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  • 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 .

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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 11:55 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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    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 .


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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 11:14 am on January 8, 2020 Permalink | Reply
    Tags: "IceCube rules out last Standard Model explanation of ANITA’s anomalous neutrino events", ANITA (the ANtarctic Impulsive Transient Antenna) experiment, , , , , Neutrinos, ,   

    From U Wisconsin IceCube Collaboration: “IceCube rules out last Standard Model explanation of ANITA’s anomalous neutrino events” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From From U Wisconsin IceCube Collaboration

    08 Jan 2020
    Madeleine O’Keefe


    Playlist: IceCube explained


    Playlist: Neutrinos from blazar TXS 0506+056

    The IceCube Neutrino Observatory is possibly the strangest telescope on Earth. From its home at the South Pole, it sits and waits for fundamental particles called neutrinos to pass through its 5,160 optical detectors buried in the ice. When a neutrino interacts with a hydrogen or oxygen atom in the ice, it produces a signal that IceCube can detect.

    But IceCube isn’t the only neutrino experiment in Antarctica. There is also the ANITA (the ANtarctic Impulsive Transient Antenna) experiment, which flies a balloon over the continent and points radio antennae toward the ground.

    2
    ANtarctic Impulsive Transient Antenna https://www.phys.hawaii.edu/~anita/

    ANITA searches for radio waves because extremely high-energy neutrinos—those hundreds of times more energetic than the ones that IceCube commonly detects—can produce intense radio signals when they smash into an atom in the ice.

    From its balloon flights, ANITA claimed to have detected a few events that appear to be signals of these extremely high-energy neutrinos, so the IceCube Collaboration decided to investigate. In a paper submitted today to The Astrophysical Journal, they outline their search for an intense neutrino source in the direction of the events detected by ANITA. The collaboration found that these neutrinos could not have come from an intense point source. Other explanations for the anomalous signals—possibly involving exotic physics—need to be considered.

    3
    Using the limits they set in this search (blue), IceCube researchers constrained the number of neutrinos that could pass through IceCube undetected (purple curve). They found that the limit on the flux corresponding to this number (purple triangle) was well below what is needed to explain ANITA’s observations (black hexagon). Credit: IceCube Collaboration

    When ANITA reported signals that looked like extremely high-energy neutrinos, physicists were puzzled. These neutrinos had arrived at an angle that suggested they had just traveled through most of the planet, which is not expected for neutrinos at these energies.

    “It’s commonly said that neutrinos are ‘elusive’ or ‘ghostly’ particles because of their remarkable ability to pass through material without smashing into something,” says Alex Pizzuto of the University of Wisconsin–Madison, one of the leads on this paper. “But at these incredible energies, neutrinos are like bulls in a china shop—they become much more likely to interact with particles in Earth.”

    Many scientists have since come up with potential explanations for these weird signals, and one possibility is that a really intense neutrino source produced them. After all, if a source produced huge numbers of neutrinos, it is more plausible that one or two made it to ANITA.

    So Pizzuto and his collaborators decided to see whether there was an intense neutrino source shooting a beam of neutrinos toward Earth—a point source. To do this, the researchers took eight years of IceCube data and looked for correlations between the locations of the ANITA events and the locations of the IceCube events.

    Since the researchers could not know how long a potential point source might have been emitting neutrinos, their analyses used three different and complementary approaches equipped to find coincidences on different timescales. Their analyses also had to account for uncertainty in the ANITA events’ directions because the events do not have definite positions on the sky.

    In all three searches, they found no evidence for a neutrino source in the direction of the strange ANITA events. This is particularly intriguing because, due to a process called tau neutrino regeneration, the extremely high-energy events that don’t make it all the way to ANITA should still be detectable by IceCube.

    “This process makes IceCube a remarkable tool to follow up the ANITA observations, because for each anomalous event that ANITA detects, IceCube should have detected many, many more—which, in these cases, we didn’t,” says Anastasia Barbano of the University of Geneva in Switzerland, another lead on this paper. “That means that we can rule out the idea that these events came from some intense point source, because the odds of ANITA seeing an event and IceCube not seeing anything are so slim.”

    When the ANITA events were detected, the main hypotheses were an astrophysical explanation (like an intense neutrino source), a systematics error (like not accounting for something in the detector), or physics beyond the Standard Model. “Our analysis ruled out the only remaining Standard Model astrophysical explanation of the anomalous ANITA events,” says Pizzuto. “So now, if these events are real and not just due to oddities in the detector, then they could be pointing to physics beyond the Standard Model.”

