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  • richardmitnick 12:37 pm on July 29, 2016 Permalink | Reply
    Tags: , , Cosmic Rays, , What Are The Most Energetic Particles In The Universe?   

    From Ethan Siegel: “What Are The Most Energetic Particles In The Universe?” 

    From Ethan Siegel

    Jul 29, 2016

    The production of a cosmic ray shower, produced by an incredibly energetic particle from far outside our Solar System. Image credit: Pierre Auger Observatory, via http://apcauger.in2p3.fr/Public/Presentation/.

    You might think of the largest and most powerful particle accelerators in the world — places like SLAC, Fermilab and the Large Hadron Collider — as the source of the highest energies we’ll ever see. But everything we’ve ever done here on Earth has absolutely nothing on the natural Universe itself! In fact, if you were interested in the most energetic particles on Earth, looking at the Large Hadron Collider — at the 13 TeV collisions occurring inside — you wouldn’t even be close to the highest energies. Sure, those are the highest human-made energies for particles, but we’re constantly bombarded all the time by particles far, far greater in energy from the depths of space itself: cosmic rays.

    An illustration of a very high energy process in the Universe: a gamma-ray burst. Image credit: NASA / D. Berry.

    You didn’t need to be in space, or even to have any type of flight, to know that these particles existed. Even before the first human beings ever left the surface of the Earth, it was widely known that up there, above the protection of the Earth’s atmosphere, outer space was filled with high-energy radiation. How did we know?

    The first clues came from looking at one of the simplest electricity experiments you can do on Earth, involving an electroscope. If you’ve never heard of an electroscope, it’s a simple device: take two thin pieces of conducting, metal foil, place them in an airless vacuum and connect them to a conductor on the outside that you can control the electric charge of.

    The electric charge on an electroscope, depending on what you charge it with, and how the leaves inside respond. Image credit: Figure 16-8 from Boomeria’s Honors Physics page, via http://boomeria.org/physicstextbook/ch16.html.

    If you place an electric charge on one of these devices — where two conducting metal leaves are connected to another conductor — both leaves will gain the same electric charge, and repel one another as a result. You’d expect, over time, for the charge to dissipate into the surrounding air, which it does. So you might have the bright idea to isolate it as completely as possible, perhaps creating a vacuum around the electroscope once you charge it up.

    But even if you do, the electroscope still slowly discharges! In fact, even if you placed lead shielding around the vacuum, it would still discharge, and experiments in the early 20th century gave us a clue as to why: if you went to higher and higher altitudes, the discharge happened more quickly. A few scientists put forth the hypothesis that the discharge was happening because high-energy radiation — radiation with both extremely large penetrating power and an extraterrestrial origin — was responsible for this.

    Victor Hess in his balloon-borne, cosmic ray experiment. Image credit: American Physical Society.

    Well, you know the deal when it comes to science: if you want to confirm or refute your new idea, you test it! So in 1912, Victor Hess conducted balloon-borne experiments to search for these high-energy cosmic particles, discovering them immediately in great abundance and henceforth becoming the father of cosmic rays.

    The early detectors were remarkable in their simplicity: you set up some sort of emulsion (or later, a cloud chamber) that’s sensitive to charged particles passing through it and place a magnetic field around it. When a charged particle comes in, you can learn two extremely important things:

    The particle’s charge-to-mass ratio and
    its velocity,

    simply dependent on how the particle’s track curves, something that’s a dead giveaway so long as you know the strength of the magnetic field you applied.

    In the 1930s, a number of experiments — both in early terrestrial particle accelerators and via more sophisticated cosmic ray detectors — turned up some interesting information. For starters, the vast majority of cosmic ray particles (around 90%) were protons, which came in a wide range of energies, from a few mega-electron-Volts (MeV) all the way up to as high as they could be measured by any known equipment! The vast majority of the rest of them were alpha-particles, or helium nuclei with two protons and two neutrons, with comparable energies to the protons.

    An illustration of cosmic rays striking Earth’s atmosphere. Image credit: Simon Swordy (U. Chicago), NASA.

    When these cosmic rays hit the top of the Earth’s atmosphere, they interacted with it, producing cascading reactions where the products of each new interaction led to subsequent interactions with new atmospheric particles. The end result was the creation of what’s called a shower of high-energy particles, including two new ones: the positron — hypothesized in 1930 by Dirac, the antimatter counterpart of the electron with the same mass but a positive charge — and the muon, an unstable particle with the same charge as the electron but some 206 times heavier! The positron was discovered by Carl Anderson in 1932 and the muon by him and his student Seth Neddermeyer in 1936, but the first muon event was discovered by Paul Kunze a few years earlier, which history seems to have forgotten!

    One of the most amazing things is that even here on the surface of the Earth, if you hold out your hand so that it’s parallel to the ground, about one muon passes through it every second.

    Image credit: Konrad Bernlöhr of the Max Planck Institute for Nuclear Physics.

    Every muon that passes through your hand originates from a cosmic ray shower, and every single one that does so is a vindication of the theory of special relativity! You see, these muons are created at a typical altitude of about 100 km, but a muon’s mean lifetime is only about 2.2 microseconds! Even moving at the speed of light (299,792.458 km/sec), a muon would only travel about 660 meters before it decays. Yet because of time dilation — or the fact that particles moving close to the speed of light experience time passing at a slower rate from the point-of-view of a stationary outside observer — these fast-moving muons can travel all the way to the surface of the Earth before they decay, and that’s where muons on Earth originate!

    Fast-forward to the present day, and it turns out that we’ve accurately measured both the abundance and energy spectrum of these cosmic particles!

    The spectrum of cosmic rays. Image credit: Hillas 2006, preprint arXiv:astro-ph/0607109 v2, via University of Hamburg.

    Particles with about 100 GeV worth of energy and under are by far the most common, with about one 100 GeV particle (that’s 10^11 eV) hitting every square-meter cross-section of our local region of space every second. Although higher-energy particles are still there, they’re far less frequent as we look to higher and higher energies.

    For example, by time you reach 10,000,000 GeV (or 10^16 eV), you’re only getting one-per-square-meter each year, and for the highest energy ones, the ones at 5 × 10^10 GeV (or 5 × 10^19 eV), you’d need to build a square detector that measured about 10 kilometers on a side just to detect one particle of that energy per year!

    How to detect a cosmic ray shower: build a giant array on the ground to — to quote Pokémon — catch ‘em all. Image credit: ASPERA / G.Toma / A.Saftoiu.

    Seems like a crazy idea, doesn’t it? It’s asking for a huge investment of resources to detect these incredibly rare particles. And yet there’s an extraordinarily compelling reason that we’d want to do so: there should be a cutoff in the energies of cosmic rays, and a speed limit for protons in the Universe! You see, there might not be a limit to the energies we can give to protons in the Universe: you can accelerate charged particles using magnetic fields, and the largest, most active black holes in the Universe could give rise to protons with energies even greater than the ones we’ve observed!

    But they have to travel through the Universe to reach us, and the Universe — even in the emptiness of deep space — isn’t completely empty. Instead, it’s filled with large amounts of cold, low-energy radiation: the cosmic microwave background!

