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  • richardmitnick 3:35 pm on March 25, 2015 Permalink | Reply
    Tags: , , , Neutrinos   

    From DESY: “Latest result from neutrino observatory IceCube opens up new possibilities for particle physics” 

    DESY
    DESY

    2015/03/24
    No Writer Credit

    South Pole detector measures neutrino oscillations with high precision

    The South Pole observatory IceCube has recorded evidence that elusive elementary particles called neutrinos changing their identity as they travel through the Earth and its atmosphere.

    1
    The IceCube laboratory at the Scott Amundsen South Pole station hosts the computers collecting the detector data (picture: Felipe Pedreros. IceCube/NSF)

    IceCube neutrino detector interior
    IceCube Neutrino Experiment interior

    The observation of these neutrino oscillations, first announced in 1998 by the Super Kamiokande experiment in Japan, opens up new possibilities for particle physics with the Antarctic telescope that was originally designed to detect neutrinos from faraway sources in the cosmos.

    Super-Kamiokande experiment Japan
    Super Kamiokande experiment

    “We are very pleased that the IceCube detector with its DeepCore array can be used to observe neutrino oscillations with high precision,” says Olga Botner, Spokesperson of the IceCube experiment. “DeepCore was designed on the initiative of Per Olof Hulth who sadly passed away recently, to significantly lower IceCube’s energy threshold. The results show that IceCube can contribute to nailing down the oscillation parameters and motivate us to pursue our plans for an IceCube upgrade called PINGU to measure neutrino properties.”

    IceCube DeepCore
    IceCube DeepCore

    IceCube PINGU
    IceCube PINGU

    “IceCube records over one hundred thousand atmospheric neutrinos every year, most of them muon neutrinos produced by the interaction of fast cosmic particles with the atmosphere,” says Rolf Nahnhauer, leading scientist at DESY. The subdetector DeepCore allows for detecting neutrinos with energies down to 10 giga-electronvolts (GeV). “According to our understanding of neutrino oscillations, IceCube should see fewer muon neutrinos at energies around 25 GeV that reach IceCube after crossing the entire Earth,” explains Rolf Nahnhauer. “The reason for these missing muon neutrinos is that they oscillate into other types.” IceCube researchers selected Northern Hemisphere muon neutrino candidates with energies between a few GeV and around 50 GeV from data taken between May 2011 and April 2014. About 5200 events were found, much below the 7000 expected in the non-oscillations scenario.

    Neutrinos remain the most mysterious of the known elementary particles. Postulated by Austrian physicist Wolfgang Pauli in 1930, it took 25 years for their experimental detection. “Neutrinos are elusive,” says Olga Botner, ” and can travel through an enormous amount of material, even the whole Earth, without interacting.” Nevertheless, physicists have built more and more sophisticated instruments to reveal the mysteries of this very light particles. One of the surprising results was that the three different types of neutrinos, electron, muon and tau neutrinos, can change their identity, transforming from one type of neutrino to another. This phenomenon is known as neutrino oscillation. “Neutrino oscillations are only possible if neutrinos have a mass,” explains Nahnhauer. “On the other hand, massive neutrinos are not explained within the otherwise so successful Standard Model of particle physics.”

    3
    Standard Model of Particle Physics. The diagram shows the elementary particles of the Standard Model (the Higgs boson, the three generations of quarks and leptons, and the gauge bosons), including their names, masses, spins, charges, chiralities, and interactions with the strong, weak and electromagnetic forces. It also depicts the crucial role of the Higgs boson in electroweak symmetry breaking, and shows how the properties of the various particles differ in the (high-energy) symmetric phase (top) and the (low-energy) broken-symmetry phase (bottom).

    The strength of the oscillation and the distances over which it develops depend on two parameters: the so-called mixing angle and the mass difference. The values of these parameters have been constrained by precise measurements of neutrinos from the sun, the atmosphere, nuclear reactors, and particle accelerators.

    The IceCube neutrino observatory at the South Pole has already demonstrated that it is a powerful tool to explore the universe by neutrinos, using the Antarctic ice sheet as its detection material. An array of more than 5000 optical sensors distributed in a cubic kilometer of the ice records the very rare collisions of neutrinos. And less than two years ago, IceCube physicists announced the discovery of the first high-energy neutrinos from the cosmos, acknowledged as “breakthrough of the year” by the journal Physics World.

    Now IceCube has proven that it can also deliver top particle physics results. The new measurement by the IceCube collaboration resulting in significantly improved constraints on the neutrino oscillation parameters has been accepted for publication by the scientific journal Physical Review D.

    Three years of IceCube data yielded a similar precision to that reached from about 15 years of Super-Kamiokande data. In contrast to the purified water in Super-Kamiokande’s 50-kiloton vessel, IceCube uses a natural target material, the glacier ice at the South Pole. IceCube’s 500 times larger observation volume produces larger event statistics in shorter times. “Both Super-Kamiokande and IceCube use the same ‘beam‘ which is atmospheric neutrinos, but at different energies. And we reach similar precision of the measurable oscillation parameters,” says Juan Pablo Yanez, postdoctoral researcher at DESY, who is the corresponding author of the paper. “The results now derived from IceCube data show errors still larger than, but already comparable to the most precise neutrino beam experiments MINOS and T2K. But as IceCube keeps taking data and improving the analyses we are hopeful to catch up soon.” adds Yanez.

