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  • richardmitnick 6:16 pm on February 13, 2020 Permalink | Reply
    Tags: , , , Neutrinos,   

    From Fermi National Accelerator Lab: “Finding hidden neutrinos with MicroBooNE” 

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    FNAL Art Image by Angela Gonzales

    From Fermi National Accelerator Lab , an enduring source of strength for the US contribution to scientific research world wide.

    February 13, 2020
    Owen Goodwin
    Davide Porzio
    Stefan Söldner-Rembold
    Yun-Tse Tsai

    Neutrinos have baffled scientists for decades as their properties and behavior differ from those of other known elementary particles. Their masses, for example, are much smaller than the masses measured for any other elementary matter particle we know. They also carry no electric charge and interact only very rarely – through the weak force — with matter. At Fermilab, a chain of accelerators generates neutrino beams so researchers can study neutrino properties and understand their role in the formation of the universe.

    Scientists working on Fermilab’s MicroBooNE experiment have published a paper [Physical Review D] describing a search for a new – hidden – type of heavier neutrino that could help explain why the masses of ordinary neutrinos are so small. It could also provide important clues about the nature of dark matter. This search is the first of its kind performed with a type of particle detector known as a liquid-argon time projection chamber.

    The MicroBooNE detector consists of a large tank of liquid argon [below], totaling 170 tons, located in an intense beam of neutrinos at Fermilab. The neutrinos originate in a beam produced by the lab’s accelerators. Some of these ordinary neutrinos will hit an argon nucleus in the tank, resulting in the production of other particles. The MicroBooNE detector then acts like a giant camera that records the particles produced in this collision.

    A heavier type of neutrino – which has been hypothesized but never observed – could also be produced in the accelerator-generated beam. These heavier types of neutrinos, scientifically called “heavy neutral leptons,” would not interact through the weak force and therefore could not hit an argon nucleus in the same way as ordinary neutrinos do. They could, however, leave a hint of their existence if they decayed into known particles inside the MicroBooNE detector.

    1
    The display shows the decay of a heavy neutrino as it would be measured in the MicroBooNE detector. Scientists use such simulations to understand what a signal in data would look like. Image: MicroBooNE collaboration

    To find such signatures of heavy neutrinos, MicroBooNE scientists devised a new method that helps them distinguish the heavy neutrino decays from ordinary neutrino scatterings on argon, and it has a lot to do with timing.

    The Fermilab neutrino beam is not a continuous stream of particles. Rather, it is pulsed, and the experimenters know when these neutrino pulses are supposed to arrive at the MicroBooNE detector: The heavy neutrinos would be more massive and therefore slower than the ordinary neutrinos – a well-tested prediction of special relativity. The trick is therefore to wait just long enough — until the ordinary neutrinos in a pulse have passed through and only heavy neutrinos could arrive.

    In the MicroBooNE detector, a heavy neutrino would appear to come out of nowhere. The only traces of its appearance would be tracks from two charged particles emerging from its decay – a muon and a pion (see figure). Using the measured angles and energies of these two daughter particles, the mass of the invisible parent particle – assumed to be the heavy neutrino — can be calculated.

    After sifting through all the MicroBooNE data, scientists found that only a handful of heavy-neutrino candidates remained. Scientists found that the origin of these candidates is consistent with being muons from cosmic rays constantly bombarding the MicroBooNE detector. In very rare cases, such a muon can mimic the two charged particles from a heavy neutral lepton.

    The heavy neutrinos – if they exist – are therefore still hiding. MicroBooNE’s results are expressed as a limit on the strength of the coupling – or mixing – of the hidden neutrinos with ordinary neutrinos. In this way, the sensitivity of the MicroBooNE detector can be translated into stringent constraints on models that predict hidden neutrino states, leading to better predictions. The short-baseline liquid-argon neutrino experiments at Fermilab are going to collect much more data in the coming years. Heavy neutrinos might not be able to hide much longer.

    See the full article here.


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

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  • 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., Neutrinos, , 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.,   

    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", , Neutrinos, , ,   

    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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    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., Neutrinos, , , The 'Zee burst' model, , ,   

    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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    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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  • richardmitnick 7:50 am on January 23, 2020 Permalink | Reply
    Tags: , , , Neutrinos, UK Research and Innovation   

    From Fermi National Accelerator Lab: “UK invests £65 million in international science projects hosted by Fermilab” 

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    From Fermi National Accelerator Lab , an enduring source of strength for the US contribution to scientific research world wide.