    An illustration of the radiation background at various redshifts in the Universe. Image credits: Earth: NASA/BlueEarth; Milky Way: ESO/S. Brunier; CMB: NASA/WMAP.

    The only places where the highest energy particles are created are around the most massive, active black holes in the Universe, all of which are far beyond our own galaxy. And if particles with energies in excess of 5 × 10^10 GeV are created, they can only travel a few million light years — max — before one of these photons, left over from the Big Bang, interacts with it and causes it to produce a pion, radiating away the excess energy and falling down to this theoretical cosmic energy limit, known as the GZK cutoff. There’s even more braking radiation — or Bremsstrahlung radiation — that arises from interactions with any particles in the interstellar/intergalactic medium. Even lower-energy particles are subject to it, and radiate energy away in droves as electron/positron pairs (and other particles) are produced. (More details here.)

    So we did the only reasonable thing for physicists to do: we built a detector that ridiculously large and looked, and saw if this cutoff existed!

    The largest cosmic ray detector in the world. Image credit: Pierre Auger Observatory in Malargüe, Argentina / Case Western Reserve U.

    The Pierre Auger Observatory has done exactly this, verifying that cosmic rays exist up to but not over this incredibly high-energy threshold, a literal factor of about 10,000,000 larger than the energies reached at the LHC! This means the fastest protons we’ve ever seen evidence for in the Universe are moving almost at the speed-of-light, which is exactly 299,792,458 m/s, but just a tiny bit slower. How much slower?

    The fastest protons — the ones just at the GZK cutoff — move at 299,792,457.999999999999918 meters-per-second, or if you raced a photon and one of these protons to the Andromeda galaxy and back, the photon would arrive a measly six seconds sooner than the proton would… after a journey of more than five million years! But these ultra-high-energy cosmic rays don’t come from Andromeda (we believe); they come from active galaxies with supermassive black holes like NGC 1275, which tend to be hundreds of millions or even billions of light years away.

    Galaxy NGC 1275, as imaged by Hubble. Image credit: NASA, ESA, Hubble Heritage (STScI/AURA).

    We even know — thanks to NASA’s Interstellar Boundary Explorer (IBEX) — that there are about 10 times as many cosmic rays out there in deep space as we detect here on-and-around Earth, as the Sun’s heliosheath protects us from the vast majority of them!


    (Although the Sun does the worst job of protecting us from the most energetic particles.) In theory, there are collisions occurring everywhere in space between these cosmic rays, and so in a very real sense of the word, the Universe itself is our ultimate Large Hadron Collider: up to ten million times more energetic than what we can perform here on Earth. And when we’ve finally reached the limits of what a collider experiment can perform on Earth, it will be back to the same techniques we used in the earliest days of cosmic ray experiments.

    Exterior view of the ISS with the AMS-02 visible in the foreground. Image credit: NASA.

    It will be back to space, to wait and see what the Universe delivers to us, and to detect the aftermath of the most energetic cosmic collisions of all.

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

  • richardmitnick 8:27 pm on April 29, 2016 Permalink | Reply
    Tags: , , , Cosmic Rays   

    From astrobites: “A PeVatron at the Galactic Center” 

    Astrobites bloc


    Apr 29, 2016
    Kelly Malone

    Science paper: Acceleration of petaelectronvolt protons in the Galactic Centre
    Authors: The HESS Collaboration
    Status: Published in Nature

    In the past, we’ve talked on this website a bit about the mysteries of galactic cosmic rays, or charged particles from outer space that are mainly made up of protons. These particles can reach PeV energies and beyond, but the shocks of supernova remnants (the origin of most galactic cosmic rays) cannot accelerate particles to these high energies. The HESS Collaboration analyzed 10 years of gamma-ray observations and have seen evidence of a PeVatron (PeV accelerator) in the center of our galaxy. If confirmed, this would be the first PeVatron in our galaxy.

    As mentioned above, the HESS Collaboration used observations of gamma rays from their array of telescopes to do this analysis.

    HESS Cherenko Array
    HESS Cherenko Array

    Gamma rays are often used to probe the nature of cosmic ray accelerators; this is because they are associated with these sites, but unlike the charged cosmic rays, they are electrically neutral and therefore don’t bend in magnetic fields on their way to Earth (i.e. they point back to the source).

    Figure 1: HESS’s very high energy gamma ray map of the Galactic Center region. The color scale shows the number of gamma rays per pixel, while the white contour lines illustrate the distribution of molecular gas. Their correlation points to a hadronic origin of gamma ray emission. The right panel is simply a zoomed view of the inner portion. (Source: Figure 1 from the paper)

    Figure 2: The red shaded area shows the 1 sigma confidence band of the measured gamma-ray spectrum of the diffuse emission in the region of interest. The red lines show different models, assuming that the gamma rays are coming from neutral pion decay after the pions have been produced in proton-proton interactions. Note the lack of cutoff at high energies, indicating that the parent protons have energies in the PeV range. The blue data points refer to another gamma-ray source in the region, HESS J1745-290. The link between these two objects is currently unknown.

    The area they studied is known as the Central Molecular Zone, which surrounds the Galactic Center. They found that the distribution of gamma rays mirrored the distribution of the gas-rich areas, which points to a hadronic (coming from proton interactions) origin of the gamma rays. From the gamma-ray luminosity and amount of gases in the area, it can be shown that there must be at least one cosmic ray accelerator in the region. Additionally, the energy spectrum of the diffuse gamma-ray emission from the region around Sagittarius A* (the location of the black hole at at the Galactic Center) does not have an observed cutoff or a break in the TeV energy range. This means that the parent proton population that created these gamma rays should have energies of ~1 PeV (the PeVatron). Just to refresh everyone’s memory, a TeV is 10^12 electronvolts, while a PeV is 10^15 electronvolts. A few TeV is about the limit of what can be produced in particle laboratories on Earth (the LHC reaches 14 TeV). A PeV is roughly 1000 times that!

    What is the source of these protons? The typical explanation for Galactic cosmic rays, supernova remnants, is unlikely here: in order to match the data and inject enough cosmic rays into the Central Molecular Zone, the authors estimate that we would need more than 10 supernova events over 1000 years. This is a very high rate that is improbable.

    Instead, they hypothesize that Sgr A* is the source of these protons.

    Sag A* NASA's Chandra X-Ray Observatory 23 July 2014, the supermassive black hole at the center of the Milky Way
    Sag A* Chandra X-Ray Observatory 23 July 2014, the supermassive black hole at the center of the Milky Way

    They could either be accelerate in the accretion flow immediately outside the black hole, or further away where the outflow terminates. They do note that the required acceleration rate is a few orders of magnitude above the current luminosity, but that the black hole may have been much more active in the past, leading to higher production rates of the protons and other nuclei. If this is true, it could solve one of the most puzzling mysteries in cosmic ray physics: the origin of the higher energy galactic cosmic rays.

    See the full article here .

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

  • richardmitnick 4:12 pm on April 21, 2016 Permalink | Reply
    Tags: , , Cosmic Rays,   

    From Goddard: “Microscopic “Timers” Reveal Likely Source of Galactic Space Radiation” 

    NASA Goddard Banner
    NASA Goddard Space Flight Center

    April 21, 2016
    Karen C. Fox
    NASA Goddard Space Flight Center, Greenbelt, Maryland

    Most of the cosmic rays that we detect at Earth originated relatively recently in nearby clusters of massive stars, according to new results from NASA’s Advanced Composition Explorer (ACE) spacecraft.