    Currently the scientists are planning an upgrade of the IceCube detector called PINGU (Precision IceCube Next Generation Upgrade). A much higher density of optical modules in the whole central region will improve the sensitivity to several fundamental questions associated with neutrinos.

    “In particular we want to measure the so called neutrino mass hierarchy – whether there are two heavier neutrinos and one light one, or whether it is the other way around.” explains Rolf Nahnhauer. “This is important to understand how neutrinos obtain masses, but also has significant relevance on how the cosmos evolves. The current results provide an important experimental confirmation that our concepts work.“

    See the full article here.

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    desi

    DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

     
  • richardmitnick 11:14 am on March 25, 2015 Permalink | Reply
    Tags: , FNAL DUNE, Neutrinos   

    From Symmetry: “The dawn of DUNE” 

    Symmetry

    March 25, 2015
    Jennifer Huber and Kathryn Jepsen

    1
    Courtesy of Fermilab

    A powerful planned neutrino experiment gains new members, new leaders and a new name.

    The neutrino experiment formerly known as LBNE has transformed. Since January, its collaboration has gained about 50 new member institutions, elected two new spokespersons and chosen a new name: Deep Underground Neutrino Experiment, or DUNE [No web site yet].

    The proposed experiment will be the most powerful tool in the world for studying hard-to-catch particles called neutrinos. It will span 800 miles. It will start with a near detector and an intense beam of neutrinos produced at Fermi National Accelerator Laboratory in Illinois. It will end with a 10-kiloton far detector located underground in a laboratory at the Sanford Underground Research Facility [SURF] in South Dakota.

    Sanford Underground Research facility
    Sanford Underground levels
    Sanford Underground Research Facility Interior
    SURF

    The distance between the two detectors will allow scientists to study how neutrinos change as they zip at close to the speed of light straight through the Earth.

    “This will be the flagship experiment for particle physics hosted in the US,” says Jim Siegrist, associate director of high-energy physics for the US Department of Energy’s Office of Science. “It’s an exciting time for neutrino science and particle physics generally.”

    In 2014, the Particle Physics Project Prioritization Panel [P5] identified the experiment as a top priority for US particle physics. At the same time, it recommended the collaboration take a few steps back and invite more international participation in the planning process.

    Physicist Sergio Bertolucci, director of research and scientific computing at CERN, took the helm of an executive board put together to expand the collaboration and organize the election of new spokespersons.

    DUNE now includes scientists from 148 institutions in 23 countries. It will be the first large international project hosted by the US to be jointly overseen by outside agencies.

    This month, the collaboration elected two new spokespersons: André Rubbia, a professor of physics at ETH Zurich, and Mark Thomson, a professor of physics at the University of Cambridge. One will serve as spokesperson for two years and the other for three to provide continuity in leadership.

    Rubbia got started with neutrino research as a member of the NOMAD experiment at CERN in the ’90s.

    CERN NOMAD
    NOMAD

    More recently he was a part of LAGUNA-LBNO, a collaboration that was working toward a long-baseline experiment in Europe. Thomson has a long-term involvement in US-based underground and neutrino physics. He is the DUNE principle investigator for the UK.

    Laguna LBNO

    Scientists are coming together to study neutrinos, rarely interacting particles that constantly stream through the Earth but are not well understood. They come in three types and oscillate, or change from type to type, as they travel long distances. They have tiny, unexplained masses. Neutrinos could hold clues about how the universe began and why matter greatly outnumbers antimatter, allowing us to exist.

    “The science is what drives us,” Rubbia says. “We’re at the point where the next generation of experiments is going to address the mystery of neutrino oscillations. It’s a unique moment.”

    Scientists hope to begin installation of the DUNE far detector by 2021. “Everybody involved is pushing hard to see this project happen as soon as possible,” Thomson says.

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 11:23 am on March 20, 2015 Permalink | Reply
    Tags: , , , Neutrinos,   

    From FNAL: “Expanding the cosmic search” 

    FNAL Home


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

    Friday, March 20, 2015
    Diana Kwon

    South Pole Telescope
    SPT

    Down at the South Pole, where temperatures drop below negative 100 degrees Fahrenheit and darkness blankets the land for six months at a time, the South Pole Telescope (SPT) searches the skies for answers to the mysteries of our universe.

    This mighty scavenger is about to get a major upgrade — a new camera that will help scientists further understand neutrinos, the ghost-like particles without electric charge that rarely interact with matter.

    The 10-meter SPT is the largest telescope ever to make its way to the South Pole. It stands atop a two-mile thick plateau of ice, mapping the cosmic microwave background (CMB), the light left over from the big bang. Astrophysicists use these observations to understand the composition and evolution of the universe, all the way back to the first fraction of a second after the big bang, when scientists believe the universe quickly expanded during a period called inflation.