    January 22, 2020
    Kurt Riesselmann

    1

    Representatives from UK Research and Innovation and the U.S. Department of Energy today signed an agreement that outlines £65 million worth of contributions that UK research institutions and scientists will make to the international Deep Underground Neutrino Experiment and related projects hosted by DOE’s Fermi National Accelerator Laboratory. DUNE will study the properties of mysterious particles called neutrinos, which could help explain more about how the universe works and why matter exists at all.

    UK scientists have held leadership positions in DUNE since the inception of the collaboration in 2015. The agreement gives the green light to build major components in the UK for this megascience project. That includes setting up the required lab space and infrastructure at UK research institutions as well as hiring and training personnel.

    The UK investments in these international science projects and participation in the design and construction of cutting-edge scientific equipment for these projects will empower UK scientists and institutions to maintain a world leader position in research for years to come.

    2
    On Jan. 22 in London, U.S. Department of Energy Office of Science Director Chris Fall, right, and Minister for Universities, Science, Research, and Innovation at the UK Department for Business, Energy and Industrial Strategy Chris Skidmore signed an agreement between DOE and UK Research and Innovation for work on the international LBNF/DUNE project, hosted by Fermilab, and Fermilab’s PIP-II and Short-Baseline Neutrino Program. Photo: DOE Office of Science.

    “The UK’s continued collaboration with the U.S. on science and innovation reinforces the importance the scientific communities of both countries place on working together to try to answer some of the biggest questions in physics, questions that have the potential to lead to profound changes in our understanding of the universe,” said Professor Mark Thomson, particle physicist and executive chair of UK’s Science and Technology Facilities Council.

    “This investment by STFC secures future access for UK scientists to the international DUNE experiment as well as giving UK scientists and engineers the chance to take leading roles in the management and development of the DUNE far detector and also the LBNF neutrino beam and the associated PIP-II accelerator,” Thomson said.

    DUNE is the first large-scale U.S.-hosted experiment run as a truly international project, with more than 1,000 scientists and engineers from over 30 countries contributing to the design, construction and operation of the facilities and scientific equipment. The UK research community is a major contributor to the DUNE collaboration, with 14 UK universities and two STFC laboratories providing essential expertise and components to the experiment and facility.

    “Our collaboration with the UK remains a cornerstone of DOE’s international partnerships in high energy physics,” said Chris Fall, director of the U.S. Department of Energy Office of Science. “Those partnerships are key to building world-class projects like PIP-II and LBNF/DUNE, hosted by Fermilab, and we are pleased to see our long history of scientific kinship with the UK in this field continue.”

    The agreement is a new chapter in the long history of UK research collaboration with the United States. UK contributions will include:

    Design and construction of superconducting particle accelerator components for Fermilab’s Proton Improvement Plan-II accelerator project, which will provide the particles that make the DUNE experiment possible. These accelerator components also have applications in other science projects and have promising potential for use in medical, industrial and environmental applications.
    Design and production of the high-power target for the Long-Baseline Neutrino Facility that scientists will use to produce the neutrinos for DUNE.

    FNAL Long-Baseline Neutrino Facility – South Dakota Site

    SURF-Sanford Underground Research Facility, Lead, South Dakota, USA

    The work, carried out at the Rutherford Appleton Laboratory in the UK, will also advance research efforts in materials science and nuclear physics.

    STFC Rutherford Appleton Laboratory at Harwell in Oxfordshire, UK

    Design and assembly of 150 very large particle detector components known as anode plane assemblies that each comprise thousands of delicate sensor wires. The APAs enable scientists to record high-resolution 3-D images of subatomic particle tracks produced in neutrino interactions.
    Development of the data acquisition systems and reconstruction software. Each DUNE module will produce one terabyte of data per second, equivalent to about 1,000 one-hour-long HD movies. Reading out this vast amount of data, and then finding and reconstructing the neutrino interactions, is one of the big challenges.
    Building and shipping major components of the Short-Baseline Near Detector, one of three detectors that make up Fermilab’s Short-Baseline Neutrino program.

    FNAL Short baseline neutrino detector

    DUNE will send neutrinos 1,300 kilometers from Fermilab in Illinois to huge particle detectors 1.5 kilometers underground at the Sanford Underground Research Facility in South Dakota in order to study neutrino oscillations. Scientists will look for the differences in behavior between neutrinos and their antimatter counterparts, antineutrinos, which could provide clues as to why we live in a matter-dominated universe.

    Surf-Dune/LBNF Caverns at Sanford

    FNAL DUNE Argon tank at SURF

    DUNE scientists will also watch for neutrinos stemming from a supernova, or star explosion, which could reveal the formation of neutron stars and black holes. Another goal of DUNE is to look for signals from proton decay. Scientists will investigate whether protons live forever or eventually decay, bringing us closer to fully understanding the fundamental forces of nature.