    Ibrahim Safa of UW–Madison, another lead on this paper, says that while it has been an exciting time for physicists trying to explain these events, “it looks like we’ll have to wait for the next generation of experiments, which will increase exposure and sensitivity, to get a clear understanding of this anomaly.”

    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 4:58 pm on December 4, 2019 Permalink | Reply
    Tags: "Locally sourced neutrinos? IceCube takes a look", , Neutrinos, , The “local universe” is defined as the volume of space surrounding the Milky Way in which most galaxies are visible to our telescopes—extending up to 300 million light-years away from us., The IceCube Neutrino Observatory detected an astrophysical neutrino—a high-energy particle from outer space—from a flaring blazar approximately 5 billion light-years away.,   

    From U Wisconsin IceCube Collaboration: “Locally sourced neutrinos? IceCube takes a look” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From From U Wisconsin IceCube Collaboration

    03 Dec 2019
    Madeleine O’Keefe


    IceCube explained

    Neutrinos from blazar

    What does “local” mean to you? Maybe your local coffee shop is around the corner from your office. Maybe your local pharmacy is a 15-minute walk from your home. But on the scale of the cosmos, the definition of local is stretched, to say the least. In fact, the “local universe” is defined as the volume of space surrounding the Milky Way in which most galaxies are visible to our telescopes—extending up to 300 million light-years away from us.

    When it comes to analyses done by the IceCube Collaboration, this is local indeed. After all, the IceCube Neutrino Observatory detected an astrophysical neutrino—a high-energy particle from outer space—from a flaring blazar approximately 5 billion light-years away. That source, called TXS 0506+056, is still the only confirmed source of astrophysical neutrinos, but it certainly does not explain all of the astrophysical neutrinos we see.

    IceCube has not yet found neutrino sources within our galaxy, but there may be sources that are not too much farther out. To test this possibility, the IceCube Collaboration recently performed an analysis scouring the local universe for potential neutrino sources. They conducted two different searches that looked for correlations between neutrino emission and dense regions in a catalog of galaxies called the 2MASS Redshift Survey (2MRS). While they did not find significant sources, they were able to put constraints on neutrino emission from nearby galaxies, which they present in a paper recently submitted to the Journal of Cosmology and Astroparticle Physics.

    2
    New limits as a result of this search, shown in two ways. Left: the limit on total flux as a function of the energy spectrum (results of the template analysis). Right: the limit on density of sources as a function of source luminosity (results of the multiplets analysis). Credit: IceCube Collaboration

    Neutrinos are tricky. They are fundamental particles but have no charge and interact very weakly, which means they can fly through light-years of matter without giving any hint that they have passed. The IceCube Neutrino Observatory was built to try and “catch” them. Embedded in the South Pole ice are over 5,000 optical modules that will light up when triggered by a flash of radiation caused by a neutrino decaying into another particle. If the neutrino decays into a particle called a muon, that muon may trigger multiple optical modules, leaving a trail of signals that scientists can trace toward the neutrino’s source—whatever that is.

    While IceCube analyses typically focus on looking to see if neutrinos originate from a few bright, intense, and faraway objects (like blazars), some researchers decided to look at the local universe, including Steve Sclafani of Drexel University in Philadelphia, PA. “We have one advantage when focused on the local universe: At the closest distances, large-scale structures—like superclusters, the supergalactic plane, filamentary structure, and local voids—exist,” he says.

    This paper describes two analyses that searched for excess neutrinos correlated with local large-scale structures. Each search tested a different hypothesis about how the neutrinos were emitted. The “template analysis” created an all-sky template of the local galaxy density to test whether the matter of the local universe was acting as a target, where ultra-high-energy cosmic rays would interact and produce neutrinos. The “multiplet analysis” tested the hypothesis that clusters of neutrinos called “multiplets” are generated by neutrino sources within the local universe.

    “The motivation for this analysis is rather simple: After 10 years of detecting astrophysical neutrinos, we would like to figure out their origin,” says Étienne Bourbeau of the Niels Bohr Institute in Copenhagen, Denmark, who led the multiplet search.

    The simplest explanation, he says, is that neutrinos are produced by astronomical objects made up of normal matter. “If that’s true, then you would expect neutrinos to come from the places in the sky where there is the most stuff,” he says.

    To find where the most “stuff” is in the universe, researchers can use catalogs of galaxies established by other astronomical observatories—here, the 2MRS survey. Their goal was to see whether neutrinos detected by IceCube correlated with our best estimate of matter density in the local universe. Galaxies are not uniformly distributed in our local universe, so if neutrinos really do come from the galaxies mapped by 2MRS, there should be more neutrino clusters from specific regions in the sky.

