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  • richardmitnick 3:42 pm on February 11, 2020 Permalink | Reply
    Tags: , , U Wisconsin IceCube and IceCube Gen-2, , , Zee burst   

    From Washington University in St.Louis: “Ultra-high energy events key to study of ghost particles” 

    Wash U Bloc

    From Washington University in St.Louis

    January 31, 2020 [Just now in social media]
    Talia Ogliore

    1
    This is the highest energy neutrino ever observed, with an estimated energy of 1.14 PeV. The IceCube Neutrino Observatory at the South Pole observed it on January 3, 2012. IceCube physicists named it Ernie. (Credit: IceCube Collaboration)

    Physicists at Washington University in St. Louis have proposed a way to use data from ultra-high energy neutrinos to study interactions beyond the standard model of particle physics. The ‘Zee burst’ model leverages new data from large neutrino telescopes such as the IceCube Neutrino Observatory in Antarctica and its future extensions.

    U Wisconsin IceCube neutrino observatory

    1

    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


    “Neutrinos continue to intrigue us and stretch our imagination. These ‘ghost particles’ are the least understood in the standard model, but they hold the key to what lies beyond,” said Bhupal Dev, assistant professor of physics in Arts & Sciences and author of a new study in Physical Review Letters.

    “So far, all nonstandard interaction studies at IceCube have focused only on the low-energy atmospheric neutrino data,” said Dev, who is part of Washington University’s McDonnell Center for the Space Sciences. “The ‘Zee burst’ mechanism provides a new tool to probe nonstandard interactions using the ultra-high energy neutrinos at IceCube.”

    Ultra-high energy events

    Since the discovery of neutrino oscillations two decades ago, which earned the 2015 Nobel Prize in physics, scientists have made significant progress in understanding neutrino properties — but a lot of questions remain unanswered.

    For example, the fact that neutrinos have such a tiny mass already requires scientists to consider theories beyond the standard model. In such theories, “neutrinos could have new nonstandard interactions with matter as they propagate through it, which will crucially affect their future precision measurements,” Dev said.

    In 2012, the IceCube collaboration reported the first observation of ultra-high energy neutrinos from extraterrestrial sources, which opened a new window to study neutrino properties at the highest possible energies. Since that discovery, IceCube has reported about 100 such ultra-high energy neutrino events.

    2
    This is the highest-energy neutrino ever observed, with an estimated energy of 1.14 PeV. It was detected by the IceCube Neutrino Observatory at the South Pole on Jan. 3, 2012. IceCube physicists named it Ernie. (Credit: IceCube collaboration)

    “We immediately realized that this could give us a new way to look for exotic particles, like supersymmetric partners and heavy decaying dark matter,” Dev said. For the previous several years, he had been looking for ways to find signals of new physics at different energy scales and had co-authored half a dozen papers studying the possibilities.

    “The common strategy I followed in all these works was to look for anomalous features in the observed event spectrum, which could then be interpreted as a possible sign of new physics,” he said.

    The most spectacular feature would be a resonance: what physicists witness as a dramatic enhancement of events in a narrow energy window. Dev devoted his time to thinking about new scenarios that could give rise to such a resonance feature. That’s where the idea for the current work came from.

    In the standard model, ultra-high energy neutrinos can produce a W-boson at resonance. This process, known as the Glashow resonance, has already been seen at IceCube, according to preliminary results presented at the Neutrino 2018 conference.

    “We propose that similar resonance features can be induced due to new light, charged particles, which provides a new way to probe nonstandard neutrino interactions,” Dev said.

    Bursting onto the neutrino scene

    Dev and his co-author Kaladi Babu at Oklahoma State University considered the Zee model, a popular model of radiative neutrino mass generation, as a prototype for their study. This model allows for charged scalars to be as light as 100 times the proton mass.

    “These light, charged Zee-scalars could give rise to a Glashow-like resonance feature in the ultra-high energy neutrino event spectrum at the IceCube Neutrino Observatory,” Dev said.

    Because the new resonance involves charged scalars in the Zee model, they decided to call it the ‘Zee burst.’

    3
    Rendering of an observation of the ultra-high energy events that feed into the ‘Zee burst’ model. (Image by Yicong Sui, Washington University)

    Yicong Sui at Washington University and Sudip Jana at Oklahoma State, both graduate students in physics and co-authors of this study, did extensive event simulations and data analysis showing that it is possible to detect such a new resonance using IceCube data.

    “We need an effective exposure time of at least four times the current exposure to be sensitive enough to detect the new resonance — so that would be about 30 years with the current IceCube design, but only three years of IceCube-Gen 2,” Dev said, referring to the proposed next-generation extension of IceCube with 10 km3 detector volume.

    “This is an effective way to look for the new charged scalars at IceCube, complementary to direct searches for these particles at the Large Hadron Collider.”

    Funding: This work was supported by US Department of Energy and by the US Neutrino Theory Network Program.

    See the full article here .

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    Wash U campus

    Washington University’s mission is to discover and disseminate knowledge, and protect the freedom of inquiry through research, teaching, and learning.

    Washington University creates an environment to encourage and support an ethos of wide-ranging exploration. Washington University’s faculty and staff strive to enhance the lives and livelihoods of students, the people of the greater St. Louis community, the country, and the world.

     
  • richardmitnick 12:31 am on February 6, 2020 Permalink | Reply
    Tags: "New optical telescope proves to be fit for the South Pole", , IceAct project: an array of air-Čerenkov telescopes., , , The telescopes use a camera based on semiconducting photosensors to detect Čerenkov light: radiation emitted when high-energy particles in the atmosphere travel faster than the speed of light in air., U Wisconsin IceCube and IceCube Gen-2   

    From U Wisconsin IceCube Collaboration: “New optical telescope proves to be fit for the South Pole” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From U Wisconsin IceCube Collaboration

    05 Feb 2020
    Madeleine O’Keefe

    The South Pole is a harsh environment: It’s far away from civilization, difficult to access, elevated over 9,000 feet above sea level, has practically zero percent humidity, receives no sunlight for nearly eight months—oh, and it’s freezing cold.

    For South Pole experiments like the IceCube Neutrino Observatory, all instruments—whether in the ice or on the surface—must undergo feasibility studies to make sure they can operate in the harsh Antarctic conditions. Optical instruments, especially, are subject to icing and snow accumulation. Recently, the IceCube Collaboration proved the successful operation of a new instrument, an imaging air-Čerenkov telescope, at the Pole. They outline the details of the study in a paper published yesterday in the Journal of Instrumentation.

    1
    A photo of the IceAct demonstrator telescope (white cylinder in foreground) on the roof of the IceCube Laboratory in 2016. Credit: IceCube Collaboration

    The IceCube Neutrino Observatory is an array of over 5,000 digital optical modules (DOMs) attached to cables that have been lowered into 86 holes drilled in the South Pole ice. This in-ice component is enhanced by a surface array called IceTop, which is made up of 162 tanks of frozen water that each contain two DOMs. Together, these arrays help researchers get a more complete picture of properties of high-energy particles from outer space, known as cosmic rays.

    As IceCube expands, the collaboration seeks ways to enhance the observatory’s sensitivity to particles called neutrinos that are produced by cosmic rays. Multiple detector systems have been proposed to boost IceCube’s sensitivity, one of which is the IceAct project: an array of air-Čerenkov telescopes.

