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  • richardmitnick 12:19 pm on March 10, 2021 Permalink | Reply
    Tags: "IceCube detection of a high-energy particle proves 60-year-old theory", Another confirmation of the Standard Model of Particle Physics., IceCube had seen a "Glashow resonance event" a phenomenon predicted by Nobel laureate physicist Sheldon Glashow in 1960., IceCube-Gen2, In fact no human-made particle accelerator on Earth current or planned could create a neutrino with that much energy., On December 6 2016 a high-energy particle called an electron antineutrino hurtled to Earth from outer space at close to the speed of light carrying 6.3 petaelectronvolts (PeV) of energy., Since IceCube started full operation in May 2011 the observatory has detected hundreds of high-energy astrophysical neutrinos and has produced a number of significant results in particle astrophysics., The result also opens up a new chapter of neutrino astronomy because it starts to disentangle neutrinos from antineutrinos., U Wisconsin IceCube Collaboration, When the proposed particle-the "W boson" was finally discovered in 1983 it turned out to be much heavier than what Glashow and his colleagues had expected back in 1960.   

    From U Wisconsin IceCube Collaboration: “IceCube detection of a high-energy particle proves 60-year-old theory” 

    U Wisconsin ICECUBE neutrino detector at the South Pole, elevation of 2,835 metres (9,301 feet)

    From U Wisconsin IceCube Collaboration

    March 10, 2021

    On December 6 2016 a high-energy particle called an electron antineutrino hurtled to Earth from outer space at close to the speed of light carrying 6.3 petaelectronvolts (PeV) of energy. Deep inside the ice sheet at the South Pole, it smashed into an electron and produced a particle that quickly decayed into a shower of secondary particles. The interaction was captured by a massive telescope buried in the Antarctic glacier, the IceCube Neutrino Observatory.

    IceCube had seen a “Glashow resonance event” a phenomenon predicted by Nobel laureate physicist Sheldon Glashow in 1960.

    1
    A visualization of the Glashow event recorded by the IceCube detector. Each colored circle shows an IceCube sensor that was triggered by the event; red circles indicate sensors triggered earlier in time, and green-blue circles indicate sensors triggered later. This event was nicknamed “Hydrangea.” Credit: IceCube Collaboration.

    With this detection, scientists provided another confirmation of the Standard Model of Particle Physics.

    Standard Model of Particle Physics (LATHAM BOYLE AND MARDUS OF WIKIMEDIA COMMONS).

    It also further demonstrated the ability of IceCube, which detects nearly massless particles called neutrinos using thousands of sensors embedded in the Antarctic ice, to do fundamental physics. The result was published on March 10 in Nature.

    Sheldon Glashow first proposed this resonance in 1960 when he was a postdoctoral researcher at what is today the Niels Bohr Institute(DK). There, he wrote a paper [Physical Review Journals Archive] in which he predicted that an antineutrino (a neutrino’s antimatter twin) could interact with an electron to produce an as-yet undiscovered particle—if the antineutrino had just the right energy—through a process known as resonance.

    When the proposed particle-the “W boson” was finally discovered in 1983 it turned out to be much heavier than what Glashow and his colleagues had expected back in 1960. The Glashow resonance would require a neutrino with an energy of 6.3 PeV, almost 1,000 times more energetic than what CERN’s Large Hadron Collider(CH) is capable of producing. In fact no human-made particle accelerator on Earth current or planned could create a neutrino with that much energy.

    But what about a natural accelerator—in space? The enormous energies of supermassive black holes at the centers of galaxies and other extreme cosmic events can generate particles with energies impossible to create on Earth. Such a phenomenon was likely responsible for the 6.3 PeV antineutrino that reached IceCube in 2016.

    2
    The electron antineutrino that created the Glashow resonance event traveled quite a distance before reaching IceCube. This graphic shows its journey; the blue dotted line is the antineutrino’s path. (Not to scale.) Credit: IceCube Collaboration.

    “When Glashow was a postdoc at Niels Bohr, he could never have imagined that his unconventional proposal for producing the W– boson would be realized by an antineutrino from a faraway galaxy crashing into Antarctic ice,” says Francis Halzen, professor of physics at the University of Wisconsin–Madison(US), the headquarters of IceCube maintenance and operations, and principal investigator of IceCube.

    Since IceCube started full operation in May 2011 the observatory has detected hundreds of high-energy astrophysical neutrinos and has produced a number of significant results in particle astrophysics, including the discovery of an astrophysical neutrino flux in 2013 and the first identification of a source of astrophysical neutrinos in 2018. But the Glashow resonance event is especially noteworthy because of its remarkably high energy; it is only the third event detected by IceCube with an energy greater than 5 PeV.

    “This result proves the feasibility of neutrino astronomy—and IceCube’s ability to do it—which will play an important role in future multimessenger astroparticle physics,” says Christian Haack, who was a graduate student at RWTH AACHEN UNIVERSITY [Rheinisch-Westfaelische Technische Hochschule(DE) while working on this analysis. “We now can detect individual neutrino events that are unmistakably of extraterrestrial origin.”

    The result also opens up a new chapter of neutrino astronomy because it starts to disentangle neutrinos from antineutrinos. “Previous measurements have not been sensitive to the difference between neutrinos and antineutrinos, so this result is the first direct measurement of an antineutrino component of the astrophysical neutrino flux,” says Lu Lu, one of the main analyzers of this paper, who was a postdoc at Chiba University(JP) during the analysis.

    “There are a number of properties of the astrophysical neutrinos’ sources that we cannot measure, like the physical size of the accelerator and the magnetic field strength in the acceleration region,” says Tianlu Yuan, an assistant scientist at the Wisconsin IceCube Particle Astrophysics Center and another main analyzer. “If we can determine the neutrino-to-antineutrino ratio, we can directly investigate these properties.”

    To confirm the detection and make a decisive measurement of the neutrino-to-antineutrino ratio, the IceCube Collaboration wants to see more Glashow resonances. A proposed expansion of the IceCube detector, IceCube-Gen2, would enable the scientists to make such measurements in a statistically significant way. The collaboration recently announced an upgrade of the detector that will be implemented over the next few years, the first step toward IceCube-Gen2.

    Glashow, now an emeritus professor of physics at Boston University(US), echoes the need for more detections of Glashow resonance events. “To be absolutely sure, we should see another such event at the very same energy as the one that was seen,” he says. “So far there’s one, and someday there will be more.”

    Last but not least, the result demonstrates the value of international collaboration. IceCube is operated by over 400 scientists, engineers, and staff from 53 institutions in 12 countries, together known as the IceCube Collaboration. The main analyzers on this paper worked together across Asia, North America, and Europe.

    “The detection of this event is another ‘first,’ demonstrating yet again IceCube’s capacity to deliver unique and outstanding results,” says Olga Botner, professor of physics at Uppsala University(SE) and former spokesperson for the IceCube Collaboration.