    DUNE will help to recruit and train the next generation of particle physicists, giving students at universities around the world the opportunity to publish scientific papers and get hands-on training on one of the world’s most advanced physics projects.

    More information about the facility and experiment can be found at http://www.fnal.gov/dune.

    See the full here.


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

    FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA

     
  • richardmitnick 3:20 pm on January 22, 2020 Permalink | Reply
    Tags: , , Geoneutrinos, , Neutrinos   

    From INFN Gran Sasso via phys.org: “Signals from inside the Earth: Borexino experiment releases new data on geoneutrinos” 

    From From INFN Gran Sasso

    via


    phys.org

    January 22, 2020
    Forschungszentrum Juelich

    1
    The diagram shows geoneutrinos from the earth’s interior measured by the Borexino detector, resulting in the final energy spectra. The x-axis shows the charge (number of photo electrons) of the signal, which is a measure of energy deposited in the detector, and the y-axis shows the number of measured events. Credit: Borexino Collaboration

    Scientists involved in the Borexino collaboration have presented new results for the measurement of neutrinos originating from the interior of the Earth. The elusive “ghost particles” rarely interact with matter, making their detection difficult. With this update, the researchers have now been able to access 53 events—almost twice as many as in the previous analysis of the data from the Borexino detector, which is located 1,400 metres below the Earth’s surface in the Gran Sasso massif near Rome. The results provide an exclusive insight into processes and conditions in the earth’s interior that remain puzzling to this day.

    INFN/Borexino Solar Neutrino detector, at Laboratori Nazionali del Gran Sasso, situated below Gran Sasso mountain in Italy

    The earth is shining, even if it is not at all visible to the naked eye. The reason for this is geoneutrinos, which are produced in radioactive decay processes in the interior of the Earth. Every second, about one million of these elusive particles penetrate every square centimetre of our planet’s surface.

    The Borexino detector, located in the world’s largest underground laboratory, the Laboratori Nazionali del Gran Sasso in Italy, is one of the few detectors in the world capable of observing these ghostly particles. Researchers have been using it to collect data on neutrinos since 2007, i.e. for over ten years. By 2019, they were able to register twice as many events as at the time of the last analysis in 2015—and reduce the uncertainty of the measurements from 27 to 18 percent, which is also due to new analysis methods.

    “Geoneutrinos are the only direct traces of the radioactive decay that occur inside the Earth, and which produce an as yet unknown portion of the energy driving all the dynamics of our planet,” explains Livia Ludhova, one of the two current scientific coordinators of Borexino and head of the neutrino group at the Nuclear Physics Institute (IKP) at Forschungszentrum Jülich.

    The researchers in the Borexino collaboration have extracted, with an improved statistical significance, the signal of geoneutrinos coming from the Earth’s mantle which lies below the Earth crust by exploiting the well-known contribution from the Earth’s uppermost mantle and crust—the so called lithosphere.

    The intense magnetic field, the unceasing volcanic activity, the movement of the tectonic plates, and mantle convection: The conditions inside the Earth are in many ways unique in the entire solar system. Scientists have been discussing the question of where the Earth’s internal heat comes from for over 200 years.

    “The hypothesis that there is no longer any radioactivity at depth in the mantle can now be excluded at the 99% confidence level for the first time. This makes it possible to establish lower limits for uranium and thorium abundances in the Earth’s mantle,” says Livia Ludhova.

    These values are of interest for many different Earth model calculations. For example, it is highly probable (85%) that radioactive decay processes inside the Earth generate more than half of the Earth’s internal heat, while the other half is still largely derived from the original formation of the Earth. Radioactive processes in the Earth therefore provide a non-negligible portion of the energy that feeds volcanoes, earthquakes, and the Earth’s magnetic field.

    The latest publication in Phys. Rev. D not only presents the new results, but also explains the analysis in a comprehensive way from both the physics and geology perspectives, which will be helpful for next generation liquid scintillator detectors that will measure geoneutrinos. The next challenge for research with geoneutrinos is now to be able to measure geoneutrinos from the Earth’s mantle with greater precision, perhaps with detectors distributed at different positions on our planet. One such detector will be the JUNO detector in China where the IKP neutrino group is involved. The detector will be 70 times bigger than Borexino which helps in achieving higher statistical significance in a short time span.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy

    INFN Gran Sasso National Laboratory (LNGS) is the largest underground laboratory in the world devoted to neutrino and astroparticle physics, a worldwide research facility for scientists working in this field of research, where particle physics, cosmology and astrophysics meet. It is unequalled anywhere else, as it offers the most advanced underground infrastructures in terms of dimensions, complexity and completeness.