    ACE allowed the research team to determine the source of these cosmic rays by making the first observations of a very rare type of cosmic ray that acts like a tiny timer, limiting the distance the source can be from Earth.

    Nebula in the constellation Carina, contains the central cluster of huge, hot stars, called NGC 3603. NASA ESA Hubble
    Nebula in the constellation Carina, contains the central cluster of huge, hot stars, called NGC 3603. NASA/ESA Hubble.

    “Before the ACE observations, we didn’t know if this radiation was created a long time ago and far, far away, or relatively recently and nearby,” said Eric Christian of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Christian is co-author of a paper on this research published April 21 in Science.

    Cosmic rays are high-speed atomic nuclei with a wide range of energy — the most powerful race at almost the speed of light. Earth’s atmosphere and magnetic field shield us from less-energetic cosmic rays, which are the most common. However, cosmic rays will present a hazard to unprotected astronauts traveling beyond Earth’s magnetic field because they can act like microscopic bullets, damaging structures and breaking apart molecules in living cells. NASA is currently researching ways to reduce or mitigate the effects of cosmic radiation to protect astronauts traveling to Mars.

    Cosmic rays are produced by a variety of violent events in space. Most cosmic rays originating within our solar system have relatively low energy and come from explosive events on the Sun, like flares and coronal mass ejections. The highest-energy cosmic rays are extremely rare and are thought to be powered by massive black holes gorging on matter at the center of other galaxies. The cosmic rays that are the subject of this study come from outside our solar system but within our Galaxy and are called galactic cosmic rays. They are thought to be generated by shock waves from exploding stars called supernovae.

    Supernova remnant Crab nebula. NASA/ESA Hubble
    Supernova remnant Crab nebula. NASA/ESA Hubble

    The galactic cosmic rays detected by ACE that allowed the team to estimate the age of the cosmic rays, and the distance to their source, contain a radioactive form of iron called Iron-60 (60Fe). It is created inside massive stars when they explode and then blasted into space by the shock waves from the supernova. Some 60Fe in the debris from the destroyed star is accelerated to cosmic-ray speed when another nearby massive star in the cluster explodes and its shock wave collides with the remnants of the earlier stellar explosion.

    60Fe galactic cosmic rays zip through space at half the speed of light or more, about 90,000 miles per second. This seems very fast, but the 60Fe cosmic rays won’t travel far on a galactic scale for two reasons. First, they can’t travel in straight lines because they are electrically charged and respond to magnetic forces. Therefore they are forced to take convoluted paths along the tangled magnetic fields in our Galaxy. Second, 60Fe is radioactive and over a period of about 2.6 million years, half of it will self-destruct, decaying into other elements (Cobalt-60 and then Nickel-60). If the 60Fe cosmic rays were created hundreds of millions of years or more ago, or very far away, eventually there would be too little left for the ACE spacecraft to detect.

    “Our detection of radioactive cosmic-ray iron nuclei is a smoking gun indicating that there has likely been more than one supernova in the last few million years in our neighborhood of the Galaxy,” said Robert Binns of Washington University, St. Louis, Missouri, lead author of the paper.

    “In 17 years of observing, ACE detected about 300,000 galactic cosmic rays of ordinary iron, but just 15 of the radioactive Iron-60,” said Christian. “The fact that we see any Iron-60 at all means these cosmic ray nuclei must have been created fairly recently (within the last few million years) and that the source must be relatively nearby, within about 3,000 light years, or approximately the width of the local spiral arm in our Galaxy.” A light year is the distance light travels in a year, almost six trillion miles. A few thousand light years is relatively nearby because the vast swarm of hundreds of billions of stars that make up our Galaxy is about 100,000 light years wide.

    There are more than 20 clusters of massive stars within a few thousand light years, including Upper Scorpius (83 stars), Upper Centaurus Lupus (134 stars), and Lower Centaurus Crux (97 stars). These are very likely major contributors to the 60Fe that ACE detected, owing to their size and proximity, according to the research team.

    ACE was launched on August 25, 1997 to a point 900,000 miles away between Earth and the Sun where it has acted as a sentinel, detecting space radiation from solar storms, the Galaxy, and beyond. This research was funded by NASA’s ACE program.

    Additional co-authors on this paper were: Martin Israel and Kelly Lave at Washington University, St. Louis, Missouri; Alan Cummings, Rick Leske, Richard Mewaldt and Ed Stone at Caltech in Pasadena, California; Georgia de Nolfo and Tycho von Rosenvinge at Goddard; and Mark Wiedenbeck at NASA’s Jet Propulsion Laboratory in Pasadena, California.

    See the full article here.

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    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.

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    NASA/Goddard Campus

  • richardmitnick 9:51 am on April 21, 2016 Permalink | Reply
    Tags: , , Cosmic Rays,   

    From SPACE.com: “What Are Cosmic Rays?” 

    space-dot-com logo


    April 21, 2016
    Elizabeth Howell

    Showers of high energy particles occur when energetic cosmic rays strike the top of the Earth’s atmosphere. Most cosmic rays are atomic nuclei: most are hydrogen nuclei, some are helium nuclei, and the rest heavier elements. Although many of the low energy cosmic rays come from our Sun, the origins of the highest energy cosmic rays remains unknown and a topic of much research. This drawing illustrates air showers from very high energy cosmic rays. Credit: Simon Swordy (U. Chicago), NASA

    Cosmic rays are atom fragments that rain down on the Earth from outside of the solar system. They blaze at the speed of light and have been blamed for electronics problems in satellites and other machinery.

    First discovered in 1912, many things about cosmic rays remain a mystery more than a century later. One prime example is exactly where they are coming from. Most scientists suspect their origins are related to supernovas (star explosions), but the challenge is that cosmic ray origins appear uniform when you look across the entire sky.


    While cosmic rays were only discovered in the 1900s, scientists knew something mysterious was going on as early as the 1780s. That’s when French physicist Charles-Augustin de Coulomb — best known for having a unit of electrical charge named after him — observed an electrically charged sphere suddenly and mysteriously not being charged any more.

    At the time, air was thought to be an insulator and not an electric conductor. With more work, however, scientists discovered that air can conduct electricity if its molecules are charged or ionized. This would most commonly happen when the molecules interact with charged particles or X-rays.

    What Are Cosmic Rays?

    Showers of high energy particles occur when energetic cosmic rays strike the top of the Earth’s atmosphere. Most cosmic rays are atomic nuclei: most are hydrogen nuclei, some are helium nuclei, and the rest heavier elements. Although many of the low energy cosmic rays come from our Sun, the origins of the highest energy cosmic rays remains unknown and a topic of much research. This drawing illustrates air showers from very high energy cosmic rays.
    Credit: Simon Swordy (U. Chicago), NASA

    Cosmic rays are atom fragments that rain down on the Earth from outside of the solar system. They blaze at the speed of light and have been blamed for electronics problems in satellites and other machinery.