    First, they defined the IceCube neutrino emission using an existing IceCube analysis, the seven-year point source search.

    3
    Template analysis’s map of local galaxy density from 2MRS. Credit: IceCube Collaboration

    For the template analysis, Sclafani and his collaborators took the 2MRS infrared catalog, weighted each galaxy, and created a template of the sky. Next, they looked for any correlation between our neutrino sky and the 2MRS sky—in other words, a correlation between neutrino emission and the large-scale features.

    Meanwhile, for the multiplet analysis, Bourbeau and his collaborators used 2MRS in a slightly different way. They tested whether the incidence of neutrino clusters in IceCube correlates significantly with the density of galaxies observed in the 2MRS catalog. They used a previously published analysis of neutrino clustering from the seven-year sample, then compared the distribution of these clusters to 10,000 random distributions of the same number of multiplets.

    4
    Normalized distribution of a selection of galaxies, taken from the 2MRS catalog (top), and location of selected multiplets, where each yellow dot represents the location of a local maximum from the seven-year point source map (bottom). Credit: IceCube Collaboration

    Ultimately, neither analysis found any significant correlation between astrophysical neutrinos or multiplets and the galaxies of the 2MRS catalog. Based on that, however, the researchers were able to put boundaries on the density and average luminosity of any hypothetical population of neutrino sources located within our local universe.

    “Although this work didn’t turn anything up, it established methods for this kind of search, and as new all-sky surveys arrive we can revisit this analysis and see if we are able to detect local galaxy neutrinos,” says Sclafani. “Even though we have one source, there is still a push to explain where all our astrophysical neutrinos are coming from.”

    Of course, Bourbeau points out, it could be possible that neutrino sources are much farther out in space. After all, TXS 0506+056 is 5 billion light-years away. Wherever the sources are, IceCube will keep looking.

    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 2:04 pm on December 1, 2019 Permalink | Reply
    Tags: "NA61/SHINE gives neutrino experiments a helping hand", , , , , Neutrinos,   

    From CERN: “NA61/SHINE gives neutrino experiments a helping hand” 

    Cern New Bloc

    Cern New Particle Event


    From CERN

    How particle measurements made by the NA61/SHINE experiment at CERN are helping neutrino experiments in the US and Japan

    1
    Inside the NA61/SHINE experiment at CERN (Image: CERN)

    Neutrinos are the lightest of all the known particles that have mass. Yet their behaviour as they travel could help answer one of the greatest puzzles in physics: why the present-day universe is made mostly of matter when the Big Bang should have produced equal amounts of matter and antimatter. In two recent papers, the NA61/SHINE collaboration reports particle measurements that are crucial for accelerator-based experiments studying such neutrino behaviour.

    Neutrinos come in three types, or “flavours”, and neutrino experiments are measuring with ever increasing detail how they and their antimatter counterparts, antineutrinos, “oscillate” from one flavour to another while they travel. If it turns out that neutrinos and antineutrinos oscillate in a different way from one another, this may partially account for the present-day matter–antimatter imbalance.

    Accelerator-based neutrino experiments look for neutrino oscillations by producing a beam of neutrinos of one flavour and measuring the beam after it has travelled a long distance. The neutrino beams are typically produced by firing a beam of high-energy protons into long, thin carbon or beryllium targets. These proton–target interactions produce hadrons, such as pions and kaons, which are focused using magnetic aluminium horns and directed into long tunnels, in which they transform into neutrinos and other particles.

    To get a reliable measurement of the neutrino oscillations, the researchers working on these experiments need to estimate the number of neutrinos in the beam before oscillation and how this number varies with the energy of the particles. Estimating this “neutrino flux” is hard, because neutrinos interact very weakly with other particles and cannot be measured easily. To get around this, researchers estimate instead the number of hadrons. But measuring the number of hadrons is also challenging, because there are too many of them to measure precisely.

    This is where experiments such as NA61/SHINE at CERN’s Super Proton Synchrotron come in. NA61/SHINE can reproduce the proton–target interactions that generate the hadrons that transform into neutrinos. It can also reproduce subsequent interactions that protons and hadrons undergo in the targets and focusing horns. These subsequent interactions can produce additional neutrino-yielding hadrons.