    LNGS is funded by the National Institute for Nuclear Physics (INFN), the Italian Institution in charge to coordinate and support research in elementary particles physics, nuclear and sub nuclear physics

    Located between L’Aquila and Teramo, at about 120 kilometres from Rome, the underground structures are on one side of the 10-kilometre long highway tunnel which crosses the Gran Sasso massif (towards Rome); the underground complex consists of three huge experimental halls (each 100-metre long, 20-metre large and 18-metre high) and bypass tunnels, for a total volume of about 180.000 m3.

    Access to experimental halls is horizontal and it is made easier by the highway tunnel. Halls are equipped with all technical and safety equipment and plants necessary for the experimental activities and to ensure proper working conditions for people involved.

    The 1400 metre-rock thickness above the Laboratory represents a natural coverage that provides a cosmic ray flux reduction by one million times; moreover, the flux of neutrons in the underground halls is about thousand times less than on the surface due to the very small amount of uranium and thorium of the Dolomite calcareous rock of the mountain.

    The permeability of cosmic radiation provided by the rock coverage together with the huge dimensions and the impressive basic infrastructure, make the Laboratory unmatched in the detection of weak or rare signals, which are relevant for astroparticle, sub nuclear and nuclear physics.

    Outside, immersed in a National Park of exceptional environmental and naturalistic interest on the slopes of the Gran Sasso mountain chain, an area of more than 23 acres hosts laboratories and workshops, the Computing Centre, the Directorate and several other Offices.

    Currently 1100 scientists from 29 different Countries are taking part in the experimental activities of LNGS.
    LNGS research activities range from neutrino physics to dark matter search, to nuclear astrophysics, and also to earth physics, biology and fundamental physics.

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

    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 5:32 pm on January 14, 2020 Permalink | Reply
    Tags: ANTARES, , Neutrinos, , ,   

    From U Wisconsin IceCube Collaboration and ANTARES: “ANTARES and IceCube combine forces to search for southern sky neutrino sources” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From From U Wisconsin IceCube Collaboration

    14 Jan 2020
    Madeleine O’Keefe

    Teamwork makes the dream work. Especially when that dream is to find sources of elusive particles called neutrinos.

    Neutrinos are chargeless, nearly massless subatomic particles. These elusive particles are abundantly produced in nuclear fusion processes in our sun or the natural radioactivity of Earth. In rare cases, we also observe high-energy neutrinos from outer space, known as astrophysical neutrinos. They fly through light-years of space at close to the speed of light without being tugged around by magnetic fields or other forces; this makes them ideal astronomical messengers, as they bring us information from the most enigmatic objects in the cosmos. But we still don’t know where they originate.

    The IceCube Neutrino Observatory in Antarctica is one experiment looking for sources of these enigmatic particles. IceCube does this with an array of 5,160 optical detectors buried in a cubic kilometer of South Pole ice; when a neutrino from outer space reaches Antarctica with enough energy, it can hit an atom in the ice and produce another particle that flies through IceCube, trailed by a cone of light called Čerenkov radiation. That cone of light triggers the detectors it passes, leaving clusters of lit-up detectors behind it.

    Meanwhile, floating in the Mediterranean Sea is a similar neutrino experiment called ANTARES.

    1

    The IceCube Collaboration recently conducted a combined IceCube-ANTARES search for neutrino point-like and extended sources in the southern sky. They didn’t find any significant evidence for cosmic neutrino sources, but the analysis shows the strong potential for combining data sets from both experiments. Their results were recently submitted to The Astrophysical Journal.

    2
    This sky map shows the result of the search for point-like sources in the whole southern sky. Higher values of -log10(p-value) indicate more significant directions. The red contour shows the position of the most significant cluster of events, which was not significant enough to be considered a source. Credit: IceCube Collaboration

    It’s an exciting time for neutrino astronomy. IceCube’s past few years of research have yielded promising results, including the discovery of the first evidence of neutrinos coming from an astrophysical source. But the origins of most of the astrophysical neutrinos that reach Earth remain unknown.

    So researchers around the world are continuing to look for neutrino sources. Giulia Illuminati of the Instituto de Física Corpuscular in Valencia, Spain, led this search, which combined data sets from IceCube and ANTARES.

    “The motivation behind this analysis lies in the fact that ANTARES and IceCube, thanks to their different sizes and locations, complement each other when looking for neutrino sources in the southern sky,” she says.

    ANTARES’s location in the Mediterranean results in a lower background for neutrino source hunting in the Southern Hemisphere, while IceCube’s larger size gives it a higher detection capability. Together, these characteristics mean an increased chance to detect sources of astrophysical neutrinos in the southern sky.