    “IceCube is a wonderful project. In just a few years of operation, the detector discovered what it was funded to discover—the highest energy cosmic neutrinos, their potential source in blazars, and their ability to aid in multimessenger astrophysics,” says Vladimir Papitashvili, program officer in the Office of Polar Programs of the National Science Foundation(US), IceCube’s primary funder. James Whitmore, program officer in NSF Division of Physics, adds, “Now, IceCube amazes scientists with a rich fount of new treasures that even theorists weren’t expecting to be found so soon.”

    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 neutrino detector interior.

    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

    U Wisconsin IceCube Gen2 facility

     
  • richardmitnick 8:39 am on December 10, 2020 Permalink | Reply
    Tags: "IceCube pipeline responds quickly to transient phenomena reported by other observatories", Bright gamma-ray bursts, Extreme blazar flares, , , , , U Wisconsin IceCube Collaboration   

    From U Wisconsin IceCube Collaboration: “IceCube pipeline responds quickly to transient phenomena reported by other observatories” 

    U Wisconsin ICECUBE neutrino detector at the South Pole, elevation of 2,835 metres (9,301 feet)

    From U Wisconsin IceCube Collaboration

    09 Dec 2020
    Madeleine O’Keefe

    The IceCube Neutrino Observatory, an array of over 5,000 light sensors embedded in a cubic-kilometer of ice at the South Pole, was built to detect astrophysical neutrinos: mysterious and nearly massless particles that carry information about the most energetic events in the cosmos. Every time IceCube sees something that might be a cosmic neutrino, it sends an alert to a network of telescopes and observatories around the world and in space, telling them to turn and look at that same spot in the sky. These other instruments see the universe in different ways; many detect photons of different wavelengths, from radio waves to gamma rays, while others detect different “messengers” entirely, like gravitational waves or neutrinos. Together, detections from different messengers give us a more complete picture of the cosmos.

    The study of the universe with multiple channels—a field known as multimessenger astronomy—is valuable for investigating a number of questions, including learning about the sources of astrophysical neutrinos, one of IceCube’s main scientific goals. So rather than just waiting for neutrinos to come to IceCube, IceCube can also follow up on detections made by other telescopes. And since IceCube can observe the entire sky simultaneously and is “on” more than 99 percent of the time, it can provide unique and valuable insight for other observatories.

    Since 2016, the IceCube Collaboration has used a fast-response analysis pipeline to perform follow-up neutrino searches on interesting detections in other messengers that might have neutrino counterparts. As of July 2020, the pipeline led to 58 analyses, none of which found significant neutrino signals but enabled researchers to constrain neutrino emission from some potential sources. The collaboration described their results in a paper recently submitted to The Astrophysical Journal.

    1
    Results of IceCube’s follow-up for the gamma-ray burst GRB190114C, one of the only GRBs to ever be detected by a ground-based gamma-ray telescope. This plot shows the flux as a function of energy, where blue tones are results from various wavelengths of light, from X-rays (left) to very high energy gamma rays (right). The upper limit on the high-energy neutrino flux, one of the results reported in the paper, is shown by the solid magenta line. Credit: IceCube Collaboration.

    “The motivation for this analysis is to take the idea of neutrino alerts and turn it on its head,” says Alex Pizzuto, a doctoral student at the University of Wisconsin–Madison and a lead on this analysis. “Instead of sending out interesting neutrinos to the community and letting observers follow up on our events, we take interesting events reported in other messengers, like photons, and check to see if there are neutrinos coming from the same object. And we do it all in real time.”

    Pizzuto and his collaborators have been doing this since 2016 when they established a fast-response analysis pipeline. The pipeline monitors various channels where astronomers announce interesting observations (such as the Gamma-ray Coordinates Network and the The Astronomer’s Telegram) and identifies potentially interesting detections. Then, IceCube researchers evaluate whether the target is a viable neutrino emitter and whether it would be useful for IceCube to check it out. If yes, the researchers determine a time frame around the event of interest and use the pipeline to rapidly perform a statistical analysis of IceCube data to see if any neutrino candidate events correlate with the target in time and direction. When the analysis is complete, the researchers send out their results via the same channels they were monitoring in the first place.

    As of July 2020, the pipeline has led to 58 analyses, none of which found a statistically significant signal of neutrinos. But the researchers were able to use the pipeline to put constraints on some of the source classes they studied, including fast radio bursts, extreme blazar flares, bright gamma-ray bursts, and gravitational waves. Pizzuto says that they are already seeing some of their limits incorporated into models of potential neutrino sources.

    “Unlike most telescopes, IceCube observes the entire sky (including both hemispheres), all the time (including both day and night),” according to Justin Vandenbroucke, a UW–Madison physics professor and another lead on the paper. “So whenever a new astrophysical transient event is reported by another observatory, we know IceCube was also looking there then. Our pipeline enables us to rapidly search for neutrinos and report the results. This real-time approach to multimessenger astrophysics has enabled the key discoveries of the field so far, and will continue to in the future.”

    Looking ahead, the researchers plan to continue running the pipeline. They hope that this analysis will identify a multimessenger source in the future. In the meantime, they are studying a variety of source classes with this tool. And there is a plan to use this pipeline to search for additional neutrinos coming from the same directions as the high-energy neutrinos that trigger IceCube alerts.

    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 neutrino detector interior.

    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

    U Wisconsin IceCube Gen2 facility

     
  • richardmitnick 4:54 pm on December 4, 2020 Permalink | Reply
    Tags: "New IceCube analysis sets upper limits on time-dependent neutrino sources", , , , , , , U Wisconsin IceCube Collaboration   

    From U Wisconsin IceCube Collaboration: “New IceCube analysis sets upper limits on time-dependent neutrino sources” 

    U Wisconsin ICECUBE neutrino detector at the South Pole, elevation of 2,835 metres (9,301 feet)

    From U Wisconsin IceCube Collaboration

    03 Dec 2020
    Madeleine O’Keefe

    The IceCube Neutrino Observatory is an unusual telescope. It uses its over-5,000 optical sensors embedded in the South Pole ice to look for signals from astrophysical neutrinos, nearly massless subatomic particles from outer space. One of IceCube’s main goals is to pinpoint sources of these neutrinos, of which there are many.

    Since a 2013 IceCube paper [Science] showed the first solid evidence for astrophysical neutrinos from cosmic accelerators, we have learned some things about the sources of these mysterious particles. In 2017, IceCube detected a neutrino coming from a blazar called TXS 0506+056, the first compelling evidence of an astrophysical neutrino source [Science] and [Science]. And a recent analysis of 10 years of IceCube data singled out another potential source: the Seyfert II galaxy NGC 1068, a type of active galactic nuclei.

