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  • richardmitnick 8:51 pm on December 17, 2014 Permalink | Reply
    Tags: , IceCube Experiment,   

    From IceCube: “Designing the future of the IceCube Neutrino Observatory” 

    icecube
    IceCube South Pole Neutrino Observatory

    17 Dec 2014
    Sílvia Bravo

    The IceCube Neutrino Observatory is a successful and large scientific facility located near the Amundsen-Scott South Pole station in Antarctica. This observatory hosts IceCube, a cubic-kilometer deep-ice particle detector that is, so far, the largest ever built – and on the surface, IceTop, an extended air shower array.

    Completed in 2010, IceCube has recently discovered astrophysical neutrinos, revealing their potential to explore our universe at energies at the PeV scale and above, where most of the universe is opaque to high-energy photons. But the big questions remain unsolved: where do these neutrinos come from? How does nature accelerate particles to such extreme energies?

    Prof. Olga Botner, IceCube spokesperson and a physics professor at the University of Uppsala, and Prof. Francis Halzen, IceCube principal investigator and a professor at the University of Wisconsin–Madison, tell us about the plans for an upgrade to the IceCube Neutrino Observatory. As an extension of the current detector, it can be built in a few years and within an affordable budget, thanks to expertise acquired with IceCube.

    a
    Artistic view of the Antarctic surface around the South Pole station, showing the position of the 86 strings of sensors in IceCube and the possible grid of the next-generation detector. Image: J.Yang/IceCube Collaboration

    Q: What has IceCube accomplished so far?

    Olga Botner (O): IceCube is the world’s foremost neutrino observatory, which, after just two years of running in its final configuration, discovered neutrinos from outer space that have energies a billion times larger than those of neutrinos produced by our Sun and a thousand times larger than any produced on Earth with man-made accelerators. The discovery of this high-energy neutrino flux is a turning point for neutrino astronomy: a dream of 50 years ago on the verge of becoming reality.

    Francis Halzen (F): The high level of the observed neutrino flux implies that a significant fraction of the energy in the non-thermal universe, powered by the gravitational energy of compact objects from neutron stars to supermassive black holes, is generated in hadronic accelerators. This tells us that we are approaching exciting times when high-energy neutrinos will reveal new sources or provide new insight on the energy generation in known sources.

    But IceCube has also been a successful detector with respect to its technical development. We developed highly successful designs for transforming natural ice into a particle detector. The optimized methods for deploying and commissioning large volume detectors in ice can be used for a next-generation detector; minimal modifications will target improvements focused on modernization, efficiency, and cost savings.

    O: This is a very important point. The detector was built within the expected time frame, within budget, and with a performance at least a factor of two better than anticipated.

    Going back to physics, I should also add that IceCube has yielded many interesting results beyond neutrino astronomy. We are studying cosmic rays, looking for signatures of the annihilations of dark matter particles into neutrinos, and investigating the properties of the neutrinos themselves. We have published competitive results in all these areas.

    Q: Why do we need a next-generation IceCube detector?

    F: We all agree on the observed spectrum of neutrinos, there’s no doubt about the discovery, but independent analyses of IceCube data have produced only on the order of 100 astrophysical neutrino events in several years. These modest numbers of cosmic neutrinos limit the ability of IceCube to be an efficient tool for neutrino astronomy over the next decade. A next-generation detector will provide an unprecedented view of the high-energy universe, taking neutrino astronomy to new levels of discovery. It is likely to resolve the question of the origin of the cosmic neutrinos recently discovered.

    O: That’s right! IceCube’s discovery of extraterrestrial neutrinos has shown us that even a cubic-kilometer detector is not enough. To fully exploit the potential for neutrino astronomy, a much larger observatory is needed. We are already working on its design. The new detector has been named IceCube-Gen2.

    Q: Is it feasible and cost-effective to build an even bigger detector at the Pole?

    O: It sure is. The good news is that the successful deployment and running of IceCube demonstrates that we have mastered the technologies to construct and operate a detector in the deep ice. The drilling systems and the optical modules for the next-generation detector will closely follow the designs that have been proven to work well—with certain modifications to improve the overall performance. This makes us confident that a next-generation detector is not only feasible but can be built in a cost-effective manner, just like IceCube.

    F: We didn’t know this before IceCube, but now we have measured the extremely long photon absorption lengths in ice. This will allow the spacing between strings of light sensors to exceed 250 m in a future IceCube extension; i.e., the instrumented volume can rapidly grow without increasing the costs much. In fact, we can build a ten-cubic-kilometer IceCube-Gen2 telescope by roughly doubling the instrumentation already deployed. Thus, a tenfold increase in astrophysical neutrino detection rates could be achieved with a cost comparable to the current IceCube detector.

    Q: And what about the time scale of this project? Will we need to wait a long time to see new results?

    O: We are aiming at an expanded array instrumenting a volume of 10 km3 for the detection of high-energy neutrinos—but also at improving the low-energy performance through deployment of a densely instrumented infill detector, PINGU, targeting neutrino mass hierarchy as its prime goal. We believe that this new IceCube-Gen2 observatory can be built within seven years of obtaining funding.

    Q: Sounds like a plan. Who is leading this next-generation IceCube?

    F: The present plan is to build IceCube following a management strategy that was successful in delivering IceCube on time and on budget. The collaboration is rapidly expanding, both in the US and in Europe and Canada. We expect that a larger fraction of the cost will be carried by significant contributions from our foreign collaborators.

    O: Exactly. The high-energy array and PINGU are both envisioned as parts of an IceCube-Gen2 observatory. A new collaboration, including IceCube members and additional institutions, is now being formed. This IceCube-Gen2 collaboration will work to develop proposals in the US and abroad to secure funding. We hope that IceCube-Gen2 will become a flagship scientific project for NSF as well as for funding agencies abroad.

    o
    This image shows a simulated high-energy event of about 60 PeV in the proposed IceCube Gen2 detector. Image: IceCube Collaboration

    Q: Can other current or in-design experiments do better than IceCube-Gen2?