    Illuminati and her collaborators performed five types of searches for point-like and extended sources of astrophysical neutrinos using ANTARES and IceCube data. (Technically, all neutrino sources are “extended,” but when they appear on the celestial sphere with a size smaller than IceCube’s angular resolution, they cannot be resolved and are called “point-like.”)

    In the first two searches, they scanned the full southern sky and a restricted region around the Galactic Center to look for significant emission of cosmic neutrinos from point-like and extended sources. In the third search, they investigated the positions of 57 astrophysical objects in a predefined list of candidate point-like emitters of high-energy neutrinos. Finally, they performed dedicated searches at the locations of two promising neutrino source candidates: the supermassive black hole Sagittarius A* and the shell-type supernova remnant RXJ 1713.7-3946.

    Ultimately, they did not find any significant point-like or extended neutrino emission, but they derived upper limits on the neutrino flux from the various analyzed sources. Even without a significant discovery, this analysis proved the high potential of joint searches for neutrino sources with ANTARES and IceCube. By combining the data sets of the two detectors, the researchers were able to improve the sensitivity in different regions of the southern sky by about a factor of 2 compared to individual analyses.

    “These results strongly motivate a joint analysis of future data sets, not only of the ANTARES and the IceCube telescopes but also of the future detectors KM3NeT and IceCube-Gen2 [below],” says Illuminati.

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

    Artist’s expression of the KM3NeT neutrino telescope

    It relies on the same principle as IceCube: It’s another three-dimensional array of optical detectors in a transparent medium (here, water instead of ice). If a high-energy neutrino hits an atom in the water, it will produce a particle and Cherenkov light that triggers the optical modules in the sea.

    The IceCube Collaboration recently conducted a combined IceCube-ANTARES search for neutrino point-like and extended sources in the southern sky. They didn’t find any significant evidence for cosmic neutrino sources, but the analysis shows the strong potential for combining data sets from both experiments. Their results were recently submitted to The Astrophysical Journal.

    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 11:55 am on January 14, 2020 Permalink | Reply
    Tags: "A voyage to the heart of the neutrino", , , , Neutrinos, , , SNOLAB- a Canadian underground physics laboratory at a depth of 2 km in Vale's Creighton nickel mine in Sudbury Ontario Canada., Super-Kamiokande experiment located under Mount Ikeno near the city of Hida Gifu Prefecture Japan, The Karlsruhe Tritium Neutrino (KATRIN) experiment, The most abundant particles in the universe besides photons., The three neutrino mass eigenstates, We know now that the three neutrino flavour states we observe in experiments – νe; νμ; and ντ – are mixtures of three neutrino mass states.   

    From CERN Courier: “A voyage to the heart of the neutrino” 


    From CERN Courier

    10 January 2020

    The Karlsruhe Tritium Neutrino (KATRIN) experiment has begun its seven-year-long programme to determine the absolute value of the neutrino mass.

    KATRIN experiment aims to measure the mass of the neutrino using a huge device called a spectrometer (interior shown)Karlsruhe Institute of Technology, Germany

    On 11 June 2018, a tense silence filled the large lecture hall of the Karlsruhe Institute of Technology (KIT) in Germany.

    2

    Karlsruhe Institute Of Technology (KIT)


    Karlsruhe Institute of Technology (KIT) in Germany.

    In front of an audience of more than 250 people, 15 red buttons were pressed simultaneously by a panel of senior figures including recent Nobel laureates Takaaki Kajita and Art McDonald. At the same time, operators in the control room of the Karlsruhe Tritium Neutrino (KATRIN) experiment lowered the retardation voltage of the apparatus so that the first beta electrons were able to pass into KATRIN’s giant spectrometer vessel. Great applause erupted when the first beta electrons hit the detector.

    In the long history of measuring the tritium beta-decay spectrum to determine the neutrino mass, the ensuing weeks of KATRIN’s first data-taking opened a new chapter. Everything worked as expected, and KATRIN’s initial measurements have already propelled it into the top ranks of neutrino experiments. The aim of this ultra-high-precision beta-decay spectroscope, more than 15 years in the making, is to determine, by the mid-2020s, the absolute mass of the neutrino.

    Massive discovery

    Since the discovery of the oscillation of atmospheric neutrinos by the Super-Kamiokande experiment in 1998, and of the flavour transitions of solar neutrinos by the SNO experiment shortly afterwards, it was strongly implied that neutrino masses are not zero, but big enough to cause interference between distinct mass eigenstates as a neutrino wavepacket evolves in time. We know now that the three neutrino flavour states we observe in experiments – νe, νμ and ντ – are mixtures of three neutrino mass states.