    The IceAct imaging air-Čerenkov telescopes are small and cost-effective. They use a camera based on novel semiconducting photosensors to detect Čerenkov light: radiation that is emitted when high-energy particles in the atmosphere travel faster than the speed of light in air. (IceCube’s DOMs also detect Čerenkov light, but it is generated by ultrafast particles passing through ice rather than air.) “Since these particles originate from cosmic rays interacting with Earth’s atmosphere, the measurement allows a precise reconstruction of the cosmic ray air-shower properties,” says Erik Ganster of RWTH Aachen University, a lead on this study.

    By detecting this Čerenkov radiation in Earth’s atmosphere, the IceAct telescopes provide IceCube with an independent detection channel for cosmic ray-induced air showers. This additional information will allow scientists to do a number of things, including benchmarking the directional accuracy of IceCube, which is important for evaluating IceCube data quality and for improving reconstruction methods.

    IceAct would also allow scientists to measure cosmic ray composition—which is extremely important to understand and validate current models for determining the origin of cosmic rays—and improve the IceTop air shower reconstruction. Finally, IceAct would reduce the muon background that originates in air showers above IceCube by providing an air shower “veto”; this will improve the search for astrophysical neutrinos from the Southern Hemisphere.

    2
    A diagram of the IceAct demonstrator telescope. Credit: IceCube Collaboration

    With these advantages in mind, IceCube researchers had to test whether this new optical system could work jointly with IceCube. So, in January 2016, they deployed the first seven-pixel IceAct demonstrator telescope at the South Pole on top of the IceCube Laboratory, located in the center of the IceTop array above the in-ice component. It took data for several months during the 2016 Antarctic winter.

    Then, using a large set of the recorded data from that time period, researchers identified events that were detected by both IceCube and IceTop so that they could analyze the properties of coincident events and compare them. They also evaluated the camera and sensor stability as well as the dependency on atmospheric conditions to measure the stability of the data taking.

    “Overall, the demonstration was successful. We proved that the operation of optical instruments under the harsh conditions of the South Pole environment is challenging but definitely possible, which is a big achievement,” says Merlin Schaufel, also of RWTH Aachen University, another lead on this study. “We were able to prove the detection of coincident air showers together with IceTop and IceCube. From the data we found that the arrival directions are very compatible with the field of view of the telescope. The camera showed a good response stability.”

    The data showed that calibration of IceCube is feasible for a telescope with a larger camera that has better image reconstruction and greater field of view.

    “The small, lightweight, and cost-effective design of the telescope, together with the proof of its robustness, is an important step toward the installation of a large array of IceAct telescopes at the South Pole,” says Ganster. He notes that the design is also interesting for observatories other than IceCube: Prototypes have already been operated with HAWC in Mexico and H.E.S.S. in Namibia, two gamma-ray observatories.

    After the successful proof-of-concept study with the seven-pixel demonstrator telescope, the researchers have deployed a 64-pixel telescope at the South Pole in 2018 and a second in 2019, about 220 meters apart. These upgraded telescopes can record roughly the same number of events in a few hours as the demonstrator telescope was able to record in a full week. The 2019 Antarctic winter, especially, provided very promising data from the two telescopes. They are able to provide stereoscopic images of the air showers that will significantly improve the reconstruction capabilities.

    More telescopes are currently under production to be deployed in the 2020-21 and 2021-22 austral summers. Adding more telescopes will further improve the stereoscopic detection and increase the total field-of-view, which the researchers say will allow them to reach their science goals.

    See the full article here .

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    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 11:58 pm on February 5, 2020 Permalink | Reply
    Tags: "Optimizing the “eyeballs” of the IceCube Neutrino Observatory", , , , U Wisconsin IceCube and IceCube Gen-2,   

    From U Wisconsin IceCube Collaboration: “Optimizing the “eyeballs” of the IceCube Neutrino Observatory” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From U Wisconsin IceCube Collaboration

    05 Feb 2020
    Madeleine O’Keefe


    Playlist: Neutrinos from blazar TXS 0506+056


    Playlist: IceCube explained

    There are over 5,000 eyeballs buried in the ice at the South Pole. Not real eyeballs, but basketball-sized devices called digital optical modules (DOMs) that serve as the eyes of the IceCube Neutrino Observatory. Each DOM contains an instrument called a photomultiplier tube (PMT) that, like your eye, is able to register small amounts of light. Unlike your eye, these devices can register single photons that can be collected and sent to computers for processing.

    IceCube’s eyes are looking for signs that elusive, subatomic particles called neutrinos are passing through the ice. Specifically, IceCube pursues neutrinos that originate far out in the universe: astrophysical neutrinos. Sometimes, when an astrophysical neutrino passes through the detector, it interacts with matter near the detector and produces a cone of light called Čerenkov radiation. When a particle of that light—a photon—hits the surface of a DOM, its minute interaction can be amplified by the PMT into a signal that the electronics are able to register.

    Researchers in the IceCube Collaboration are always looking for ways to improve the understanding of the PMTs so they can get the highest-quality data from the DOMs. Most recently, they implemented a new method for more accurately characterizing individual PMT charge distributions, which was shown to improve PMT calibration and simulation. The method is described in a technical report, “In-situ calibration of the single-photoelectron charge response of the IceCube photomultipliers,” submitted recently to the Journal of Instrumentation.

    1
    The black histogram is an example charge distribution from DOM 1 string 1 (also known as “Mouse Trap”). A photon incident on the surface of the PMT would ideally be measured as generating one photoelectron (PE), which is why the horizontal axis is scaled such that the distribution peaks at this value, but other physical processes create shape in this distribution. Researchers can use the complete fit to this distribution (red) to extract the shape of what a pure sample of single photoelectrons would look like (blue). This blue shape describes the distribution of recorded signals generated from single photons. Credit: IceCube Collaboration.

    When a photon of Čerenkov light reaches a PMT inside a DOM, it will first encounter the photocathode, which in turn ejects an electron. That electron will be attracted to a charged plane (dynode) inside the PMT that then releases several new electrons. These electrons are attracted by the next dynode, which ejects even more electrons, and so on. This continues until an avalanche of electrons hits the final plane (anode). The pulse of charge generated by this avalanche is then digitized and the electrical output is sent up through a cable to the IceCube computing laboratory. The PMT’s ability to amplify the signal from photocathode to anode is known as its “gain.”

    Many factors make it difficult to determine the actual gain on an individual PMT, and using the wrong gain in simulations can cause problems. This has happened in previous IceCube analyses, leading to small but detectable disagreements between the simulation and the experimental data, especially in charge-related variables such as the average charge collected per PMT, per event. Since simulations are used to analyze IceCube data, it is important to find the accurate gain for PMTs.

    But no two PMTs are exactly the same. So researchers express the expected charge that a single photon generates in a given PMT as a probability curve, known as the single photoelectron (SPE) charge distribution. (Observed charge is often rescaled in units of photoelectrons.) The measured gain can also be used for evaluating the long-term stability of the detector and the accuracy of previous calibrations.

    One of the problems the researchers had to address was contamination in the signal. “A single photon produces a single electron at the photocathode,” explains Spencer Axani of the Massachusetts Institute of Technology, who led this analysis. “This electron then gets amplified, and the average resulting charge, about 107 electrons, is what we call an SPE. But the amplification is a statistical process, and there are a lot of physical processes that can lead to additional smearing of the amplified charge of an individual photon.”