    However, sources of most astrophysical neutrinos remain unknown, and the IceCube Collaboration continues to search for them using a variety of analysis methods. In a paper submitted yesterday to The Astrophysical Journal, the collaboration describes a time-dependent all-sky scan using five years of IceCube data as well as a specific analysis of blazar 3C 279. The method involves looking for neutrinos clustered in both time and space—in other words, neutrinos that came from the same spot in the sky and arrived within a certain period. This analysis, which is an update of a previous time-dependent all-sky scan from 2015, did not reveal any new neutrino point sources.

    3
    IC86 II-IV sky map in equatorial coordinates showing the pretrial p-values for the best-fit flare hypothesis tested in each direction of the sky. The strongest time-dependent Gaussian-like signal is in the northern sky with a post-trial p-value of 17.7%. The solid black curve indicates the Galactic plane, and the hottest spot in each hemisphere is in a black circle. Credit: IceCube Collaboration.

    We don’t know a lot about neutrino sources, which makes it a challenge to look for them. IceCube researchers perform many different searches under different hypotheses, including time-integrated searches (used to find the potential source NGC 1068) and time-dependent searches. Unlike time-integrated searches, time-dependent searches consider the neutrinos’ times of arrival at IceCube, focusing on neutrinos clustered in both space and time. Time-dependent searches have a better discovery potential than time-integrated searches for a potential continuous emission of neutrino signal that lasts less than 100 days. Plus, searching for neutrinos that cluster both spatially and temporally helps further separate potential neutrino signals from background, as researchers expect the background flux of neutrinos to be constant in time.

    IceCube researchers took the time-dependent approach for the all-sky scan of five years of IceCube data. “We developed this likelihood method over the years starting with my time at the University of Wisconsin–Madison,” says Teresa Montaruli, now a professor in the particle physics department at the University of Geneva in Switzerland.

    “We don’t assume anything about the source, but only search for clustering of astrophysical neutrinos in space and time over the whole sky,” says Stéphanie Bron, a PhD student at the University of Geneva and a lead on this analysis.

    Montaruli, Bron, and their colleagues examined the sky in 0.1-by-0.1 degree squares and calculated whether neutrino data in each square was compatible with what they expected for background. The point found to be least compatible with background in each hemisphere was deemed the “hottest spot.”

    Over the five years that the researchers scanned, no new astrophysical neutrino point source was found. The most significant hotspot was compatible with background fluctuation and was not associated with a known gamma-ray source. However, the second-most significant hotspot was compatible with the location of TXS 0506+056, the blazar from the 2017 detection, though it was not a significant result in this analysis. Bron says this discrepancy is because they did not focus the scan on this part of the sky. “Because we are not looking only in the direction of TXS, but scanning the whole sky, we are penalized by the huge trial factor, which greatly reduces the final significance of the result,” she says. “It is interesting to see in practice the kind of effect that those trial factors might have, and this really points to the importance of using multimessenger signals to drive the search for cosmic neutrinos.”

    The researchers also tried their method in a more focused search. With measurements from the Fermi-LAT gamma-ray telescope, they targeted blazar 3C 279, which underwent an exceptionally bright flare on June 16, 2015.

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope.

    Seeing gamma rays and neutrino emission from the same source would be a strong indication of a cosmic ray source, so this blazar was an ideal object to examine.

    For this part of the analysis, researchers only looked at the sky in the direction of the blazar and only analyzed eleven days of IceCube data centered on the day of the flare. Alas, the analysis revealed no significant results. However, the researchers were able to establish an upper limit to constrain a model of the number of neutrino events associated with this specific flare of 3C 279 that IceCube should detect under certain assumptions about the gamma-ray emission observed by Fermi-LAT.

    Still, Montaruli, Bron, and their colleagues believe that this type of time-dependent analysis should continue. “Even though the analyzed data sets didn’t lead to any significant results, a future data set might,” says Bron. “The nice thing about this kind of analysis is that it doesn’t depend on any assumption about the shape, duration, or source of the signal. So it is sensitive to a whole range of phenomena, including gamma-ray bursts and active galactic nuclei, but also phenomena that maybe we don’t even know exist. And this is the exciting part to me!”

    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 neutrino detector interior.

    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

    U Wisconsin IceCube Gen2 facility

     
  • richardmitnick 10:14 am on November 13, 2020 Permalink | Reply
    Tags: "Can a high-energy neutrino detector see low-energy neutrinos?", , , , U Wisconsin IceCube Collaboration   

    From U Wisconsin IceCube Collaboration: “Can a high-energy neutrino detector see low-energy neutrinos?” 

    U Wisconsin ICECUBE neutrino detector at the South Pole, elevation of 2,835 metres (9,301 feet)

    From U Wisconsin IceCube Collaboration

    12 Nov 2020
    Madeleine O’Keefe

    Over the past decade, the burgeoning field of neutrino astronomy has made huge strides, from the first indication of very high energy neutrinos coming from outside our solar system announced in 2013 to the first observed extragalactic source of high-energy neutrinos in 2017. But there is still a lot to learn about these mysterious, lightweight subatomic particles and what they can teach us about the universe.

    The IceCube Neutrino Observatory, an array of over 5,000 light detectors embedded in a cubic kilometer of ice at the South Pole, is the largest neutrino telescope on Earth. In the past, most IceCube searches for astrophysical neutrinos focused on high-energy neutrinos, specifically, neutrinos with energies between and electronvolts (TeV to PeV). Other neutrino detectors around the world, such as Super-Kamiokande in Japan, carry out searches for neutrinos with lower energies.

    Super-Kamiokande Detector, located under Mount Ikeno near the city of Hida, Gifu Prefecture, Japan.

    In a paper submitted recently to the Journal of Cosmology and Astroparticle Physics, the IceCube Collaboration describes a search for sub-TeV neutrino emission from astrophysical “transient” sources, which are sources that emit neutrinos primarily within a relatively short window of time. This is the first transient result from IceCube to use all neutrino flavors in the 1-100 GeV energy region. In the absence of any observed sources in three years of archival IceCube data, the researchers established new limits on the number of transients in a volume of space per year, known as the volumetric rate of transients.

    2
    New upper bounds on the volumetric rate of transient neutrino point sources as a function of their bolometric neutrino energy that were determined from this research. This is compared to models for high- and low-luminosity gamma-ray bursts (see Murase et al. 2013; Liang et al. 2007). The light blue bands show the declination dependencies of the upper bounds. The left panel shows results based on sources with a mean energy of 20 GeV, while the right panel is based on a mean energy of 100 GeV. Credit: IceCube Collaboration.

    Gamma-ray bursts (GRBs) are quick, extremely energetic explosions of gamma ray light that are frequently explored as possible transient sources of neutrinos. Some scenarios predict that GRBs emit neutrinos of low energies (~10-100 GeV) without the usual gamma ray counterpart. This could happen, for example, if relativistic GRB jets are “choked off” by a dense envelope of matter before they become visible via their bright gamma-ray display; even if gamma rays cannot make it out, neutrinos (especially low-energy neutrinos) can get through and reach Earth.