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

    SNOLAB, a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario

    SNOLAB, Sudbury, Ontario, Canada.

    Though not massless, neutrinos are exceedingly light. Previous experiments designed to directly measure the scale of neutrino masses in Mainz and Troitsk produced an upper limit of 2 eV for the neutrino mass – a factor 250,000 times smaller than the mass of the otherwise lightest massive elementary particle, the electron. Nevertheless, neutrino masses are extremely important for cosmology as well as for particle physics. They have a number density of around 336 cm–3, making them the most abundant particles in the universe besides photons, and therefore play a distinct role in the formation of cosmic structure. Comparing data from the Planck satellite together with data from galaxy surveys (baryonic acoustic oscillations) with simulations of the evolution of structure yields an upper limit on the sum of all three neutrino masses of 0.12 eV at 95% confidence within the framework of the standard Lambda cold-dark matter (ΛCDM) cosmological model.

    Lamda Cold Dark Matter Accerated Expansion of The universe http scinotions.com the-cosmic-inflation-suggests-the-existence-of-parallel-universes
    Alex Mittelmann, Coldcreation

    Considerations of “naturalness” lead most theorists to speculate that the exceedingly tiny neutrino masses do not arise from standard Yukawa couplings to the Higgs boson, as per the other fermions, but are generated by a different mass mechanism. Since neutrinos are electrically neutral, they could be identical to their antiparticles, making them Majorana particles. Via the so-called seesaw mechanism, this interesting scenario would require a new and very high particle mass scale to balance the smallness of the neutrino masses, which would be unreachable with present accelerators.

    5
    Inner space KATRIN’s main spectrometer, the largest ultra-high-vacuum vessel in the world, contains a dual-layer electrode system comprising 23,000 wires to shield the inner volume from charged particles. Credit: KATRIN

    As neutrino oscillations arise due to interference between mass eigenstates, neutrino-oscillation experiments are only able to determine splittings between the squares of the neutrino mass eigenstates. Three experimental avenues are currently being pursued to determine the neutrino mass. The most stringent upper limit is currently the model-dependent bound set by cosmological data, as already mentioned, which is valid within the ΛCDM model. A second approach is to search for neutrinoless double-beta decay, which allows a statement to be made about the size of the neutrino masses but presupposes the Majorana nature of neutrinos.

    U Washington Majorana Demonstrator Experiment at SURF

    The third approach – the one adopted by KATRIN – is the direct determination of the neutrino mass from the kinematics of a weak process such as beta decay, which is completely model-independent and depends only on the principle of energy and momentum conservation.

    6
    Fig. 1. The beta spectrum of tritium (left), showing in detail the effect of different neutrino masses on the endpoint (right). Credit: CERN

    The direct determination of the neutrino mass relies on the precise measurement of the shape of the beta electron spectrum near the endpoint, which is governed by the available phase space (figure 1). This spectral shape is altered by the neutrino mass value: the smaller the mass, the smaller the spectral modification. One would expect to see three modifications, one for each neutrino mass eigenstate. However, due to the tiny neutrino mass differences, a weighted sum is observed. This “average electron neutrino mass” is formed by the incoherent sum of the squares of the three neutrino mass eigenstates, which contribute to the electron neutrino according to the PMNS neutrino-mixing matrix. The super-heavy hydrogen isotope tritium is ideal for this purpose because it combines a very low endpoint energy, Eo, of 18.6 keV and a short half-life of 12.3 years with a simple nuclear and atomic structure.

    KATRIN is born

    Around the turn of the millennium, motivated by the neutrino oscillation results, Ernst Otten of the University of Mainz and Vladimir Lobashev of INR Troitsk proposed a new, much more sensitive experiment to measure the neutrino mass from tritium beta decay. To this end, the best methods from the previous experiments in Mainz, Troitsk and Los Alamos were to be combined and upscaled by up to two orders of magnitude in size and precision. Together with new technologies and ideas, such as laser Raman spectroscopy or active background reduction methods, the apparatus would increase the sensitivity to the observable in beta decay (the square of the electron antineutrino mass) by a factor of 100, resulting in a neutrino-mass sensitivity of 0.2 eV. Accordingly, the entire experiment was designed to the limits of what was feasible and even beyond (see “Technology transfer delivers ultimate precision” box).

    _______________________________________________
    7
    Precise The electron transport and tritium retention system. Credit: KIT

    Many technologies had to be pushed to the limits of what was feasible or even beyond. KATRIN became a CERN-recognised experiment (RE14) in 2007 and the collaboration worked with CERN experts in many areas to achieve this. The KATRIN main spectrometer is the largest ultra-high vacuum vessel in the world, with a residual gas pressure in the range of 10–11 mbar – a pressure that is otherwise only found in large volumes inside the LHC ring – equivalent to the pressure recorded at the lunar surface.