    So Axani and his collaborators used a specially designed pulse selection software to remove some forms of contamination, allowing them to extract a sample of single photoelectrons from the data. They then used a newly developed fitting algorithm to create an SPE charge template per DOM.

    This extraction of SPE distributions allowed for an improved description of the detector in simulation and several interesting studies. For example, Axani and his collaborators inserted the SPE charge templates into simulation, which improved the data-simulation agreement in charge-related variables. This led to accurate determination of the gain setting and therefore allowed researchers to confirm that previous calibration had been done properly. The more accurate gain will also improve future calibration.

    They also used the measured distributions to search for changes in the fitted quantities (for example, what fractions of photons get properly or poorly amplified by the PMTs) over time. No changes were observed, which indicates that the calibration of the detector is properly accounting for the slow aging of the PMT.

    Lastly, researchers used the SPE charge template to investigate correlations between the measured charge distribution from each DOM and their corresponding hardware. The IceCube detector includes two sets of DOMs—high quantum efficiency and standard efficiency DOMs—and Axani and his collaborators found that the shape of the SPE charge templates for these two subsets are somewhat different. Now, their differences have been modeled.

    “Overall, we are pleased with the improvement that we saw in the agreement between the experimental data and the simulated data for charge-related variables,” says Martin Rongen of RWTH Aachen University, another lead on this analysis. He and Axani say their method can also be used to more accurately set the gain on the in-ice PMTs in future data-taking periods, thus improving the overall calibration of the detector.

    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 4:17 pm on January 31, 2020 Permalink | Reply
    Tags: , , Glashow resonance, In 2012 the IceCube collaboration reported the first observation of ultra-high energy neutrinos from extraterrestrial sources., Interactions beyond the standard model of particle physics., , , , The 'Zee burst' model, U Wisconsin IceCube and IceCube Gen-2, ,   

    From Washington University in St.Louis via phys.org: “Ultra-high energy events key to study of ghost particles” 

    Wash U Bloc

    From Washington University in St.Louis

    via


    phys.org

    January 31, 2020
    Talia Ogliore

    1
    Physicists in Arts & Sciences have proposed a new way to leverage data from large neutrino telescopes such as the IceCube Neutrino Observatory in Antarctica. Credit: Felipe Pedreros/IceCube and National Science Foundation

    Physicists at Washington University in St. Louis have proposed a way to use data from ultra-high energy neutrinos to study interactions beyond the standard model of particle physics. The ‘Zee burst’ model leverages new data from large neutrino telescopes such as the IceCube Neutrino Observatory in Antarctica and its future extensions.

    U Wisconsin IceCube neutrino observatory

    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

    DM-Ice at IceCube

    “Neutrinos continue to intrigue us and stretch our imagination. These ‘ghost particles’ are the least understood in the standard model, but they hold the key to what lies beyond,” said Bhupal Dev, assistant professor of physics in Arts & Sciences and author of a new study in Physical Review Letters.

    “So far, all nonstandard interaction studies at IceCube have focused only on the low-energy atmospheric neutrino data,” said Dev, who is part of Washington University’s McDonnell Center for the Space Sciences. “The ‘Zee burst’ mechanism provides a new tool to probe nonstandard interactions using the ultra-high energy neutrinos at IceCube.”

    Ultra-high energy events

    Since the discovery of neutrino oscillations two decades ago, which earned the 2015 Nobel Prize in physics, scientists have made significant progress in understanding neutrino properties—but a lot of questions remain unanswered.

    For example, the fact that neutrinos have such a tiny mass already requires scientists to consider theories beyond the standard model. In such theories, “neutrinos could have new nonstandard interactions with matter as they propagate through it, which will crucially affect their future precision measurements,” Dev said.

    2
    This is the highest-energy neutrino ever observed, with an estimated energy of 1.14 PeV. It was detected by the IceCube Neutrino Observatory at the South Pole on Jan. 3, 2012. IceCube physicists named it Ernie. Credit: IceCube collaboration

    In 2012, the IceCube collaboration reported the first observation of ultra-high energy neutrinos from extraterrestrial sources, which opened a new window to study neutrino properties at the highest possible energies. Since that discovery, IceCube has reported about 100 such ultra-high energy neutrino events.

    “We immediately realized that this could give us a new way to look for exotic particles, like supersymmetric partners and heavy decaying dark matter,” Dev said. For the previous several years, he had been looking for ways to find signals of new physics at different energy scales and had co-authored half a dozen papers studying the possibilities.

    “The common strategy I followed in all these works was to look for anomalous features in the observed event spectrum, which could then be interpreted as a possible sign of new physics,” he said.

    The most spectacular feature would be a resonance: what physicists witness as a dramatic enhancement of events in a narrow energy window. Dev devoted his time to thinking about new scenarios that could give rise to such a resonance feature. That’s where the idea for the current work came from.

    In the standard model, ultra-high energy neutrinos can produce a W-boson at resonance. This process, known as the Glashow resonance, has already been seen at IceCube, according to preliminary results presented at the Neutrino 2018 conference.

    “We propose that similar resonance features can be induced due to new light, charged particles, which provides a new way to probe nonstandard neutrino interactions,” Dev said.

    3
    Rendering of an observation of the ultra-high energy events that feed into the ‘Zee burst’ model. Credit: Yicong Sui, Washington University

    Bursting onto the neutrino scene

    Dev and his co-author Kaladi Babu at Oklahoma State University considered the Zee model, a popular model of radiative neutrino mass generation, as a prototype for their study. This model allows for charged scalars to be as light as 100 times the proton mass.

    “These light, charged Zee-scalars could give rise to a Glashow-like resonance feature in the ultra-high energy neutrino event spectrum at the IceCube Neutrino Observatory,” Dev said.

    Because the new resonance involves charged scalars in the Zee model, they decided to call it the ‘Zee burst.’

    Yicong Sui at Washington University and Sudip Jana at Oklahoma State, both graduate students in physics and co-authors of this study, did extensive event simulations and data analysis showing that it is possible to detect such a new resonance using IceCube data.

    “We need an effective exposure time of at least four times the current exposure to be sensitive enough to detect the new resonance—so that would be about 30 years with the current IceCube design, but only three years of IceCube-Gen 2,” Dev said, referring to the proposed next-generation extension of IceCube with 10 km3 detector volume.

    “This is an effective way to look for the new charged scalars at IceCube, complementary to direct searches for these particles at the Large Hadron Collider.”

    See the full article here .

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    About Science X in 100 words

    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
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    Washington University’s mission is to discover and disseminate knowledge, and protect the freedom of inquiry through research, teaching, and learning.

    Washington University creates an environment to encourage and support an ethos of wide-ranging exploration. Washington University’s faculty and staff strive to enhance the lives and livelihoods of students, the people of the greater St. Louis community, the country, and the world.