    F: Well, we have strong competitors. Early efforts for cubic-kilometer neutrino detectors focused on deep-water-based detectors, including DUMAND, Lake Baikal, and ANTARES. So far, there is no cubic-kilometer neutrino detector in deep water, but these experiments have paved the way toward the proposed construction of KM3NeT in the Mediterranean Sea and GVD in Lake Baikal.

    O: These new projects, GVD in Lake Baikal and KM3NeT in the Mediterranean, are presently in the prototyping or early construction phase. They will eventually provide a complementary view of the sky to that of an Antarctic observatory.

    Q: Should we expect IceCube-Gen2 to be as successful as IceCube? That may be the desire, but are there objective reasons to think so?

    O: The main one is that we already have established the existence of a flux of high-energy neutrinos. What we now need are substantial number of events to further characterize this flux in terms of energy spectrum, a possible energy cut-off, flavor composition, and provenance. We just need a larger detector to do this in a reasonable time. The higher event rates in a larger array will also improve the chances of correlating our neutrino events with observations by the new generation of high-energy gamma-ray telescopes and gravitational wave detectors, together charting the non-thermal universe.

    F: The larger samples of high-energy neutrinos with improved angular resolution and energy measurement will give us a detailed understanding of the source distribution. This sample will reveal an unobstructed view of the universe at energies at PeV and above. Those are unexplored wavelengths where most of the universe is opaque to high-energy photons. As Olga was mentioning, the operation of IceCube-Gen2 in coincidence with other telescopes and detectors will present totally novel opportunities for multimessenger astronomy and multiwavelength follow-up campaigns to obtain a truly complete picture of astrophysical sources.

    + Info IceCube-Gen2: A Vision for the Future of Neutrino Astronomy in Antarctica, IceCube Collaboration: M.G. Aartsen et al. arxiv.org/abs/1412.5106

    This white paper presents early studies toward a next-generation IceCube detector with the aim of instrumenting a 10 km3 volume of clear glacial ice at the South Pole and delivering an order of magnitude increase in astrophysical neutrino samples of all flavors.

    Read also a short description of IceCube-Gen2 on the IceCube w

    See the full article here.

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    ICECUBE neutrino detector
    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

     
  • richardmitnick 4:30 pm on December 12, 2014 Permalink | Reply
    Tags: , IceCube Experiment,   

    From IceCube: “Drilling IceCube: a story of innovation, expertise and strong will “ 

    icecube
    IceCube South Pole Neutrino Observatory

    12 Dec 2014
    Silvia Bravo

    Building a cubic-kilometer telescope at the South Pole seemed a chimera even for some of those involved in the project. But AMANDA had proven that if such a detector were built, it would allow great science to come.

    The goal was simple in words but seemingly impossible in practice: 86 boreholes, each 60 cm in diameter and 2,500 m deep, had to be drilled and instrumented in seven austral summer seasons. Safety was a must, fuel needed to be used cautiously and the South Pole environment was just unavoidable.

    And yet, IceCube was completed in the seventh construction season. By that time, at the end of 2010, the IceCube drilling team had beaten all records: less time and fuel per borehole, optimized hole shapes with almost perfect vertical alignment over the 2.5-km depth, and only a few safety-related issues. How was this possible? Blame the talent, expertise and strong will of a great team.

    c
    Some of the crew at the South Pole during the last drill season for IceCube. From left to right, Hanna Blomstrom, an anonymous IceCube collaborator, Matt Newcomb, Dennis Dulling, Terry Benson, Richard Wipperfurth, Jim Haugen and Sven Lindstrom. Image: Jim Haugen. IceCube/NSF.

    Four years after IceCube’s completion and with new projects and drilling seasons on the horizon, the team that led this feat has explained the details of IceCube drilling in two papers published today in the journal Annals of Glaciology.

    “Although there was a lot of experience from AMANDA drilling, drilling for IceCube was a whole new ballgame. We continued learning lessons about the equipment and our techniques to the bitter end, but by the final seasons the drill and its crew were a well-oiled machine,” explains Terry Benson, a drill engineer at the Physical Sciences Laboratory (PSL), who started working on the IceCube drill as a young student and was one of the drill leaders during the last two construction seasons.

    “It would have been impossible to build IceCube without PSL. With them, we overcame every challenge and the results were impressive,” says Prof. Albrecht Karle, the IceCube associate director for Science and Instrumentation.

    Drilling to depths that almost reach the Antarctic bedrock also meant a larger diameter for the holes, since water starts to freeze immediately. And working at the South Pole meant that logistics and resources had to be extremely well planned and economized.

    “It was important to conserve the expensive fuel so we wanted to avoid overdrilling the holes. However, if a hole was made slightly too small, so that a string got stuck, both the hole and the string of instrumentation could be be lost. This would have been a very expensive mistake. It was extremely important to have a good understanding of hole size and freeze back rate,” explains Lee Greenler, a mechanical engineer also at PSL, who led the team developing the heat transfer calculations that allowed the optimization of the drilling process.

    i
    Image from the last IceCube drilling season at the South Pole. On the left, the hose reel for the over 2,500 meters long hose used to drill the IceCube holes. Image: Jim Haugen. IceCube/NSF.

    The drilling process started with four weeks of preparation and a crew of about 30 people. The seasonal equipment site (SES), which provided electricity and a stable supply of hot pressurized water, and the tower operations site (TOS) had to be excavated and commissioned. The SES remained stationary throughout each drill season, while drilling towers moved from one hole to another.

    “We were drilling around-the-clock, with three 9-hours shifts and only Sundays off. In season 2009-2010, when we drilled 20 holes, we sent 88 people to the Pole, but also over 450,000 liters of fuel and almost 300 tons of cargo,” explains Jim Haugen, an instrumentation engineering manager at WIPAC, who has been leading the logistics of the IceCube polar seasons since construction began.