    The NA61/SHINE collaboration has previously measured hadrons generated in experiments at 31 GeV/c proton energy (where c is the speed of light) to help predict the neutrino flux in the Tokai-to-Kamioka (T2K) neutrino-oscillation experiment in Japan. The collaboration has also been gathering data at 60 and 120 GeV/c energies to benefit the MINERνA, NOνA and DUNE experiments at Fermilab in the US. The analysis of these datasets is progressing well and has most recently led to two papers: one describing measurements of interactions of protons with carbon, beryllium and aluminium, and another reporting measurements of interactions of pions with carbon and beryllium.

    “These results are crucial for Fermilab’s neutrino experiments,” says Laura Fields, an NA61/SHINE collaboration member and co-spokesperson for MINERνA. “To predict the neutrino fluxes for these experiments, researchers need an extremely detailed simulation of the entire beamline and all of the interactions that happen within it. For that simulation we need to know the probability that each type of interaction will happen, the particles that will be produced, and their properties. So interaction measurements such as the latest ones will be vital to make these simulations much more accurate,” she explains.

    “Looking into the future, NA61/SHINE will focus on measurements for the next generation of neutrino-oscillation experiments, including DUNE and T2HK in Japan, to enable these experiments to produce high-precision results in neutrino physics,” Fields concludes.

    See also this Experimental Physics newsletter article.

    See the full article here.


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

    Stem Education Coalition

    Meet CERN in a variety of places:

    Quantum Diaries
    QuantumDiaries

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    CERN ATLAS Image Claudia Marcelloni CERN/ATLAS


    ALICE

    CERN/ALICE Detector


    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN map

    CERN LHC Tunnel

    CERN LHC particles

     
  • richardmitnick 12:52 pm on November 20, 2019 Permalink | Reply
    Tags: JUNO, Neutrinos, , Putting neutrino masses in their place (soon!) with the IceCube Upgrade and JUNO,   

    From U Wisconsin IceCube Collaboration: “Putting neutrino masses in their place (soon!) with the IceCube Upgrade and JUNO” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From From U Wisconsin IceCube Collaboration

    18 Nov 2019
    Madeleine O’Keefe

    If you are asked to find the weight of an everyday object like a book or coffee mug, you can simply weigh it on a scale. But when the object is very, very light—like a particle—measuring mass gets very tricky. And when you get to particles as light as neutrinos, the difficulty in measuring their mass is a huge problem. Solving it could alter the way we understand nature.

    Neutrinos are chargeless, fundamental particles that are abundant in the universe. They interact in three varieties, known as flavors. Perhaps confusingly, they travel as states of three different masses that don’t exactly correlate with these flavors, called neutrinos 1, 2, and 3. As a result, neutrinos can change, or oscillate, from one flavor to another depending on their energy and distance from their source.

    But physicists don’t know which mass state is the heaviest. Either neutrino 3 is heavier than neutrinos 1 and 2, known as the “normal ordering” of neutrino masses, or neutrino 3 is lighter than the other two, known as “inverted ordering.” Which is correct represents the current question of neutrino mass ordering, one of the biggest outstanding problems in neutrino physics today.

    With two new neutrino experiments on the horizon—the IceCube Upgrade and the Jiangmen Underground Neutrino Observatory (JUNO)—physicists will soon have access to more sensitive measurements of neutrino oscillations. In anticipation of this, the IceCube Collaboration and the JUNO Collaboration have studied the combined performance of their respective experiments, which employ very distinct and complementary routes in order to resolve the neutrino mass ordering. In a paper submitted recently to Physical Review D, they show that a combined analysis could eliminate the wrong mass ordering in as few as three years from the start of data taking.

    1
    Expected duration of data taking required for the IceCube Upgrade and the 8-reactor configuration of JUNO to rule out the wrong neutrino mass ordering. Time is shown as a function of the two most important parameters that affect the measurement. The yellow square marks the researchers’ nominal assumption. Credit: IceCube Collaboration

    The IceCube Upgrade is an extension of the IceCube Neutrino Observatory, an array of over 5,000 optical modules buried in a cubic kilometer of ice at the South Pole. The Upgrade, scheduled to deploy during the 2022-2023 polar season, will insert more than 700 new optical modules into DeepCore, the center of the IceCube array, enabling higher sensitivity to neutrinos with low energies produced in the atmosphere.

    Meanwhile, JUNO is a 20-kiloton liquid scintillator detector currently under construction near Jiangmen in southern China. Though the nominal assumption is that JUNO will measure neutrinos from 10 nuclear reactor cores, there may only be eight running when they anticipate starting to take data in 2021. This was taken into consideration for this analysis.