     
  • richardmitnick 8:33 am on January 18, 2020 Permalink | Reply
    Tags: "IceCube performs the first-ever search for neutrinos from the sun’s atmosphere", , , , U Wisconsin IceCube and IceCube Gen-2   

    From U Wisconsin IceCube Collaboration: “IceCube performs the first-ever search for neutrinos from the sun’s atmosphere” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From U Wisconsin IceCube Collaboration

    17 Jan 2020
    Madeleine O’Keefe

    Neutrinos are lightweight, elusive, and abundant particles; trillions stream through your body every second. Many of these neutrinos are produced when cosmic rays (energetic particles from outer space) interact with nuclei in Earth’s atmosphere, triggering a shower of secondary particles, including neutrinos. Specifically, these are known as atmospheric neutrinos.

    But this process is not exclusive to Earth. The sun, the largest body in the solar system, also has an atmosphere. As cosmic rays propagate throughout space, they also enter the solar atmosphere and interact with nuclei there. Secondary showers in the solar atmosphere produce gamma rays and neutrinos that can be detected here on Earth. Recently, gamma rays from the sun were observed here by a space telescope, Fermi-LAT, but experimental studies have yet to show any neutrinos from solar cosmic ray interactions.

    The IceCube Collaboration recently performed the first-ever experimental search for these so-called “solar atmospheric neutrinos.” Such a detection would have important implications for understanding solar magnetic fields and how cosmic rays propagate in the inner solar system, and it could even provide additional background to solar dark matter searches. But after investigating seven years of IceCube data, IceCube researchers did not detect any solar atmospheric neutrinos and so set an upper limit on the flux. Their results are outlined in a paper that was recently submitted to the Journal of Cosmology and Astroparticle Physics.

    1
    A diagram showing neutrinos and gamma rays being generated in the solar atmosphere and flying toward IceCube and Fermi-LAT, respectively. (Not to scale.) Credit: Seongjin In, IceCube Collaboration

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    “One main difference between neutrinos produced in Earth’s atmosphere compared to the sun’s is the density of each atmosphere where the cosmic ray interactions occur,” says Seongjin In of Sungkyunkwan University in Seoul, South Korea, a lead on this analysis. Because of the different densities, we expect a greater flux for solar atmospheric neutrinos than Earth atmospheric neutrinos when looking at high-energy neutrinos—i.e., above 10^12 electronvolts (teravolt, or TeV) levels. Fortunately, IceCube is optimized to study these energy ranges.

    In and his collaborators investigated IceCube data collected between 2010 and 2017. “We tracked the sun in the sky and selected IceCube data within a circular window of five degrees in angular distance from the center of the sun,” he says. “We then calculated a score for the data that reflects whether it could be explained with the background prediction only.” In other words, if the distribution of neutrino energy and the angular distance differed from what they expected, it could indicate that some neutrinos were produced in the sun’s atmosphere.

    Ultimately, they found no evidence of solar atmospheric neutrinos; their observation was consistent with the background predictions. But In and his colleagues were able to set an upper limit on the solar atmospheric neutrino flux.

    3
    Limits for solar atmospheric neutrinos in IceCube (black dashed lines). Other points are the results of gamma-ray experiments. Credit: IceCube Collaboration

    Importantly, this is the first experimental search for solar atmospheric neutrinos and the first experimental bound on its flux. And it certainly won’t be the last. There is already another search being carried out at Sungkyunkwan University by one of In’s colleagues.

    After all, it’s possible that the researchers just weren’t looking at the right time. “If the neutrino flux modulates similarly to that of gamma rays, then the flux of solar atmospheric neutrinos may increase during the solar minimum,” says In, referring to the natural period of least solar activity in the sun’s 11-year cycle. “That means there might be a higher chance of observing solar atmospheric neutrino with data collected in the next solar minimum in 2020.”

    There is still much to find out about solar atmospheric neutrinos, and IceCube will continue to be part of the search.

    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.

    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 3:46 pm on January 9, 2020 Permalink | Reply
    Tags: , , , , , , , U Wisconsin IceCube and IceCube Gen-2   

    From Symmetry: “Expanding a neutrino hunt in the South Pole” 

    Symmetry Mag
    From Symmetry<

    01/09/20
    Diana Kwon

    1
    Photo by Martin Wolf, IceCube/NSF

    A forthcoming upgrade to the IceCube detector will provide deeper insights into the elusive particles.

    Underneath the vast, frozen landscape of the South Pole lies IceCube, a gigantic observatory dedicated to finding ghostly subatomic particles called neutrinos. Neutrinos stream through the Earth from all directions, but they are lightweight, abundant and hardly interact with their surroundings.

    The IceCube detector consists of an array of 86 strings festooned with more than 5000 sensors, like round, basketball-sized Christmas lights. They reach more than 2 kilometers (more than 1 mile) down through layers of Antarctic ice that have accumulated over hundreds of thousands of years.

    A small fraction of the neutrinos that pass through the ice collide with its atoms and spit out showers of particles, some of which can be spotted by IceCube’s sensors as sparks of blue light. By probing the light patterns, scientists can identify and assess the elusive particles, some of which originate beyond our solar system.

    In July 2019 the IceCube collaboration announced that the US National Science Foundation had granted it $23 million to put toward a $37 million upgrade, with additional financial support coming from Michigan State University, the University of Wisconsin–Madison, and agencies in Germany and Japan.

    The upgrade will add seven more strings of sensors to the detector, along with new instruments meant to characterize the ice. This extension will allow physicists to better understand how neutrinos oscillate between their three flavors: electron, muon and tau. Scientists also plan to make more precise measurements of IceCube’s icy interior to get a closer look at neutrinos from far out in the universe.

    U Wisconsin IceCube neutrino observatory

    U Wisconsin ICECUBE neutrino detector at the South Pole

    U Wisconsin IceCube experiment at the South Pole



    U Wisconsin ICECUBE neutrino detector at the South Pole


    IceCube Gen-2 DeepCore PINGU


    IceCube reveals interesting high-energy neutrino events

    3
    When cosmic neutrinos crash into the IceCube detector, the interactions generate secondary particles that travel faster than the speed of light through the ice, producing a detectable faint blue glow. Courtesy of Nicolle R. Fuller/NSF/IceCube

    Extraterrestrial signals

    One of the main aims of IceCube, which is run by an international group of more than 300 scientists from 12 different countries, is to identify cosmic neutrinos. They know which neutrinos come from afar by the extraordinarily high levels of energy they have when they crash into the Earth, compared to their more local counterparts. By studying these alien particles, physicists hope to identify the powerful cosmic accelerators that form beams of ultra-high energy particles.

    IceCube had its first major breakthrough in 2013 when it identified two ultra-high energy neutrinos from outside the solar system. These events, dubbed Bert and Ernie, became the first of many cosmic neutrino detections, says Olga Botner, a physicist at Uppsala University in Sweden and former spokesperson of IceCube.

    “We knew we were in business,” she says. “We could observe not only the atmosphere but also neutrinos from outside our own galaxy. That was huge.”

    Four years later, IceCube physicists made a detection of an extraterrestrial neutrino that sparked a search for a glimpse of its source by scientists at astronomical observatories around the globe. This worldwide hunt allowed scientists to pinpoint the particle’s birthplace: an extremely luminous galaxy called a blazar. A blazar acts like a cosmic accelerator, spitting out a constant stream of particles from its core.

    “Working on IceCube is very exciting,” says Delia Tosi, an assistant scientist at the Wisconsin IceCube Particle Astrophysics Center (WIPAC). “There is no space for boredom.”