    First discovered in 1912, many things about cosmic rays remain a mystery more than a century later. One prime example is exactly where they are coming from. Most scientists suspect their origins are related to supernovas (star explosions), but the challenge is that cosmic ray origins appear uniform when you look across the entire sky.


    While cosmic rays were only discovered in the 1900s, scientists knew something mysterious was going on as early as the 1780s. That’s when French physicist Charles-Augustin de Coulomb — best known for having a unit of electrical charge named after him — observed an electrically charged sphere suddenly and mysteriously not being charged any more.

    At the time, air was thought to be an insulator and not an electric conductor. With more work, however, scientists discovered that air can conduct electricity if its molecules are charged or ionized. This would most commonly happen when the molecules interact with charged particles or X-rays.

    But where these charged particles came from was a mystery; even attempts to block the charge with large amounts of lead were coming up empty. On Aug. 7, 1912, physicist Victor Hess flew a high-altitude balloon to 17,400 feet (5,300 meters). He discovered three times more ionizing radiation there than on the ground, which meant the radiation had to be coming from outer space.

    But tracing cosmic ray “origin stories” took more than a century. In 2013, NASA’s Fermi Gamma-ray Space Telescope released results from observing two supernova remnants in the Milky Way: IC 433 and W44.

    NASA/Fermi Telescope
    NASA/Fermi Telescope

    An artist’s illustration of a supernova explosion, which sends off shock waves that accelerate protons to the point that they become cosmic rays, a process called Fermi acceleration. Many details of Fermi acceleration are unknown, but data from NASA’s Fermi Gamma-ray Space Telescope provide overwhelming evidence that Fermi acceleration is responsible for cosmic rays. Image released Feb. 14, 2013.
    Credit: Greg Stewart/SLAC National Accelerator Laboratory

    Among the products of these star explosions are gamma-ray photons, which (unlike cosmic rays) are not affected by magnetic fields. The gamma rays studied had the same energy signature as subatomic particles called neutral pions. Pions are produced when protons get stuck in a magnetic field inside the shockwave of the supernova and crash into each other.

    In other words, the matching energy signatures showed that protons could move at fast enough speeds within supernovas to create cosmic rays.

    Current science

    We know today that galactic cosmic rays are atom fragments such as protons (positively charged particles), electrons (negatively charged particles) and atomic nuclei. While we know now they can be created in supernovas, there may be other sources available for cosmic ray creation. It also isn’t clear exactly how supernovas are able to make these cosmic rays so fast.

    Cosmic rays constantly rain down on Earth, and while the high-energy “primary” rays collide with atoms in the Earth’s upper atmosphere and rarely make it through to the ground, “secondary” particles are ejected from this collision and do reach us on the ground.

    But by the time these cosmic rays get to Earth, it’s impossible to trace where they came from. That’s because their path has been changed as they travelled through multiple magnetic fields (the galaxy’s, the solar system’s and Earth’s itself.)

    According to NASA, cosmic rays therefore come equally from all directions of the sky. So scientists are trying to trace back cosmic ray origins by looking at what the cosmic rays are made of. Scientists can figure this out by looking at the spectroscopic “signature” each nucleus gives off in radiation, and also by weighing the different isotopes (types) of elements that hit cosmic ray detectors.

    The result, NASA adds, shows very common elements in the universe. Roughly 90 percent of cosmic ray nuclei are hydrogen (protons) and 9 percent are helium (alpha particles). Hydrogen and helium are the most abundant elements in the universe and the origin point for stars, galaxies and other large structures. The remaining 1 percent are all elements, and it’s from that 1 percent that scientists can best search for rare elements to make comparisons between different types of cosmic rays.

    Scientists can also date the cosmic rays by looking at radioactive nuclei that decrease over time. Measuring the “half life” of each nuclei gives an estimate of how long the cosmic ray has been out there in space.

    Space radiation concerns

    Earth’s magnetic field and atmosphere shields the planet from 99.9 percent of the radiation from space. However, for people outside the protection of Earth’s magnetic field, space radiation becomes a serious hazard. An instrument aboard the Curiosity Mars rover during its 253-day cruise to Mars revealed that the radiation dose received by an astronaut on even the shortest Earth-Mars round trip would be about 0.66 sievert. This amount is like receiving a whole-body CT scan every five or six days.

    A dose of 1 sievert is associated with a 5.5 percent increase in the risk of fatal cancers. The normal daily radiation dose received by the average person living on Earth is 10 microsieverts (0.00001 sievert).

    The moon has no atmosphere and a very weak magnetic field. Astronauts living there would have to provide their own protection, for example by burying their habitat underground.

    The planet Mars has no global magnetic field. Particles from the sun have stripped away most of Mars’ atmosphere, resulting in very poor protection against radiation at the surface. The highest air pressure on Mars is equal to that at an altitude of 22 miles (35 kilometers) above the Earth’s surface. At low altitudes, Mars’ atmosphere provides slightly better protection from space radiation.

    See the full article here .

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  • richardmitnick 10:31 am on March 24, 2016 Permalink | Reply
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    From astrobites: “A new galactic component of cosmic rays?” 

    Astrobites bloc


    Mar 24, 2016
    Kelly Malone

    Title: A large light-mass component of cosmic rays at 1017 – 1017.5 eV from radio observations
    Authors: The LOFAR Collaboration
    First Author’s Institution: Astrophysical Institute, Vrije Universiteit Brussel; Department of Astrophysics/IMAPP, Radboud University Nijmegen
    Status: Published in Nature

    Cosmic rays are the highest-energy naturally occurring particles in the universe. Their energies can approach orders of magnitude higher than anything the Large Hadron Collider can produce! Although these particles (including protons and the nuclei of helium, iron, and nitrogen) were discovered in the early 1900s, there are still many unanswered questions about where they come from, how they get accelerated to such high energies, and their mass composition. Today’s paper studies the mass composition of cosmic rays in the energy range of 1017 to 1017.5 eV. Cosmic rays at these energies are thought to come from inside our galaxy.

    When a cosmic ray hits the Earth’s atmosphere, it interacts with the air molecules in the atmosphere and creates a cascade of particles known as an air shower. This shower gets bigger and bigger, with the total energy of the primary cosmic ray split between all the particles that are created. Eventually the secondary particles do not have enough energy for the shower to keep growing; it begins to shrink and die out at this point. The air shower is accompanied by radiation that can be detected at radio wavelengths, partially created by electrons and positrons accelerating in the geomagnetic field (see this paper for an in-depth discussion of the physics involved). This radio emission changes as the shower grows and dies out, making it sensitive to a quantity known as Xmax. Xmax (also called the atmospheric depth at shower maximum) is the column density of the atmosphere over the full path the particle travels. Different species of cosmic rays will have different values of Xmax.

    ASTRON LOFAR Radio Antenna Bank
    LOFAR’s core, located in the Netherlands (Source: LOFAR/ASTRON)

    All the data for this analysis was taken using the Low Frequency Array (LOFAR), a radio telescope that looks quite different from what one typically envisions when they hear the word “telescope”. It consists of thousands of antennas. Most of them are located in the Netherlands, although there are a few stations in other European countries, creating a very large collecting area. Signals from individual antennas are digitized and combined before analysis begins.