    So, using neutrino data collected with the IceCube-DeepCore subarray [below] between April 2012 and May 2015, IceCube collaborators searched for any low-energy neutrinos that were coincident in time and direction in a way that indicated a neutrino emission from a transient astrophysical phenomenon. Their analysis consisted of two parts: First, the researchers selected time windows in which there were particularly large densities of neutrino events. Next, they looked within each time window for neutrino events that came from points in the sky that were spatially close.

    Among the three years of archival data, the researchers found no transient neutrino emission. Consequently, they were able to place an upper limit on the volumetric rate of astrophysical transient sources.

    When the researchers compared their current upper limit to theoretical estimates, they found that they would need a significantly larger detector or improvements in analysis techniques in order to detect a transient point source by chance. Fortunately, IceCube’s low-energy neutrino triggering, simulations, and angular location algorithms have improved over the years and continue to improve.

    “Although we didn’t find any sources, it was exciting to explore the intersection between astro- and particle physics by utilizing all three neutrino flavors in the search for astrophysical phenomena that to this day remain unobserved,” says Mia-Louise Nielsen, a graduate student at the Niels Bohr Institute and one of the main analyzers.

    Along with IceCube collaborators, the researchers are now adapting the method used here to a real-time analysis to complement the existing high-energy real-time alert systems. Currently, the alert system notifies observatories around the world whenever IceCube sees a high-energy neutrino candidate event that meets certain criteria; adapting this analysis would extend the alerts’ energy range down to 10 GeV, opening up a new, unexplored energy regime for real-time follow-up.

    “Multimessenger astronomy has entered a new era when it comes to using high-energy neutrinos to view the wider universe,” says Jason Koskinen, an associate professor at the Niels Bohr Institute. “With this analysis, we are taking some of the first steps in using lower energy neutrinos to probe an otherwise unexplored energy region.”

    The authors point out that, while this analysis was optimized for a specific class of GRBs, it is also sensitive to many other transient neutrino emitters that may exist in the sub-TeV region but have not yet been predicted by theorists. With the forthcoming IceCube Upgrade in the early 2020s and the possibility of making correlations with other astrophysical messengers, a new multimessenger discovery is perhaps just around the corner.

    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 neutrino detector interior.

    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

    U Wisconsin IceCube Gen2 facility

     
  • richardmitnick 9:40 am on September 25, 2020 Permalink | Reply
    Tags: , Ice­Cube made history in 2013 when it reported intercepting the first extra­galactic neutrinos., , P-ONE will consist of seven groups of 10 detector strings creat­ing an instrument volume of about 3 km3., , , The new facility will be located at a depth of about 2.6 km in the Cas­cadia Basin some 200 km from the coast of British Columbia., U Wisconsin IceCube Collaboration,   

    From physicsworld.com: “Astronomers plan huge neutrino observatory in the Pacific Ocean” 

    From physicsworld.com

    18 Sep 2020
    Edwin Cartlidge

    1
    Ocean bound: P-ONE will consist of seven groups of 10 detector strings, creating an instrument larger than the existing IceCube experiment (pictured). (Courtesy: IceCube Collaboration/NSF.)

    Astrophysicists in Germany and North America have published plans to build the world’s larg­est neutrino telescope on the sea floor off the coast of Canada.

    The Pacific Ocean Neutrino Experiment (P-ONE) is designed to snare very-high-energy neutrinos generated by extreme events from beyond our galaxy.

    Neutrino telescopes observe the Čerenkov radiation that is emitted when neutrinos passing through the Earth interact very occasionally with atomic nuclei resulting in the production of fast-moving secondary particles. Being uncharged and exceptionally inert, neutrinos can penetrate gas and dust as they travel through the universe, allowing astronomers in principle to identify the exceptionally energetic phenomena that generate them. Photons from such events, in contrast, are absorbed on their journey.

    The world’s largest neutrino tele­scope, known as IceCube, consists of dozens of strings of photomultiplier tubes suspended in holes drilled deep into the ice at the South Pole.

    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 neutrino detector interior.

    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.

    IceCube Gen-2 DeepCore PINGU annotated.

    DM-Ice II at IceCube annotated.

    Covering a volume of 1 km3, Ice­Cube made history in 2013 when it reported intercepting the first extra­galactic neutrinos. Four years later it then recorded an event that could be tied to a very distant, bright galactic nucleus known as a blazar, thanks to concurrent gamma-ray observations.

    According to P-ONE head, Elisa Resconi at the University of Munich, IceCube’s 2017 result strictly speak­ing only constitutes “evidence” for the blazar source. To really claim a discovery and pinpoint the origin of other cosmic neutrinos, she argues, requires the construction of addi­tional neutrino observatories as well as the extension of IceCube. “We are now on the verge of opening up neutrino astronomy,” she says, “but if we base this process on just one telescope it could take a really long time, perhaps decades.”

    Heading underwater

    P-ONE will consist of seven groups of 10 detector strings creat­ing an instrument volume of about 3 km3. Being larger than IceCube, it will detect rarer, higher-energy neutrinos, and will be most sensi­tive at a few tens rather than a hand­ful of teraelectronvolts. It will also observe a different part of the sky, mainly capturing neutrinos from the southern hemisphere rather than the north. But there will be some over­lap between the two, says Resconi, potentially allowing independent observations of the same event.

    The new facility will be located at a depth of about 2.6 km in the Cas­cadia Basin, some 200 km from the coast of British Columbia. As such, it will take advantage of pre-existing infrastructure – an 800 km-long loop of fibre-optic cable operated by the University of Victoria’s Ocean Net­works Canada that supplies power and ferries data to and from existing sea-floor instruments.

    Having already confirmed that this site has the necessary optical prop­erties by sending down two initial strings of light emitters and sensors in 2018, the P-ONE collaboration are now planning to deploy a steel cable with addi­tional detectors to investigate the site – including spectrometers, lidars and a muon detector. The plan then, says Resconi, is to install the first part of the observatory – a ring containing seven 1 km-long strings – around the end of 2023. And if that succeeds, the researchers will then apply for the bulk of the $50–100m needed to complete the project, with personnel costs adding roughly $100m more.

    Resconi hopes that the full obser­vatory will be installed and taking data by the end of the decade. But she describes this timeline as “very ambitious”. In addition to delays caused by the ongoing COVID- 19 pandemic, she says it will be a challenge to ensure that the detec­tors work as planned – given the huge pressures and the presence of salt and sea creatures, which together make the seabed such a harsh environment.

    Indeed, scientists had already planned on operating a cubic-kilome­tre scale neutrino telescope known as KM3NeT on the floor of the Mediter­ranean Sea back in 2014, which was delayed to 2020.