    Where most cosmic neutrinos come from remains a mystery. But IceCube’s scientific repertoire has expanded since those first discoveries. Scientists also use IceCube to examine how neutrinos change from one type to another—which could help determine whether there are new types of neutrinos that we don’t yet know about—as well as to search for dark matter and characterize how light travels though Antarctic ice.

    “When we started IceCube, we were 90% focused on finding point sources of astrophysical neutrinos,” says Kael Hanson, a physicist and director of WIPAC. “We really had no idea, when we were designing the experiment, how rich the science program would eventually become.”

    An upgrade on ice

    With the forthcoming upgrade, more than 700 new sensors spread across seven strings will be added to the center of IceCube.

    The core is already more densely packed with strings than the rest of the detector, which makes it better able to detect particles at low energies. The new sensors will push that sensitivity even further. “We’re pushing the energy threshold down by a factor of 10,” Hanson says.

    The denser core will make it possible for the scientists to examine the hundreds of thousands of atmospheric neutrinos that bombard the detector each year in more detail. This will allow physicists to make more accurate measurements of the tau neutrino, which can then be used to better understand neutrino oscillations—specifically, how muon neutrinos convert to tau neutrinos.

    “We don’t quite understand how neutrinos can spontaneously morph from one flavor to another,” Botner says. “If discrepancies exist between our predictions and what we observe, this would be a hint of unknown neutrino kinds—the so-called sterile neutrino.”

    To insert new strings into the detector, scientists must drill deep holes into the ice using a high-pressure stream of hot water. During the upgrade, scientists will deploy additional calibration instruments, such as cameras and light sources, along with the detectors to help them characterize the ice.

    When water refreezes around the strings—a process that can take several weeks—the ice that forms can contain dust and bubbles. These imperfections make it more difficult to see signs of neutrinos.

    Not only will characterizing the ice make it possible for scientists to more accurately assess future observations, researchers will also be able to apply this new knowledge to previously collected data. “In principle, we can recalibrate all the data and improve our ability to point back to a source,” says Dawn Williams, a particle astrophysicist at the University of Alabama.

    The IceCube collaboration plans to start drilling in late 2022. In the meantime, the group is preparing the sensors and other components of the upgrade as well as the software that will be used to run the upgraded detector. The team expects to start collecting data in the spring of 2023.

    The upgrade also serves an additional purpose: to test new sensor designs that scientists hope might be deployed in IceCube-Gen2, a proposed detector that would be 10 times the size of the current one. The super-sized observatory would allow scientists to conduct even more precise measurements of neutrinos and detect more ultra-high-energy particles from outer space, heightening the possibly of pinpointing their sources.

    See the full article here .


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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 10:42 am on November 14, 2019 Permalink | Reply
    Tags: "What can cascade events tell us about neutrino sources?", , , , U Wisconsin IceCube and IceCube Gen-2   

    From U Wisconsin IceCube Collaboration: “What can cascade events tell us about neutrino sources?” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From From U Wisconsin IceCube Collaboration

    13 Nov 2019
    Madeleine O’Keefe

    On a dark, clear night, you can look up and see the Milky Way galaxy: billions of stars shining in visible light. But we also expect our galaxy to “shine” in neutrinos, elusive particles whose origins are still mysterious. There are cosmic-ray sources within our galaxy, so these sources must also produce neutrinos.

    Cosmic rays produced by high-energy astrophysics sources (ASPERA collaboration – AStroParticle ERAnet)

    We cannot see neutrinos with our eyes, but the IceCube Neutrino Observatory can detect them. IceCube “sees” with 5,160 optical sensors buried deep in glacial ice at the South Pole.

    When neutrinos pass through IceCube, they will sometimes leave signals, known as “events,” primarily as either tracks or cascades. The former occur when a neutrino collides with matter in or near IceCube, resulting in a high-energy muon that travels a long distance, leaving an elongated “track” of signals in its wake. Cascades happen when all or most of the neutrino’s energy is deposited in a small region and results in a nearly spherical event, making it hard to measure the direction from which the parent neutrino came.

    Cascades are more difficult to reconstruct than tracks, which are usually used in searches for astrophysical neutrino sources, but they have their own advantages, including providing a better measurement of neutrino energy. By studying cascade events, researchers enhance IceCube’s sensitivity to possible neutrino sources in the southern sky, including the Galactic Center.

    In a paper published today in The Astrophysical Journal, the IceCube Collaboration outlined recent results from a source search that used seven years of data from cascade events. While they did not find any statistically significant sources of neutrino emissions, this work is an improvement on the previous source search with cascades.

    1
    Results from the all-sky scan for neutrino point sources, with the center and plane of the Milky Way shown by the grey dot and curve, respectively. No statistically significant emission was identified. Credit: IceCube Collaboration

    Cascades have the advantage that atmospheric backgrounds are small and relatively uniform throughout the sky. IceCube collaborators previously used two years of cascades in a similar analysis. The current work is an improvement on that analysis in three ways: the use of seven years of data, greatly improved directional reconstruction, and the added emphasis on testing for possible sources within the Milky Way.

    To perform their analysis, IceCube scientists first improved the directional reconstruction by using a deep convolutional neural network inspired by recent work in image recognition, rather than the traditional statistical approach. “In principle, the traditional approach should perform better,” says Mike Richman, a postdoctoral researcher at Drexel University and the lead on the analysis, “but in practice, our model of the glacial ice is sufficiently complex that it’s difficult to guarantee that method converges on the optimal result.”

    Richman credits fellow IceCube collaborator Mirco Huennefeld of Universität Dortmund for his extensive work on the angular reconstruction used in the analysis. “Mirco has trained a model with an implicit understanding of the detector and the ice, and it’s able to obtain good results without resorting to expensive numerical scans.”

    Armed with this improved reconstruction applied to seven years of data, the researchers performed two types of analysis: searches for point sources and searches for broad emission regions in our galaxy. The point source searches included a scan of the whole sky, a scan over 74 preselected potential sources, and a test for sum-total emission from three short lists of interesting supernova remnants. The broad emission regions included gas and dust distributed throughout the Milky Way and the giant “Fermi bubbles” near the center of our galaxy. Many of these tests were the most sensitive performed to date by any experiment.

    Ultimately, the researchers did not find evidence for neutrino emission. However, they did acknowledge an interesting trend: As the Milky Way measurements become more sensitive (from using just IceCube tracks, to IceCube tracks and ANTARES events [The Astrophysical Journal Letters], and now to just IceCube cascades), the result becomes increasingly significant. Furthermore, the galactic neutrino energy spectrum suggested by the cascade data agrees with previous IceCube work with tracks. While not conclusive, this is consistent with emission that is just below the sensitivity of analyses done so far.

    This work solidifies the importance of using all neutrino flavors to search for sources—at least with current-generation detectors. Going forward, Richman says they plan to improve the cascade analysis by applying the latest reconstructions to data collected over more time and extending to even lower energies (below 1 TeV). They expect data from the IceCube Upgrade to reduce systematic uncertainties, leading to still better sensitivity.

    In the future, the plan is to study additional source types, including ones with time-dependent—and potentially very short-lived—emission. They also plan to combine IceCube tracks and cascades and ultimately to perform a “global” analysis that includes all event types from all available data.

    See the full article here .