    Cosmic Microwave Background  Planck
    CMB per ESA/Planck

    ESA Planck
    ESA/Planck

    One of the goals of the SPT is to determine the masses of the neutrinos, which were produced in great abundance soon after the big bang. Though nearly massless, because neutrinos exist in huge numbers, they contribute to the total mass of the universe and affect its expansion. By mapping out the mass density of the universe through measurements of CMB lensing, the bending of light caused by immense objects such as large galaxies, astrophysicists are trying to determine the masses of these elusive particles.

    To conduct these extremely precise measurements, scientists are installing a bigger, more sensitive camera on the telescope. This new camera, SPT-3G, will be four times heavier and have a factor of about 10 more detectors than the current camera. Its higher level of sensitivity will allow researchers to make extremely precise measurements of the CMB that will hopefully make it possible to cosmologically detect neutrino mass.

    South Pole Telescope SPT-3G Camera
    SPT-3G

    “In the next several years, we should be able to get to the sensitivity level where we can measure the number of neutrinos and derive their mass, which will tell us how they contribute to the overall density of the universe,” explained Bradford Benson, the head of the CMB Group at Fermilab. “This measurement will also enable even more sensitive constraints on inflation and has the potential to measure the energy scale of the associated physics that caused it.”

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    A wafer of detectors for the SPT-3G camera undergoes inspection at Fermilab. Photo: Bradford Benson, University of Chicago and Fermilab

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    This photo shows an up-close look at a single SPT-3G detector. Photo: Volodymyr Yefremenko, Argonne National Laboratory

    SPT-3G is being completed by a collaboration of scientists spanning the DOE national laboratories, including Fermilab and Argonne, and universities including the University of Chicago and University of California, Berkeley. The national laboratories provide the resources needed for the bigger camera and larger detector array while the universities bring years of expertise in CMB research.

    “The national labs are getting involved because we need to scale up our infrastructure to support the big experiments the field needs for the next generation of science goals,” Benson said. Fermilab’s main role is the initial construction and assembly of the camera, as well as its integration with the detectors. This upgrade is being supported mainly by the Department of Energy and the National Science Foundation, which also supports the operations of the experiment at the South Pole.

    Once the camera is complete, scientists will bring it to the South Pole, where conditions are optimal for these experiments. The extreme cold prevents the air from holding much water vapor, which can absorb microwave signals, and the sun, another source of microwaves, does not rise between March and September.

    The South Pole is accessible only for about three months during the year, starting in November. This fall, about 20 to 30 scientists will head down to the South Pole to assemble the camera on the telescope and make sure everything works before leaving in mid-February. Once installed, scientists will use it to observe the sky over four years.

    “For every project I’ve worked on, it’s that beginning — when everyone is so excited not knowing what we’re going to find, then seeing things you’ve been dreaming about start to show up on the computer screen in front of you — that I find really exciting,” said University of Chicago’s John Carlstrom, the principal investigator for the SPT-3G project.

    See the full article here.

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 9:24 am on March 20, 2015 Permalink | Reply
    Tags: , , Neutrinos   

    From FNAL- “Frontier Science Result: MINERvA – The MINERvA test beam program: trust but verify” 

    FNAL Home


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

    Friday, March 20, 2015
    Rik Gran, University of Minnesota – Duluth

    1
    This plot shows the energy deposited in the MINERVA test beam detector divided by the incoming kinetic energy of the pion as a function of the kinetic energy of the pion. No image credit

    All particle physics experiments rely on computer simulations of their detectors to make measurements, but neutrino experiments struggle to test these simulations using particles that are created from the neutrino beam itself.

    Neutrino interactions often produce charged particles such as muons or electrons, and they knock one or more protons or neutrons out of the nucleus. Neutrino interactions also produce quark-antiquark pairs called pions (see earlier MINERvA results from February, August and January). Each of these different particles gives us a view inside the nucleus, but to make these precise measurements, MINERvA needs to understand what these particles do once they exit the nucleus and enter the rest of the detector.

    We could simply trust a computer package (called Geant4) that simulates particle interactions, but to be rigorous, we verify that package. To do this we use a well-calibrated low-energy beam of pions, protons, muons and electrons from the Fermilab Test Beam Facility and a scaled-down version of the full MINERvA detector that is made of planes of scintillator, lead and steel. This smaller detector, which can be configured to replicate the downstream third of the neutrino detector, uses the same materials, electronics and calibration strategy.

    FNAL Minerva
    MINERvA

    We took data for six weeks in the summer of 2010 using the scaled-down detector and have been poring over this data ever since to measure many different aspects of the way the detector performs.

    With these data we were able to address, for one, how the kinetic energy of a pion entering our detector is translated into an energy measurement. When we use a popular Geant4 model for low-energy pions interacting in the simulated detector, the prediction is a good, though not perfect, description of the data. The experiment was designed to test the simulation, and the systematic uncertainties are small enough that we can assign a small uncertainty on how well Geant4 predicts the pion’s energy.

    We also used the test beam data to measure details about the scintillator material itself to improve the model of the detector geometry and electronics. We also improved how we calibrate both the test beam and the neutrino detector.

