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  • richardmitnick 1:29 pm on February 23, 2019 Permalink | Reply
    Tags: "An important step towards understanding neutrino masses", , , , , U Wisconsin IceCube and IceCube Gen-2   

    From U Wisconsin IceCube Collaboration: “An important step towards understanding neutrino masses” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From From U Wisconsin IceCube Collaboration

    22 Feb 2019
    Sílvia Bravo

    Neutrinos are used to investigate a broad spectrum of physics topics, ranging from the extreme universe to the underlying symmetries of nature. These intriguing particles may have the answer to a few, long-standing open questions in physics and astronomy. In particular, neutrinos themselves are the origin of still unresolved and maybe totally new physics.

    One of the main open questions in neutrino physics is the relative mass of the three neutrino types, a property known as the neutrino mass ordering. Is the third neutrino more massive than the other neutrinos, in what scientists call the normal ordering (NO), or is it lighter, referred to as inverted ordering (IO)? In a new paper by the IceCube Collaboration, physicists use the inner and denser DeepCore detector within IceCube to try to answer this question. A weak preference is shown for NO, a result that is complementary to and in agreement with results from other experiments. This paper has been submitted to the European Physical Journal.

    1
    The negative log-likelihood (LLH) as a function of sin2(θ23) for Analysis A, relative to the global minimum LLHmin. The preference for NO over IO is visible over all the range of sin2 (θ23) with the best-fit for both orderings being in the lower octant (sin2 (θ23) < 0.5). Image: IceCube Collaboration

    When neutrinos travel through space and matter, they oscillate, meaning they change their flavor (electron, muon or tau) depending on their energy and the propagation distance. This quantum effect is explained by the fact that neutrino mass states, i.e. those for which the mass is a well-defined property, are not the same as the neutrino flavor states, the states in which neutrinos interact. These mass states are called neutrinos 1, 2 and 3.

    But we know very little about neutrino mass, except that for all neutrinos it is very small and that nature may work fairly differently depending on which neutrino is more massive. Some unification theories, for example, predict a normal mass ordering. Also depending on this mass ordering, the outcomes of a supernova explosion might be different.

    Several current and future long-baseline accelerator experiments, as well as experiments with atmospheric neutrinos and reactor neutrinos, are targeting a precise measurement of the mass ordering. For atmospheric neutrinos, the propagation through Earth induces a small modulation of the oscillation of neutrinos below 15 GeV, at about the lowest neutrino energies detected in IceCube. Interestingly, this modulation depends on the mass ordering. The high statistics of detected neutrinos within IceCube allows us to search for this small effect.

    In this study, researchers performed two independent analyses, both using three years of IceCube data and targeting this challenging measurement of the neutrino mass ordering with low-energy atmospheric neutrinos in IceCube. “When we embarked on this new analysis we were not aware of all the experimental challenges that we had to solve to measure the faint signals of these low-energy neutrinos with a sufficient precision,” says Martin Leuermann, a main analyzer of this study who worked on this analysis as a PhD candidate at RWTH Aachen University.

    Both analyses obtain a consistent result within their uncertainties and a small preference for NO. Although the ordering signature is very weak, it provides a complimentary measurement. Unlike beam experiments, this result is independent of the CP-violating phase, another important parameter for characterizing neutrino oscillations. Another valuable outcome of this study is the successful implementation and verification of analysis methods that have been prototyped for future extensions of IceCube such as PINGU or the imminent IceCube Upgrade.

    The IceCube Upgrade is already underway and is expected to be completed by 2023. It will deploy new sensors within DeepCore, which will greatly enhance the accuracy of detecting these lowest energy neutrinos in IceCube that are most critical for this measurement. “We have now proven that the concept of future extensions of IceCube do work in practice and thus we can look forward to unprecedented measurements of neutrino properties,” says Steven Wren, also a main analyzer of this study who worked on this analysis as a PhD candidate at the University of Manchester.

    See the full article here .

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    Stem Education Coalition
    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.

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

     
  • richardmitnick 4:01 pm on February 18, 2019 Permalink | Reply
    Tags: A new technique dubbed STeVE for “starting TeV events, A second technique called LESE for low-energy starting events, , , , Both of these techniques introduce a new online event selection filter that selects starting events based on an initial fast reconstruction, , , Gamma-ray emission, However gamma rays can also be produced in environments where neutrino emission would be disfavored, , Searches combining both techniques result in an effective area comparable to ANTARES which thanks to its location in the Mediterranean Sea has a priori a better neutrino view of our galaxy, STeVE and LESE where tested with 3 and 4 years of IceCube data respectively, The gamma-ray galactic sky shows a large concentration of sources in the Southern Hemisphere, The highest energy gamma rays could be produced in the same mechanisms that produce the highest energy neutrinos, U Wisconsin IceCube and IceCube Gen-2   

    From U Wisconsin IceCube Collaboration: “Improving searches for galactic sources of high-energy neutrinos” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    18 Feb 2019
    Sílvia Bravo

    The search for sources of high-energy neutrinos and cosmic rays has revealed neutrinos from distant galaxies and from all over the sky traveling through the Antarctic ice. Closer sources, though, those that could produce neutrino emission in the Milky Way, have been more elusive.

    In IceCube, the signature of sources such as galactic supernova remnants peaks at low energies, well below 100 TeV, where the large background of atmospheric muons is difficult to filter out. The bulk of galactic neutrino emission is expected in the southern sky, where the Earth cannot serve as a natural filter to remove the million-to-one muon-neutrino signal. In a recent paper by the IceCube Collaboration, two new techniques improve searches at energies from 100 TeV down to 100 GeV. When tested with a few years of IceCube data, these new selections improve the sensitivity and discovery potential, allowing for the first time the search for galactic point-like sources using track events created by muon neutrinos that in many cases are indistinguishable from atmospheric muon tracks. These results have just been submitted to the journal Astroparticle Physics.