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    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 8:41 am on October 22, 2019 Permalink | Reply
    Tags: "New all-sky search reveals potential neutrino sources", , , , , , , U Wisconsin IceCube and IceCube Gen-2   

    From U Wisconsin IceCube Collaboration: “New all-sky search reveals potential neutrino sources” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From From U Wisconsin IceCube Collaboration

    21 Oct 2019
    Madeleine O’Keefe

    For over a century, scientists have been observing very high energy charged particles called cosmic rays arriving from outside Earth’s atmosphere. The origins of these particles are very difficult to pinpoint because the particles themselves do not travel on a straight path to Earth. Even gamma rays, a type of high-energy photon that offers a little more insight, are absorbed when traversing long distances.

    The IceCube Neutrino Observatory, an array of optical modules buried in a cubic kilometer of ice at the South Pole, hunts for cosmic-ray sources inside and outside our galaxy—extending to galaxies more than billions of light years away—using hints from elusive particles called neutrinos. These neutrinos are expected to be produced by cosmic-ray collisions with gas or radiation near the sources.

    Unlike cosmic rays, neutrinos are not absorbed or diverted on their way to Earth, making them a practical tool for locating and understanding cosmic accelerators. If scientists can find a source of high-energy astrophysical neutrinos, this would be a smoking gun for a cosmic-ray source.

    After 10 years of searching for origins of astrophysical neutrinos, a new all-sky search provides the most sensitive probe of time-integrated neutrino emission of point-like sources. The IceCube Collaboration presents the results of this scan in a paper submitted recently to Physical Review Letters.

    1
    The pre-trial probability of the observed signal being due to background in a 5×5 degree window around the most significant point in the Northern Hemisphere (the hottest spot); the black cross marks the Fermi-3FGL coordinates of the galaxy NGC 1068. Credit: IceCube Collaboration

    Tessa Carver led this analysis under the supervision of Teresa Montaruli in the Département de Physique Nucléaire et Corpusculaire at the University of Geneva in Switzerland. “IceCube has already observed an astrophysical flux of neutrinos, so we know they exist and are detectable—we just don’t know exactly where they come from,” says Carver, now a postdoc at Cardiff University. “It is only a matter of time and precision until we can identify the sources behind this neutrino flux.”

    The principle challenge in searching for astrophysical neutrino sources with IceCube is the overwhelming background of events induced by cosmic-ray interactions in our atmosphere. The signal of faint neutrino sources needs to be extracted via sophisticated statistical analysis techniques.

    Using these methods, Carver and her collaborators “scanned” across the entire sky to look for point-like neutrino sources at arbitrary locations. This scanning method is able to identify very bright neutrino sources that could be invisible in gamma rays, which are also produced in cosmic-ray collisions.

    In order to be sensitive to dimmer sources, they also analyzed 110 galactic and extragalactic source candidates, which have been observed via gamma rays. They then combined the results obtained for individual sources in this list in a “population analysis,” which looks for a higher-than-expected rate of significant results from the individual source list search. This allows researchers to find significant neutrino emission, even if sources in the list are too weak to be observed individually.

    Researchers also employed a “stacking search” for three catalogs of gamma-ray sources within our galaxy. This search layers together all the emission from groups of known objects of the same type under the assumption that they have well-known emission properties. While it can significantly reduce the per-source emission required to observe a large excess of signal over the background, this search is limited in that it requires more knowledge of the sources in the catalog.

    2
    Skymap of -log10(plocal), where plocal is the local pre-trial p-value, for the area between ±82 degrees declination in equatorial coordinates. The Northern and Southern Hemisphere hotspots, defined as the most significant plocal in the given hemisphere, are indicated with black circles. Credit: IceCube Collaboration

    While the different analyses did not discover steady neutrino sources, the results are nevertheless exciting: some of the objects in the catalog of known sources showed a higher neutrino flux than expected, with excesses at the 3σ-level. In particular, the all-sky scan revealed that the “hottest” location in the sky is just 0.35 degrees away from the starburst galaxy NGC 1068, which has a 2.9σ excess over background. NGC 1068 is one of the closest black holes to us; it is embedded in a star-forming region with lots of matter for neutrinos to interact with while the high-energy gamma rays are attenuated, as shown by Fermi and MAGIC measurements.

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    MAGIC Čerenkov telescopes at the Observatorio del Roque de los Muchachos (Garfia, La Palma, Spain)), Altitude 2,396 m (7,861 ft)

    This is the most significant excess seen besides TXS 0506-056, the 2017 source that IceCube found to be coincident with a gamma ray flare. Still, these potential neutrino sources require more data with a more-sensitive detector, like IceCube-Gen2, to be confirmed.

    The researchers also found that the Northern Hemisphere source catalog as a whole differed from background expectations with a significance of 3.3σ. Carver says these results demonstrate a strong motivation to continue to analyze the objects in the catalog. Time-dependent analyses, which search for flares of peaked emission, and the possibility of correlating neutrino emission with electromagnetic or gravitational wave observations for these and other sources may provide additional evidence of neutrino emission and insights into the neutrinos’ origin. With continued data-taking, more refined direction reconstruction, and the upcoming IceCube Upgrade, further improvements in sensitivity are on the horizon.

    “We are lucky to have the unique opportunity to be the first people to map the universe with neutrinos, which provides a brand-new perspective,” says Carver. “Also, this progress in neutrino astronomy is accompanied by great strides in gravitational wave physics and cosmic-ray physics.”

    Montaruli adds, “While we are at the dawn of a new era in astronomy that observes the universe not just with light, this is the first time we have begun to see potentially significant excesses of candidate neutrino events around interesting extragalactic objects in time-independent searches.”

    See the full article here .

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    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 2:46 pm on October 2, 2019 Permalink | Reply
    Tags: , , The neutrino event IceCube 170922A and the distant BL Lac object active galaxy TXS 0506+056, This was the first neutrino from outer space whose origin could be confirmed., U Wisconsin IceCube and IceCube Gen-2   

    From Max Planck Institute for Radio Astronomy: “Neutrino produced in a cosmic collider far away” 


    From Max Planck Institute for Radio Astronomy

    October 02, 2019

    Priv.-Doz. Dr. Silke Britzen
    Phone:+49 228 525-280
    sbritzen@mpifr-bonn.mpg.de
    Max Planck Institute for Radio Astronomy,Bonn

    Prof. Dr. Christian Fendt
    Phone:+49 6221 528-387
    fendt@mpia-hd.mpg.de.
    Max Planck Institute for Radio Astronomy,Heidelberg

    Max-Planck-Institut für Astronomie,
    Dr. Norbert Junkes
    Press and Public Outreach
    Phone:+49 228 525-399
    njunkes@mpifr-bonn.mpg.de
    Max Planck Institute for Radio Astronomy,Bonn

    Link between IceCube neutrino event and distant radio galaxy resolved

    The neutrino event IceCube 170922A, detected at the IceCube Neutrino Observatory at the South Pole, appears to originate from the distant active galaxy TXS 0506+056, at a light travel distance of 3.8 billion light years. TXS 0506+056 is one of many active galaxies and it remained a mystery, why and how only this particular galaxy generated neutrinos so far.

    An international team of researchers led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, studied high-resolution radio observations of the source between 2009 and 2018, before and after the neutrino event. The team proposes that the enhanced neutrino activity during an earlier neutrino flare and the single neutrino could have been generated by a cosmic collision within TXS 0506+056. The clash of jet material close to a supermassive black hole seems to have produced the neutrinos.

