appear like any other region of the sky to regular optical telescopes.

    According to the researchers, the odds that the hotspot is a statistical fluke rather than real are only 1.4 in 10,000.

    The hotspot region of the sky lies near the supergalactic plane, which contains local galaxy clusters such as the Ursa Major cluster, the Coma cluster and the Virgo cluster.

    The research, which is an international collaboration of over 100 scientists, was recently accepted for publication in the Astrophysical Journal Letters.

    Discovered in 1912, cosmic rays are thought to consist of the bare protons of hydrogen nuclei, or the centers of heavier elements. The powerful particles stream in from various regions of the sky, with energies reaching as high as 300 billion billion electron volts. Cosmic rays are classified as “ultrahigh-energy” if they carry the energy of 1 billion billion electron volts, comparable to a fast-pitch baseball.

    While low-energy cosmic rays come from stars like the sun over the course of their life or explosive deaths, the origins of more energetic rays remain a mystery.

    Suggested progenitors for the more powerful cosmic rays include Active Galactic Nuclei (AGN), where material is sucked into supermassive black holes at the center of galaxies, or gamma-ray bursts from the explosive supernova death of massive stars. Other potential causes include shockwaves from noisy radio galaxies and colliding galaxies. More exotic possibilities include the decay of “cosmic strings,” hypothetical one-dimensional defects proposed by string theory.

    Ultrahigh-energy cosmic rays stem from outside the Milky Way, but are weakened by interactions with the cosmic microwave background radiation — the leftover fingerprint from the Big Bang that kicked off the universe.

    Cosmic Background Radiation Planck
    Cosmic background Radiation from ESA/Planck

    As a result, 90 percent of the detected ultrahigh-energy cosmic rays originate within 300 million light-years of Earth.

    According to Jui, a separate study currently in progress suggests that the distribution of ultrahigh-energy cosmic rays in the northern sky is related to concentrations of large-scale structures like clusters and superclusters of galaxies.

    super
    A map of the Superclusters and voids nearest to Earth

    “It tells us there is at least a good chance these are coming from matter we can see, as opposed to a different class of mechanisms where you are producing these particles with exotic processes,” Jui said.

    The Telescope Array houses 523 detectors spread over 300 square miles of desert. Physicists hope to make the observatory more sensitive by doubling the number of detectors and quadrupling the area they cover, which should capture more cosmic rays.

    “With more events, we are more likely to see structure in that hotspot blob, and that may point us toward the real sources,” Jui said.

    A preprint of the article may be found online at arXiv.org

    See the full article here.


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  • richardmitnick 8:50 am on July 8, 2014 Permalink | Reply
    Tags: , , , cosmic, Cosmic Rays, ,   

    From space.com 

    space-dot-com logo

    July 08, 2014
    Nola Taylor Redd

    A hotspot of powerful, ultrahigh-energy particles streams toward Earth from beneath the handle of the Big Dipper constellation. This collection of cosmic rays may help scientists nail down the origin point of the powerful particles, a century-old mystery.

    bd

    “This puts us closer to finding out the sources — but no cigar yet,” Gordon Thomson, of the University of Utah, said in a statement. Thomson is the co-principle investigator for the Telescope Array cosmic ray observatory in southern Utah, which discovered the hotspot, and one of the 125 researchers on the project.

    tel
    One telescope in the array

    “All we see is a blob in the sky, and inside this blob there is all sorts of stuff — various types of objects — that could be the source,” he added. “Now we know where to look.” [8 Baffling Astronomy Mysteries]

    A hundred-year-old mystery

    Gordon worked with an international team of scientists to capture 72 ultarhigh-energy cosmic rays with the Telescope Array over a period of five years. If powerful cosmic ray sources spread evenly across the sky, the resulting waves should also be evenly distributed. Instead, 19 of the detected signals came from a 40-degree circle that makes up only six percent of the sky. The hot spot lies in the constellation Ursa Major, home of the Big Dipper.

    “We have a quarter of our events in that circle instead of 6 percent,” collaborator Charlie Jui, also from the University of Utah, said in the same statement.

    Jui describes the hotspot’s location as “a couple of hand widths below the Big Dipper’s handle.” The region would appear like any other region of the sky to regular optical telescopes.

    According to the researchers, the odds that the hotspot is a statistical fluke rather than real are only 1.4 in 10,000.

    The hotspot region of the sky lies near the supergalactic plane, which contains local galaxy clusters such as the Ursa Major cluster, the Coma cluster and the Virgo cluster.

    The research, which is an international collaboration of over 100 scientists, was recently accepted for publication in the Astrophysical Journal Letters.

    Discovered in 1912, cosmic rays are thought to consist of the bare protons of hydrogen nuclei, or the centers of heavier elements. The powerful particles stream in from various regions of the sky, with energies reaching as high as 300 billion billion electron volts. Cosmic rays are classified as “ultrahigh-energy” if they carry the energy of 1 billion billion electron volts, comparable to a fast-pitch baseball.

    While low-energy cosmic rays come from stars like the sun over the course of their life or explosive deaths, the origins of more energetic rays remain a mystery.