    The study was conducted by researchers at Johannes Gutenberg-Universität Mainz in Germany, including PhD students Jan Weldert and Thomas Ehrhardt. “We wanted to find out whether the power of the phenomenological mass ordering sensitivity study by Blennow and Schwetz carried over to a realistic modeling of JUNO and IceCube and investigate which role the imminent IceCube Upgrade will play in the analysis,” says Weldert.

    To combine JUNO and the IceCube Upgrade, the researchers first assumed that each experiment had run for a certain amount of time, then simulated the predicted experimental outcomes. These outcomes vary depending on whether the neutrino masses follow normal ordering or inverted ordering. Next, they performed a statistical test that told them how much more likely it would be for both outcomes to occur simultaneously as the result of normal or inverted ordering. Since JUNO and IceCube are highly sensitive to very different manifestations of neutrino oscillation, their test had strong discrimination power.

    They found that combining results from JUNO and the IceCube Upgrade could definitively rule out the wrong mass ordering—as in, the mass ordering that is not true in nature—on a timescale of three to seven years.

    “The holy grail for the neutrino mass ordering would be to reject the wrong hypothesis with a 5σ result. Neither the Upgrade nor JUNO can reach that by themselves—nor can any of the other experiments currently out there,” says Sebastian Böser, a professor of physics at Universität Mainz who helped lead the study. “But if we combine JUNO and the IceCube Upgrade, 5σ might be there already in 2026, with three years of data from each.”

    Even if JUNO was only operating on eight reactor cores instead of 10, the researchers found they could reject the wrong mass ordering with the coveted 5σ after about 3.5 or 5.5 years, assuming normal ordering or inverted ordering, respectively.

    The researchers also studied a combined analysis with JUNO and PINGU, a proposed low-energy extension of IceCube that takes the concept of the Upgrade even further. They showed that this combination would only need half the time to determine the mass ordering.

    “Our results underline the importance of pursuing complementary experimental approaches toward solving the remaining riddles posed by neutrinos,” says Ehrhardt. “Their mass ordering is particularly elusive and has certainly been keeping us on our toes.”

    The obvious next step is to turn this into a real analysis, not just a simulation study. But first things first: both JUNO and the Upgrade must be built and take some data. Then, the two collaborations can work together so that the exciting potential of this combined measurement can be realized.

    But if it can all come together, there may be exciting results in the future. “IceCube can play an important role for the neutrino mass ordering discovery,” says Weldert.

    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 10:27 am on November 19, 2019 Permalink | Reply
    Tags: "A new view into the history of the universe", , Neutrinos, ,   

    From Symmetry: “A new view into the history of the universe” 

    Symmetry Mag
    From Symmetry<

    11/19/19

    Diana Kwon

    With an upgrade to the Super-Kamiokande detector, neutrino physicists will gain access to the supernovae of the past.

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

    In 1987, the explosion of a gigantic star created a brilliant light show within the Large Magellanic Cloud, a small, satellite galaxy orbiting the Milky Way. The cataclysmic event, also known as a supernova, was visible from telescopes on Earth.

    Large Magellanic Cloud. Adrian Pingstone December 2003

    This is an artist’s impression of the SN 1987A remnant. The image is based on real data and reveals the cold, inner regions of the remnant, in red, where tremendous amounts of dust were detected and imaged by ALMA. This inner region is contrasted with the outer shell, lacy white and blue circles, where the blast wave from the supernova is colliding with the envelope of gas ejected from the star prior to its powerful detonation. Image credit: ALMA / ESO / NAOJ / NRAO / Alexandra Angelich, NRAO / AUI / NSF.

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    But before the light from the stellar blast reached our planet, three observatories, including the Kamiokande neutrino observatory in Japan, picked up signals from another type of particle produced in the blast: neutrinos.

    Neutrino particles, though elusive, carry away almost all of the energy released by these exploding stars. By examining them, physicists can better understand the properties of neutrinos and probe the inner workings of supernovae.

    “There’s really no way to look inside the heart of a dying star except via neutrinos,” says Mark Vagins, an experimental physicist at University of Tokyo’s Kavli Institute for the Physics and Mathematics of the Universe.

    For the last three decades, physicists have patiently waited for the next nearby supernova. Luckily, waiting is no longer the only option.

    The successor to Kamiokande, called Super-Kamiokande, is about to get an upgrade. Adding the rare earth element gadolinium to Super-K will allow scientists to search for neutrinos not only from future supernovae, but also from stellar explosions in our universe’s history.