    KM3NeT Digital Optical Module (DOM) in the laboratory .www.km3net.org.

    Artist’s expression of the KM3NeT neutrino telescope.

    According to col­laboration member Feifei Huang, just two of the 230 strings due to be installed off the coast of southern Italy are so far in place, while another site in French waters currently has six out of a planned 115 strings running – with completion not foreseen until 2026 and 2024 respectively.

    Resconi says that part of the problem with that project is a lack of specialist personnel, with the physicists essentially doing everything themselves – for example, their self-built junction boxes, which connect cables on the sea floor, having failed. She hopes that the experience acquired by Ocean Networks Canada will mean a similar fate can be avoided for P-ONE. With 30 or 40 people dedicated to laying cables in the ocean, she says that her team “can focus on the physics”.

    See the full article here .


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    Please help promote STEM in your local schools.


    Stem Education Coalition

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  • richardmitnick 9:50 am on August 26, 2020 Permalink | Reply
    Tags: "Searching for transient neutrino sources with the help of gamma rays", , High-Altitude Water Čerenkov (HAWC) Gamma-Ray Observatory, , , U Wisconsin IceCube Collaboration   

    From U Wisconsin IceCube Collaboration: “Searching for transient neutrino sources with the help of gamma rays” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From U Wisconsin IceCube Collaboration

    26 Aug 2020
    Madeleine O’Keefe

    2017 was a momentous year for the field of multimessenger astronomy. In August, a neutron star collision produced a gravitational wave that was observed by the LIGO and Virgo collaborations at nearly the exact same time a gamma-ray burst was detected by the Fermi space telescope.

    MIT /Caltech Advanced aLigo

    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    A month later, the IceCube Neutrino Observatory recorded an astrophysical neutrino event that was followed by a weeklong gamma-ray flare detected by the Fermi and MAGIC telescopes.

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

    These landmark detections proved that astronomers could gain a more complete understanding of the universe by combining observations of different wavelengths and, for the first time since 1987 when a supernova was last observed, different messenger particles from a variety of detectors across the globe.

    Understanding how and where these messenger particles are produced, and using these observations to explore the physics of the universe, requires an ongoing stream of multimessenger detections. The Astrophysical Multimessenger Observatory Network (AMON) can help with that. Created in 2013 to facilitate the interaction of different observatories, AMON recently commissioned real-time multimessenger alerts that notify the astrophysical community when two or more observatories detect an interesting “coincidence” of events that may be worthy of follow-up observations. Their analysis takes advantage of abundant subthreshold data from the IceCube Neutrino Observatory and the High-Altitude Water Čerenkov (HAWC) gamma-ray observatory.

    HAWC High Altitude Čerenkov Experiment, a
    US Mexico Europe collaboration 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

    In a paper submitted today to The Astrophysical Journal, the AMON team, together with the IceCube and HAWC collaborations, presents the analysis approach that they developed and reveal the first results from their analysis, as applied to three years of archival data from 2015 to 2018. Among those three years, they identified two coincident events that met their criteria for distribution as a public alert, but there were no particularly important astronomical sources seen near either position. Going forward, real-time analyses of data from the IceCube and HAWC observatories will allow interesting coincidences to be identified and reported as they happen, enabling quick follow-up observations from astronomers around the world.

    3
    Sky maps of the two statistically interesting coincidences found in three years of archival IceCube and HAWC data. Positions of the individual events are marked with dots. The best-fit combined positions are marked with a cross. Credit: AMON, HAWC Collaboration, IceCube Collaboration.

    The IceCube Neutrino Observatory is an array of over 5,000 light sensors frozen into a cubic kilometer of ice below the surface at the South Pole. HAWC, located in a very different, mountainside environment in Puebla, Mexico, is an array of 300 aboveground water tanks that hold four light sensors each. Both are designed to observe Cherenkov radiation—light emitted when charged particles travel at close to the speed of light in ice or water—that is produced by high-energy particles sent to Earth by the most cataclysmic events in the universe.

    The bulk of the data collected by IceCube and HAWC are dominated by background particles produced in Earth’s atmosphere, rather than in cosmic sources, making it difficult to determine whether any individual event is of interest for astrophysical studies. But there could still be signal events hidden among those subthreshold data. And that’s where AMON comes in.

    The AMON algorithm is designed to analyze subthreshold data from IceCube and HAWC in real time. It looks for coincidences between IceCube neutrino events and HAWC “hotspots”—locations on the sky where a higher-than-expected number of gamma-ray events were observed over the course of a day. To be considered a coincident event, the neutrino event must have arrived within a window of time that matches the HAWC hotspot and must be close to the HAWC hotspot localization on the sky. Once a coincidence is found and reported, researchers can carry out follow-up observations to identify any new or unusual sources near that position.

    In their paper, the researchers report a systematic analysis of archival IceCube and HAWC data, from June 2015 to August 2018, with the AMON algorithm. Within the three years of nearly continuous data collection by both observatories, two coincident neutrino–gamma-ray clusters were judged sufficiently interesting that they would have been distributed as public alerts if the analysis had been running in real time. The analysis shows that both coincidences are very rare—with one occurring once per year and the second every 30 years—but still not rare enough to support a claim that they must be from cosmic sources.

    Next, the researchers referred to astronomical catalogs in search of interesting or unusual objects that might have emitted neutrinos and gamma rays near the two coincident clusters. They found some known galaxies and quasars but no sources so unusual that they stood out on their own. Still, the story isn’t over; follow-up optical or X-ray observations of select nearby sources might provide further clues as to whether they are related to the reported neutrino–gamma-ray clusters.

    “These events illustrate the power of this approach to be able to identify statistically rare clusters of neutrinos and gamma rays—cosmic ‘needles in a haystack,’ as it were—as intended,” says Hugo Alberto Ayala Solares, a postdoctoral researcher at Pennsylvania State University and the lead on this analysis.

    In November 2019, AMON, IceCube, and HAWC initiated the real-time version of this analysis. A couple of months later, on February 2, the first real-time alert from this system went out, but this cluster also did not lead to any high-confidence association with a source.

    Next time a statistically rare coincidence of neutrinos and gamma rays is observed, AMON systems will once again send out an alert to AMON follow-up partners as well as the astrophysical community through the Gamma-Ray Coordinates Network (GCN). “If the universe is in a generous mood, these observations may lead to discovery of the next multimessenger source,” says Derek Fox, a co-principal investigator of AMON and associate professor of astronomy and astrophysics at Pennsylvania State University.