    1
    The differential discovery potential at −60° declination for LESE (light blue), STeVE (dark blue), the combined selection (LESE +STeVE) (red), a cascade point-source search (gray), a starting tracks search targeting higher energies (MESE) (gray dashed), throughgoing (light gray dashed), all with the IceCube detector, and of the ANTARES point-like source search (black). In this plot, all results are calculated for an equal three-year exposure. Image: IceCube Collaboration

    Scientists have speculated that at high energies neutrino emission should be associated with gamma-ray emission, since the highest energy gamma rays could be produced in the same mechanisms that produce the highest energy neutrinos. However, gamma rays can also be produced in environments where neutrino emission would be disfavored.

    The gamma-ray galactic sky shows a large concentration of sources in the Southern Hemisphere, where both the galactic center and the majority of the galactic plane are seen from Earth. This is, thus, a region worth exploring with IceCube to look for potential neutrino emission from the same sources that produce the gamma rays.

    However, the most successful searches for high-energy neutrinos select particle interactions that start in the detector—both cascade- and track-like events—or track-like events that come from the northern sky. Track-like events are those that provide a good pointing resolution, which on average is well below 1 degree.

    In previous searches for astrophysical neutrinos using events with the interaction vertex within the detector, a fairly high energy cut was also applied to obtain an efficient selection. The concern is that the majority of galactic neutrino emission could happen at lower energies and, thus, might be removed with this cut. To lower this energy threshold and still preserve a good pointing resolution in the southern sky, researchers have looked closer at track events in IceCube.

    In a new technique dubbed STeVE, for “starting TeV events,” the selection focuses on neutrino events between 10 and 100 TeV and uses techniques developed in a previous IceCube analysis (link to MESE news 414) to remove the background of multiple parallel atmospheric muon events, which has proved to be a resistant background at low energies. In addition, this event selection strategy exploits the difference in the observed photon pattern of bundles of low-energy atmospheric muons compared to individual high-energy muons.

    In a second technique, called LESE, for low-energy starting events, the selection was optimized for neutrinos below 10 TeV. At low energies and due to the small granularity of the IceCube detector, with strings of sensors deployed at horizontal distances of 125 meters, it’s easier for muon tracks to enter the detector without significant energy deposition detected by the outer layers of sensors, which mimics a muon neutrino interacting within the detector volume. LESE aims at selecting track-like events with energies as low as 100 GeV, leveraging the experience gained with veto-based selection techniques in searches for dark matter.

    Both of these techniques introduce a new online event selection filter that selects starting events based on an initial fast reconstruction. This new filter is the first to accept starting events from the entire southern sky while maintaining as large as possible active detector volume.

    STeVE and LESE where tested with 3 and 4 years of IceCube data, respectively, in a search for sources of astrophysical neutrinos anywhere in the southern sky and for neutrino emission from the direction of 96 known gamma-ray sources. No significant excess of neutrino emission was found, but the techniques have proven to be sensitive to strong galactic sources of low-energy astrophysical neutrinos.

    “Studying starting events from the southern sky at these energies poses many new challenges,” explains Rickard Ström, a main analyzer who worked on this study as a PhD candidate at Uppsala University. “We leveraged expertise from previous searches for point sources and exotic signatures such as dark matter. This was the first time IceCube was able to study point sources in the southern sky at these energies and using tracks with degree precision,” adds Ström.

    Searches combining both techniques result in an effective area comparable to ANTARES, which thanks to its location in the Mediterranean Sea has a priori a better neutrino view of our galaxy. STeVE and LESE selections reduce the muon background to a few thousand events per year and significantly improve IceCube’s sensitive and discovery potential of point-like sources in the southern sky with neutrinos with energies below 100 TeV.

    From From U Wisconsin IceCube Collaboration

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition
    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.

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

     
  • richardmitnick 4:19 pm on February 4, 2019 Permalink | Reply
    Tags: , In a recent multimessenger partnership IceCube researchers have joined efforts with Pan-STARRS1 astronomers to follow up high-energy neutrino alerts, , U Wisconsin IceCube and IceCube Gen-2   

    From U Wisconsin IceCube Collaboration: “Pan-STARRS1 far vision at the service of neutrino sources” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From From U Wisconsin IceCube Collaboration

    04 Feb 2019
    Sílvia Bravo

    Pan-STARSS1, a 1.8-meter-diameter optical telescope on the island of Maui is the world’s leading near-Earth object discovery telescope. However, its large digital camera, with almost 1.4 billion pixels, can also detect galactic and extragalactic transient phenomena and has a great potential for the discovery of supernovas, some of which could be sources of high-energy neutrinos.

    Pann-STARS 1 Telescope, U Hawaii, situated at Haleakala Observatories near the summit of Haleakala in Hawaii, USA, altitude 3,052 m (10,013 ft)

    In a recent publication submitted to Astronomy and Astrophysics, the IceCube Collaboration and Pan-STARRS1 scientists have searched for counterpart transient optical emission associated with IceCube high-energy neutrino alerts. When following five alerts sent during 2016-17, researchers found one supernova worth studying, SN PS16cgx. However, a more detailed analysis showed that it is most likely a Type Ia supernova, i.e., the result of a white dwarf explosion, which is not expected to produce neutrinos.

    1
    Pan-STARRS1 riz-band false-colour 1′ × 1′subsection of the field of PS16cgx. North is up, east is left.

    Neutrino emission is expected in large amounts from supernovas, but in many cases these neutrinos have typical energies in the MeV range and are not associated with high-energy cosmic rays.

    Very high energy neutrinos, which point to cosmic-ray sources, can be produced in some types of supernovas and usually only during a very short time. Astronomers have detected more than ten thousand extragalactic supernovas, and a few more in the Milky Way––if we take into account early observations by the naked eye or with the first telescopes––but to date none of them has proven to be a source of astrophysical TeV-and-above neutrinos.