    We have continually fed back all of these improvements into the neutrino analysis since the test beam program started. This has been a benefit to other programs too. For example, the low-energy beamline design and hardware is now being used in MCenter for the LArIAT experiment.

    The results have been recommended for publication in Nuclear Instruments and Methods A. MINERvA has also started a second round of higher-energy test beam measurements to match the new higher-energy neutrino beam to understand still more about the way this detector performs.

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    Josh Devan of the College of William and Mary in 2010 helps assemble the low-energy test beam run detector. No image credit

    3
    Pictured here is part of the test beam crew. From left: Anne Norrick (College of William and Mary), Rob Fine (University of Rochester), Carrie McGivern (University of Pittsburgh), Leo Bellantoni, (Fermilab, front), Dan Ruterbories (University of Rochester, in red), Aaron Bercellie (University of Rochester), Manuel Alejandro Ramirez (University of Guanajuato), Geoff Savage (Fermilab).No image credit

    See the full article here.

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 11:07 am on March 9, 2015 Permalink | Reply
    Tags: , Neutrinos   

    From ars technica: “Imaging a supernova with neutrinos” 

    Ars Technica
    ars technica

    Mar 4, 2015
    John Timmer

    1
    Two men in a rubber raft inspect the wall of photodetectors of the partly filled Super-Kamiokande neutrino (BNL)

    There are lots of ways to describe how rarely neutrinos interact with normal matter. Duke’s Kate Scholberg, who works on them, provided yet another. A 10 Mega-electron Volt gamma ray will, on average, go through 20 centimeters of carbon before it’s absorbed; a 10 MeV neutrino will go a light year. “It’s called the weak interaction for a reason,” she quipped, referring to the weak-force-generated processes that produce and absorb these particles.

    But there’s one type of event that produces so many of these elusive particles that we can’t miss it: a core-collapse supernova, which occurs when a star can no longer produce enough energy to counteract the pull of gravity. We typically spot these through the copious amounts of light they produce, but in energetic terms, that’s just a rounding error: Scholberg said that 99 percent of the gravitational energy of the supernova goes into producing neutrinos.

    Within instants of the start of the collapse, gravity forces electrons and protons to fuse, producing neutrons and releasing neutrinos. While the energy that goes into producing light gets held up by complicated interactions with the outer shells of the collapsing star, neutrinos pass right through any intervening matter. Most of them do, at least; there are so many produced that their rare interactions collectively matter, though our supernova models haven’t quite settled on how yet.

    But our models do say that, if we could detect them all, we’d see their flavors (neutrinos come in three of them) change over time, and distinct patterns of emission during the star’s infall, accretion of matter, and then post-supernova cooling. Black hole formation would create a sudden stop to their emission, so they could provide a unique window into the events. Unfortunately, there’s the issue of too few of them interacting with our detectors to learn much.

    The last nearby supernova, SN 1987a, saw a burst of 20 electron antineutrinos be detected about 2.5 hours before the light from the explosion became visible.

    2
    Remnant of SN 1987A seen in light overlays of different spectra. ALMA data (radio, in red) shows newly formed dust in the center of the remnant. Hubble (visible, in green) and Chandra (X-ray, in blue) data show the expanding shock wave.

    ALMA Array

    NASA Hubble Telescope
    Hubble

    NASA Chandra Telescope
    Chandra

    (Scholberg quipped that the Super-Kamiokande detector “generated orders of magnitude more papers than neutrinos.”) But researchers weren’t looking for this, so the burst was only recognized after the fact.

    Super-Kamiokande experiment Japan
    Super-Kamiokande detector

    That’s changed now. Researchers can go to a Web page hosted by Brookhaven National Lab and have an alert sent to them if any of a handful of detectors pick up a burst of neutrinos. The Daya Bay, IceCube, and Super-Kamiokande detectors are all part of this program.) When the next burst of neutrinos arrives, astronomers will be alert and searching for the source.

    Daya Bay
    Daya Bay

    ICECUBE neutrino detector
    IceCube

    “The neutrinos are coming!” Scholberg said. “The supernovae have already happened, their wavefronts are on their way.” She said estimates are that there are three core collapse supernovae in our neighborhood each century and, by that measure, “we’re due.”

    If that supernova has occurred in the galactic core, it will put on quite a show. Rather than detecting individual events, the entire area of ice monitored by the IceCube detector will end up glowing. The Super-Kamiokande detector will see 10,000 individual neutrinos; “It will light up like a Christmas tree,” Scholberg said.

    It’ll be an impressive show, and it’s one that I’m sure most physicists (along with me) hope happen in their lifetimes. But if it takes a little time, the show may be even better. There are apparently plans afoot to build a “Hyper-Kamiokande,” which would be able to detect 100,000 neutrinos from a galactic core supernova. Imagine how many papers that would produce.

    See the full article here.