    Drilling an IceCube hole meant shooting hot water at 80ºC through an instrumented drill head at the end of a continuous hose of about 2,500 meters. Then, during the ream phase, the drill was raised while the hot water continued to flow, enlarging the hole and keeping non-frozen water in contact with the hole walls so that it took longer to freeze back. Once 60 IceCube sensors (DOMs) were deployed, the hole completely froze around them over the following week or so.

    An independent firn drill was used for the first 50 meters, since this first layer of lower density snow does not hold water. This improved system, designed after the first seasons proved the old firn drill to be very slow, allowed an increase from 13 to 18 or more holes drilled per season.

    l
    Image from the last IceCube drilling season at the South Pole. Two drill towers were deployed to allow continuous drilling. On the front, one of the IceTop tanks. Image: Jim Haugen. IceCube/NSF.

    To drill IceCube was not an easy job, but the results now presented in these two papers show that it is possible to do large-scale production ice drilling in the Antarctic environment in a safe, efficient and predictable way. Dynamic engineering techniques based on year-to-year lessons learned and on retention of experienced crew members were critical in turning a chimera into the successful IceCube Neutrino Observatory.

    IceCube Enhanced Hot Water Drill functional description, T. Benson, J. Cherwinka, M. Duvernois, A. Elcheikh, F. Feyzi, L. Greenler, J. Haugen, A. Karle, M. Mulligan, R. Paulos. Annals of Glaciology 55(68) (2014) 105-114. doi:10.3189/2014AoG68A032.

    Modeling hole size, lifetime and fuel consumption in hot-water ice drilling, L. Greenler, T. Benson, J. Cherwinka, A. Elcheikh, F. Feyzi, A. Karle, R. Paulos. Annals of Glaciology 55(68) (2014) 115-123. doi:10.3189/2014AoG68A033.

    See the full article here.

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    ICECUBE neutrino detector
    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

     
  • richardmitnick 4:11 pm on December 12, 2014 Permalink | Reply
    Tags: , IceCube Experiment,   

    From IceCube: “More on astrophysical neutrinos yet no track of charmed mesons” 

    icecube
    IceCube South Pole Neutrino Observatory

    07 Oct 2014
    Silvia Bravo

    A search for neutrino interactions inside IceCube brought evidence of an extraterrestrial neutrino flux. Now the IceCube Collaboration has expanded the search, lowering the range of deposited energy down to 1 TeV. The goal was a better understanding of the different contributions to the neutrino flux in IceCube and hopefully to measure the charmed-meson component for the first time.

    The results of this study, submitted today to Physical Review D, have again proven neutrinos from charmed-meson decays to be elusive. The good news is the results set a more stringent upper limit on their contribution, only 1.52 times the theoretical benchmark prediction used in previous IceCube analyses. IceCube researchers have also derived new constraints on the diffuse astrophysical neutrino spectrum, .

    d
    Deposited energy spectra from the northern and southern skies (points) with the best fit combination of atmospheric and astrophysical contributions from table below. Above 10 TeV, an extra component is required to account for the observed high-energy events, especially those in the southern sky. The excess over the best fit sum around 30 TeV is interpreted as a statistical fluctuation. Image: IceCube Collaboration

    High-energy neutrinos may be produced either by the interaction of cosmic rays in the Earth’s atmosphere, the so-called atmospheric neutrinos, or in the vicinity of distant astrophysical accelerators like black holes and neutron stars, the so-called astrophysical neutrinos.

    Whether atmospheric or astrophysical, neutrinos come in different flavors, but their rates and their energy and direction distributions can help us distinguish the different contributions to the overall flux and learn more about their origins and production mechanisms.

    Atmospheric neutrinos are mainly muon neutrinos produced in 2-body decays of charged pions and kaons. The electron neutrino component is primarily due to 3-body decays of charged and neutral kaons. And there’s still a third contribution from the decays of heavy, short-lived mesons containing charm quarks, which create approximately the same amount of muon and electron neutrinos. However, this third prompt contribution has never been conclusively observed.

    Astrophysical neutrinos, which may have been created by diffusive shock acceleration in the vicinity of cosmic ray sources, will arrive to Earth with an equal ratio for the three flavors (muon, electron and tau neutrinos) and with an energy spectrum expected to follow that of the progenitor protons (e ). Thus, their flux will exceed that of atmospheric neutrinos at very high energies.

    The current search was looking for neutrino-induced interactions starting in the IceCube detector with energies between 1 TeV and beyond a few PeV, exploring for the first time the region between 10 and 100 TeV, where neutrinos from charmed-meson decays in the atmosphere should be observable. There were 388 events found in IceCube data from 2010-2012, which should include contributions from conventional and prompt atmospheric neutrinos, and extraterrestrial neutrinos, along with a small but nearly irreducible background of penetrating atmospheric muons that go undetected before depositing a large fraction of their energy in the glacial ice in a single, catastrophic loss.

    t
    Table: Results for the best fit parameters and number of events attributable to each neutrino component.

    The best fit of each of these contributions to the observed neutrino flux in IceCube shows a good agreement with previous results, except in the region around 30 TeV in the southern sky (see figure and table above) where an extra component might be required to account for the observed events.

    “Isolating neutrino interactions is more difficult at these lower energies, but we are seeing interesting things. Some, like the observation of the atmospheric neutrino flux at the observed level, were expected and are a nice confirmation of our understanding of the IceCube detector,” explains Jakob van Santen, a graduate student at WIPAC at the University of Wisconsin–Madison. “Others, like the excess over our simple model of the astrophysical neutrino flux in the southern sky around 30 TeV, a region where we expect our vetoes to remove nearly all atmospheric muons and neutrinos, were a surprise. While the deviation isn’t statistically significant, this may be a hint that our simplest model for the astrophysical neutrino flux is incomplete. To find out more, we’ll need more data.”