    Fig. 1: the distribution of p-values for the proton and helium fractions in the four-component model that was used. The black shape shows where the p-value is > 0.01. For p>0.01, the p+He fraction (the “light elements”) is at least 0.38 and may be as high at 0.98.

    The LOFAR Collaboration measured Xmax and found it consistent with measurements from other, non-radio experiments. They then used the expected values of Xmax for different cosmic ray species from Monte Carlo simulations and found the best fit to the data came from a four-component model with proton, helium, nitrogen, and iron cosmic rays. The first two of those are much lighter and are therefore known as the “light-mass component”. They found that the best fit allowed within systematic uncertainties gives a light-mass fraction of cosmic rays of somewhere between 38% and 98%.

    This is interesting because we know from cosmic ray theories that in the energy range they studied, galactic sources should dominate over extragalactic ones. The mass composition of the main galactic component of the cosmic rays (CRs from supernova remnants) is expected to be heavier. Therefore, this lighter mass-component must come from a second source of galactic cosmic rays. Possibilities include a class of extremely energetic sources (such as Wolf-Rayet stars exploding), past galactic gamma-ray bursts, or a re-acceleration of the main, original component of galactic cosmic rays.

    See the full article here .

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    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

  • richardmitnick 9:39 am on March 3, 2016 Permalink | Reply
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    From AAAS: “Mysterious cosmic rays may come from a place not so far away” 



    Mar. 2, 2016
    Daniel Clery

    ASTRON LOFAR Radio Antenna Bank
    Astron LOFAR antennae

    LOFAR map

    Cosmic rays—high energy particles that rain down on Earth from deep space—are something of a mystery: What are they made of? Where do they come from? And how do they gain such enormous energies—far above those achieved with the world’s best particle accelerators? Now, a radio telescope originally designed to study the early universe may help answer some of those questions, or it might just deepen the mystery.

    Cosmic rays are typically protons or atomic nuclei of elements such as helium, carbon, or iron. The most energetic have energies more than 10 million times greater than those in the world’s most powerful atom smasher, the Large Hadron Collider. Physicists aren’t sure what astrophysical process could accelerate particles to such energies. Possible culprits include the lingering remains of supernovae, the explosions that occur when massive stars run out of fuel and die; and active galactic nuclei, superheated galaxies with supermassive black holes at their centers that spew out energy at prodigious rates.

    Studying cosmic rays is difficult, however. On their journey through space they are deflected this way and that by magnetic fields, making it difficult to figure out where they’ve come from. The high-energy ones are also very rare, and none of them get very far once they reach Earth’s atmosphere; they’re instantly destroyed in collisions with the air at high altitude. To study the highest energy cosmic rays, physicists use vast arrays of particle detectors on the ground to pick up the “air shower” of debris created by the high altitude collisions or telescopes to spot the flash of light caused by the debris particles as they slow down in the atmosphere.

    But now there is a new way to detect cosmic rays. A team has made use of a collection of radio telescopes known as the Low Frequency Array (LOFAR), which is centered in the Netherlands but has outposts in several other northern European countries. LOFAR does not have large steerable dishes like other radio telescopes, but is instead made up of many thousands of simple wire antennas staked out on the ground in dozens of “stations.” The antennas essentially pick up everything coming from space, and it is then up to a superfast processor cluster to sift through the data and focus on a particular phenomenon or part of the sky.

    The main aim of LOFAR is to study the era in the early universe when the very first stars and galaxies were forming and ionizing all the interstellar gas around them. But the cosmic ray team is able to piggyback on normal astronomical observations in their search for air showers. As the debris particles from the cosmic ray collision cascade down through the atmosphere, their interactions with each other and Earth’s magnetic field produce a radio signal that is detectable by LOFAR’s antennas. The team can’t scour through all the data 24/7, there’s just too much. So the researchers installed particle detectors on the ground that can alert the system that an air shower has just happened. When a particle detector trips the alarm, LOFAR’s cosmic ray system grabs the previous 5 seconds of data that is held in the system’s buffer, knowing that the signal from an air shower is somewhere in it.

    The team had earlier modeled what these radio signals would look like and when they started observing with LOFAR they struck gold very quickly. “A half of all observations agreed absolutely [with the models]. They fit perfectly, which is a rare experience in experimental physics,” says team member Heino Falcke, an astrophysicist at Radboud University in Nijmegen, the Netherlands. Using this technique, the researchers were able to measure how far down into the atmosphere the cascade of particles went before it reached its maximum size. That depth could tell them what sort of particle the original cosmic ray was—proton, helium nucleus, or something heavier.

    As the scientists report today in Nature, about 80% of the more than 120 events analyzed turned out to be light cosmic rays—protons or helium nuclei. That’s not entirely unexpected. The LOFAR team probed particles with a range of energies between 1017 and 1017.5 electron-volts (eV). “A terra incognita,” Falcke says, which is hard to reach with other techniques. “The compositional data is very sparse.” This range occupies a middle ground between lower energy cosmic rays expected from sources in our galaxy and higher energy cosmic rays from much more distant galaxies. Current theory suggests that the highest energy cosmic rays are mostly protons rather than heavier nuclei. But the researchers say that you wouldn’t expect as big a fraction as 80% at energies below 1017.5 eV.

    Also, Falcke says, there are hints in the distribution of particles across the range of energy they studied, that some of those light cosmic rays may have come from sources in our galaxy. That would be surprising because it is not thought that local accelerators, such as supernova remnants, can achieve energies for protons higher than 1015 eV. Falcke acknowledges that this interpretation “remains speculative. It’s a first step,” he says. If it holds up, however, it only deepens the mystery of cosmic rays, because it implies that there is some object or mechanism within our galaxy—as yet unknown —that is able to boost particles to these supercharged speeds.

    But such a conclusion would be “challenging” to current astrophysical explanations, says Andrew Taylor, an astrophysicist at the Dublin Institute for Advanced Studies. He thinks the evidence is not yet there that they come from a source in our galaxy rather than an extragalactic one. “It’s too early to make definitive statements,” he says, but “both would be interesting.”

    Taylor does think the new technique holds great promise for the future, because of its ability to identify types of particle and the fact that it can operate day or night in any weather (optical techniques of observing air showers only work on clear moonless nights). “Radio can gather data much faster,” he says. “It will provide a whole new set of opportunities to explore.”

    See the full article here .

    The American Association for the Advancement of Science is an international non-profit organization dedicated to advancing science for the benefit of all people.

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  • richardmitnick 12:52 pm on July 26, 2015 Permalink | Reply
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    From Business Insider: “Physicists are still puzzled by a particle that seems to defy the laws of physics” 

    Business Insider logo

    Business Insider

    Jun. 4, 2015
    Natalie Wolchover, Quanta Magazine

    NASA, ESA, S. Baum and C. O’Dea (RIT), R. Perley and W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA

    On the night of October 15, 1991, the “Oh-My-God” particle streaked across the Utah sky.

    A cosmic ray from space, it possessed 320 exa-electron volts (EeV) of energy, millions of times more than particles attain at the Large Hadron Collider, the most powerful accelerator ever built by humans.