    In a recent multimessenger partnership, IceCube researchers have joined efforts with Pan-STARRS1 astronomers to follow up high-energy neutrino alerts, looking for counterpart electromagnetic emission. For small flares of neutrinos, such as the case of individual IceCube alerts, the associated electromagnetic emission can be the only way to single out a potential neutrino source. This was the case, for example, in the identification of the first likely source of high-energy neutrinos and cosmic rays following a 290-TeV neutrino detected in IceCube in September 2017.

    Moreover, only a detailed understanding of mulimessenger and multiwavelength emission can reveal the processes that power the most extreme environments in the universe.

    In fact, IceCube’s high-energy realtime alerts program was launched in 2016 to boost these types of follow-ups, trying to catch transient phenomena that would otherwise be only serendipitously observed by several telescopes at the same time.

    Pan-STARRS1 followed five of the IceCube alerts sent during the first two years of operation of the realtime program. The first alert was sent on April 27, 2016, and turned out to be the only one with a prospective counterpart emission from Pan-STARRS1 observations.

    Transient PS16cgx showed a rising light curve over two days, which is a typical signature of a young supernova, possibly undergoing a potential explosion epoch where very high energy neutrinos could be produced.

    Initial spectral observations were not able to clarify whether this was a Type Ia supernova, which is not expected to emit high-energy neutrinos, or a Type Ic supernova, a stripped core-collapse supernova that could be a cosmic-ray generator and, thus, an emitter of high-energy neutrinos.

    After further inspection, looking for more detailed features of the electromagnetic emission spectrum, researchers concluded that the observations are in reasonable agreement with emission expected from a Type Ia supernova and that, at the same time, there is no specific argument to support a classification as a Type Ic supernova. Therefore, scientists think that the IceCube neutrino and PS16cgx are not related.

    Looking at the rate of high-energy alerts with good pointing resolution in IceCube––currently, fewer than ten per year––researchers estimate that one could expect a true association of a supernova and a high-energy neutrino once every two years, assuming that all IceCube alerts can be followed up. These results also support expanding the redshift range, i.e., the distance of the transient sources, of these joint searches, which would increase the number of transient phenomena observed and, thus, the discovery potential of neutrino and cosmic-ray sources.

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition
    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 2:50 pm on February 1, 2019 Permalink | Reply
    Tags: a long-term neutrino–gamma-ray partnership, , , , , Fermi-LAT collaboration, Learning from blazars, , U Wisconsin IceCube and IceCube Gen-2   

    From U Wisconsin IceCube Collaboration: “Learning from blazars, a long-term neutrino–gamma-ray partnership” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

    From From U Wisconsin IceCube Collaboration

    31 Jan 2019
    Sílvia Bravo

    Each breakthrough in neutrino astronomy is followed by a myriad of ideas on how to further exploit IceCube data. After the discovery of a flux of very high energy neutrinos in 2013, improvements and variations of the veto technique—which now can select neutrinos from the huge atmospheric muon background in all directions—are currently used at least as often as the initial technique, which used the Earth as a filter and only selected neutrinos from the Northern Hemisphere.

    More recently, the identification of the first likely source of high-energy neutrinos and cosmic rays, the gamma-ray blazar TXS 0506+056 (TXS hereafter), has boosted new analyses to learn about the extreme universe using multimessenger astronomy approaches.

    In a new paper by the IceCube Collaboration in partnership with scientists from the Fermi-LAT collaboration and the ASAS-SN telescopes, researchers went back to eight years of archived IceCube data searching for high-energy neutrino events that could have triggered an alert such as IC-170922A, the neutrino that initiated a surge of observations across the electromagnetic spectrum, which culminated with the identification of TXS as its source.

    NASA/Fermi LAT

    ASAS-SN’s hardware. Off the shelf Mark Elphick-Los Cumbres Observatory

    A second neutrino, dubbed IC-141209A, was found in spatial coincidence with blazar GB6 J1040+0617 (GB6 hereafter), a plausible but unconfirmed source of this neutrino that will be further investigated for flares of lower energy neutrinos.

    The results of this long-term search of high-energy neutrino emission from blazars also confirm that this type of active galaxy cannot account for the majority of the diffuse neutrino flux seen by IceCube and that the source of most of the high-energy neutrinos is still unknown. These results have recently been submitted to Astronomy and Astrophysics.

    In 2017, the multimessenger observations of TXS triggered by the IceCube alert built up unique and wide-ranging data from which astronomers are still deciphering a new understanding of blazars. The finding of a second plausible neutrino source in a pool of fewer than 40 high-energy events turns blazar GB6 into an object worth studying in more depth.

    “We studied the archival neutrino alerts and checked to see if a known Fermi-LAT source was within the 90% error contour. Besides TXS, GB6 was the only source which fulfilled our selection criteria,” explains Simone Garrappa, a PhD candidate at DESY and one of the main analyzers of this work

    In this paper, researchers have looked at gamma-ray and multiwavelength emission from GB6 and compared it to TXS. Blazar GB6 is a source of similar luminosity, but while Fermi-LAT had observed a long period of enhanced emission from TXS at the time of the detection of IC-170922A, GB6 showed modest gamma-ray activity when neutrino IC-141209A was emitted. However, GB6 also showed a bright optical flare recorded by the ASAS-SN telescopes, which was almost 10 times the typical emission during a low-state period. Looking at the 10-year gamma-ray light curve, scientists show that GB6 was going through a period of enhanced activity around the time when the high-energy neutrino was detected, which together with expectations for neutrino emission from current blazar models makes this blazar a plausible source of neutrino IC-141209A. Both sources are also located at a similar declination, near the horizon from the South Pole, which is the region where IceCube is most sensitive to high-energy neutrinos.