    “Every few seconds, a supernova happens somewhere in the universe, and they are all producing neutrinos,” says Masayuki Nakahata, the spokesperson for Super-K. “By using this new technology, we will be able to detect those neutrinos.”

    Separating signal from noise

    The Super-K observatory lies under Mount Ikeno, in a mine 3300 feet below the ground in central Japan. The detector is encased within a cylindrical stainless-steel tank as tall as the Statue of Liberty. Its interior is filled with 50,000 tons of ultra-pure water and lined with approximately 13,000 photosensors—golden bulbs that detect the flashes of light produced as neutrinos pass through.

    In the early 2000s, the Super-K collaboration tried to detect neutrinos from past supernovae, which are collectively known as the diffuse supernova neutrino background. In theory, Super-K was large enough to find these particles. But the signal was being concealed by “background noise” produced by other processes.

    Neutrinos come in three different “flavours”: electron neutrino, muon neutrino and tau neutrino. Supernovae release both neutrinos and their antimatter counterparts, antineutrinos, in various flavors, but the ones that most commonly interact within detectors like Super-K are electron antineutrinos. When one these particles comes in contact with hydrogen molecules in the Super-K detector, it releases a positron, along with another particle. This process creates a flash of light that Super-K’s sensors can identify.

    The problem is, a number of other particles—including the electron neutrinos that constantly stream from the sun and pass through Super-K far more often than electron antineutrinos from supernovae—produce the same signal.

    While at a neutrino conference in Munich in 2002, Vagins and his colleague John Beacom, a theoretical physicist now at the Ohio State University, came up with a solution to this problem. “John and I decided that there had to be a way to see these darn things,” Vagins says. “We talked about many different approaches and pretty quickly realized that we were going to have to use gadolinium.”

    The duo realized that gadolinium, a rare earth metal, would be a valuable addition to Super-K due to a certain property. Gadolinium is uniquely effective at gobbling up the other kind of particle an electron antineutrino produces when it hits the purified water in Super-K detector: a neutron.

    If gadolinium were added to the Super-K detector, it would interact with a neutron released by an electron antineutrino to generate a second pulse of light.

    Dual light flashes, which Vagins and Beacom have dubbed “gadolinium heartbeats,” would come only from electron antineutrinos—they would not be produced by electron neutrinos from the sun or in interactions with other particles that until now have obscured the detection of supernova electron antineutrinos.

    “We expect the background to be reduced by a factor 10,000,” Vagins says. “It’s a tremendous gain.”

    Convincing the crowd

    When Beacom and Vagins initially pitched the idea of adding gadolinium to Super-K to the collaboration, it was not greeted with the level of enthusiasm they expected. Their colleagues were impressed by the capability of this technique, but they worried that gadolinium could harm the multi-million-dollar detector.

    Researchers worried that gadolinium might corrode the steel, alter the transparency of the water, or introduce radioactivity into the detector. “There was a huge list of issues, and we had to go through those one at a time and show that no, it was not a problem,” Vagins says.

    There were also other challenges to overcome, such as figuring out how to dissolve the gadolinium into the water. This doesn’t happen naturally. (The answer: Combine it with sulfate to make gadolinium sulfate, a salt.)

    To test the feasibly of their plan, Super-K scientists built a miniature version of the detector called Evaluating Gadolinium’s Action on Detector Systems, or EGADS. This scaled-down version of the detector was lined with 240 photosensors and had room for 200 tons of water. The team filled the prototype tank with gadolinium-loaded ultrapure water, then left it closed for around two-and-a-half years while running tests to assess the detector’s capabilities.

    Meanwhile, Beacom and his team have been gearing up for the forthcoming upgrade by conducting theoretical assessments, such as examining the details of the background signals within the gadolinium-loaded detector and the signals that can be seen within it.

    The Super-K collaboration approved the gadolinium upgrade in June 2015. But the final test came in 2017, when a group of scientists, including Vagins, donned protective bunny suits (as human skin is highly radioactive, at least in comparison to ultrapure water) and opened EGADS up to assess whether there were any signs of damage.

    “That was a pretty nervous moment,” Vagins recalls. “But when we opened up, everything was still shiny and pretty. That was pretty much the final selling point for everybody.”

    Upgrading the detector

    The Super-K collaboration will start loading the detector with gadolinium next spring. They plan to start at 0.01% gadolinium and gradually add more. At a concentration of 0.01%, gadolinium will already be able to capture around half of the neutrons that appear in the detector.