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    Ars Technica was founded in 1998 when Founder & Editor-in-Chief Ken Fisher announced his plans for starting a publication devoted to technology that would cater to what he called “alpha geeks”: technologists and IT professionals. Ken’s vision was to build a publication with a simple editorial mission: be “technically savvy, up-to-date, and more fun” than what was currently popular in the space. In the ensuing years, with formidable contributions by a unique editorial staff, Ars Technica became a trusted source for technology news, tech policy analysis, breakdowns of the latest scientific advancements, gadget reviews, software, hardware, and nearly everything else found in between layers of silicon.

    Ars Technica innovates by listening to its core readership. Readers have come to demand devotedness to accuracy and integrity, flanked by a willingness to leave each day’s meaningless, click-bait fodder by the wayside. The result is something unique: the unparalleled marriage of breadth and depth in technology journalism. By 2001, Ars Technica was regularly producing news reports, op-eds, and the like, but the company stood out from the competition by regularly providing long thought-pieces and in-depth explainers.

    And thanks to its readership, Ars Technica also accomplished a number of industry leading moves. In 2001, Ars launched a digital subscription service when such things were non-existent for digital media. Ars was also the first IT publication to begin covering the resurgence of Apple, and the first to draw analytical and cultural ties between the world of high technology and gaming. Ars was also first to begin selling its long form content in digitally distributable forms, such as PDFs and eventually eBooks (again, starting in 2001).

     
  • richardmitnick 10:01 am on February 27, 2015 Permalink | Reply
    Tags: ARA, , Neutrinos   

    From ARA: Under Construction 

    Askaryan Radio Array

    Askaryan Radio Array

    The Askaryan Radio Array (ARA) is an extremely large neutrino detector under construction near the South Pole. ARA is designed to detect and measure high-energy neutrinos from space by observing the radio pulses they generate as they travel through the ice. The detector elements are buried in the ice, about 200 meters (669 feet) deep. The radio pulse comes from the so-called Askaryan Effect in which a shower of particles in a dense material coherently emits radio frequency energy. This effect has been observed experimentally, and the ARA collaboration hopes to use the detector to make a groundbreaking measurement of the highest energy neutrinos.

    1

    Science

    People have always been curious about the celestial objects surrounding us—the stars, the planets, and the galaxies that make up the cosmos. The phenomena and objects outside of the Earth’s atmosphere have been observed for centuries, first by eye and then by telescopes. “Classical” astronomy has always used visible light (photons), and since the mid-20th century has used other frequencies of electromagnetic radiation: photons of higher energy (such as x-rays and gamma rays) and lower energy (such as radio waves). Neutrinos give us a different, new, and exciting way to look deep into astrophysical objects.

    The GZK neutrinos that are the primary science aim of the ARA detector are cosmogenic neutrinos inevitably produced by the highest energy cosmic rays. These cosmic rays, a century-old problem, are charged nuclei from space coming from unknown astrophysical sources. Looking at neutrinos, particles that are not bent in magnetic fields, provides a different way to potentially uncover the source of cosmic rays.

    2

    3

    Background

    Until recently, high-energy particle physics research has been dominated by collider physics. As costs associated with the construction of increasingly powerful colliders has grown, attention has turned to “natural” accelerators capable of attaining particle energies 10 million times higher than terrestrial colliders. The detection of such cosmic ray particles at the Earth’s surface then provides information on those celestial accelerators and brings particle physics to the energy frontier.

    Understanding the origins of cosmic rays has been a challenge since their discovery by Victor Hess nearly a century ago. It is now thought that most cosmic rays are ordinary nuclei accelerated to high energies in dynamic electric and magnetic fields associated with supernova explosions in our galaxy; however, this explanation is not sufficient to account for the highest energy particles, which now observationally exceed 10^20 eV.

    Although ultrahigh-energy cosmic rays (UHECR) likely originate throughout the Universe, those observed at Earth must be produced locally since such UHECR lose energy while propagating through the CMB ( , etc.). This process (discussed by Greisen and Zatsepin and Kuzmin – GZK) not only causes energy loss for the primary particle, but creates secondary particles of extremely high energy. It is these secondary particles, particularly UHE neutrinos, which may be used to test models of the origins of UHECR. With no electric charge, neutrinos experience no scattering or energy loss, and so provide an appropriate probe of the GZK source distribution even to high redshift. Since UHECR have been observed, the GZK neutrino flux models have a solid basis, although extrapolation of source models to higher redshift introduces some uncertainty. Thus, while UHECR tell us about the recent Universe, UHE neutrino detection will provide crucial information at higher redshifts of =1-4, during the epoch of structure formation. In addition to the “guaranteed” GZK neutrinos, it is likely that the sources of UHECR will produce neutrinos directly. For example, production of UHECR may entail -acceleration followed by , with subsequent escape of the neutron; ensuing weak decays must also produce neutrinos. Cosmological relics may also decay or annihilate to produce a subdominant UHE neutrino flux.

    Estimated event rates depend not just on the neutrino flux, but also on the neutrino-nucleon cross section in a region beyond the reach of accelerator experiments. The ARA detector is sized based on calculated Standard Model cross sections. With sufficient statistics, these predictions can be tested by determining the differential event rate near the horizon. An extreme possibility would be to discover significantly enhanced cross sections, such as those that occur in fundamental theories with extra dimensions.