    The spectral index for astrophysical neutrinos is larger than 2.2, which may be a hint for a galactic neutrino component of this flux. At higher energies, though, neutrinos from extragalactic sources would be the dominant ones. However, the best fit to this index hardens to 2.25 if the energy threshold is raised to 60 TeV, again an indication that we need more data to understand the neutrino flux with energies around 30 TeV in IceCube.

    Atmospheric and Astrophysical Neutrinos above 1 TeV Interacting in IceCube, IceCube Collaboration: M.G. Aartsen et al. Submitted to Physical Review D, arXiv.org:1410.1749

    See the full article here.

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    ICECUBE neutrino detector
    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

     
  • richardmitnick 9:20 pm on December 11, 2014 Permalink | Reply
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    From Wisconsin: “IceCube pushes neutrinos to the forefront of astronomy” From 2013 but Worth the Read 

    U Wisconsin

    University of Wisconsin

    Nov. 21, 2013
    Jill Sakai

    i
    This is the second highest-energy neutrino ever observed. IceCube physicists named it Bert. Twenty-eight events with energies around and above 30 TeV were observed in an all-sky search for high-energy neutrino events with vertices contained in the IceCube neutrino detector. Image: IceCube Collaboration

    The IceCube Neutrino Observatory, a particle detector buried in the Antarctic ice, is a demonstration of the power of the human passion for discovery, where scientific ingenuity meets technological innovation. Today, nearly 25 years after the pioneering idea of detecting neutrinos in ice, the IceCube Collaboration announces the observation of 28 very high-energy particle events that constitute the first solid evidence for astrophysical neutrinos from cosmic accelerators.

    “This is the first indication of very high-energy neutrinos coming from outside our solar system, with energies more than one million times those observed in 1987 in connection with a supernova seen in the Large Magellanic Cloud,” says Francis Halzen, principal investigator of IceCube and the Hilldale and Gregory Breit Distinguished Professor of Physics at the University of Wisconsin–Madison. “It is gratifying to finally see what we have been looking for. This is the dawn of a new age of astronomy.”

    ICECUBE neutrino detector
    IceCube neutrino detector interior
    The IceCube Laboratory at the Amundsen-Scott South Pole Station

    The IceCube Laboratory at the Amundsen-Scott South Pole Station, in Antarctica, hosts the computers collecting raw data. Only events selected as interesting for physics studies are sent to UW–Madison, where they are prepared for use by any member of the IceCube Collaboration.

    Details of the research appear in a manuscript published in the Nov. 22, 2013 issue of the journal Science.

    Because they rarely interact with matter, the nearly massless subatomic particles called neutrinos can carry information about the workings of the highest-energy and most distant phenomena in the universe. Billions of neutrinos pass through every square centimeter of the Earth every second, but the vast majority originate either in the sun or in the Earth’s atmosphere.

    Far rarer are neutrinos from the outer reaches of our galaxy or beyond, which have long been theorized to provide insights into the powerful cosmic objects where high-energy cosmic rays may originate: supernovas, black holes, pulsars, active galactic nuclei and other extreme extragalactic phenomena.

    IceCube, run by the international IceCube Collaboration and headquartered at the Wisconsin IceCube Particle Astrophysics Center (WIPAC) at UW–Madison, was designed to accomplish two major scientific goals: measure the flux, or rate, of high-energy neutrinos, and try to identify some of their sources.

    The analysis presented in the Science paper reveals the first high-energy neutrino flux ever observed, a highly statistically significant signal (more than 4 sigma) that meets expectations for neutrinos originating in cosmic accelerators.

    f
    Francis Halzen

    “From hints in earlier IceCube analyses, we have used improved analysis methods and more data to make a significant step forward in our search for the elusive astrophysical signal,” says collaboration spokesperson Olga Botner, of Uppsala University. “We are now working hard on improving the significance of our observation, and on understanding what this signal means and where it comes from.”

    “IceCube is a wonderful and unique astrophysical telescope — it is deployed deep in the Antarctic ice but looks over the entire universe, detecting neutrinos coming through the Earth from the northern skies, as well as from around the southern skies,” says Vladimir Papitashvili of the National Science Foundation (NSF) Division of Polar Programs.

    “The IceCube Neutrino Observatory has opened a new era in neutrino astrophysical observations,” adds Jim Whitmore of the NSF’s Physics Division, who with Papitashvili manages operation of the observatory and the associated U.S. research projects. “It is in the forefront of the entire field of neutrino astronomy, now delivering observations that have been long-awaited by both theorists and experimentalists.”

    The 28 high-energy neutrinos were found in data collected by the IceCube detector from May 2010 to May 2012 and analyzed for neutrino events exceeding 50 teraelectronvolts (TeV) coming from anywhere in the sky. The events cannot be explained by other neutrino fluxes, such as those from atmospheric neutrinos, nor by other high-energy events, such as muons produced by the interaction of cosmic rays in the atmosphere.

    “Now that we have the full detector we have the sensitivity to see these events. After seeing hundreds of thousands of atmospheric neutrinos, we have finally found something different,” Halzen explains. “We’ve been waiting for this for so long.”

    IceCube is comprised of 5,160 digital optical modules suspended along 86 strings embedded in a cubic kilometer of ice beneath the South Pole. The National Science Foundation-supported observatory detects neutrinos through the tiny flashes of blue light, called Cherenkov light, produced when neutrinos interact in the ice.

    The IceCube detector was completed in December 2010 after seven years of construction. It was built on time and on budget and in its first two years has performed above its design specifications.

    “It is gratifying to finally see what we have been looking for. This is the dawn of a new age of astronomy.”
    Francis Halzen

    “The success of IceCube builds on the efforts of hundreds of people around the world,” says Botner. “IceCube collaborators made it all happen — from the design and the deployment in a harsh environment, proving the feasibility of the concept, to data harvesting and physics analysis. All required concerted efforts that ultimately have led to the observations presented in this paper. Now the collaboration is addressing a further challenge: how to make IceCube a big contributor to astronomy.”