    As shown by the events in 2017, having information from all possible messengers helps researchers obtain a better picture of a variety of astrophysical phenomena. Implementing searches in real time, as with AMON, will advance the field of multimessenger astronomy further and bring us closer to a deeper understanding of 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
    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

    U Wisconsin IceCube Gen2 facility

     
  • richardmitnick 1:36 pm on August 19, 2020 Permalink | Reply
    Tags: "IceCube-Gen2 will open a new window on the universe", , , U Wisconsin IceCube Collaboration   

    From U Wisconsin IceCube Collaboration: “IceCube-Gen2 will open a new window on the universe” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From U Wisconsin IceCube Collaboration

    18 Aug 2020
    Madeleine O’Keefe

    On December 18, 2010, IceCube’s final DOM (digital optical module) was lowered into a hole in the ice at the South Pole. After seven years of construction—and many more years of international collaboration around design and planning—the IceCube Neutrino Observatory was complete. The detector now had 5,160 DOMs on 86 cables (“strings”) frozen into a cubic kilometer of the Antarctic glacier ice, waiting for signals from tiny, ghostlike particles from outer space called neutrinos.

    Since then, IceCube has done exactly what it was built to do: use astrophysical neutrinos to peer into the otherwise indiscernible universe, where light and other particles are obstructed. In the past decade, the IceCube Collaboration has published over 150 papers on astrophysics, neutrino physics, dark matter, glaciology, cosmic ray physics, instrumentation, and much more. Most notably, IceCube detected the first high-energy astrophysical neutrinos in 2013 and led the effort in the first-ever identification of a source of extragalactic neutrinos and high-energy cosmic rays in 2018—a discovery that proved the potential of neutrinos in multimessenger astronomy.

    2

    But to make new physics discoveries and continue to probe the mysteries of the universe, bigger and more sensitive detectors are needed. Enter IceCube-Gen2.

    In a white paper recently submitted to the Journal of Physics G, the international IceCube-Gen2 Collaboration outlines the need for and design of a next-generation extension of IceCube. By adding new optical and radio instruments to the existing detector, IceCube-Gen2 will increase the annual rate of cosmic neutrino observations by an order of magnitude, and its sensitivity to point sources will increase to five times that of IceCube.

    “IceCube-Gen2 will build upon two discoveries by IceCube,” says Albrecht Karle, an IceCube-Gen2 coordinator based at the University of Wisconsin–Madison. “One is the presence of a large cosmic neutrino flux at high energies; the other is the exceptional clarity of the ice. By optimizing the design, we can scale the detector up by one order of magnitude with very similar instrumentation.”

    Projected to be completed in 2033 with construction costs around $350 million, IceCube-Gen2 is designed to address some of the biggest questions in multimessenger astronomy and neutrino physics.

    U Wisconsin IceCube Gen2 facility

    “Publishing a white paper is an important milestone for every future research project,” says Markus Ackermann, head of the IceCube group at DESY in Zeuthen, Germany. “With this document, we want to share our enthusiasm about the scientific potential of IceCube-Gen2 with the broader scientific community and outline a path toward the realization of this exciting project.”

    IceCube-Gen2’s design is a major endeavor that will entail years of construction. The first step is already underway with the NSF-sponsored IceCube Upgrade, which will add seven strings with new and enhanced optical modules to DeepCore, the center of the IceCube array. The next phase will be to add the rest of the 120 new strings, which will be spaced about 240 meters apart in a sunflower-like pattern around IceCube that is designed to encompass a large volume while avoiding “corridors” through which misleading signals may pass. The new optical modules, which should be able to collect nearly three times as many photons as current IceCube DOMs, will be spaced 16 meters apart on the string, between 1.3 and 2.6 kilometers below the surface, resulting in a total detector volume of nearly eight cubic kilometers.

    Near the surface, IceCube-Gen2 will have a new radio component made up of detector “stations” covering an area of approximately 500 square kilometers. Each station consists of three strings holding radio antennas that will be deployed close to the surface of the ice. This array will detect radio emission generated in the ice by particle showers, allowing scientists to reconstruct the energy of the shower and arrival direction of the neutrino.

    4
    Top view of the envisioned IceCube-Gen2 Neutrino Observatory facility at the South Pole. From left to right: The radio array consisting of 200 stations. IceCube-Gen2 strings in the optical high-energy array, with 120 new strings (shown as orange points) spaced 240 m apart and instrumented with optical modules over a vertical length of 1.25 km. The total instrumented volume in this design is 7.9 times larger than the current IceCube detector array (blue points). On the far right, the layout for the seven IceCube Upgrade strings relative to existing IceCube strings is shown. Credit: IceCube Collaboration

    IceCube-Gen2 is designed to address some of the mysteries that persist in neutrino and multimessenger astronomy. Specifically, the extension will allow us to resolve the high-energy neutrino sky at energies higher than ever before (energies up to EeV, or 10^18 eV), investigate cosmic particle acceleration through multimessenger observations, reveal the sources and propagation of the highest energy particles in the universe, and probe fundamental physics with high-energy neutrinos. These advancements will shape the next era of multimessenger astronomy and revolutionize our understanding of the high-energy universe.

    “Over the past 30 years we have seen the exciting evolution of neutrino observations, from first neutrino detections using early instruments deployed deep in glacial ice sheets to the long-sought discovery of high-energy astrophysical neutrinos with IceCube,” says Darren Grant of Michigan State University, spokesperson for the current IceCube Collaboration. “IceCube-Gen2 represents the timely opportunity to build on existing expertise and technological advances to move from the discovery era to precision neutrino astronomy.”

    The collaboration already knows that IceCube-Gen2 is logistically possible. The construction of IceCube demonstrated the ability to build and deploy instruments on time and on budget in an Antarctic glacier at the South Pole—one of the most inhospitable environments on the planet. While there will be logistics challenges in such a large project, the collaboration is prepared to meet them, always taking into account that South Pole is hosting a multitude of scientific projects with their own logistical needs.

    From a global perspective, IceCube-Gen2 will transform the multimessenger astrophysics landscape; once built, the extended detector will join a network of other large-scale observatories that survey the sky in gamma rays, gravitational waves, and cosmic rays.

    “Neutrinos are but a recent addition to the palette of tools that help us explore the cosmos,” says Olga Botner, head of the IceCube group at Uppsala University in Sweden. “While IceCube opened a new window onto the distant, violent universe, with IceCube-Gen2 we will look further, with more precision and over a larger energy range. IceCube-Gen2 will play an essential role in the era of multimessenger astronomy, paving the way for new, groundbreaking discoveries.”

    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

    U Wisconsin IceCube Gen2 facility

     
  • richardmitnick 7:31 pm on July 1, 2020 Permalink | Reply
    Tags: "Sun’s shadow on IceCube shines light on solar magnetic field", Atmospheric muons: particles produced by cosmic rays interacting in Earth’s atmosphere, Cosmic rays are high-energy charged particles that reach Earth from all over the sky., How the cosmic-ray Sun shadow changes at different energy regimes., The solar magnetic field, U Wisconsin IceCube Collaboration   

    From U Wisconsin IceCube Collaboration: “Sun’s shadow on IceCube shines light on solar magnetic field” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From U Wisconsin IceCube Collaboration

    01 Jul 2020
    Madeleine O’Keefe

    Go outside on a sunny day and you will see an abundance of shadows. Trees, dogs, buildings, people—anything that obstructs sunlight casts a shadow. The Sun also casts its own shadow, in a way—not by blocking light, but by blocking cosmic rays that would have reached Earth if the Sun were not in the way, an effect aptly called the “cosmic-ray Sun shadow.”