    The detection of GZK neutrinos is an experimental challenge at the frontier of neutrino astronomy, which has progressed over the last half century from initial detections of low-energy thermal neutrinos from our sun, to detection of modest-energy neutrinos produced by cosmic ray interactions in the Earth’s atmosphere, to the current successful efforts of the IceCube and Antares collaborations to detect higher energy neutrinos from sources outside our solar system. With each increase in neutrino energy, the required detector increases in size to compensate for the dramatic decrease in flux with energy. At one cubic kilometer, the IceCube observatory is still too small to detect GZK neutrinos with a reasonable rate, and the technology is too costly to scale up to the 100 or more cubic kilometers envisioned here. With the primary goal of discovering GZK neutrinos and establishing the spectrum, the proposed ARA radio receiver array is necessarily sparse. We maintain energy sensitivity down to ~eV by adopting a modular ”station” design. Based on data taken by our initial testbed station in 2011, we estimate the angular resolution for the reconstructed direction of the incoming neutrino at . At high redshift ( ), GZK neutrinos are produced within 6 Mpc ( ) of the associated UHECR source. Our proposed instrument is not likely to perform classical neutrino astronomy, but the energy resolution (dominated by intrinsic electroweak physics rather than detector systematics) is sufficient to enable measurement of neutrino-nucleon cross sections, and the sky distribution of events will verify basic operation of the detector and identify the source events as cosmic neutrinos.

    See the full article here.

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    4
    The ARA collaboration, July 2013, at OSU meeting

     
  • richardmitnick 5:05 pm on February 23, 2015 Permalink | Reply
    Tags: , , Neutrinos,   

    From Scientific American: “Higgs Boson Could Explain Matter’s Dominance over Antimatter” 

    Scientific American

    Scientific American

    February 20, 2015
    Clara Moskowitz

    1
    Computer simulation of particle tracks from an LHC collision that produced a Higgs boson.
    CERN

    The stars, the planets and you and I could just as easily be made of antimatter as matter, but we are not. Something happened early in the universe’s history to give matter the upper hand, leaving a world of things built from atoms and little trace of the antimatter that was once as plentiful but is rare today. A new theory published February 11 in Physical Review Letters suggests the recently discovered Higgs boson particle may be responsible—more particularly, the Higgs field that is associated with the particle.

    The Higgs field is thought to pervade all of space and imbue particles that pass through it with mass, akin to the way liquid dye gives Easter eggs color when they are dunked in. If the Higgs field started off with a very high value in the early universe and decreased to its current lower value over time, it might have briefly differentiated the masses of particles from their antiparticles along the way—an anomaly, because antimatter today is characterized by having the same mass but opposite charge as its matter counterpart. This difference in mass, in turn, could have made matter particles more likely to form than antimatter in the cosmos’ early days, producing the excess of matter we see today. “It is a nice idea that deserves further study,” says physicist Kari Enqvist of the University of Helsinki, who was not involved in the new study but who has also researched the possibility that the Higgs field lowered over time. “There is a very high probability for the Higgs field to have a high initial value after inflation.”

    The inflation of the universe

    Inflation is a theorized early epoch of the universe in which spacetime rapidly ballooned. “Inflation has a very peculiar property; it allows fields to jump around,” says study leader Alexander Kusenko of the University of California, Los Angeles. During inflation, which radically altered the universe in a span much less than a second, the Higgs field might have hopped from one value to another due to quantum fluctuations and could have gotten stuck at a very high value when inflation ended. From there it would have settled down into its lower “equilibrium” value, but while it was changing its constantly varying value could have given matter particles different masses than their antimatter counterparts. Because lighter particles require less energy to form they arise more often. Thus, if matter was lighter, it could have quickly become more plentiful.

    The reason the Higgs field would have had such an easy time of jumping around during inflation is that the measured mass of the Higgs boson, the particle associated with the field, is relatively low. The boson appeared in 2012 inside the Large Hadron Collider (LHC) in Switzerland, revealing its mass to be about 126 GeV (giga-electron volts), or roughly 118 times the mass of the proton.

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

    That is somewhat lighter than it could have been, according to various theories. Think of the Higgs field as a valley between two cliffs. The value of the field is akin to the elevation of the valley, and the mass of the boson determines the slope of the cliff walls. “If you have a very curved valley then you probably have very steep sides,” Kusenko says. “That’s what we discovered. This value tells us that the walls are not very steep—that means the Higgs field could jump around and go very far” to other valleys at higher elevations. Enqvist agrees that the Higgs could very well have started off much higher than it is today. Whether or not this caused the matter to split from antimatter is “somewhat more speculative,” he says.

    A new particle

    Such splitting would depend on the presence of a theorized particle that has gone undetected so far: a so-called heavy Majorana neutrino. Neutrinos are fundamental particles that come in three flavors (electron, muon and tau). A fourth neutrino might also exist, however, that is expected to be much heavier than the others and thus more difficult to detect (because the heavier a particle is, the more energy a collider must produce to create it). This particle would have the strange virtue of being its own antimatter partner. Instead of a matter and antimatter version of the particle, the matter and antimatter Majorana neutrinos would be one and the same.