    The IceCube Neutrino Observatory was built under a NSF Major Research Equipment and Facilities Construction grant, with assistance from partner funding agencies around the world. The NSF’s Division of Polar Programs and Physics Division continue to support the project with a Maintenance and Operations grant, along with international support from participating institutes and their funding agencies. UW–Madison is the lead institution, and the international collaboration includes 250 physicists and engineers from the U.S., Germany, Sweden, Belgium, Switzerland, Japan, Canada, New Zealand, Australia, U.K. and Korea.

    c

    See the full article here.

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    In achievement and prestige, the University of Wisconsin–Madison has long been recognized as one of America’s great universities. A public, land-grant institution, UW–Madison offers a complete spectrum of liberal arts studies, professional programs and student activities. Spanning 936 acres along the southern shore of Lake Mendota, the campus is located in the city of Madison.

     
  • richardmitnick 7:13 pm on November 24, 2014 Permalink | Reply
    Tags: , , , , IceCube Experiment,   

    From IceCube: Video on Neutrinos Parts 1 and 3 Previously Missing 

    icecube
    IceCube South Pole Neutrino Observatory

    The good folks at http://icecube.wisc.edu/ pointed me to these missing videos. You previously saw only Part 2

    Part 1
    Solar Neutrinos: Verifying how the Sun shines has led to the discovery of neutrino flavor conversion and that neutrinos are massive.

    Part 3
    Neutrinoless double beta decay experiment in the Canfranc Underground Laboratory.
    The search for a property of the neutrino that might explain why matter defeated antimatter.

    Watch, enjoy, learn.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    ICECUBE neutrino detector
    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

     
  • richardmitnick 3:12 pm on November 21, 2014 Permalink | Reply
    Tags: , , , , IceCube Experiment,   

    From IceCube: “Neutrino, measuring the unexpected” 

    icecube
    IceCube South Pole Neutrino Observatory

    Francis Halzen, IceCube Principal Investigator, explains the search for high-energy neutrinos in this three party story of neutrinos. Produced by IFIC, Directed by Javier Diez. [Sorry, I cannot come up with Parts 1 and 3. But this video stands on its own merit.]

    Watch, enjoy. learn.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    ICECUBE neutrino detector
    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

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  • richardmitnick 9:05 pm on November 17, 2014 Permalink | Reply
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    From IceCube: “A new polar season for IceCube” 

    icecube
    IceCube South Pole Neutrino Observatory

    17 Nov 2014
    Silvia Bravo

    After a long winter, South Pole inhabitants are getting used to the sunlight again. Up north, a bunch of IceCubers are getting ready for their Antarctic adventure. For some of them, it’s all about the excitement of a first trip to Antarctica. For some others, it’s an almost annual appointment that makes their job a special one.

    Erik Beiser and Stephan Richter, the new 2014-15 IceCube winterovers, stepped onto South Pole ice on November 6 with the first flight of the season. They are there to stay for a year: first enjoying the hectic months of the austral summer at the Admundsen-Scott South Pole Station, and then becoming two of the solitary souls in the darkness of the austral winter.

    4
    Four IceCube winterovers: from left to right, Erik and Stephan (2014-2015), Dag and Ian (2013-2014). Image: Ralf Auer. IceCube/NSF.

    Now it’s time to finish their training. The incoming winterovers have learned about the IceCube data taking systems in Madison and also about other South Pole systems in Denver. Their expertise is further solidified on-ice through their interactions with the outgoing winterovers, Dag Larsen and Ian Rees.

    Other activities during this season include the maintenance and updates of the computing and power units in the IceCube Lab (ICL). “This year, new power distribution units will allow IceCube winterovers to monitor some of our custom-built readout systems, the so-called DOMHubs, from the station without requiring them to walk out to the laboratory,” says Ralf Auer, who is the system administrator for the South Pole data center. The walk to the ICL is about 1 km long, a short scenic route when the weather is nice that can feel like a long nightmare with wind and temperature approaching -100 F.

    path
    The path to the ICL in October 2014. Image: Dag Larsen. IceCube/NSF

    “The remote-controlled units will help to reduce detector downtime and start data taking faster after a system crash,” explains Auer. Ian and Dag, now leaving the Pole, have set a new record for IceCube uptime, at 99.5% on average during the last year. The new system might help Erik and Stephan, the brand new winterovers, to improve this register.

    Moreover, the disk array storage deployed last year has proven to be stable and reliable and will grow to become the main on-site IceCube data storage system, replacing the old magnetic tapes.

    Also new for this season are planned IceTop measurements to better understand how the accumulated snow might be affecting the performance of the detector. About 20-25 cm of snow accumulates on top of each IceTop tank every year, with snow heights up to 2.5 m measured these days. “Initially, we thought that we could keep snow level limited, but currently snow management is too expensive at the Pole. As the accumulated snow grows, we want to improve our understanding of its impact on what IceTop measures,“ explains Sam De Ridder, a graduate student at University of Ghent, who will be traveling to Antarctica in early January.

    IceTop was designed to detect the showers of particles created by the interaction of cosmic rays with the atmosphere. However, due to the accumulated snow, IceTop is becoming more and more sensitive to muons compared to the electromagnetic part of the air shower. A good knowledge of the muon signal in the shower is very important for measurements of the cosmic ray composition but also for using IceTop as a veto for neutrino searches in IceCube.

    For this reason, several measurements of the muon signal around the tanks will be performed during this season, as well as more detailed measurements of the snow density. “We are pretty confident that with these measurements we can improve the handling of the snow in IceTop and gain more knowledge for the future IceCube surface extensions,” adds De Ridder.

    pl
    The arrival of an LC-130 is a sign that the summer activities are ongoing. Image: IceCube/NSF

    Even with the IceTop measurements and some further activities, this is not a busy season for IceCube. “It will be a light workload for Cubers at the Pole this year, probably the least amount of activity for IceCube since the 2002/2003 season. Our population is down to 16 compared to 100 during peak construction. We are shipping only 3800 pounds of cargo, and we used to have about 25,000 pounds for each IceCube string,” says Jim Haugen, who is responsible for IceCube’s South Pole planning and logistics.