    Even though the inner surface was instrumented with a complex dual-layer wire electrode system for background suppression and electric-field shaping, this extreme vacuum was made possible by rigorous material selection and treatment in addition to non-evaporable getter technology developed at CERN. KATRIN’s almost 40 m-long chain of superconducting magnets with two large chicanes was put into operation with the help of former CERN experts, and a 223Ra source was produced at ISOLDE for background studies at KATRIN.

    CERN ISOLDE Looking down into the ISOLDE experimental hall

    A series of 83mKr conversion electron sources based on implanted 83Rb for calibration purposes was initially produced at ISOLDE. At present these are produced by KATRIN collaborators and further developed with regard to line stability.

    Conversely, the KATRIN collaboration has returned its knowledge and methods to the community. For example, the ISOLDE high-voltage system was calibrated twice with the ppm-accuracy KATRIN voltage dividers, and the magnetic and electrical field calculation and tracking programme KASSIOPEIA developed by KATRIN was published as open source and has become the standard for low-energy precision experiments. The fast and precise laser Raman spectroscopy developed for KATRIN is also being applied to fusion technology.
    _______________________________________________

    KIT was soon identified as the best place for such an experiment, as it had the necessary experience and infrastructure with the Tritium Laboratory Karlsruhe. The KIT board of directors quickly took up this proposal and a small international working group started to develop the project. At a workshop at Bad Liebenzell in the Black Forest in January 2001, the project received so much international support that KIT, together with nearly all the groups from the previous neutrino-mass experiments, founded the KATRIN collaboration. Currently, the 150-strong KATRIN collaboration comprises 20 institutes from six countries.

    It took almost 16 years from the first design to complete KATRIN, largely because many new technologies had to be developed, such as a novel concept to limit the temperature fluctuations of the huge tritium source to the mK scale at 30 K or the high-voltage stabilisation and calibration to the 10 mV scale at 18.6 kV. The experiment’s two most important and also most complex components are the gaseous, windowless molecular tritium source (WGTS) and the very large spectrometer. In the WGTS, tritium gas is introduced in the midpoint of the 10 m-long beam tube, where it flows out to both sides to be pumped out again by turbomolecular pumps. After being partially cleaned it is re-injected, yielding a closed tritium cycle. This results in an almost opaque column density with a total decay rate of 1011 per second. The beta electrons are guided adiabatically to a tandem of a pre- and a main spectrometer by superconducting magnets of up to 6 T. Along the way, differential and cryogenic pumping sections including geometric chicanes reduce the tritium flow by more than 14 orders of magnitude to keep the spectrometers free of tritium (figure 2).

    6
    Fig. 2. The 70 m-long KATRIN setup showing the key stages and components. Credit: CERN

    The KATRIN spectrometers operate as so-called MAC-E filters, whereby electrons are guided by two superconducting solenoids at either end and their momenta are collimated by the magnetic field gradient. This “magnetic bottle” effect transforms almost all kinetic energy into longitudinal energy, which is filtered by an electrostatic retardation potential so that only electrons with enough energy to overcome the barrier are able to pass through. The smaller pre-spectrometer blocks the low-energy part of the beta spectrum (which carries no information on the neutrino mass), while the 10 m-diameter main spectrometer provides a much sharper filter width due to its huge size.

    The transmitted electrons are detected by a high-resolution segmented silicon detector. By varying the retarding potential of the main spectrometer, a narrow region of the beta spectrum of several tens of eV below the endpoint is scanned, where the imprint of a non-zero neutrino mass is maximal. Since the relative fraction of the tritium beta spectrum in the last 1 eV below the endpoints amounts to just 2 × 10–13, KATRIN demands a tritium source of the highest intensity. Of equal importance is the high precision needed to understand the measured beta spectrum. Therefore, KATRIN possesses a complex calibration and monitoring system to determine all systematics with the highest precision in situ, e.g. the source strength, the inelastic scattering of beta electrons in the tritium source, the retardation voltage and the work functions of the tritium source and the main spectrometer.