    Suggested progenitors for the more powerful cosmic rays include Active Galactic Nuclei (AGN), where material is sucked into supermassive black holes at the center of galaxies, or gamma-ray bursts from the explosive supernova death of massive stars. Other potential causes include shockwaves from noisy radio galaxies and colliding galaxies. More exotic possibilities include the decay of “cosmic strings,” hypothetical one-dimensional defect proposed by string theory.

    Ultrahigh-energy cosmic rays stem from outside the Milky Way, but are weakened by interactions with the cosmic microwave background radiation — the leftover fingerprint from the Big Bang that kicked off the universe. As a result, 90 percent of the detected ultrahigh-energy cosmic rays originate within 300 million light-years of Earth.

    Cosmic Background Radiation Planck
    CMB via ESA/Planck

    According to Jui, a separate study currently in progress suggests that the distribution of ultrahigh-energy cosmic rays in the northern sky is related to concentrations of large-scale structures like clusters and superclusters of galaxies.

    map
    Map of voids and superclusters within 500 million light years from Milky May

    “It tells us there is at least a good chance these are coming from matter we can see, as opposed to a different class of mechanisms where you are producing these particles with exotic processes,” Jui said.

    The Telescope Array houses 523 detectors spread over 300 square miles of desert. Physicists hope to make the observatory more sensitive by doubling the number of detectors and quadrupling the area they cover, which should capture more cosmic rays.

    “With more events, we are more likely to see structure in that hotspot blob, and that may point us toward the real sources,” Jui said.

    A preprint of the article may be found online at arXiv.org

    See the full article here.


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  • richardmitnick 3:09 pm on February 14, 2013 Permalink | Reply
    Tags: , , , Cosmic Rays, , ,   

    From NASA Goddard: More on Cosmic Rays 

    A neat little video courtesy of NASA’s Goddard Space Flight Center.


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  • richardmitnick 2:52 pm on February 14, 2013 Permalink | Reply
    Tags: , , , Cosmic Rays, , ,   

    From ESO: “Clues to the Mysterious Origin of Cosmic Rays” 

    VLT probes remains of medieval supernova

    Contacts

    Sladjana Nikolić
    Max Planck Institute for Astronomy
    Heidelberg, Germany
    Tel: +49 6221 528 438
    Email: nikolic@mpia.de

    Glenn van de Ven
    Max Planck Institute for Astronomy
    Heidelberg, Germany
    Tel: +49 6221 528 275
    Email: glenn@mpia.de

    Richard Hook
    ESO, La Silla, Paranal, E-ELT & Survey Telescopes Press Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    Very detailed new observations with ESO’s Very Large Telescope (VLT) of the remains of a thousand-year-old supernova have revealed clues to the origins of cosmic rays. For the first time the observations suggest the presence of fast-moving particles in the supernova remnant that could be the precursors of such cosmic rays. The results are appearing in the 14 February 2013 issue of the journal Science.

    four cells
    VLT/VIMOS observations of the shock front in the remnant of SN1006

    In the year 1006 a new star was seen in the southern skies and widely recorded around the world. It was many times brighter than the planet Venus and may even have rivaled the brightness of the Moon. It was so bright at maximum that it cast shadows and it was visible during the day. More recently astronomers have identified the site of this supernova and named it SN 1006. They have also found a glowing and expanding ring of material in the southern constellation of Lupus (The Wolf) that constitutes the remains of the vast explosion.

    It has long been suspected that such supernova remnants may also be where some cosmic rays — very high energy particles originating outside the Solar System and travelling at close to the speed of light — are formed. But until now the details of how this might happen have been a long-standing mystery.

    A team of astronomers led by Sladjana Nikolić (Max Planck Institute for Astronomy, Heidelberg, Germany [1]) has now used the VIMOS instrument on the VLT to look at the one-thousand-year-old SN 1006 remnant in more detail than ever before.

    vimos
    VIMOS – VIsible MultiObject Spectrograph

    They wanted to study what is happening where high-speed material ejected by the supernova is ploughing into the stationary interstellar matter — the shock front. This expanding high-velocity shock front is similar to the sonic boom produced by an aircraft going supersonic and is a natural candidate for a cosmic particle accelerator.

    sf
    Schlieren photograph of an attached shock on a sharp-nosed supersonic body.

    For the first time the team has not just obtained information about the shock material at one point, but also built up a map of the properties of the gas, and how these properties change across the shock front. This has provided vital clues to the mystery.

    The results were a surprise — they suggest that there were many very rapidly moving protons in the gas in the shock region. While these are not the sought-for high-energy cosmic rays themselves, they could be the necessary seed particles, which then go on to interact with the shock front material to reach the extremely high energies required and fly off into space as cosmic rays.”

    See the full article with complete scholarly apparatus here.

    Visit ESO in Social Media-

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    THE BASIC TOOLS OF E.S.O.
    i1
    Paranal Platform The VLT

    ESO NTT

    NTT – New Technology Telescope


    La Silla


    ALMA Atacama Large Millimeter/submillimeter Array

    i2
    The European Extremely Large Telescope
    VISTAVISTA (the Visible and Infrared Survey Telescope for Astronomy)


    Atacama Pathfinder Experiment telescope (APEX)

    ESO, European Southern Observatory, builds and operates a suite of the world’s most advanced ground-based astronomical telescopes.


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