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

    The particle was going so fast that in a yearlong race with light, it would have lost by mere thousandths of a hair. Its energy equaled that of a bowling ball dropped on a toe. But bowling balls contain as many atoms as there are stars. “Nobody ever thought you could concentrate so much energy into a single particle before,” said David Kieda, an astrophysicist at the University of Utah.

    Five or so miles from where it fell, a researcher worked his shift inside an old, rat-infested trailer parked atop a desert mountain. Earlier, at dusk, Mengzhi “Steven” Luo had switched on the computers for the Fly’s Eye detector, an array of dozens of spherical mirrors that dotted the barren ground outside. Each of the mirrors was bolted inside a rotating “can” fashioned from a section of culvert, which faced downward during the day to keep the sun from blowing out its sensors. As darkness fell on a clear and moonless night, Luo rolled the cans up toward the sky.

    Fly's Eye Detector
    Fly’s Eye detector

    “It was a pretty crude experiment,” said Kieda, who operated the Fly’s Eye with Luo and several others. “But it worked — that was the thing.”

    The Fly’s Eye array operated out of Dugway Proving Ground, a military base in the desert of western Utah, from 1981 to 1993; it pioneered the “air fluorescence technique” for determining the energies and directions of ultra high-energy cosmic rays based on faint light emitted by nitrogen air molecules as the cosmic-ray air shower traverses the atmosphere. In 1991, the Fly’s Eye detected a cosmic ray that still holds the world record for highest-energy particle.


    The faintly glowing contrail of the Oh-My-God particle (as the computer programmer and Autodesk founder John Walker dubbed it in an early Web article) was spotted in the Fly’s Eye data the following summer and reported after the group spent an extra year convincing themselves the signal was real. The particle had broken a cosmic speed limit worked out decades earlier by Kenneth Greisen, Georgiy Zatsepin and Vadim Kuzmin, who argued that any particle energized beyond approximately 60 EeV will interact with background radiation that pervades space, thereby quickly shedding energy and slowing down. This “GZK cutoff” suggested that the Oh-My-God particle must have originated recently and nearby — probably within the local supercluster of galaxies. But an astrophysical accelerator of unimagined size and power would be required to produce such a particle. When scientists looked in the direction from which the particle had come, they could see nothing of the kind.

    “It’s like you’ve got a gorilla in your backyard throwing bowling balls at you, but he’s invisible,” Kieda said.

    Where had the Oh-My-God particle come from? How could it possibly exist? Did it really? The questions motivated astrophysicists to build bigger, more sophisticated detectors that have since recorded hundreds of thousands more “ultrahigh-energy cosmic rays” with energies above 1 EeV, including a few hundred “trans-GZK” events above the 60 EeV cutoff (though none reaching 320 EeV). In breaking the GZK speed limit, these particles challenged one of the farthest-reaching predictions ever made. It seemed possible that they could offer a window into the laws of physics at otherwise unreachable scales — maybe even connecting particle physics with the evolution of the cosmos as a whole. At the very least, they promised to reveal the workings of extraordinary astrophysical objects that had only ever been twinkles in telescope lenses. But over the years, as the particles swept brushstrokes of light across sensors in every direction, instead of painting a telltale pattern that could be matched to, say, the locations of supermassive black holes or colliding galaxies, they created confusion. “It’s hard to explain the cosmic-ray data with any particular theory,” said Paul Sommers, a semiretired astrophysicist at Pennsylvania State University who specializes in ultrahigh-energy cosmic rays. “There are problems with anything you propose.”

    Only recently, with the discovery of a cosmic ray “hotspot” in the sky, the detection of related high-energy cosmic particles, and a better understanding of physics at more familiar energies, have researchers secured the first footholds in the quest to understand ultrahigh-energy cosmic rays. “We’re learning things very rapidly,” said Tim Linden, a theoretical astrophysicist at the University of Chicago.

    Ankle Problems

    Thousands of cosmic rays bombard each square foot of Earth’s atmosphere every second, and yet they managed to elude discovery until a series of daring hot-air-balloon rides in the early 1910s. As the Austrian physicist Victor Hess ascended miles into the atmosphere, he observed that the amount of ionizing radiation increased with altitude. Hess measured this buzz of electrically charged particles even during a solar eclipse, establishing that much of it came from beyond the sun. He received a Nobel Prize in physics for his efforts in 1936.

    Cosmic rays, as they became known, arc through Earth’s magnetic field from every direction, and with a smooth spread of energies. (At sea level, we experience the low-energy, secondary radiation produced as the cosmic rays crash through the atmosphere.) Most cosmic rays are single protons, the positively charged building blocks of atomic nuclei; most of the rest are heavier nuclei, and a few are electrons. The more energetic a cosmic ray is, the rarer it is. The rarest of all, those that are labeled “ultrahigh-energy” and exceed 1 EeV, strike each square kilometer of the planet only once per century.

    Plotting the number of cosmic rays that sprinkle detectors according to their energies produces a downward-sloping line with two bends — the energy spectrum’s “knee” and “ankle.” These seem to mark transitions to different types of cosmic rays or progressively larger and more powerful sources. The question is, which types, and which sources?

    Like many experts, Karl-Heinz Kampert, a professor of astrophysics at the University of Wuppertal in Germany and spokesperson for the Pierre Auger Observatory, the world’s largest ultrahigh-energy cosmic ray detector, believes cosmic rays are accelerated by something like the sonic booms from supersonic jets, but on grander scales.

    Pierre Auger Observatory
    Pierre Auger Observatory

    Shock acceleration, as it’s called, “is a fundamental process which you find on any scale in the universe,” Kampert said, from solar flares to star explosions (supernovas) to rapidly spinning stars called pulsars to the enormous lobes emanating from mysterious, super-bright galaxies known as active galactic nuclei. All are cases of heated matter (or “plasma”) flowing faster than the speed of sound, producing an expanding shock wave that accumulates a crust of protons and other particles. The particles reflect back and forth across the shock wave, trapped between the magnetic field of the plasma and the vacuum of empty space like little balls ping-ponging between table and paddle. A particle gains energy with every bounce. “Then it will escape,” Kampert said, “and move through the universe and be detected by an experiment.”

    Cosmic rays are most likely energized through “shock acceleration,” reflecting back and forth across a shock wave that is produced when plasma flows faster than the speed of sound. The stronger and larger the magnetic field of the plasma, the more energy it can impart to a particle. Ultrahigh-energy cosmic rays surpass 1 exa-electron volt (EeV).

    Trying to match different shock waves to parts of the cosmic-ray energy spectrum puts astrophysicists on shaky ground, however. They would expect the knee and ankle to mark the highest points to which protons and heavier nuclei (respectively) can be energized in the shock waves of supernovas — the most powerful accelerators in our galaxy. Calculations suggest the protons should max out around 0.001 EeV, and indeed, this aligns with the knee. Heavier nuclei from supernova shock waves are thought to be capable of reaching 0.1 EeV, making this number the expected transition point to more powerful sources of “extragalactic” cosmic rays. These would be shock waves from singular objects that aren’t found in the Milky Way or in most other galaxies, and which could well be galaxy-size themselves. However, the measured ankle of the spectrum — “the only place where it looks like there’s a clear transition,” Sommers said — lies around 5 EeV, an order of magnitude past the theoretical maximum for galactic cosmic rays. No one is sure what to make of the discrepancy.