    The detailed, long-term study of high-energy emission from TXS did not show any significant increased activity in gamma rays during a second, lower-energy neutrino flare detected by IceCube in 2014/15 archived data. The study of lower-energy neutrino emission from GB6 is still under investigation and will bring new insights into the processes that power blazars.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition
    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 6:03 pm on December 17, 2018 Permalink | Reply
    Tags: , , , U Wisconsin IceCube and IceCube Gen-2   

    From U Wisconsin IceCube Collaboration: “IceCube and HAWC unite efforts to dissect the cosmic-ray anisotropy” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

    From From U Wisconsin IceCube Collaboration

    17 Dec 2018
    Sílvia Bravo

    HAWC High Altitude Cherenkov Experiment, located on the flanks of the Sierra Negra volcano in the Mexican state of Puebla at an altitude of 4100 meters(13,500ft), at WikiMiniAtlas 18°59′41″N 97°18′30.6″W. searches for cosmic rays

    It was only a few years ago that IceCube provided the first view of the arrival direction distribution of cosmic rays in the Southern Hemisphere. Observations in the Northern Hemisphere, including those from the HAWC gamma-ray observatory earlier this year, had already shown that the number of cosmic rays hitting the atmosphere varied depending on their direction and energy. The anisotropy patterns found in the Southern Hemisphere supported models that pointed to the local interstellar magnetic field as the origin of the dominant effects of this observation.

    In an attempt to better understand the anisotropy, the IceCube Neutrino Observatory and HAWC have united their efforts to study cosmic-ray arrival directions in both hemispheres at the same primary energy. The goal of this combined observation was to get a nearly full-sky coverage to study the propagation of cosmic rays with median energy of 10 TeV through our local interstellar medium as well as the interactions between interstellar and heliospheric magnetic fields. Results have just been accepted for publication in The Astrophysical Journal and include measurements on how the anisotropy modulations are distributed over different angular scales.

    1
    he all-sky distribution in relative intensity of 10 TeV cosmic rays (CR) obtained with the HAWC and IceCube observation. Blue means deficit with respect to the mean CR flux and red excess. On the left, the white arrow indicates the direction of motion of the solar system through the local interstellar medium; the black lines indicate the local interstellar magnetic field lines outside of the heliosphere. On the right, the view of the opposite side of the sky.

    Cosmic rays swirling through space constantly bombard Earth from every direction. Out of every 1,000 cosmic rays there is at most one cosmic ray with a preferred (nonrandom) arrival direction. We refer to this as anisotropy, and this tiny 0.1% effect is what scientists would like to decipher.

    The variations are small but significant and show two different amplitude scales, a large-scale anisotropy with variations of one per mille and a small-scale anisotropy with variations of one per ten thousand.

    The cosmic-ray anisotropy is associated with the distribution of the cosmic ray sources and with the properties of the magnetic fields through which the cosmic rays propagate. However, the limited field of view of any ground-based experiment prevents us from capturing the anisotropy features that are wider than the observable sky.

    The angular variations of this anisotropy support the contribution of two different mechanisms: the mean propagation along the turbulent interstellar magnetic field, which is expected to isotropically diffuse cosmic rays, and the deflection in nearby magnetic fields—the local interstellar magnetic field (LIMF) and the heliosphere—whose relative contribution depends on energy.

    Ground-based experiments typically require averaging the number of cosmic rays along each declination band, to estimate its response to a perfectly isotropic flux. This has the effect of washing out the vertical (north-south) component of the anisotropy. On the other hand, the heliospheric deflections induced on the cosmic-ray particle distribution by the long interstellar propagation are partially aligned along the LIMF and not significantly affected by the north-south blindness.

    In this study, IceCube and HAWC joined efforts to get a full-sky coverage that captures for the first time a full, unbiased picture of the cosmic-ray anisotropy. The work used five years of IceCube data, from May 2011 to May 2016, and two years of HAWC data, from May 2015 and May 2017.

    The fit of the IceCube-HAWC observed anisotropy at 10 TeV shows the expected alignment with the LIMF. Researchers then used this deviation to derive the north-south component of the dipole anisotropy.

    Previous studies of the anisotropy have shown that the dominant dipole variation starts to decrease around 10 TeV and then to abruptly increase again at energies around 100 TeV. This had been explained as a possible effect of the heliosphere, which has a much larger impact for lower energy cosmic rays.

    Deviations of the anisotropy from the LIMF could be due to the motion of the observer and/or to the effects of the heliosphere on the LIMF. However, only a full-sky study of the cosmic-ray anisotropy at different energies will make it possible to distinguish between these or other possible effects, thus enabling a deeper understanding of the properties of the LIMF and the heliosphere.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition
    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 1:44 pm on November 10, 2018 Permalink | Reply
    Tags: A pair of inspiraling neutron stars, A possible scenario would be a neutrino created in the relativistic outflows of a merger of binary neutron stars or black holes or the core-collapse of a supernova all cataclysmic cosmic environments , , , , , , , , , , , The detection of gravitational waves and neutrinos from a single source would set a new milestone in multimessenger astronomy, The scrutiny of an astrophysical source with three different messengers would not only be the next breakthrough in the field but would also confirm that multimessenger astronomy is the only path to a , U Wisconsin IceCube and IceCube Gen-2   

    From U Wisconsin IceCube Collaboration: “Multimessenger searches for sources of gravitational waves and neutrinos” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

    From From U Wisconsin IceCube Collaboration

    09 Nov 2018
    Sílvia Bravo

    1
    Artist’s now iconic illustration of two merging neutron stars. The rippling space-time grid represents gravitational waves that travel out from the collision, while the narrow beams show the bursts of gamma rays and neutrinos that are shot out just seconds after the gravitational waves. Image: NSF/LIGO/Sonoma State University/A. Simonnet

    Last year was an extraordinary year for multimessenger astrophysics. In August 2017, a gravitational wave and its electromagnetic counterpart emission were detected from a pair of inspiraling neutron stars. Only a month later, a high-energy neutrino was detected at the South Pole and electromagnetic follow-up observations helped identify the first likely source of very high energy neutrinos and cosmic rays.

