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  • richardmitnick 10:27 am on May 12, 2020 Permalink | Reply
    Tags: , , , , , Neutrinoless double beta decay, ,   

    From Lawrence Berkeley National Lab: “Berkeley Lab COVID-19 related research and additional information. News Center CUORE Underground Experiment in Italy Carries on Despite Pandemic” 

    From Lawrence Berkeley National Lab

    May 12, 2020
    Glenn Roberts Jr.
    (510) 520-0843

    Laura Marini, a postdoctoral researcher at UC Berkeley and a Berkeley Lab affiliate who serves as a run coordinator for the underground CUORE experiment, shares her experiences of working on CUORE and living near Gran Sasso during the COVID-19 pandemic. (Credit: Marilyn Sargent/Berkeley Lab)

    Note: This is the first part in a recurring series highlighting Berkeley Lab’s ongoing work in international physics collaborations during the pandemic.

    As the COVID-19 outbreak took hold in Italy, researchers working on a nuclear physics experiment called CUORE at an underground laboratory in central Italy scrambled to keep the ultrasensitive experiment running and launch new tools and rules for remote operations.

    This Cryogenic Underground Observatory for Rare Events experiment – designed to find a never-before-seen process involving ghostly particles known as neutrinos, to explain why matter won out over antimatter in our universe, and to also hunt for signs of mysterious dark matter – is carrying on with its data-taking uninterrupted while some other projects and experiments around the globe have been put on hold.

    Finding evidence for these rare processes requires long periods of data collection – and a lot of patience. CUORE has been collecting data since May 2017, and after upgrade efforts in 2018 and 2019 the experiment has been running continuously.

    Before the pandemic hit there were already tools in place that stabilized the extreme cooling required for CUORE’s detectors and provided some remote controls and monitoring of CUORE systems, noted Yury Kolomensky, senior faculty scientist at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the U.S. spokesperson for CUORE.

    The rapid global spread of the disease, and related restrictions on access to the CUORE experiment at Gran Sasso National Laboratory (Laboratori Nazionali del Gran Sasso, or LNGS, operated by the Italian Nuclear Physics Institute, INFN) in central Italy, prompted CUORE leadership and researchers – working in three continents – to act quickly to ramp up the remote controls to prepare for an extended period with only limited access to the experiment.

    CUORE experiment,at the Italian National Institute for Nuclear Physics’ (INFN’s) Gran Sasso National Laboratories (LNGS) in located in the Abruzzo region of central Italy,a search for neutrinoless double beta decay

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

    Just days before the new restrictions went into effect at Gran Sasso, CUORE leadership on March 4 made the decision to rapidly deploy a new remote system and to work out the details of how to best maintain the experiment with limited staffing and with researchers monitoring in different time zones. The new system was fully operational about a week later, and researchers at Berkeley Lab played a role in rolling it out.

    “We were already planning to transition to remote shift operations, whereby a scientist at a home institution would monitor the systems in real time, respond to alarms, and call on-site and on-call personnel in case an emergency intervention is needed,” Kolomensky said, adding, “We were commissioning the system at the time of the outbreak.”

    Brad Welliver, a postdoctoral researcher, served as Berkeley Lab’s lead developer for the new remote monitoring system, and Berkeley Lab staff scientist Brian Fujikawa was the overall project lead for the enhanced remote controls, collectively known as CORC, for CUORE Online/Offline Run Check.

    Fujikawa tested controls for starting and stopping the data collection process, and also performed other electronics testing for the experiment from his home in the San Francisco Bay Area.

    He noted that the system is programmed to send email and voice alarms to the designated on-shift CUORE researcher if something is awry with any CUORE system. “This alarm system is particularly important when operating CUORE remotely,” he said, as in some cases on-site workers may need to visit the experiment promptly to perform repairs or other needed work.

    Development of so-called “slow controls,” which allow researchers to monitor and control CUORE equipment such as pumps and sensors, was led by Joe Johnston at the Massachusetts Institute of Technology.

    “Now we can perform most of the operations from 6,000 miles away,” Kolomensky said.

    And many participants across the collaboration continue to play meaningful roles in the experiment from their homes, from analyzing data and writing papers to participating in long-term planning and remote meetings.

    Despite access restrictions at Gran Sasso, experiments are still accessible for necessary work and checkups. The laboratory remains open in a limited way, and its staff still maintains all of its needed services and equipment, from shuttles to computing services.