    3
    Illustration by Sandbox Studio, Chicago with Steve Shanabruch

    To prepare for the addition of gadolinium, last year, scientists opened up Super-K for the first time in 12 years to do some repairs. This included replacing broken phototubes, adding new piping, cleaning the interior, and sealing a leak. Since it first started running, Super-K has been losing around 1 ton of water per day, Nakahata says. This was not a problem when the tank was filled with water. Now that gadolinium is being added, however, they will need to make sure the liquid does not seep into the environment.

    Gadolinium poses about the same health risk as table salt, Vagins says. “A typical individual would have to directly consume ounces of gadolinium to have problems, and since at full loading the water in Super-K will be just 0.1% gadolinium, one could drink a gallon a day right out of the tank without trouble,” he says. “Even though gadolinium is relatively harmless, we don’t want to potentially be leaking that into the mountain range or the community.”

    Gadolinium-loaded Super-K will search for neutrinos from all past supernovae in the universe at once. Each supernova makes a tremendous number of neutrinos, but the chances of detecting one from supernovae outside the Milky Way are tiny, Beacom explains. But by looking at the entire diffuse supernova neutrino background, it’ll be possible to identity around two to six neutrinos per year.

    Those neutrinos will allow physicists to address some of the many unsolved mysteries about supernovae. For example, by making it possible to examine neutrinos from supernovae throughout our universe’s history, the upgraded detector will help scientists better identify the characteristics of a typical stellar explosion.

    Gadolinium will also make Super-K much more sensitive to proton decay—a phenomena which has yet to be observed—and better able to separate neutrinos from antineutrinos.

    “I think the gadolinium loading of Super-K is a very exciting development,” says André de Gouvêa, a theoretical particle physicist at Northwestern University who is not involved with the upgrade. “I am confident we will learn something interesting about the history of the universe, supernova explosions, and the properties of neutrinos.”

    Eventually, Vagins hopes the Hyper-Kamiokande collaboration—which in 2018 was granted seed funding toward the construction of a successor to Super-K that will hold a whopping 260,000 tons of water—will also add gadolinium to its detector.

    In the meantime, there are already a number of other detectors that are planning to use gadolinium in a similar way. These include the XENONnT experiment at Gran Sasso National Laboratory in Italy, which searches for dark matter particles, and the Water Cherenkov Monitor of Antineutrinos (WATCHMEN), a US- and UK-funded experiment based in UK’s Boulby mine that will test the feasibility of identifying nuclear reactors by monitoring the telltale antineutrinos they produce.

    XENON1T at Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy

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

    Vagins expects to see even more enthusiasm for gadolinium once Super-K scientists prove its worth. “I think once we’re running Super-K with gadolinium, and people get used to the physics advantages, it’ll be hard to stop future experiments from doing it,” he says.

    See the full article here .


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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 10:42 am on November 14, 2019 Permalink | Reply
    Tags: "What can cascade events tell us about neutrino sources?", , Neutrinos, ,   

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

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From From U Wisconsin IceCube Collaboration

    13 Nov 2019
    Madeleine O’Keefe

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

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

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

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

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

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

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

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

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

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

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

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

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

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

    See the full article here .

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

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

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

     
  • richardmitnick 5:31 pm on November 7, 2019 Permalink | Reply
    Tags: , , Neutrinos, Neutrinos and antineutrinos, ,   

    From Fermi National Accelerator Lab: “Gotta catch ’em all: new NOvA results with neutrinos and antineutrinos” 

    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.

    November 7, 2019
    Steven Calvez
    Erika Catano Mur

    The latest results from the Fermilab NOvA experiment are taking us closer to describing the most basic properties of the mysterious neutrino — the most abundant particle of matter in the universe.

    Neutrinos appear in a variety of natural processes, from formidable supernova explosions and nuclear reactions in the sun to radioactive decays in your banana. They are also produced in abundance in nuclear reactors and particle accelerators. Yet neutrinos barely interact with matter: a light-year of lead would hardly stop your average neutrino. Their elusive nature makes them extremely challenging to study, which explains both why we still know very little about their properties and why many scientists and experiments around the world have so much fun hunting them down.

    The observation that neutrinos are able to change type — a behavior called oscillation — proved that neutrinos have masses, albeit very small. This phenomenon explains how neutrinos that are produced in one of the three “flavor” states (electron neutrino, muon neutrino or tau neutrino) transition in and out of these types as they travel a certain distance and may be detected as a different type. The probability of these transitions depends on a number of factors: the energy of the neutrino, the distance between the particle beam source and the detector, the differences in neutrino masses, the amount of blending between neutrino types, which scientists describe with three “mixing” angles, and additional complex phases.