    Start-up and beyond

    After intense periods of commissioning during 2018, the tritium source activity was increased from its initial value of 0.5 GBq (which was used for the inauguration measurements) to 25 GBq (approximately 22% of nominal activity) in spring 2019. By April, the first KATRIN science run had begun and everything went like clockwork. The decisive source parameters – temperature, inlet pressure and tritium content – allowed excellent data to be taken, and the collaboration worked in several independent teams to analyse these data. The critical systematic uncertainties were determined both by Monte Carlo propagation and with the covariance-matrix method, and the analyses were also blinded so as not to generate bias. The excitement during the un-blinding process was huge within the KATRIN collaboration, which gathered for this special event, and relief spread when the result became known. The neutrino-mass square turned out to be compatible with zero within its uncertainty budget. The model fits the data very well (figure 3) and the fitted endpoint turned out to be compatible with the mass difference between 3He and tritium measured in Penning traps. The new results were presented at the international TAUP 2019 conference in Toyama, Japan, and have recently been published.

    7
    Fig. 3. The beta-electron spectrum in the vicinity of its endpoint with 50 times enlarged error bars and a best-fit model (top) and fit residuals (bottom). Credit: CERN

    This first result shows that all aspects of the KATRIN experiment, from hardware to data-acquisition to analysis, works as expected. The statistical uncertainty of the first KATRIN result is already smaller by a factor of two compared to previous experiments and systematic uncertainties have gone down by a factor of six. A neutrino mass was not yet extracted with these first four weeks of data, but an upper limit for the neutrino mass of 1.1 eV (90% confidence) can be drawn, catapulting KATRIN directly to the top of the world of direct neutrino-mass experiments. In the mass region around 1 eV, the limit corresponds to the quasi-degenerated neutrino-mass range where the mass splittings implied by neutrino-oscillation experiments are negligible compared to the absolute masses.

    The neutrino-mass result from KATRIN is complementary to results obtained from searches for neutrinoless double beta decay, which are sensitive to the “coherent sum” mββ of all neutrino mass eigenstates contributing to the electron neutrino. Apart from additional phases that can lead to possible cancellations in this sum, the values of the nuclear matrix elements that need to be calculated to connect the neutrino mass mββ with the observable (the half-life) still possess uncertainties of a factor two. Therefore, the result from a direct neutrino-mass determination is more closely connected to results from cosmological data, which give (model-dependent) access to the neutrino-mass sum.

    A sizeable influence

    Currently, KATRIN is taking more data and has already increased the source activity by a factor of four to close to its design value. The background rate is still a challenge. Various measures, such as out-baking and using liquid-nitrogen cooled baffles in front of the getter pumps, have already yielded a background reduction by a factor 10, and more will be implemented in the next few years. For the final KATRIN sensitivity of 0.2 eV (90% confidence) on the absolute neutrino-mass scale, a total of 1000 days of data are required. With this sensitivity KATRIN will either find the neutrino mass or will set a stringent upper limit. The former would confront standard cosmology, while the latter would exclude quasi-degenerate neutrino masses and a sizeable influence of neutrinos on the formation of structure in the universe. This will be augmented by searches for physics beyond the Standard Model, such as for sterile neutrino admixtures with masses from the eV to the keV scale.

    Standard Model of Particle Physics

    Neutrino-oscillation results yield a lower limit for the effective electron-neutrino mass to manifest in direct neutrino-mass experiments of about 10 meV (50 meV) for normal (inverse) mass ordering. Therefore, many plans exist to cover this region in the future. At KATRIN, there is a strong R&D programme to upgrade the MAC-E filter principle from the current integral to a differential read-out, which will allow a factor-of-two improvement in sensitivity on the neutrino mass. New approaches to determine the absolute neutrino-mass scale are also being developed: Project 8, a radio-spectroscopy method to eventually be applied to an atomic tritium source; and the electron-capture experiments ECHo and HOLMES, which intend to deploy large arrays of cryogenic bolometers with the implanted isotope 163Ho. In parallel, the next generation of neutrinoless double beta decay experiments like LEGEND, CUPID or nEXO (as well as future xenon-based dark-matter experiments) aim to cover the full range of inverted neutrino-mass ordering. Finally, refined cosmological data should allow us to probe the same mass region (and beyond) within the next decades, while long-baseline neutrino-oscillation experiments, such as JUNO, DUNE and Hyper-Kamiokande, will probe the neutrino-mass ordering implemented in nature. As a result of this broad programme for the 2020s, the elusive neutrino should finally yield some of its secrets and inner properties beyond mixing.

    See the full article here .


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    Please help promote STEM in your local schools.


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    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    CERN/ATLAS detector

    ALICE

    CERN/ALICE Detector


    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN map

    CERN LHC Grand Tunnel

    CERN LHC particles

     
  • richardmitnick 3:46 pm on January 9, 2020 Permalink | Reply
    Tags: , , , , Neutrinos, , ,   

    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 .


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

    Please help promote STEM in your local schools.


    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
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