    The results are published in Astronomy & Astrophysics, October 02, 2019.

    1
    TXS 0506+056. The neutrino event IceCube 170922A appears to originate in the interaction zone of the two jets.
    © IceCube Collaboration, MOJAVE, S. Britzen, & M. Zajaček

    On July 12, 2018, the IceCube collaboration announced the detection of the first high-energy neutrino, IceCube-170922A, which could be traced back to a distant cosmic origin. While the cosmic origin of neutrinos had been suspected for quite some time, this was the first neutrino from outer space whose origin could be confirmed. The “home” of this neutrino is an Active Galactic Nucleus (AGN) – a galaxy with a supermassive black hole as central engine. An international team could now clarify the production mechanism of the neutrino and found an equivalent to a collider on Earth: a cosmic collision of jetted material.

    AGN are the most energetic objects in our Universe. Powered by a supermassive black hole, matter is being accreted and streams of plasma (so-called jets) are launched into intergalactic space. BL Lac objects form a special class of these AGN, where the jet is directly pointing at us and dominating the observed radiation. The neutrino event IceCube-170922A appears to originate from the BL Lac object TXS 0506+056, a galaxy at a redshift of z=0.34, corresponding to a light travel distance of 3.8 billion light years. An analysis of archival IceCube data by the IceCube Collaboration had revealed evidence of an enhanced neutrino acitvity earlier, between September 2014 and March 2015.

    Other BL Lac Objects show properties quite similar to those of TXS 0506+056. „It was a bit of a mystery, however, why only TXS 0506+056 has been identified as neutrino emitter“, explains Silke Britzen from the Max Planck Institute for Radio Astronomy (MPIfR), the lead author of the paper. „We wanted to unravel what makes TXS 0506+056 special, to understand the neutrino creation process and to localize the emission site and studied a series of high resolution radio images of the jet.“

    Much to their surprise, the researchers found an unexpected interaction between jet material in TXS 0506+056. While jet plasma is usually assumed to flow undisturbed in a kind of channel, the situation seems different in TXS 0506+056. The team proposes that the enhanced neutrino activity during the neutrino flare in 2014–2015 and the single EHE neutrino
    IceCube-170922A could have been generated by a cosmic collision within the source.

    This cosmic collision can be explained by new jet material clashing into older jet material. A strongly curved jet structure provides the proper set up for such a scenario. Another explanation involves the collision of two jets in the same source. In both scenarios, it is the collision of jetted material which generates the neutrino. Markus Böttcher from the North-West University in Potchefstroom (South Africa), a co-author of the paper, performed the calculations with regard to the radiation and particle emission. „This collision of jetted material is currently the only viable mechanism which can explain the neutrino detection from this source. It also provides us with important insight into the jet material and solves a long-standing question whether jets are leptonic, consisting of electrons and positrons, or hadronic, consisting of electrons and protons, or a combination of both. At least part of the jet material has to be hadronic – otherwise, we would not have detected the neutrino.“

    In the course of the cosmic evolution of our Universe, collisions of galaxies seem to be a frequent phenomenon. Assuming that both galaxies contain central supermassive black holes, the galactic collision can result in a black hole pair at the centre. This black hole pair might eventually merge and produce the supermassive equivalent to stellar black hole mergers as detected in gravitational waves by the LIGO/Virgo collaboration.

    AGN with double black holes at a small separation of only light years have been pursued for many years. However, they seem to be rare and difficult to identify. In addition to the collision of jetted material, the team also found evidence for a precession of the central jet of TXS 0506+056. According to Michal Zajaček from the Center for Theoretical Physics, Warsaw: „This precession can in general be explained by the presence of a supermassive black hole binary or the Lense-Thirring precession effect as predicted by Einstein’s theory of general relativity. The latter could also be triggered by a second, more distant black hole in the centre. Both scenarios lead to a wandering of the jet direction, which we observe.“

    Christian Fendt from the Max Planck Institute for Astronomy in Heidelberg is amazed: „The closer we look at the jet sources the more complicated the internal structure and jet dynamics appears. While binary black holes produce a more complex outflow structure, their existence is naturally expected from the cosmological models of galaxy formation by galaxy mergers.”

    Silke Britzen stresses the scientific potential of the findings: „It’s fantastic to understand the neutrino generation by studying the insides of jets. And it would be a breakthrough if our analysis had provided another candidate for a binary black hole jet source with two jets.“

    It seems to be the first time that a potential collision of two jets on scales of a few light years has been reported and that the detection of a cosmic neutrino might be traced back to a cosmic jet-collision.

    While TXS 0506+056 might not be representative of the class of BL Lac objects, this source could provide the proper setup for a repeated interaction of jetted material and the generation of neutrinos.

    ——————————-
    Background Information:

    U Wisconsin ICECUBE neutrino detector at the South Pole

    The IceCube Neutrino Observatory is designed to observe the cosmos from deep within the South Pole ice.

    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

    Encompassing a cubic kilometer of ice, IceCube searches for nearly massless subatomic particles called neutrinos. These high-energy astronomical messengers provide information to probe the most violent astrophysical sources: events like exploding stars, gamma-ray bursts, and cataclysmic phenomena involving black holes and neutron stars.

    MOJAVE (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) is a long-term program to monitor radio brightness and polarization variations in jets associated with active galaxies visible in the northern sky. The Very Long Baseline Array (VLBA) is a system of ten radio telescopes which are operated from Socorro, New Mexico. The ten radio antennas work together as an array using very long baseline interferometry.

    NRAO/VLBA

    A BL Lac Object is a special subclass of an Active Galactic Nucleus (AGN). An AGN is a compact region at the center of a galaxy that has a much higher than normal luminosity over at least some portion of the electromagnetic spectrum. This luminosity is non-thermal and produced by accretion of matter close to a central black hole. The jet of a BL Lac Object is directed at the observer giving a unique radio emission spectrum.

    Authors of the original paper in “Astronomy & Astrophysics” are Silke Britzen, Christian Fendt, Markus Böttcher, Michal Zajaček, Frederic Jaron, Ilya Pashchenko, Anabella Araudo, Vladimir Karas, and Omar Kurtanidze. Silke Britzen, the first author, and also Michal Zajaček and Frederic Jaron are affiliated to the MPIfR.

    Besides MPIfR, affiliations of the authors include the Max-Planck-Institut für Astronomie (Heidelberg, Germany), the Centre for Space Research (North-West University, Potchefstroom, South Africa), the I. Physikalisches Institut, (Universität Köln, Germany), the Center for Theoretical Physics, (Polish Academy of Sciences, Warsaw, Poland), the Institute of Geodesy and Geoinformation (University of Bonn, Germany), the Astro Space Center, (Lebedev Physical Institute, Russian Academy of Sciences, Russia), the Astronomical Institute and the Institute of Physics (Czech Academy of Sciences, Prague, Czech Republic) and the Abastumani Observatory in Georgia.

    See the full article here .

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    Please help promote STEM in your local schools.

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    MPIFR/Effelsberg Radio Telescope, Germany

    The Max Planck Institute for Radio Astronomy (German: Max-Planck-Institut für Radioastronomie) is located in Bonn, Germany. It is one of 80 institutes in the Max Planck Society (German: Max-Planck-Gesellschaft).