    Researchers from US, Germany, Belgium and Korea will make sure that everything is ready for another year of data-taking. “I am excited for the 10 IceCube first-timers who will be working at Pole this year. It’s always thrilling to arrive at Pole, but nothing beats that first time when the Herc glides to a stop and the loadmaster opens the door flooding the plane with very cold air prior to leaving the plane,” adds Haugen.

    Among the fortunate Antarctic travelers, Armando Caussade of Puerto Rico is the NSF/PolarTREC teacher who will participate in some of the IceCube activities and engage more Hispanic students in astrophysics research. Follow his journal here.

    See the full article here.

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    ICECUBE neutrino detector
    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

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  • richardmitnick 4:45 pm on November 13, 2014 Permalink | Reply
    Tags: , , DM-Ice, IceCube Experiment, WIPAC   

    From IceCube: “DM-Ice collaborators discuss dark matter search” 

    icecube
    IceCube South Pole Neutrino Observatory

    Deep in the ice at the South Pole, the IceCube Neutrino Observatory sits and waits for high-energy particles to pass in its midst. However, another detector, DM-Ice, is situated among IceCube’s strings, partnering with its technology for a different purpose: the search for dark matter. Currently, the only detector to make a strong claim to have seen a dark matter signal is DAMA, at the Gran Sasso National Laboratory in Italy. DM-Ice aims to carry out a definitive test of DAMA’s claim.

    DM-Ice at IceCube
    DM-Ice

    DAMA at Gran Sasso
    DAMA II at Gran Sasso
    DAMA at Gran Sasso

    Among the established WIPAC community are two enthusiastic physicists who can reveal some of the mystery behind the search for dark matter. Reina Maruyama of Yale University has been the principal investigator of DM-Ice since its inception in 2010, during her time as a WIPAC researcher. Among her team of collaborators is Matt Kauer, a postdoc at WIPAC, who is currently working to advance the development of the detector to its full scale.

    two
    Matt Kauer and Reina Maruyama at WIPAC during a meeting of the DM-Ice Collaboration.

    Q: Can you explain to us what dark matter is?

    Matt (M): Dark matter makes up approximately 27% of all matter and energy in our universe right now. But, in fact, no one really knows what this matter is, where it comes from, or what it interacts with. There are a handful of theories explaining what dark matter could be, but we have yet to confirm its origin and nature.

    Reina (R): From the luminosity of stars, we can infer their mass. From measuring the speed of rotation of stars, we can also infer their mass and the mass of objects that they rotate around. The second measurement gives us masses much higher than the first, which leads us to believe that there must be much more mass out there than we can see. We call this dark matter. There are other observations that point toward the existence of this invisible mass, like seeing light from distant stars bent around invisible objects. The question is, what is this matter. One of our favorite hypotheses is the so-called WIMP (Weakly interacting massive particles) model. If the dark matter we see out there is made of WIMPs, we might be able to see their interaction with ordinary matter, even if this happens very occasionally.

    dm
    DM-Ice detector and dark matter modulation explained. Graphic: Jamie Yang/WIPAC.

    Q: What is the goal of DM-Ice?

    R: DM-Ice really started with a request from the dark matter community. For the last 15 years, the DAMA collaboration has claimed that they have observed dark matter. Their signature is coming from an annual modulation in the number of observed dark matter induced interactions in the DAMA detector, due to the orbit of the Earth around the Sun. The flux of dark matter from the galactic halo on Earth should be higher in early June, when the rotational speed of our planet is added to that of the Sun with respect to the galaxy. In early December, when these two velocities are in the opposite directions, the dark matter signature should be smaller. Since DAMA announced these results, there have been ongoing discussions in the community about whether what DAMA is seeing is really a dark matter signature or just some background fluctuation.

    M: DAMA is located in Italy, under the Gran Sasso Mountain, while DM-Ice is buried in the Antarctic ice at the South Pole. From our location, we have a reversed phase of environmental backgrounds with respect to the Northern Hemisphere while the dark matter signature is the same in both hemispheres. Thus, seeing an annual modulation with DM-Ice that’s consistent with DAMA’s dark matter signature would be a smoking-gun confirmation.

    R: Right. DAMA’s results have been out there for a very long time, and there are many concerns that the dark matter community has expressed about them. Although the DAMA collaboration has tried to address every concern that people have raised, the truth is that there are many things that can vary annually. We’re trying to look for a very, very small signal, and there are many possibilities that could mimic the signature that DAMA sees.

    Q: A deployment at the South Pole is never a simple task. What’s the story behind DM-Ice?

    R: The idea came when IceCube was being deployed, back in 2009. Having a detector in the Southern Hemisphere is a great choice, since it allows a cross check of systematics. Francis Halzen (the IceCube PI) and I talked a lot about it, and finally I agreed to at least take a look and assess if it was feasible. I first thought it was the craziest idea, but then I went to the Pole for work related to IceCube and saw what it’s like to work there. And I saw how fantastic this team was, and I came back thinking that this was actually possible. And that’s what we did; we put together a prototype for DM-Ice, starting from scratch.

    M: Quickly obtaining NaI crystals for the detector seemed challenging, but there was an elegant solution. The NAIAD experiment was an old dark matter experiment from the early 2000’s in the Boulby mine in the U.K. The experiment had been decommissioned but the crystals were still in storage at the mine, so we talked with them, and they shipped us two of their crystals for DM-Ice. Those are the crystals now taking data at the South Pole.

    Q: And all this happened very fast, didn’t it?

    R: Yes. DM-Ice was designed and built in nine months and we deployed the prototype during the next polar season at the end of 2010, the final IceCube construction season. The result of this intense year of work is what’s operating at the South Pole now.

    M: It’s pretty amazing. The teams at PSL (Physical Sciences Laboratory), WIPAC, and in general the IceCube community, made this possible. They supported us with the design and manufacturing of the material components and electronics. The logistics of getting an experimental apparatus to the South Pole requires a lot of coordination. We work with IceCube and WIPAC to maintain the data acquisition electronics at the South Pole.