    Laura Marini, a postdoctoral researcher at UC Berkeley who serves as a run coordinator for CUORE and is now living near Gran Sasso, is among a handful of CUORE researchers who still routinely visits the lab site.

    “As a run coordinator, I need to make sure that the experiment works fine and the data quality is good,” she said. “Before the pandemic spread, I was going underground maybe not every day, but at least a few times a week.” Now, it can be about once every two weeks.

    Sometimes she is there to carry out simple fixes, like a stuck computer that needs to be restarted, she said. Now, in addition to the requisite hard hat and heavy shoes, Marini – like so many others around the globe who are continuing to work – must wear a mask and gloves to guard against the spread of COVID-19.

    The simple act of driving into the lab site can be complicated, too, she said. “The other day, I had to go underground and the police stopped me. So I had to fill in a paper to declare why I was going underground, the fact that it was needed, and that I was not just wandering around by car,” she said. Restrictions in Italy prevent most types of travel.

    Laura Marini now wears a protective mask and gloves, in addition to a hard hat, during her visits to the CUORE experiment site. (Credit: Gran Sasso National Laboratory – INFN)

    CUORE researchers note that they are fortunate the experiment was already in a state of steady data-taking when the pandemic hit. “There is no need for continuous intervention,” Marini said. “We can do most of our checks by remote.”

    She said she is grateful to be part of an international team that has “worked together on a common goal and continues to do so” despite the present-day challenges.

    Kolomensky noted some of the regular maintenance and upgrades planned for CUORE will be put off as a result of the shelter-in-place restrictions, though there also appears to be an odd benefit of the reduced activity at the Gran Sasso site. “We see an overall reduction in the detector noise, which we attribute to a significantly lower level of activity at the underground lab and less traffic in the highway tunnel,” he said. Researchers are working to verify this.

    CUORE already had systems in place to individually and remotely monitor data-taking by each of the experiment’s 988 detectors. Benjamin Schmidt, a Berkeley Lab postdoctoral researcher, had even developed software that automatically flags periods of “noisy” or poor data-taking captured by CUORE’s array of detectors.

    Kolomensky noted that work on the CORC remote tools is continuing. “As we have gained more experience and discovered issues, improvements and bug fixes have been implemented, and these efforts are still ongoing,” he said.

    CUORE is supported by the U.S. Department of Energy Office of Science, Italy’s National Institute of Nuclear Physics (Instituto Nazionale di Fisica Nucleare, or INFN), and the National Science Foundation (NSF). CUORE collaboration members include: INFN, University of Bologna, University of Genoa, University of Milano-Bicocca, and Sapienza University in Italy; California Polytechnic State University, San Luis Obispo; Berkeley Lab; Lawrence Livermore National Laboratory; Massachusetts Institute of Technology; University of California, Berkeley; University of California, Los Angeles; University of South Carolina; Virginia Polytechnic Institute and State University; and Yale University in the US; Saclay Nuclear Research Center (CEA) and the Irène Joliot-Curie Laboratory (CNRS/IN2P3, Paris Saclay University) in France; and Fudan University and Shanghai Jiao Tong University in China.

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    In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

    Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

    Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

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  • richardmitnick 11:55 am on January 14, 2020 Permalink | Reply
    Tags: "A voyage to the heart of the neutrino", , , Neutrinoless double beta decay, , , , 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.


    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.

    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.

    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).

    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).

    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.

    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.

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  • richardmitnick 3:31 pm on September 5, 2019 Permalink | Reply
    Tags: , , , , Neutrinoless double beta decay, , ,   

    From Techniche Universitat Munchen: “Closing in on elusive particles” 

    Techniche Universitat Munchen

    From Techniche Universitat Munchen

    Working on the germanium detector array in the clean room of Gran Sasso underground laboratory.
    Image: J. Suvorov / GERDA

    Prof. Dr. Stefan Schönert
    Technical University of Munich
    Experimental Astroparticlephysics (E15)
    Tel.: +49 89 289 12511
    E-Mail: schoenert@ph.tum.de

    Major steps forward in understanding neutrino properties.

    In the quest to prove that matter can be produced without antimatter, the GERDA experiment at the Gran Sasso Underground Laboratory is looking for signs of neutrinoless double beta decay. The experiment has the greatest sensitivity worldwide for detecting the decay in question. To further improve the chances of success, a follow-up project, LEGEND, uses an even more refined decay experiment.