    When they travel close to the Sun, some are blocked by the Sun while others are deflected by the Sun’s magnetic field, which thus affects the cosmic-ray Sun shadow. As IceCube determined in an analysis published in 2019, we can learn about the solar magnetic field by studying its impact on the cosmic-ray Sun shadow.

    The IceCube Collaboration recently performed a succeeding analysis to try to expand our understanding of the solar magnetic field by studying the time-dependent cosmic-ray Sun shadow, this time using seven years of data. They also wanted to explore how the cosmic-ray Sun shadow changes at different energy regimes. The results, recently submitted to Physical Review D, show that more solar activity leads to a weaker Sun shadow. There were also indications that, in times of high solar activity, the shadow becomes stronger at higher energies—a hint at Sun-shadow energy dependence that will be explored more in future studies.

    1
    A graphic representation of cosmic rays getting blocked by the Sun, creating the “cosmic-ray Sun shadow.” Credit: Julia Becker Tjus et al.

    To study cosmic rays with IceCube, the researchers looked at IceCube data containing atmospheric muons: particles produced by cosmic rays interacting in Earth’s atmosphere. Frederik Tenholt, an IceCube collaborator at Ruhr-Universität Bochum in Germany, worked on this analysis for his PhD dissertation in the Plasma-Astroparticle Physics group led by professor Julia Tjus.

    “In order to study the temporal variation of the cosmic-ray Sun shadow and compare it to solar magnetic field models, we basically had to achieve two things,” says Tenholt.

    First, Tenholt and his collaborators had to analyze seven years of IceCube data. Here, different data reduction steps had to be performed in order to reconstruct the cosmic-ray Sun shadow for each of the seven years. Next, to understand the shadow, the team developed and implemented a simulation framework that simulates particle propagation in different solar magnetic field models as well as allows researchers to make predictions for the expected cosmic-ray Sun shadow based on specific models.

    Upon completing the analysis, Tenholt and his collaborators found that the data revealed a decreasing linear relationship between solar activity and Sun shadow strength. “In other words,” says Tenholt, “more solar activity—i.e., a stronger magnetic field—leads to a shallower, or weaker, Sun shadow.”

    2
    This plot compares the shadow strength as observed in the data (black dots) to that predicted by simulations, including different models of the solar magnetic field (red and blue). Credit: IceCube Collaboration.

    They also tested two models of the Sun’s magnetic field to see which one best matched observations. It turned out that both models within statistical uncertainties still describe the observed shadows equally well.

    Lastly, when they looked at the behavior of the shadow at different energies, they found indications that, in times of high solar activity, the shadow becomes deeper/stronger at higher energies, in agreement with theoretical predictions. To examine times of low solar activity, the researchers will need more data and an improved energy estimation.

    3
    Energy dependence of the Sun shadow for the analyzed time periods. Angular resolution effects have already been subtracted. Credit: IceCube Collaboration.

    “This is the first time that solar magnetic field models have been assessed using data from a huge neutrino detector like IceCube by directly comparing the measured cosmic-ray Sun shadow to predictions on the data rate level,” says Tenholt. “This study sets a starting point for studying different phenomena related to solar physics—like the coronal magnetic field, coronal mass ejections, or the solar wind—by using data from IceCube.”

    By using IceCube data, this study was able to probe the solar magnetic field within a few solar radii from the solar surface—a place for which there are no in-situ measurements. In the future, it might be possible to constrain the properties of the Sun’s magnetic field using IceCube data. And by further improving the energy resolution for cosmic-ray–induced IceCube data, it will be possible to study the cosmic-ray Sun shadow at different energies and thereby explore its energy dependence—something that Johan Wulff of Ruhr-Universität Bochum, another lead on this analysis, is planning to do soon.

    “I am very excited to work on this analysis for my master’s thesis as it bridges the gap between theoretical solar magnetic field models and experimental IceCube data analysis,” says Wulff. “Such a broad issue allows me to develop skills on both, the experimental and theoretical side of physics. By working on an improved energy reconstruction, I hope to open the door for energy-dependent shadow studies and investigations of magnetic field effects at different energies.”

    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 10:31 am on June 20, 2020 Permalink | Reply
    Tags: "Machine-learning method allows IceCube to study cosmic rays at new-low energies", Now IceCube has found a way to detect cosmic rays of lower energies previously unreachable by IceTop., The IceTop surface array is made up of 81 stations spaced about 125 meters apart spread over a square kilometer at the South Pole., The new method also reduces the gap between IceTop and measurements from instruments like balloons and satellites., They calculated that the method lowers the threshold of the energy spectrum from 2 PeV to 250 TeV (1012 electronvolts)—nearly an order of magnitude., They implemented a new two-station trigger as well as the machine-learning method developed to analyze these events., U Wisconsin IceCube Collaboration   

    From U Wisconsin IceCube Collaboration: “Machine-learning method allows IceCube to study cosmic rays at new-low energies” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From U Wisconsin IceCube Collaboration

    16 Jun 2020
    Madeleine O’Keefe


    Neutrinos from blazar TXS 0506+056


    IceCube explained

    The IceCube Neutrino Observatory is primarily known for detecting hard-to-catch particles, called neutrinos, using its cubic-kilometer array of light sensors buried under the ice at the geographic South Pole. But IceCube also has a surface component, known as IceTop, that detects cosmic rays—charged particles that reach Earth from outer space at high energies. (Some of the same particles interact near their cosmic sources to produce the astrophysical neutrinos that IceCube sees.)

    The IceTop surface array [below] is made up of 81 stations spaced about 125 meters apart spread over a square kilometer at the South Pole. Each station consists of two tanks separated by 10 meters that each house two optical sensors frozen in water. When cosmic rays collide with particles in Earth’s atmosphere, they create secondary showers of particles, called “air showers.” The particles from these air showers are detected by IceTop’s tanks, allowing scientists to reconstruct the original cosmic ray’s energy and direction.

    Now, IceCube has found a way to detect cosmic rays of lower energies previously unreachable by IceTop. In a paper submitted to Physical Review D, “Cosmic Ray Spectrum from 250 TeV to 10 PeV using IceTop,” the IceCube Collaboration explains how they implemented a new two-station trigger as well as the machine-learning method developed to analyze these events.