    Past the ankle, at around 60 EeV, the line dips toward zero, forming a sort of toe. This is probably the GZK cutoff, the point beyond which cosmic rays can only tarry for so long before losing energy to ambient cosmic microwaves generated by a phase transition in the early universe. The existence of the cutoff, which Kampert calls “the only firm prediction ever made” about cosmic rays, was established in 2007 by the Fly’s Eye’s successor — the High Resolution Fly’s Eye experiment, or HiRes. From there, the energy spectrum reduces to a trickle of trans-GZK cosmic rays, finally ending, at 320 EeV, with a single data point: the Oh-My-God particle.

    The presence of the GZK cutoff means that the laws of physics are operating as expected. Rather than disproving those laws, trans-GZK cosmic rays probably do originate nearby (reaching Earth before ambient microwaves sap their energy). But where, and how? For a maddening 20 years, the particles appeared to come from everywhere and nowhere in particular. But finally a hotspot has developed in the Northern Hemisphere. Could this be the invisible gorilla hurtling bowling balls toward Earth?


    Getting Hotter

    In Utah, a three-hour drive from the site of the original Fly’s Eye, its latest descendant sprawls across the desert: a 762-square-kilometer grid of detectors called the Telescope Array. The experiment has been tracking the multi-billion-particle “air showers” produced by ultrahigh-energy cosmic rays since 2008. “We’ve been watching the hotspot increase in statistical significance for several years,” said Gordon Thomson, a professor of physics and astronomy at the University of Utah and spokesperson for the Telescope Array.

    Of the 87 cosmic rays surpassing 57 EeV detected thus far by the Telescope Array, 27 percent come from 6 percent of the sky. The hotspot centers on the constellation Ursa Major.

    The hotspot of trans-GZK cosmic rays, which centers on the constellation Ursa Major, was initially too weak to be taken seriously. But in the past year, it has reached an estimated statistical significance of “four sigma,” giving it a 99.994 percent chance of being real. Thomson and his team must reach five-sigma certainty to definitively claim a discovery. (Thomson hopes this will happen in the group’s next data analysis, due out in June.) Already, theorists are treating the hotspot as an anchor for their ideas.

    “It’s really exciting,” said Linden. With more data, he explained, the location of the source can be pinpointed within the hotspot (which gets smeared out by the deflection of cosmic rays as they pass through the galaxy’s and Earth’s magnetic fields). By tracking other types of particles coming from the same spot in the sky, “you have a model of how the source works over many orders of magnitude in energy,” he said. The invisible gorilla would materialize.

    Meanwhile, some of those other particles are slowly piling up in the sensors of the IceCube detector, a cable-infused, cubic-kilometer block of ice buried beneath the South Pole. For the past four years, IceCube has monitored the rare ice tracks of neutrinos, lightweight elementary particles that usually flit right through matter and thus require immense efforts to detect, but which are produced in abundance from physical processes throughout the universe.

    Every so often, cosmic neutrinos interact with atoms and produce radiation as they pass through IceCube; their directions of travel trace a new map of the cosmos that can be compared to the maps of ultrahigh-energy cosmic rays and those of light. In 2013, IceCube scientists reported the observation of the first-ever very-high-energy neutrinos — a pair of 0.001-EeV particles nicknamed “Bert” and “Ernie” that might have come from the same sources that yield ultrahigh-energy cosmic rays. Neutrinos have a big advantage over cosmic rays as messengers from the most powerful objects in the universe: Because they are electrically neutral, they move in straight lines. “Since neutrinos travel to us uninhibited from the source, they might be able to open up a new window on the universe,” said Olga Botner of Uppsala University in Sweden, IceCube’s spokesperson.

    IceCube neutrino detector interior

    At the South Pole, the IceCube Neutrino Observatory is approaching the mystery of ultrahigh-energy cosmic rays by hunting related cosmic neutrinos, which interact with atoms every so often while passing through the sensor-infused, cubic-kilometer block of ice.

    Of the 54 high-energy neutrinos that IceCube has detected as of its latest analysis, reported in early May, four originate from the vicinity of the cosmic-ray hotspot. (Neutrinos can enter the detector after traveling through Earth from the northern sky.) This “hint of a correlation,” as Linden described it, could be a clue: Cosmic rays take longer to get to Earth than neutrinos, so a common source would have to have been pumping out energetic particles for many years. Short-lived source candidates such as gamma-ray bursts would be ruled out in favor of stable objects — perhaps a star-forming galaxy with a supermassive black hole at its center. “In the next few years we’re going to get that many more neutrinos, and we’ll see how this correlation plays out,” Linden said. For now, though, the correlation is very weak. “I’m not staking my foot in the ground,” he said.

    Alongside cosmic rays and neutrinos, cosmic “gamma rays” (high-energy photons) will serve as a third messenger in the coming years. They’re the subject of several major searches including the HESS (High Energy Stereoscopic System) experiment in Namibia — named in honor of the father of cosmic rays — and VERITAS (Very Energetic Radiation Imaging Telescope Array System) in Arizona, for which Kieda, the former Fly’s Eye scientist, now works. The combination of cosmic-ray, neutrino and gamma-ray data should help locate and sharpen astrophysicists’ picture of the most powerful accelerators in the universe. The search will organize around the hotspot.

    HESS Cherenko Array
    H.E.S.S. Array

    Veritas Telescope
    U Arizona/VERITAS

    Thomson has his money on threads of galaxies and dark matter called “filaments” that are draped throughout the cosmos and which, at hundreds of millions of light-years long, are among the largest structures in existence. There’s a filament in the direction of the hotspot. “It’s probably something in the filament,” Thomson said. In any case, he added, “we have an idea now of interesting places to look. And all we need to do is collect more data.”

    Draining the Pool

    Kampert, of the Pierre Auger Observatory, is approaching the mystery of ultrahigh-energy cosmic rays from a different direction, by asking: What are they?

    Victor Hess discovered cosmic rays in a series of hot-air-balloon rides in Austria between 1911 and 1913, concluding that “a radiation of very high penetrating power enters our atmosphere from above.”

    Some astrophysicists say the Auger Observatory has been “unlucky.” Covering 3,000 square kilometers of Argentina grasslands, it collects far more data than the Telescope Array, but it does not see a hotspot in the Southern Hemisphere with anywhere near the prominence of the one in the north. It has detected evidence of a slight concentration of trans-GZK cosmic rays in the sky that overlays an active galactic nucleus called Centaurus A as well as another filament. But Kampert says Auger might never collect enough data to prove this so-called “warm spot” is real. Still, the dearth of clues is a mystery in itself.

    “It’s a very rich data set and we don’t see anything,” said Sommers, who helped design and organize the Auger Observatory. “That’s absolutely amazing to me. Back in the 1980s I would have bet good money that if we had the statistics we have now, there would be obvious hotspots and patterns. It makes me really wonder.”

    Kampert thinks he and his colleagues must simply get smarter about how they look for hotspots, which are surely there; the local region of the universe is not uniformly blanketed by objects capable of accelerating particles to trans-GZK energies. The problem is magnetic deflection, he said. Galactic and extragalactic magnetic fields bend protons five to 10 degrees off-course, and they bend heavier nuclei many times that, depending on the number of protons they contain. Auger’s analysis of its air-shower events (which integrates cutting-edge results from particle collisions at the Large Hadron Collider) suggests that the highest-energy cosmic rays tend to be on the heavy side, consisting of carbon or even iron nuclei.