    Since then, the dream of astrophysicists has been to join neutrinos and gravitational waves in the detection of a multimessenger source. According to our understanding of the extreme universe, a possible scenario would be a neutrino created in the relativistic outflows of a merger of binary neutron stars or black holes or the core-collapse of a supernova, all cataclysmic cosmic environments that should also produce gravitational waves.

    The IceCube, LIGO, Virgo, and ANTARES collaborations have used data from the first observing period of Advanced LIGO and from the two neutrino detectors to search for coincident neutrino and gravitational wave emission from transient sources.

    The goal was to explore the discovery potential of a multimessenger observation, i.e., of a source detection that needs both messengers to confirm its astrophysical origin. Scientists did not find any significant coincidence. The results, recently submitted to The Astrophysical Journal, set a constraint on the density of these sources.

    The detection of gravitational waves and neutrinos from a single source would set a new milestone in multimessenger astronomy, allowing the simultaneous study of the inner and outer processes powering high-energy emission from astrophysical objects.

    A joint detection would also significantly improve the localization of the source and enable faster and more precise electromagnetic follow-up observations. The scrutiny of an astrophysical source with three different messengers would not only be the next breakthrough in the field but would also confirm that multimessenger astronomy is the only path to a profound understanding of the extreme universe.

    Even though the current search was very limited in time, researchers have set a strong constraint for joint emission from core-collapse supernovas, while binary mergers remain secure as potential multimessenger sources of gravitational waves and high-energy neutrinos.

    This study used datasets, spanning less than 2.5 months, that are also limited by LIGO’s sensitivity, which will soon improve by a factor of 2. The addition of new LIGO and Virgo data as well as from IceCube and ANTARES will greatly increase the sensitivity of joint searches. In the longer term, future next-generation neutrino and gravitational wave detectors will boost the potential of discovery for these searches.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    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 2:19 pm on November 8, 2018 Permalink | Reply
    Tags: , , , , During the daylight season at the South Pole as the Sun moves in circles above the horizon IceCube can track the Sun’s position by the decrease in the number of high-energy particles that reach the , , The Sun also casts a shadow on IceCube, U Wisconsin IceCube and IceCube Gen-2   

    From U Wisconsin IceCube Collaboration: “The Sun also casts a shadow on IceCube” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

    07 Nov 2018
    Sílvia Bravo

    From From U Wisconsin IceCube Collaboration

    During the daylight season at the South Pole, as the Sun moves in circles above the horizon, IceCube can track the Sun’s position by the decrease in the number of high-energy particles that reach the detector from its direction. This is what scientists call a cosmic-ray shadow, because the decline in particles is due to cosmic rays being stopped by the Sun on their way from their sources to Earth.

    The IceCube Collaboration has measured the Sun’s cosmic-ray shadow for the first time, from data covering a period of five years. The results, submitted today to The Astrophysical Journal, show a clear but different shadow pattern every year. When looking at the yearly variation, scientists have found that the shadow pattern follows changes in the solar activity, which we know are correlated with the strength of the Sun’s magnetic field. Thus, this study opens a new line of research for the Antarctic neutrino observatory: the study of the Sun’s magnetic field using IceCube cosmic-ray data.

    1
    Seasonal results for the 2-D binned maps of the Sun shadow. Each map uses data from November through February of each season. Image: IceCube Collaboration

    A few people get to spend a full year at the South Pole, accumulating countless stories that will be told over and over again after returning home. But only once during a year at the Pole does the Sun rise over the horizon, launching a dance of shadows that rotate each day around the clock.

    Deep in the ice, IceCube detects a relativistic particle about three thousand times per second. In most cases, a million to one, it is a muon created by cosmic ray interactions in the Earth’s atmosphere. When the Sun is up, some of these cosmic rays are stopped by the Sun on their way to the Earth’s atmosphere, which results in a small drop in the number of muons coming from that direction, creating a Sun shadow in the detector. In a similar way, IceCube can also track the passage of the Moon during the several days each month that it is visible at the South Pole.

    “With the data we analyzed—covering only about half of a solar cycle—we already see a clear variation of the Sun shadow. With more data, we will be able to prove in a statistically significant way that this variation actually correlates with solar activity,” explains Fabian Bos, who worked on this study as a PhD candidate at Ruhr Universität Bochum in Germany.

    As expected, IceCube data confirms that cosmic rays are stopped by both the Sun and the Moon. But while the Moon shadow remains steady year after year, the Sun casts a different shadow each year. The reason for this disparity is related to the magnetic field of the Sun, and physicists would like to gather more data to learn every detail about it.

    “The exciting news is that now we can compare our results to simulations of the Sun’s cosmic ray shadow,” says Frederik Tenholt, who is now also working on this topic for his PhD dissertation. “The solar magnetic field is a core ingredient of such simulations, which will enable the study of the solar magnetic field using IceCube data in a region where it is currently inaccessible to in situ measurements.“

    More massive than electrons, muons hit Earth from all directions and will travel a few kilometers through matter before they are absorbed. Thus, only those created in the southern sky will make it to IceCube, adding up to 100 billion muons detected every year.

    The reliability of the Moon shadow is proof that IceCube’s performance is very stable and that its angular resolution is well below one degree. Changes in the Sun shadow pattern are not yet well understood, but the shadow width seems to increase for years with increased solar activity, i.e., with a larger number of sunspots. In future analyses, and with data samples covering a longer period of time, IceCube plans to use these cosmic-ray muons to study in more detail the Sun’s magnetic field, which is known to change with a cycle of 22 years.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition
    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.

     
    • amjad 1:02 am on November 13, 2018 Permalink | Reply

      nice post keep posting such wonderful stuff for information every student get benefitted with that.