    1
    Fermilab’s NOvA neutrino experiment studies neutrino oscillations using a powerful neutrino beam produced by the lab’s accelerator complex. The beam, made of muon neutrinos, is sent to NOvA’s two detectors — one located at Fermilab and one located about 800 kilometers away in Minnesota, pictured here.

    Fermilab’s NOvA neutrino experiment studies neutrino oscillations using the powerful NuMI neutrino beam produced by the lab’s accelerator complex. The beam, made of muon neutrinos, is sent to NOvA’s two detectors — one located at Fermilab and one located about 800 kilometers away in Minnesota. The NOvA far detector looks to identify the fraction of muon neutrinos in the NuMI beam that oscillated into electron neutrinos (called electron neutrino appearance) and the fraction of muon neutrinos that oscillated to a different flavor (called muon neutrino disappearance).

    The NuMI beam is generally described as a muon neutrino beam, but it can also be made of muon antineutrinos. The antineutrino is the antiparticle of the neutrino. Just as muon neutrinos can oscillate into electron neutrinos, muon antineutrinos can oscillate into electron antineutrinos.

    Experimentalists can use information from the combination of the measurements of electron and muon neutrinos, as well as their antiparticle equivalents, to draw their conclusions. For example, if the oscillation rates of antineutrinos compared to those of neutrinos are different, the implication could be a violation of a symmetry called charge parity, commonly called CP. The existence of this type of CP violation is one of the great unknowns in particle physics that NOvA is investigating.

    NOvA’s latest measurements of neutrino oscillation parameters have been published in Physical Review Letters. The data were recorded between 2014 and 2019 and correspond to 8.85 x 1020 protons-on-target of neutrino beam and 12.33 x 1020 protons-on-target of antineutrino beam. This represents a 78% increase in the amount of antineutrino data compared to NOvA’s previous results, presented at the Neutrino 2018 conference.

    NOvA identified 27 electron antineutrino candidate events in the NOvA far detector, compared to the 10.3 events expected if muon antineutrinos did not oscillate into electron antineutrinos. This remains the strongest evidence (4.4 sigma) of electron antineutrino appearance in a muon antineutrino beam for a long-baseline experiment. (In particle physics, 3 sigma is usually considered “strong evidence” that the conclusions of the data analysis are unlikely to be a fluke, while 5 sigma means that the experimental results qualify as a discovery.)

    In addition to those 27 electron antineutrino events, 102 surviving muon antineutrino candidates were detected in the far detector, where 476 events would have been expected if muon antineutrinos did not oscillate at all. NOvA scientists combined these new events with previously recorded neutrino data and analyzed them jointly. Pictures of such neutrino and antineutrino events as recorded by the NOvA far detector are shown below.

    3
    Four events observed in the NOvA far detector, classified as muon (left) or electron (right) neutrino interactions, with the beam in neutrino (top) or antineutrino (bottom) mode. Each panel shows two views of the same event, and the color represents the energy deposited by particles that emerged from the interaction. The latest NOvA results comprise four data samples with 113 muon neutrino to muon neutrino, 58 muon neutrino to electron neutrino, 102 muon antineutrino to muon antineutrino and 27 muon antineutrino to electron antineutrino candidates.

    The results help scientists chip away another problem in neutrino physics: the ordering of the three neutrino masses — which of the three is the lightest? NOvA’s combined neutrino-antineutrino appearance and disappearance fit shows a preference (1.9 sigma) for what is called normal mass ordering: The three neutrino mass states are ordered m1 ≤ m2 ≤ m3.

    NOvA is also working to measure one of the least known oscillation parameters, θ23, that governs the degree of flavor mixing in the third mass state. The fit shows a slight preference (1.6 sigma) for the value of this angle to be in the upper octant (θ23 > 45 degrees) and therefore points towards an absence of symmetry in the way muon and tau neutrino flavors contribute to the third neutrino mass state. The data recorded thus far does not allow us to draw conclusions about CP violation in neutrino interactions.

    The experiment is scheduled to collect new data until 2025. NOvA collaborators are continually working to improve the experiment and analysis techniques to potentially provide a definitive statement about the neutrino mass ordering, the value of θ23, and strong constraints on the CP-violating phase. These measurements are paramount if we want to understand the neutrino properties and the role they played in the formation of the universe as we know it.

    This work is supported in part by the DOE Office of Science and the National Science Foundation.

    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.

     
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