    This two-faced quality would have made neutrinos into a bridge that allowed matter particles to cross over into antimatter particles and vice versa in the early universe. Quantum laws allow particles to transform into other particles for brief moments of time. Normally they are forbidden from converting between matter and antimatter. But if an antimatter particle, say, an antielectron neutrino turned into a Majorana neutrino, it would cease to know whether it was matter or antimatter and could then just as easily convert to a regular electron neutrino as turn back into its original antielectron neutrino self. And if the neutrino happened to be lighter than the antineutrino back then, because of the varying Higgs field, then the neutrino would have been a more likely outcome—potentially giving matter a leg up on antimatter.

    “If true, this would solve a big mystery in particle physics,” says physicist Don Lincoln of the Fermi National Accelerator Laboratory in Illinois, who was not involved in the study. Yet the Majorana neutrino “is entirely speculative and has eluded discovery, even though the LHC experiments have a vigorous research program looking for it. Researchers will certainly keep this idea in mind as they dig through the new data the LHC will begin generating in the early summer this year.”

    Kusenko and his colleagues also have another hope for finding additional support for their theory. The Higgs field process they envision could have created magnetic fields with particular properties that would still inhabit the universe today—and if so, they might be detectable. If found, the existence of such fields would provide evidence that the Higgs field really did decrease in value long ago. The scientists are trying to calculate just what the magnetic field properties would be and whether experiments have a plausible hope of seeing them, but the option raises the tantalizing hope that their theory could have testable consequences—and maybe a chance to solve the antimatter mystery after all.

    See the full article here.

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  • richardmitnick 1:25 pm on February 3, 2015 Permalink | Reply
    Tags: , , Neutrinos   

    From FNAL: “Director’s Corner – Electron neutrinos from supernovae” 

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

    1
    Fermilab Director Nigel Lockyer wrote this column

    Neutrino research has the potential to lead to discoveries that rival the observation of the Higgs boson. And just as with the successful search for the Higgs, the question of the nature of neutrinos is being investigated by different teams using different methods.

    Here at Fermilab we are very familiar with one method — the study of neutrinos created from high-power particle accelerators. But at last month’s ELBNF collaboration meeting, Duke University Professor Kate Scholberg gave a fascinating introduction to the future use of a large, deep underground liquid-argon detector (currently referred to as ELBNF) to study neutrinos from supernovae in our galaxy. In Scholberg’s words:

    “When massive stars run out of nuclear fuel, they collapse in on themselves, forming ultradense neutron stars and, in some cases, even black holes. Just as gravitational potential energy turns to kinetic energy when you drop an object, the vast energy of the star’s infall must be released somehow. Some will be released in an enormous supernova explosion, but 100 times more is released in the form of neutrinos, particles famous for their feeble interactions with matter. Because neutrinos interact so weakly, they escape the supernova with nearly all of the collapse energy within only tens of seconds, creating an intense burst of all three flavors of neutrinos and antineutrinos with energies of a few tens of MeV.

    Sanford Underground Research Facility Interior
    Sanford Underground Research Facility

    “Neutrinos are also known for their ability to transform from one flavor to another. The time, energy and flavor evolution of the burst not only tells the story of the star’s destruction and the creation of its exotic compact progeny, but will also give us insight into the properties of neutrinos themselves. The different flavors tell different stories. The electron flavor neutrinos have a particularly interesting story to tell — they are emitted in an initial flash (tens of milliseconds) as protons and electrons are squeezed together to make neutrons and are more likely to bear the signatures of explosion processes and flavor oscillations.

    “On Earth we have a chance to witness the unfolding of a Milky Way core-collapse supernova by observing the neutrino burst in large underground neutrino detectors. About four explosions per century are expected. Observing the different flavor components of the burst is a bit like making a movie in different colors.

    “Different kinds of detectors are sensitive to different neutrino flavors. Existing large water and scintillator detectors (such as Super-K, IceCube, KamLAND, LVD Daya Bay and Borexino) are primarily sensitive to electron antineutrinos, which interact with free protons. Argon, in contrast, has unique sensitivity to electron neutrinos. A large underground liquid-argon detector like ELBNF would enable us to clearly record the birth of the neutron star and will bring new understanding of neutrino flavor transformation.”

    Super-Kamiokande experiment Japan
    Super-Kamioka

    ICECUBE neutrino detector
    IceCube

    KamLAND
    KamLAND

    Daya Bay
    Daya Bay

    Borexino Solar Neutrino detector
    Borexino

    See the full article here.

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    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

     
  • richardmitnick 12:30 pm on January 27, 2015 Permalink | Reply
    Tags: , FNAL ELBNF, Neutrinos   

    From FNAL: “From the Deputy Director ELBNF is born” 

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

    Tuesday, Jan. 27, 2015
    Joe Lykken

    At approximately 6:15 p.m. CST on January 22, 2015, the largest and most ambitious experimental collaboration for neutrino science was born.