      Like

  • richardmitnick 5:35 pm on October 4, 2018 Permalink | Reply
    Tags: , IceCube Upgrade for precision neutrino physics and astrophysics kicks off, , , U Wisconsin IceCube and IceCube Gen-2   

    From U Wisconsin IceCube Collaboration: “IceCube Upgrade for precision neutrino physics and astrophysics kicks off” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

    From From U Wisconsin IceCube Collaboration

    04 Oct 2018
    Sílvia Bravo

    That IceCube has big plans for a larger and improved neutrino detector is not a secret. This week, the launch of the so-called IceCube Upgrade—which will deploy seven new strings at the bottom of the detector array—sets a milestone in what IceCubers have designed as an incremental extension of the Antarctic detector. The IceCube Neutrino Observatory currently consists of a cubic-kilometer of pristine ice at depths between 1.5 and 2.5 kilometers near the Amundsen-Scott South Pole Station, a U.S. research facility operated by the National Science Foundation (NSF).

    The IceCube Upgrade is a midscale NSF project with an estimated total award of $23M that will be managed through a cooperative agreement with the University of Wisconsin–Madison (UW–Madison)––home institution of the Wisconsin IceCube Particle Astrophysics Center, the team that led IceCube construction and currently operates the observatory. On October 1, 2018, a first increment of $1M has been released to allow IceCube headquarters to set in place the operational and management systems and prepare the final design review that will establish the baseline for the construction funding in early 2019.

    UW–Madison together with Michigan State University (MSU), Penn State University, the University of Alabama, and the University of Maryland colead this project with support from the IceCube Collaboration. Further contributions of more than $3M each from funding agencies in Germany and Japan as well as MSU in the U.S. will fund the production of the new optical modules, the light sensors that capture the interaction of neutrinos with the Antarctic ice. Almost eight years after construction was completed, the IceCube scientific program has resulted in outstanding breakthrough measurements in neutrino and multimessenger astronomy, including the discovery of very high energy astrophysical neutrinos, the identification of the first likely source of neutrinos and cosmic rays, and world-leading analyses in neutrino oscillations and searches for dark matter and other new physics.

    The new strings will increase the light collection in what is already a denser region of the gigaton neutrino detector, the DeepCore infill array. By decreasing the separation between IceCube strings from 125 to 75 meters and the distance between light sensors along a string from 17 to 7 meters, DeepCore reduced the energy threshold from the TeV-and-above scale suitable for neutrino astrophysics to the GeV scale required for measurements of neutrino properties at the highest energies. The seven new strings will be deployed with vertical and horizontal spacings that are three times smaller than DeepCore and will also include advanced calibration devices.

    1
    The sensors of the IceCube Upgrade will be deployed with vertical and horizontal spacings three times smaller than DeepCore. Credit: IceCube-Gen2 Collaboration.

    This state-of-the-art instrumentation will dramatically boost IceCube’s performance at the lowest energies, increasing the samples of atmospheric neutrinos by a factor of ten, and will enhance the pointing resolution of astrophysical neutrinos. As a result of this upgrade, IceCube will yield the world’s best measurements in neutrino oscillations as well as critical measurements that could provide evidence for new physics in the neutrino sector. The new calibration devices will advance our understanding of the response variability of the light sensors in both current and new strings, resulting in enhanced reconstruction of cascade events and better identification of tau neutrinos. Cascade signatures are the light patterns of more than 75% of astrophysical neutrinos and currently have a poorer pointing resolution than the so-called tracks––cascades allow reconstructing the direction of the incoming neutrino with a typical angular resolution of 5-10 degrees, while tracks point to the neutrino’s origin to within less than 1 degree. It was a track detected in September 2017 that triggered the multimessenger efforts that identified blazar TXS 056+56 as the first likely source of high-energy neutrinos and cosmic rays. The refined calibration of the existing sensors will also enable a reanalysis of more than ten years of archival data and increase the discovery potential of neutrino sources.

    The IceCube Upgrade will provide a superior overall instrument for a fraction of the investment made in the construction of the IceCube Neutrino Observatory, which was funded with an NSF Major Research Equipment and Facilities construction grant and supported with smaller contributions from international agencies in Belgium, Germany, Japan, and Sweden.

    This project is a first step in a long process developing IceCube-Gen2, a much larger extension of the IceCube Neutrino Observatory that will increase the in-ice instrumented volume by a factor of ten while integrating other techniques for neutrino and cosmic ray detection, such as radio antennas and surface scintillators.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition
    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 10:34 am on September 6, 2018 Permalink | Reply
    Tags: , , , , U Wisconsin IceCube and IceCube Gen-2   

    From Science Node: “Putting neutrinos on ice” 

    Science Node bloc
    From Science Node

    29 Aug, 2018
    Ken Chiacchia
    Jan Zverina

    1
    IceCube Collaboration/Google Earth: PGC/NASA U.S. Geological Survy Data SIO,NOAA, U.S. Navy, NGA, GEBCO Landsat/Copernicus.

    Identification of cosmic-ray source by IceCube Neutrino Observatory depends on global collaboration.

    Four billion years ago—before the first life had developed on Earth—a massive black hole shot out a proton at nearly the speed of light.

    Fast forward—way forward—to 45.5 million years ago. At that time, the Antarctic continent had started collecting an ice sheet. Eventually Antarctica would capture 61 percent of the fresh water on Earth.

    Thanks to XSEDE resources and help from XSEDE Extended Collaborative Support Service (ECSS) experts, scientists running the IceCube Neutrino Observatory in Antarctica and their international partners have taken advantage of those events to answer a hundred-year-old scientific mystery: Where do cosmic rays come from?