    Q: When we read about DM-Ice we learn that it’s a sodium iodide detector. How exactly does a sodium iodide detector work?

    R: Sodium iodide detectors have existed for the last 50 or more years. This crystal is transparent, dense and has low backgrounds, all of which are important properties when you are trying to look for interactions of yet-to-be-observed particles that very rarely interact. And when they do interact, they could look like interactions induced by well-known particles.

    The detection principle is quite simple. We measure dark matter interactions by recording the recoil of target nuclei scattered by a WIMP. When the sodium iodide nuclei get a kick from scattered WIMPs, they would essentially excite electrons in the detector. As the electrons decay back down to their ground state they emit light. Then we collect that light using photomultiplier tubes (PMTs), just like in IceCube, and depending on how many photons come out, it could tell us the energy of that interaction.

    Q: What is the difference between a dark matter reaction and just another particle reaction?

    M: The amplitude and shape of the interaction are the relevant parameters. With a typical dark matter interaction in DM-Ice, we expect on the order of 100 to 200 photons to be emitted during the nuclear relaxation. This translates to a very small energy range we’re interested in. The shape of the signal, or the time-scale over which the photons are emitted, also provides information about the type of particle interaction being observed.

    R: Detecting this collision with a very distinct energy signature would be an indication of dark matter, but on top of that, if we can observe the annual modulation we have mentioned, with the correct phase and correct rate, then we have an additional signature for dark matter.

    mr
    Maruyama at South Pole for DM-Ice deployment. Image: DM-Ice Collaboration.

    Q: So, what is the detector’s current status as of 2014?

    M: DM-Ice 17 is taking data right now in the ice at the South Pole, mainly as a proof of concept for a full-scale deployment in the ice. We now have 17.5 kilograms of target material from the crystals we inherited from NAIAD, but these crystals are a little too high in internal backgrounds for a competitive analysis. We are currently collaborating with vendors to develop much cleaner crystals for use in the full-scale detector.

    R: As Matt says, our prototype is too small and too high in background to really be able to test DAMA, but we have proved that we can deploy and operate a dark matter detector at the Pole. The challenge is now to build the full-scale detector, which would be sensitive enough to see what DAMA sees. We have good teams at Yale, WIPAC, and other places in the U.S., Canada, and the U.K. contributing to our efforts.

    M: Here at WIPAC, the DM-Ice team consists of six people, contributing through different analysis and R&D projects geared toward the full-scale 250kg detector. We are, for example, working with two prototype crystals that we have underground at FNAL in Chicago and measuring the potassium backgrounds in those crystals.

    Q: What is the near future for DM-Ice?

    R: Our job is to be ready when IceCube is ready to drill again at the Pole, hopefully deploying the planned detector extensions. When IceCube drills again, we will have improved DM-Ice detectors that can go in the ice as well. In the meantime, we will run a similar sort of DM-Ice detector in the Northern Hemisphere. It would be a test to reproduce what DAMA found with an independent detector. However, we might just find the same result that DAMA did, without really learning much more about its origin.

    The original idea was to put this detector at the South Pole because it is really the ultimate test. If we see the same signature as DAMA, it would be very difficult to attribute it to the seasons. If we don’t see the same annual modulation that DAMA sees, then the scenario of it being dark matter can be ruled out, even if we don’t know the origin of that signal. Basically, we would be able to confirm or rule out DAMA’s claims of a dark matter observation.

    Q: Can you tell us more about what we can learn from a northern detector?

    R: There are different scenarios that could come from a northern deployment. You see no annual modulation, or you see the same signature as DAMA. If the signature is there, we might be able to test some background hypotheses to figure out what is there aside from dark matter. But we might also end up with a dark matter-only possible scenario, as DAMA did. I think we still have to bring this detector to some other location to verify that the dark matter signature phase stays the same everywhere on Earth to confirm that it’s due to dark matter. In summary, we might learn a few things from a northern run or we might not, but if we go straight to the Southern Hemisphere, then it’s one shot and we would have a definitive answer.

    Q: Will WIPAC be an important partner for a northern detector as well?

    M: Oh yes! WIPAC and our collaborators at the PSL, also at UW–Madison, contribute far beyond the South Pole expertise and logistics.

    R: I would say that’s what is unique about WIPAC and the University of Wisconsin—the existence of a scientific institution coupled with a very good technical and university-oriented engineering center. Being able to build big things at a university is rare, and I think that’s why IceCube was successful and why the DM-Ice demonstrator was possible. Yale also has similar capabilities, and together there is great intellectual and technical support behind DM-Ice.

    The team of collaborators working alongside Maruyama and Kauer include distinguished WIPAC physicists Francis Halzen and Albrecht Karle, and engineers Perry Sandstrom and Jeff Cherwinka, as well as students Antonia Hubbard, Walter Pettus, Bethany Reilly, and Zack Pierpoint from the UW–Madison and Yale communities.

    See the full article here.

    Please help promote STEM in your local schools.
    STEM Icon

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    ICECUBE neutrino detector
    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

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  • richardmitnick 3:39 pm on October 28, 2014 Permalink | Reply
    Tags: , IceCube Experiment,   

    From ICECUBE: “Atmospheric neutrino oscillations measured with three years of IceCube data” 

    icecube
    IceCube South Pole Neutrino Observatory

    28 Oct 2014
    Silvia Bravo

    The IceCube Neutrino Observatory at the South Pole continues to contribute new ways to tackle some of the big questions in astrophysics and neutrino physics research. Results on extraterrestrial neutrinos, cosmic-ray anisotropy, dark matter searches and now neutrino oscillations have proven IceCube to be a powerful tool for exploring the unknown universe using high-energy particles produced in Nature.