    It was inspired by a confluence of scientific mysteries and technological advances, engendered by the P5 report and the European Strategy update, and midwifed by firm tugs from Fermilab, CERN and Brookhaven Lab. Going by the placeholder name ELBNF (Experiment at the Long Baseline Neutrino Facility), the newborn had the impressive heft of 145 institutions from 23 countries.

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    The new Institutional Board (IB), convened by interim chair Sergio Bertolucci, unanimously approved a Memorandum of Collaboration that launches the election of spokespeople and a process to develop bylaws. The IB also endorsed an international governance plan for oversight of ELBNF detector projects, in concert with the construction of the LBNF facility hosted by Fermilab.

    The goal of this international collaboration is crystal clear: a 40-kiloton modular liquid argon detector deep underground at the Sanford Underground Research Facility, exposed to a megawatt-class neutrino beam from Fermilab, with the first 10 kilotons in place by 2021. This goal will enable a comprehensive investigation of neutrino oscillations that can establish the presence of CP violation for leptons, unequivocally determine the neutrino mass ordering and strongly test our current neutrino paradigm. A high-resolution near detector on the Fermilab site will have its own rich physics program, and the underground far detector will open exciting windows on nucleon decay, atmospheric neutrinos, and neutrino bursts from supernova detonations.

    Unlike most births, this one took place at an international meeting hosted by Fermilab; there was room for nearly all the friends and family of accelerator-based neutrino experiments. One of the critical items flagged at this meeting is to find a better name for the new collaboration. Here are a few of my unsolicited attempts:

    nuLAND = neutrino Liquid ArgoN Detector

    GOLDEN = Giant OsciLlation Detector Experiment for Neutrinos

    Think you can do better? Go ahead. My older son, a high-priced management consultant, offered another one pro bono: NEutrino Research DetectorS.

    I am too young to have been in the room when ATLAS and CMS (or for that matter CDF and D0) came into being, but last week I had the thrill of being part of something that had the solid vibe of history being made. The meeting website is here.

    See the full article here.

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  • richardmitnick 2:30 pm on January 9, 2015 Permalink | Reply
    Tags: , , Neutrinos   

    From FNAL “Frontier Science Result: MINERvA Who let the pions out (of the nucleus)?” 

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

    Friday, Jan. 9, 2015
    Steve Dytman, University of Pittsburgh

    Neutrinos are odd particles: They rarely interact in matter and can change character back and forth over time in a process called oscillation. When neutrinos do interact with matter, however, they do so in ways that are similar to how other high-energy particles produced by Fermilab accelerators interact: by making still more particles. So even though neutrinos themselves contain no quarks, they are still able to produce pions, quark-antiquark pairs that can be either charged or neutral. At today’s Joint Experimental-Theoretical Physics Seminar, MINERvA will release its new result on how neutral pions are produced in a beam of antineutrinos from Fermilab’s NuMI beamline.

    4
    This plot shows what a neutral pion looks like in the MINERvA detector when produced with a muon. Colors correspond to energy deposited in each triangular scintillator bar.

    A previous MINERvA result described how charged, rather than neutral, pions are made from neutrinos. At least “on paper,” that result is similar to today’s new result. Both of these interactions are predicted to happen and even to have similar probabilities.

    However, they leave very different footprints in detectors and so present different challenges. In fact the neutral pion’s footprint is a worry for oscillation experiments because it can look like something it’s not. So oscillation experiments need good measurements of how many neutral pions are made in neutrino and antineutrino beams.

    Measuring both charged- and neutral-pion production at similar neutrino energies also helps us better understand the nucleus with which a neutrino interacts, since the two different kinds of pions see the nucleus differently as they exit it. Before the research that led to today’s result, though, only a few dozen neutral pion-antineutrino events have ever been seen in a single experiment.

    Neutral pions are harder to see than charged pions because they decay very rapidly and must be detected through their decay products — two neutral photons, which interact on average about a foot away from where the neutral pion decayed in the first place. For today’s result, the neutral pion is produced at the same time as a muon, which is a heavier version of an electron.

    This new measurement adds more than 400 new events to the world’s collection for this novel interaction and tells us much more about how neutrinos and pions are both affected by the nucleus.

    There has been a lot of interest in pion production because the best theories are unable to describe previous MiniBooNE measurements of charged pions. Although the best calculation was also unable to reproduce the MINERvA charged-pion data, it failed in a different way, extending the controversy. Experimenters don’t stop, though. They just keep trying to find another way to measure what’s happening inside the nucleus until they understand it. Now MINERvA’s new result, which sees better agreement between the best calculation and the prediction (see figure below), paints a new picture of the nucleus.

    2
    This plot shows the cross section (likelihood per proton or neutron) of a neutral pion and an antimuon being made from an antineutrino as a function of the pion momentum. The two different models represent turning on and off the effects of the nucleus where the neutrino interacted. The effects of the nucleus were clearly “turned on” in the data. The inner error bars are statistical and the outer error bars are the total uncertainties.

    t
    Trung Le of Rutgers University will present MINERvA’s latest results at today’s wine and cheese seminar at 4 p.m. in One West.

    See the full article here.

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    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

     
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