    U Wisconsin IceCube neutrino observatory

    U Wisconsin ICECUBE neutrino detector at the South Pole

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

    Making straight the path

    First identified in 1912, cosmic rays have puzzled scientists. The higher in the atmosphere you go, the more of them you can measure. The Earth’s thin shell of air, scientists came to realize, was protecting us from potentially harmful radiation that filled space. Most cosmic ray particles consist of a single proton. That’s the smallest positively charged particle of normal matter.

    Cosmic ray particles are ridiculously powerful. Gonzalo Merino, computing facilities manager for the Wisconsin IceCube Particle Astrophysics Center at the University of Wisconsin-Madison (UW), compares the force of a proton accelerated by the LHC, the world’s largest atom-smasher, as similar to the force of a mosquito flying into a person.

    LHC

    CERN map


    CERN LHC Tunnel

    CERN LHC particles

    By comparison, the “Oh-My-God” cosmic ray particle detected by the University of Utah in 1991 hit with the force of a baseball flying at 58 miles per hour.

    Because cosmic-ray particles are electrically charged, they would be pushed and pulled by every magnetic field they encounter along the way. Cosmic rays would not travel in a straight line, particularly if they came from some powerful object far away in the Universe. You can’t figure out where they originated from by their direction when they hit Earth.

    Particle-physics theorists came to the rescue.

    “If cosmic rays hit any matter around them, the collision will generate secondary products,” Merino says. “A byproduct of any high-energy interaction with the protons that make up much of a cosmic ray will be neutrinos.”

    Neutrinos respond to gravity and to what’s known as the weak subatomic force, like most matter. But they aren’t affected by the electromagnetic forces that send cosmic rays on a drunkard’s walk. Scientists realized that the intense showers of protons at the source of cosmic rays had to be hitting matter nearby, producing neutrinos that can be tracked back to their source.

    The shape of water

    But if the matter that makes up your instrument can’t interact with an incoming neutrino, how are you going to detect it? The answer lay in making the detector big.

    “The probability that a neutrino will interact with matter is extremely low, but not zero,” Merino explains. “If you want to see neutrinos, you need to build a huge detector so that they collide with matter at a reasonable rate.”

    2
    Multimessenger astronomy combines information from different cosmic messenger—cosmic rays, neutrinos, gamma rays, and gravitational waves—to learn about the distant and extreme universe. Courtesy IceCube Collaboration.

    Enter the Antarctic ice shelf. The ice here is nearly pure water and could be used as a detector. From 2005 through 2010, a UW-led team created the IceCube Neutrino Observatory by drilling 86 holes deep in the ice, re-freezing detectors in the holes. Their new detector consisted of 5,160 detectors suspended in a huge ice cube six-tenths of a mile on each side.

    The IceCube scientists weren’t quite ready to detect cosmic-ray-associated neutrinos yet. While the IceCube observatory was nearly pure water, it wasn’t completely pure. As a natural formation, its transparency might differ a bit from spot to spot, which could affect detection.

    “Progress in understanding the precise optical properties of the ice leads to increasing complexity in simulating the propagation of photons in the instrument and to a better overall performance of the detector,” says Francis Halzen, a UW professor of physics and the lead scientist for the IceCube Neutrino Observatory.

    GPUs to the rescue

    The collaborators simulated the effects of neutrinos hitting the ice using traditional supercomputers containing standard central processing units (CPUs). They realized, though, that portions of their computations would instead work faster on graphics-processing units (GPUs), invented to improve video-game animation.

    “We realized that a part of the simulation is a very good match for GPUs,” Merino says. “These computations run 100 to 300 times faster on GPUs than on CPUs.”

    Madison’s own GPU cluster and collaborators’ campuses’ GPU systems helped, but it wasn’t enough.

    3

    Then Merino had a talk with XSEDE ECSS expert Sergiu Sanielevici from the Pittsburgh Supercomputing Center (PSC), lead of XSEDE’s Novel and Innovative Projects.

    Pittsburgh Supercomputing Center 3000 cores, 6 TFLOPS

    Sanielevici filled him in on the large GPU capability of XSEDE supercomputing systems. The IceCube team wound up using a number of XSEDE machines for GPU and CPU computations: Bridges at PSC, Comet at the San Diego Supercomputer Center (SDSC), XStream at Stanford University and the collection of clusters available through the Open Science Grid Consortium.

    3
    Bridges at PSC

    SDSC Dell Comet supercomputer at San Diego Supercomputer Center (SDSC)

    Stanford U Cray Xstream supercomputer

    The IceCube scientists could not assume that their computer code would run well in the XSEDE system. Their massive and complex flow of calculations could have slowed down considerably had the new machines conflicted with it. ECSS expertise was critical to making the join-up smooth.

    “XSEDE’s resources integrated seamlessly; that was very important for us,” Merino says. “XSEDE has been very collaborative, extremely open in facilitating that integration.”
    Paydirt

    Their detector built and simulated, the IceCube scientists had to wait for it to detect a cosmic neutrino. On Sept. 22, 2017, it happened. An automated system tuned to the signature of a cosmic-ray neutrino sent a message to the members of the IceCube Collaboration, an international team with more than 300 scientists in 12 countries.

    This was important. A single neutrino detection would not have been proof by itself. Scientists at observatories that detect other types of radiation expected from cosmic rays needed to look at the same spot in the sky.

    4
    Blazars are a type of active galaxy with one of its jets pointing toward us. It emits both neutrinos and gamma rays that could be detected by the IceCube Neutrino Observatory as well as by other telescopes on Earth and in space. Courtesy IceCube/NASA.

    They found multiple types of radiation coming from the same spot in the sky as the neutrino. At this spot was a “blazar” called TXS 0506+056, about 4 billion light years from Earth. A type of active galactic nucleus (AGN), a blazar is a huge black hole sitting in the center of a distant galaxy, flaring as it eats the galaxy’s matter. Blazars are AGNs that happen to be pointed straight at us.

    The scientists think that the vast forces surrounding the black hole are likely the catapult that shot cosmic-ray particles on their way toward Earth. After a journey of 4 billion years across the vastness of space, one of the neutrinos created by those particles blazed a path through IceCube’s detector.