    By combining the already existing radio astronomy faculty of the University of Bonn led by Otto Hachenberg with the new Max Planck institute the Max Planck Institute for Radio Astronomy was formed. In 1972 the 100-m radio telescope in Effelsberg was opened. The institute building was enlarged in 1983 and 2002.

    The institute was founded in 1966 by the Max-Planck-Gesellschaft as the “Max-Planck-Institut für Radioastronomie” (MPIfR).

    The foundation of the institute was closely linked to plans in the German astronomical community to construct a competitive large radio telescope in (then) West Germany. In 1964, Professors Friedrich Becker, Wolfgang Priester and Otto Hachenberg of the Astronomische Institute der Universität Bonn submitted a proposal to the Stiftung Volkswagenwerk for the construction of a large fully steerable radio telescope.

    In the same year the Stiftung Volkswagenwerk approved the funding of the telescope project but with the condition that an organization should be found, which would guarantee the operations. It was clear that the operation of such a large instrument was well beyond the possibilities of a single university institute.

    Already in 1965 the Max-Planck-Gesellschaft (MPG) decided in principle to found the Max-Planck-Institut für Radioastronomie. Eventually, after a series of discussions, the institute was officially founded in 1966.

    The Max Planck Society for the Advancement of Science (German: Max-Planck-Gesellschaft zur Förderung der Wissenschaften e. V.; abbreviated MPG) is a formally independent non-governmental and non-profit association of German research institutes founded in 1911 as the Kaiser Wilhelm Society and renamed the Max Planck Society in 1948 in honor of its former president, theoretical physicist Max Planck. The society is funded by the federal and state governments of Germany as well as other sources.

    According to its primary goal, the Max Planck Society supports fundamental research in the natural, life and social sciences, the arts and humanities in its 83 (as of January 2014)[2] Max Planck Institutes. The society has a total staff of approximately 17,000 permanent employees, including 5,470 scientists, plus around 4,600 non-tenured scientists and guests. Society budget for 2015 was about €1.7 billion.

    The Max Planck Institutes focus on excellence in research. The Max Planck Society has a world-leading reputation as a science and technology research organization, with 33 Nobel Prizes awarded to their scientists, and is generally regarded as the foremost basic research organization in Europe and the world. In 2013, the Nature Publishing Index placed the Max Planck institutes fifth worldwide in terms of research published in Nature journals (after Harvard, MIT, Stanford and the US NIH). In terms of total research volume (unweighted by citations or impact), the Max Planck Society is only outranked by the Chinese Academy of Sciences, the Russian Academy of Sciences and Harvard University. The Thomson Reuters-Science Watch website placed the Max Planck Society as the second leading research organization worldwide following Harvard University, in terms of the impact of the produced research over science fields.

     
  • richardmitnick 4:22 pm on September 20, 2019 Permalink | Reply
    Tags: "Testing a new technique to search for neutrino point-source populations", , , , , , NPTF-non-Poissonian template fit, U Wisconsin IceCube and IceCube Gen-2   

    From U Wisconsin IceCube Collaboration: “Testing a new technique to search for neutrino point-source populations” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From From U Wisconsin IceCube Collaboration

    20 Sep 2019
    Madeleine O’Keefe

    Neutrinos are one of the best sources of information about extreme-energy astrophysical phenomena at the far reaches of the observable universe. These intergalactic messengers are able to travel through space unaffected by magnetic fields or other forces. This means that, in theory, if we can measure a neutrino’s incident direction accurately enough, we could trace it back to its source and identify what produced it.

    When a number of neutrinos are associated with a single object in the sky, that object is called a “point source.” The IceCube Neutrino Observatory—an array of 5,160 optical modules embedded in a cubic kilometer of South Pole ice—has already performed a number of point source searches but has yet to identify any significant clustering of neutrinos that would be indicative of a single bright source. This might indicate that most of the neutrinos IceCube detects are not originating from a small number of bright sources, but instead a larger population of dim sources.

    The IceCube Collaboration performed a search for these populations using a technique called the non-Poissonian template fit (NPTF) and published their findings in a paper being submitted to The Astrophysical Journal. This was the first time the NPTF was used on IceCube neutrino data, and while they did not find any neutrino point-source populations, they proved the technique’s viability.

    1
    Left: A simulated image of a purely diffuse emission, where the fluctuations are only due to Poisson noise. Right: A simulated image of emission from a population of point sources. Note the larger fluctuations for the point sources (exaggerated to make the effect more easily discernible); this effect is what was used to determine the presence and properties of a population of point sources. Credit: IceCube Collaboration.

    The NPTF technique has a number of advantages over traditional point source search techniques, and it has been used widely with gamma-ray data. But this was the first time it was used for IceCube neutrino data.

    “We wanted to see whether a totally different approach to searching for point sources, based purely on the modification to the statistics of the basic count map, could be a viable technique to apply to the IceCube dataset,” says Nicholas Rodd of the University of California, Berkeley, one of the leads on this analysis.

    “When we take images of the sky, whether they are taken with cameras or neutrino telescopes, there is a certain amount of ‘graininess’ that is due to natural statistical fluctuations, which is called Poisson noise,” explains Institute for Data, Systems and Society postdoctoral associate Gabriel Collin, another lead author on this paper.

    The math behind Poisson noise assumes that the neutrinos are produced by one large continuous physical process, resulting in a “diffuse emission.” However, if the neutrinos are instead being produced by compact astronomical objects—which is what Rodd and Collin expect—then the graininess is enhanced, leading to fluctuations larger than the Poisson model predicts. The presence of these non-Poissonian fluctuations can indicate how many point sources are producing the neutrinos and how bright or dim they are.

    In this analysis, Rodd and Collin used the NPTF, which predicts the size of the fluctuations for a given theoretical model of the population of neutrino-producing astronomical objects. This formulation can detect the presence of a population of point sources even when the effect is slight, beyond what the human eye can discern.

    They ran IceCube neutrino data through their formulation, but did not find evidence of a population of point sources. This null result rules out certain theoretical models of these populations, and the analysis ultimately demonstrated that the NPTF could successfully be applied to the IceCube dataset.

    2
    This figure shows that, for a population of sources with a given intrinsic brightness (x-axis) and density throughout the universe (y-axis), the NPTF excludes populations in the white space. Such null observations still have important implications, including allowing researchers to quantify how much objects like galaxy clusters are dimmer in neutrinos than photons (here, photon brightness is depicted by “x”). Credit: IceCube Collaboration.

    The NPTF can perform a number of searches that are difficult with other techniques, such as searching for populations of sources that are not distributed uniformly in all orientations on the sky. And although the NPTF is currently less sensitive than other techniques in some parts of the parameter space, there are many options to extend the method’s reach and significantly enhance its sensitivity.

    “The goal of our analysis was to lay the groundwork for future work that leverages advanced statistical tools such as this non-Poissonian fluctuation model,” says Collin. “We hope that, through this effort, we can build a better bridge between the theoretical and experimental community in neutrino astronomy, and encourage future point-source population searches to publish their results in a similar fashion.”

    Looking toward the future, Collin says he and Rodd hope to develop even more powerful statistical tools that can be used to search for point-source populations—not just in neutrino astronomy, but in gamma-ray, X-ray, and optical astronomy as well.

    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.

    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

     
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