    “If at the highest energies we have [heavier nuclei], then your sky is always fuzzy or smeared out,” Kampert said. “It would be like doing astronomy from the bottom of a swimming pool.”

    He and his team hope to update their experiment with the ability to identify the composition of cosmic rays on an event-by-event basis. This will allow them to look for correlations between only the lightest, least deflected particles. “Composition is really the key to understanding the origin of the highest-energy particles,” he said.

    And the shift toward heavier nuclei at the far end of the cosmic-ray energy spectrum could be a major clue itself. Just as supernovas accelerate protons no further than the “knee” of the spectrum and can propel only heavier nuclei beyond that point, so too might the most powerful astrophysical accelerators in the universe peter out. Scientists could be glimpsing the true edge of the cosmic-ray spectrum: the points where protons, and then helium, carbon and iron, max out. Measuring this falloff will help expose how the giant accelerators work — and favor certain candidates over others.

    Theorists still struggle to imagine any of those candidates producing the sprinkle of particles in the 200-EeV range or the Oh-My-God particle at 320 — even if they are made of iron. “How you get a [320 EeV] particle is not easy from any theory,” Thomson said. “But it was there. It happened.”

    Even that fact is called into question. Back in the early 1990s, Sommers, who was temporarily working at the University of Utah, helped the Fly’s Eye scientists analyze their 320-EeV signal. But although the “big event” (as he calls it) was “pretty well measured by the standards of the time,” the Fly’s Eye hadn’t fully transitioned away from being a “monocular” experiment, analogous to one fly’s eye rather than two (a second eye was under construction); it lacked the precision and redundancy of later stereoscopic arrays. Sommers said that although no serious reasons for doubting the energy estimate are known, “one must be suspicious of it now. With vastly greater exposure, the more precise, new observatories have failed to detect any particle of such high energy. The flux of particles at energies that high must be so low that it would have been an incredible fluke that the Fly’s Eye detected one.”

    The error bars that went into calculating the Oh-My-God particle’s energy might all have been off in the wrong direction at the same time. If so, it was a lucky mistake for the field, motivating new experiments without greatly misleading researchers, since many other trans-GZK particles have followed. And if the Oh-My-God particle was a mistake, well, probably no one will ever know.

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  • richardmitnick 9:03 am on May 29, 2015 Permalink | Reply
    Tags: , , , Cosmic Rays   

    From AAAS: “Japan to enlarge massive cosmic ray array in Utah” 



    27 May 2015
    Adrian Cho

    Physicists will nearly double the number of particle detectors like this one in the vast Telescope Array. John Matthews, University of Utah

    Every once in a while, a cosmic ray—a subatomic particle from outer space—strikes the atmosphere with an energy 10 million times higher than a human made particle accelerator has ever achieved. Physicists don’t know where such mind-bogglingly energetic particles come from, but they could be closing in on an answer thanks to the expansion of one of the world’s biggest cosmic ray experiments.

    Japan will spend $3.7 million to nearly quadruple the size of the Telescope Array (TA), which currently consists of 507 particle detectors spread across 700 square kilometers of Utah desert. The detectors sense the avalanche of particles, or what physicists call an “extensive air shower,” triggered when a ray hits the atmosphere. Physicists will deploy 400 more loosely spaced detectors to stretch TA’s area to about 2500 square kilometers—twice the area of New York City—says Yoshiki Tsunesada, a physicist and TA team member at the Tokyo Institute of Technology. From the size and direction of an air shower, physicists can deduce the energy and direction of the original ray. Researchers hope to complete the expansion in 2017. Japan paid two-thirds of the current array’s $25 million cost.

    The expansion, known simply as TAx4 or “TA times four,” could help researchers pin down the origins of the highest energy rays, in which a single subatomic particle can carry as much energy as a golf ball plunging to the green. Physicists have yet to find the sources of the rays. However, last July TA researchers reported an excess of rays with an energy above 60 exa–electron volts (EeV) coming from the general direction of the constellation Ursa Major, which includes the Big Dipper. “We’ve got about 20 events in a cluster with a width of about 20 degrees,” says Hiroyuki Sagawa, a physicist at the University of Tokyo and co-spokesperson for the TA team. If the rays come equally from everywhere, then such a circle ought to contain about five rays, Sagawa says. “If we obtain more data we may observe structure within the hotspot,” he says.

    The expansion will also make TA almost as big as its rival, the Pierre Auger Observatory in Argentina, which has 1600 particle detectors of a different design spread over 3000 square kilometers.

    Pierre Auger Observatory
    Pierre Auger Observatory

    In 2007, the Auger collaboration reported that the highest energy cosmic rays appear to come from the fiery hearts of certain galaxies. However, that correlation has not held up as Auger has continued to collect more data. Auger commenced taking data in 2005, and TA in 2008, and over the years the teams have disagreed on several key results. For example, TA physicists argue that—as most physicists expected—the highest energy rays are protons, whereas Auger physicists argue they may include heavier atomic nuclei.

    Years ago, Auger physicists had argued for building a twin version of their array in the Northern Hemisphere. Now, with its expansion, TA will effectively play that role. “With two [equal-sized] observatories we can see the whole sky,” Sagawa says. “That’s very important,” he says, as the hemispheres may look different in cosmic rays.

    Like Auger, TA also features batteries of specialized telescopes that on clear, moonless nights can detect the faint light, or fluorescence, produced by an extensive air shower. Such telescope observations provide a better measure of the energy of the shower and are key for calibrating the array of surface detectors: By comparing the readout of the fluorescence telescopes and surface detectors on the same events, physicists can figure out how to better estimate a shower’s energy from the surface detector alone. TA currently has three batteries of telescopes and researchers are hoping the U.S. National Science Foundation (NSF) will pay for two more, says Douglas Bergman, a physicist at the University of Utah in Salt Lake City.

    The TA team is hoping NSF will spend about $1 million mainly for building the new batteries, Bergman says. Researchers already have the telescopes themselves from a previous experiment, he says. Physicists applied to NSF last fall and will do so again this fall, Bergman says. “I think the prospects would be better in the sense of there being this exciting news from Japan,” Bergman says.

    Even some TA physicists caution that with more data the hotspot may not hold up. “I personally am still in doubt whether it is real,” Tsunesada says. In the past, many tantalizing cosmic ray results have failed to pan out, he notes. In fact, Tsunesada says, if the expanded TA and Auger don’t detect sources of the highest energy rays, the search could come to an end. “This could be the last chance for us air-shower researchers,” Tsunesada says. Others are more optimistic. For example, Sagawa notes, it may be possible to study air showers over a vastly larger area using space-borne fluorescence telescopes.

    See the full article here.

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  • richardmitnick 3:10 pm on April 28, 2015 Permalink | Reply
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    From Symmetry: “AMS results create cosmic ray puzzle” 


    April 15, 2015
    Sarah Charley

    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 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.

    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.

    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.

    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.

    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?


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