    The IceCube scientists went back over nine and a half years of detector data, before they’d set up their automated warning. They found several earlier detections from TXS 0506+056, greatly raising their confidence.

    The findings led to papers in the prestigious journal Science and Science in July 2018. Future work will focus on confirming that blazars are the source—or at least a major source—of the high-energy particles that fill the Universe.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    Science Node is an international weekly online publication that covers distributed computing and the research it enables.

    “We report on all aspects of distributed computing technology, such as grids and clouds. We also regularly feature articles on distributed computing-enabled research in a large variety of disciplines, including physics, biology, sociology, earth sciences, archaeology, medicine, disaster management, crime, and art. (Note that we do not cover stories that are purely about commercial technology.)

    In its current incarnation, Science Node is also an online destination where you can host a profile and blog, and find and disseminate announcements and information about events, deadlines, and jobs. In the near future it will also be a place where you can network with colleagues.

    You can read Science Node via our homepage, RSS, or email. For the complete iSGTW experience, sign up for an account or log in with OpenID and manage your email subscription from your account preferences. If you do not wish to access the website’s features, you can just subscribe to the weekly email.”

     
  • richardmitnick 2:09 pm on August 31, 2018 Permalink | Reply
    Tags: , , , U Wisconsin IceCube and IceCube Gen-2   

    From U Wisconsin IceCube Collaboration: “Understanding inelasticity in high-energy neutrino interactions with IceCube” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

    From From U Wisconsin IceCube Collaboration

    31 Aug 2018
    Sílvia Bravo


    Once or twice per day, a muon neutrino interacts with a molecule of ice near one of the 5,000 sensors of the IceCube Neutrino Observatory. This weak interaction mediated by W boson is what scientists call a charged-current interaction, which produces a hadronic shower and a muon. The muon travels across the detector in a straight line, following almost the same direction as the original neutrino.

    This hadronic shower carries a fraction of the energy of the original neutrino, a parameter known as inelasticity. A better understanding of the inelasticity of neutrino interactions provides another way of deepening our knowledge of the unique physics hiding behind ghostly neutrinos.

    The IceCube Collaboration has recently presented its first measurements of the neutrino inelasticity, which are also the first-ever at very high energies—from 1 TeV up to nearly 800 TeV. The inelasticity distribution was found to be in good agreement with Standard Model prediction and was later used to perform other measurements, such as charm production in neutrino interactions or flavor composition of astrophysical neutrinos.

    These measurements are summarized in a paper recently submitted to Physical Review D and, together with previous measurements of the neutrino cross-section, show the potential of astrophysical and atmospheric neutrinos as a tool for particle and nuclear physics at high energies.

    2
    The mean inelasticity obtained from the fit in five bins of reconstructed energy. Vertical error bars indicate the 68% confidence interval for the mean inelasticity, and horizontal error bars indicate the expected central 68% of neutrino energies in each bin. The predicted mean inelasticity is shown in blue for neutrinos and in green for antineutrinos. A flux-averaged mean inelasticity is shown in red. Credit: IceCube Collaboration

    Scientists analyzed five years of IceCube data looking for starting multi-TeV neutrino interactions and found 2,650 tracks and 965 cascades. These tracks are mostly charged-current muon neutrino interactions for which the energy and inelasticity were measured.

    “The measurement of inelasticity was made possible with concepts from machine learning. Using thousands of simulated neutrino interactions, we were able to train a computer algorithm to learn the energy of the hadronic shower and the muon from the complicated pattern of light detected by IceCube’s sensors,” explains Gary Binder, who worked in this analysis during his PhD at the University of California, Berkeley.

    Neutrino inelasticity depends on the momentum distribution of quarks and antiquarks within nuclei. For example, the production of charm quarks is sensitive to the number of strange sea quarks in the nucleus. And a fit to IceCube data revealed charm quark production with more than 90% confidence.

    On the other hand, the inelasticity distributions for neutrinos and antineutrinos are somewhat different, and IceCube data allows to measure the ratio of antineutrinos to neutrinos produced in cosmic-ray air showers.

    “This analysis shows that IceCube can make significant contributions to the study of neutrino interactions, probing energies that are far beyond those accessible with terrestrial accelerators,” explains Spencer Klein, an IceCube researcher at Lawrence Berkeley National Laboratory and at University of California, Berkeley, and a coauthor of this work.

    This first measurement of the neutrino inelasticity at high energies also proved to be useful for studies of the astrophysical neutrino flux. The inclusion of inelasticity in an otherwise standard IceCube fit provides tighter constraints on the flavor composition of astrophysical neutrinos.

    This study developed a new approach to reconstructing starting tracks. It measured, separately, the energy of the cascade produced by the neutrino interaction and the muon that emerged from it. The sum gives the total energy, and the ratio of the cascade energy to the total energy is the inelasticity. The new technique produces a far more accurate energy estimate for starting tracks, which can be used to better probe the astrophysical neutrino energy spectrum¬¬––the current study found that starting tracks are consistent with other IceCube measurements.

    These results confirm that large-scale neutrino detectors can measure the inelasticity distribution of high-energy neutrinos, but the cubic-kilometer Antarctic detector has not yet reached the sensitivity that will enable precision tests of the neutrino sector and thus rigorous searches for new physics. Looking ahead, the inclusion of inelasticity in future IceCube starting event analyses will further tighten the constraints on the presence of tau neutrinos. More generally, inelasticity measurements are now known to be a robust tool for future, larger neutrino telescopes, such as the ten-cubic kilometer IceCube-Gen2 or the Mediterranean neutrino detector KM3NeT.

    3
    Artistic expression of KMNeT http://www.km3net.org

    5
    KM3NeT Digital Optical Module (DOM) in the laboratory. http://www.km3net.org

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition
    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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