    Last year, an initial measurement of the neutrino oscillation parameters was a hint that IceCube could become an important detector for studying neutrino oscillations. Today, the IceCube Collaboration has submitted new results to Physical Review Letters that present an improved measurement of the oscillation parameters, via atmospheric muon neutrino disappearance, which is compatible and comparable in precision to those of dedicated oscillation experiments such as MINOS, T2K or Super-Kamiokande.

    graph
    90 % confidence contours of the result in comparison with the ones of the most sensitive experiments. To the sides of the figure, the log-likelihood profiles for individual oscillation parameters are given. Normal mass hierarchy is assumed. Image: IceCube Collaboration

    Super-Kamiokande was the first experiment to claim the discovery of neutrino oscillations in 1998 from observing a deficit of atmospheric muon neutrino interactions in its detector.

    In contrast to the man-made, water-filled vessel of Super-Kamiokande, IceCube uses a natural target material, the glacier ice at the South Pole. This has the advantage of a much larger observation volume and therefore a larger number of events at shorter time scales. A disadvantage is that the optical properties of ice are more complex. The corresponding uncertainties are taken into account in the systematical errors of the IceCube result.

    “Today, both Super-Kamiokande and IceCube use the same “beam,” which is atmospheric neutrinos, but at different energies. And we reach a similar precision for the determination of the measurable oscillation parameters,” says Juan Pablo Yanez, a postdoctoral researcher at DESY and corresponding author of this paper. “But as IceCube keeps taking data and we keep improving our analyses, we might see important improvements in our collaboration results soon,” adds Yanez.

    IceCube records over one hundred thousand atmospheric neutrinos every year, most of them muon neutrinos produced by the interaction of cosmic rays with the atmosphere. DeepCore, a subdetector of the Antarctic neutrino observatory, allows the detection of neutrinos with energies down to 10 GeV.

    According to our understanding of neutrino oscillations, in which neutrinos can change their type on their trip through matter and space, IceCube should see fewer muon neutrinos at energies around 25 GeV and that reach IceCube after crossing the entire Earth. The reason for these missing muon neutrinos is that many oscillate into other flavors that are not seen by the detector or not selected in this analysis.

    IceCube researchers selected muon neutrino candidates with energies between a few GeV and around 50 GeV and coming from the Northern Hemisphere from data taken between May 2011 and April 2014. About 5,200 events were found, much below the 7,000 expected in the non-oscillations scenario.

    The parameters that best describe the IceCube data, and (normal mass hierarchy assumed), show uncertainties still larger than but already comparable to the neutrino-accelerator experiments. Stay tuned for further news about neutrino oscillations in IceCube!

    + Info “Determining neutrino oscillation parameters from atmospheric muon neutrino disappearance with three years of IceCube DeepCore data,” IceCube Collaboration: M.G. Aartsen et al. Submitted to Physical Review Letters, arXiv.org:1410.7227

    See the full article here.

    ICECUBE neutrino detector
    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

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  • richardmitnick 8:00 pm on September 17, 2014 Permalink | Reply
    Tags: , , , , IceCube Experiment   

    From IceCube: “An improved measurement of the atmospheric neutrino flux in IceCube “ 

    icecube
    IceCube South Pole Neutrino Observatory

    17 Sep 2014
    Silvia Bravo

    Cosmic neutrinos in IceCube are the vogue these days, but atmospheric neutrinos are the popular ones if we look at the number of hits in the detector. Those neutrinos, created by the interaction of cosmic rays in the Earth’s atmosphere, are the main background in searches for astrophysical neutrinos.

    The IceCube Collaboration has submitted a paper today to the European Physical Journal C describing a new analysis scheme for the measurement of the atmospheric neutrino spectrum with the IceCube detector. The analysis was performed using data from May 2009 to May 2010, when the detector was running with a configuration of 59 of the final 86 strings.

    The spectrum was measured introducing a novel unfolding technique in the energy range from 100 GeV to 1 PeV, extending previous results of AMANDA by almost an order of magnitude. The new analysis also uses an improved selection, with results that showed a reduced atmospheric muon background contamination of 5 to 6 orders of magnitude and an 8% increase in the signal efficiency.

    The unfolded atmospheric neutrino spectrum agrees with both previous experimental results and the current theoretical models. The new method reduces the impact of the systematic uncertainties on the measured flux, but at high energies they are still too large to allow for conclusive results about a prompt and/or an astrophysical component of the overall flux.

    graph
    Comparison of the unfolding result obtained using IceCube in the 59-string configuration to previous experiments. Theoretical models are shown for comparison. Image: IceCube Collaboration.

    The analysis scheme presented in this paper introduces a machine learning algorithm for the final event selection that uses 25 event variables to distinguish between atmospheric muon tracks and tracks produced by neutrino-induced muons.

    “IceCube is a great detector for measuring atmospheric
    muon neutrinos. Those are, in fact, the vast majority of the neutrinos we detect. And by using tools and algorithms from data mining we can detect even more,” explains Tim Ruhe, a researcher at TU Dortmund University, in Germany.

    For every neutrino detected by IceCube, about a million atmospheric muons are observed. A common way to look for neutrinos in this huge muon background consists of selecting only upgoing muon tracks, since muons created by the interaction of cosmic rays with the atmosphere will be absorbed by the Earth when approaching IceCube from below. Thus, if the event reconstruction and selection were perfect, the remaining muon tracks would have been created by the interaction of a neutrino with the ice in or around the IceCube detector.

    However, previous to this analysis, the muon background rejection in IceCube was only 99.9% efficient because about 1,000 originally downgoing muons per every neutrino seen by IceCube were falsely reconstructed as upgoing tracks. With the new selection algorithm, IceCube researchers were able to reject 99.9999% of the incoming background events.

    + Info “Development of a General Analysis and Unfolding Scheme and its Application to Measure the Energy Spectrum of Atmospheric Neutrinos with IceCube,” IceCube Collaboration: M.G. Aartsen et al. Submitted to The European Physical Journal C, arXiv.org:1409.4535

    See the full article here.

    ICECUBE neutrino detector

    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

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