    1
    IceTop geometry with positions of all tanks. The marked boundary in the center indicates the six stations used to define the two-station trigger. Credit: IceCube Collaboration

    The cosmic-ray energy spectrum is the distribution of cosmic rays based on their energies. Precise measurements of the energy spectrum and elemental composition are necessary to understand cosmic-ray sources, acceleration, and propagation.

    The more energetic the cosmic ray, the more IceTop stations its air shower hits. Previously, energy spectrum analyses only used air showers that triggered five or more IceTop stations, which resulted in an energy spectrum ranging from 2 PeV (1015 electronvolts) to a few EeV (1018 electronvolts). To lower the energy threshold and study lower-energy cosmic rays, IceCube scientists must use data from air showers with signals on fewer than five stations.

    But three- or four-station events were previously ignored—even though the data were collected—because it was so difficult to reconstruct the cosmic ray’s primary energy and direction of arrival with so few stations. Two-station events were not even collected because they’re even more difficult to reconstruct.

    So IceCube collaborator Ramesh Koirala, a PhD student at the University of Delaware at the time, developed a trigger that would collect these two-station events from stations less than 50 meters away from each other. Then, collaborators developed a method to reconstruct their primary energy and direction with reasonable accuracy using a machine-learning technique called random forest regression. Based on reconstructed energies, they calculated that the method lowers the threshold of the energy spectrum from 2 PeV to 250 TeV (1012 electronvolts)—nearly an order of magnitude.

    The new method also reduces the gap between IceTop and measurements from instruments like balloons and satellites. Since these instruments detect cosmic rays directly, they can determine the composition of cosmic rays more accurately than IceTop’s indirect measurements.

    “One of the reasons to lower the energy threshold is to overlap the IceTop spectrum with energy spectra from direct measurement,” says Koirala, who is now a postdoctoral researcher at Nanjing University in China. “This gives us an extra handle in our composition analysis. Also, lowering the energy threshold gives IceTop the full coverage of the ‘knee’ region, which is one of the major features of the cosmic-ray energy spectrum.”

    2
    The cosmic-ray energy spectrum from 250 TeV to 10 PeV using two-station events. Cosmic-ray flux using IceTop data scaled by E^1.65 and compared with flux from other experiments. The shaded region indicates the systematic uncertainties. The energy spectra from a previous IceTop analysis as well as from ATIC-02, HAWC, KASCADE, KASCADE-Grande, TALE, Tibet III, and Tunka are also plotted to compare with the energy spectrum from this analysis. Credit: IceCube Collaboration

    This analysis is the first to make use of the closely spaced detectors to extend the measurement of the cosmic-ray energy spectrum.

    “The next step for the future will be to use events that pass the two-station trigger on the surface and that also have signals in the array of IceCube DOMs two kilometers below the surface,” says Thomas Gaisser, an emeritus professor at the University of Delaware and another lead on this paper. The ratio of the deep signal to the surface signal will give scientists information about the nuclear composition of those primary cosmic-ray particles that initiate the cascades detected by IceTop.

    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 12:50 pm on April 4, 2020 Permalink | Reply
    Tags: "Pulsar wind nebulae explored as possible cosmic-ray accelerators", U Wisconsin IceCube Collaboration, Ultimately the researchers did not find significant correlation of IceCube neutrinos and the 35 pulsar wind nebulae.   

    From U Wisconsin IceCube Collaboration: “Pulsar wind nebulae explored as possible cosmic-ray accelerators” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From U Wisconsin IceCube Collaboration

    03 Apr 2020
    Madeleine O’Keefe

    A giant star will go out with a bang: When it dies, it explodes in a supernova, leaving behind a diffuse cloud of gas and dust around its own small, compact core, often in the form of a neutron star. A pulsar is a rapidly rotating neutron star with an extremely strong magnetic field that beams electromagnetic radiation as it spins, like an interstellar lighthouse. Some pulsars also generate a strong wind of charged particles, resulting in a type of nebula called a “pulsar wind nebula.”

    Pulsar wind nebulae might explain how and where charged particles called cosmic rays get accelerated to their high energies. And neutrinos, the nearly massless subatomic particles studied by the IceCube Neutrino Observatory at the South Pole, can help researchers get closer to figuring that out.

    In a paper recently submitted to The Astrophysical Journal, the IceCube Collaboration outlines an analysis that searched for neutrino emission from 35 pulsar wind nebulae in 9.5 years of IceCube data. They did not find any significant correlation, so the researchers set upper limits on total neutrino emission from these objects.

    1
    Upper limits on the hadronic contribution to the gamma-ray flux from pulsar wind nebulae found under the four hypotheses considered in this analysis projected against the total and individual gamma-ray fluxes from the 35 sources. Credit: IceCube Collaboration

    Astronomers know that pulsar wind nebulae emit gamma rays at energies on the scale of a trillion electronvolts (known as a teraelectronvolt, TeV); in fact, according to observations, they are the most abundant TeV gamma-ray emitters in the Milky Way, and some models predict that they are also sources of cosmic rays and neutrinos.

    Cosmic rays are highly energetic subatomic particles that we detect coming from outer space. When they interact with surrounding molecules or radiation, they produce gamma rays and neutrinos. But since gamma rays can also be produced without cosmic ray interaction, just detecting them doesn’t tell us much. Seeing gamma rays and neutrinos from a particular source, however, would be a smoking gun for a cosmic-ray accelerator.

    So, in search of neutrino correlation, IceCube collaborators performed an analysis of 35 pulsar wind nebulae with observed TeV gamma-ray emission. They then evaluated the significance of the possible correlation using four different hypotheses: First they assumed that the possible neutrino emission is proportional to the high-energy gamma-ray flux associated with the sources. They also assumed that all sources have equal probability of emitting neutrinos as well as the hypothesis that sources with faster spinning central pulsars are preferred. Finally, they examined whether younger sources are preferred because they can be more energetic.

    Ultimately, the researchers did not find significant correlation of IceCube neutrinos and the 35 pulsar wind nebulae. Therefore, they set upper limits on the maximum neutrino flux that can be expected from these sources. They also limited the fraction of hadronic gamma rays in the total gamma-ray flux observed from the sources, providing constraints for the modeling of pulsar wind nebulae.

    “The presence of hadrons in pulsar wind nebulae has significant impact on our understanding of the particle acceleration in these major gamma-ray emitters in the Milky Way,” says Ali Kheirandish, a postdoc at Pennsylvania State University and one of the leads on this analysis. “Even a small contribution of ions can help resolve tensions in the modeling of the high-energy emission from pulsar winds, and the obtained upper limits on the hadronic contributions in this analysis aim at overcoming this obstacle.”

    According to Qinrui Liu, a graduate student at the University of Wisconsin–Madison and another lead on this analysis, “These results bring us closer to eventually understanding whether pulsar wind nebulae are sites of very high energy cosmic-ray acceleration.”

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    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

     
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