    MPG GERmanium Detector Array (GERDA) at Gran Sasso, Italy

    LEGEND Collaboration

    LEGEND experiment at Gran Sasso looking for signs of neutrinoless double beta decay

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

    While the Standard Model of Particle Physics has remained mostly unchanged since its initial conception, experimental observations for neutrinos have forced the neutrino part of the theory to be reconsidered in its entirety.

    Standard Model of Particle Physics

    Neutrino oscillation was the first observation inconsistent with the predictions and proves that neutrinos have non-zero masses, a property that contradicts the Standard Model. In 2015, this discovery was rewarded with the Nobel Prize.

    Are neutrinos their own antiparticles?

    Additionally, there is the longstanding conjecture that neutrinos are so-called Majorana particles: Unlike all other constituents of matter, neutrinos might be their own antiparticles. This would also help explain why there is so much more matter than antimatter in the Universe.

    The GERDA experiment is designed to scrutinize the Majorana hypothesis by searching for the neutrinoless double beta decay of the germanium isotope 76Ge: Two neutrons inside a 76Ge nucleus simultaneously transform into two protons with the emission of two electrons. This decay is forbidden in the Standard Model because the two antineutrinos – the balancing antimatter – are missing.

    The Technical University of Munich (TUM) has been a key partner of the GERDA project (GERmanium Detector Array) for many years. Prof. Stefan Schönert, who heads the TUM research group, is the speaker of the new LEGEND project.

    The GERDA experiment achieves extreme levels of sensitivity

    GERDA is the first experiment to reach exceptionally low levels of background noise and has now surpassed the half-life sensitivity for decay of 1026 years. In other words: GERDA proves that the process has a half-life of at least 1026 years, or 10,000,000,000,000,000 times the age of the Universe.

    Physicists know that neutrinos are at least 100,000 times lighter than electrons, the next heaviest particles. What mass they have exactly, however, is still unknown and another important research topic.

    In the standard interpretation, the half-life of the neutrinoless double beta decay is related to a special variant of the neutrino mass called the Majorana mass. Based the new GERDA limit and those from other experiments, this mass must be at least a million times smaller than that of an electron, or in the terms of physicists, less than 0.07 to 0.16 eV/c2 [1] SCIENCE.

    Consistent with other experiments

    Also other experiments limit the neutrino mass: the Planck mission provides a limit on another variant of the neutrino mass: The sum of the masses of all known neutrino types is less than 0.12 to 0.66 eV/c2.

    The tritium decay experiment KATRIN at the Karlsruhe Institute of Technology (KIT) is set-up to measure the neutrino mass with a sensitivity of about 0.2 eV/c2 in the coming years. These masses are not directly comparable, but they provide a cross check on the paradigm that neutrinos are Majorana particles. So far, no discrepancy has been observed.

    From GERDA to LEGEND

    During the reported data collection period, GERDA operated detectors with a total mass of 35.6 kg of 76Ge. Now, a newly formed international collaboration, LEGEND, will increase this mass to 200 kg of 76Ge until 2021 and further reduce the background noise. The aim is to achieve a sensitivity of 1027 years within the next five years.

    More information:

    GERDA is an international European collaboration of more than 100 physicists from Belgium, Germany, Italy, Russia, Poland and Switzerland. In Germany, GERDA is supported by the Technical Universities of Munich and Dresden, the University of Tübingen and the Max Planck Institutes for Physics and for Nuclear Physics. German funding is provided by the German Federal Ministry of Education and Research (BMBF), the German Research Foundation (DFG) via the Excellence Cluster Universe and SFB1258, as well as the Max Planck Society.

    Prof. Schönert received an ERC Advanced Grant for preparatory work on the LEGEND project in 2018. A few days ago, Prof. Susanne Mertens received an ERC grant for her work on the KATRIN experiment. In the context of that experiment, she will search for so-called sterile neutrinos.

    KATRIN Experiment schematic


    KIT Katrin experiment

    [1] In particle physics masses are specified not in kilograms, but rather in accordance with Einstein’s equation E=mc2: electron volts [eV] divided by the speed of light squared. Electron volts are a measure of energy. This convention is used to circumvent unfathomably small units of mass: 1 eV/c2 corresponds to 1.8 × 10-36 kilograms.

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    Techniche Universitat Munchin Campus

    Techniche Universitat Munchin is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

  • richardmitnick 12:19 pm on April 9, 2019 Permalink | Reply
    Tags: All the miners get very dirty but all the SNOLAB people are clean so the difference between them is stark., , Neutrinoless double beta decay, , Paul Dirac won the Nobel Prize in 1933 after calculating that every particle in the universe must have a corresponding antiparticle., , SNO-Sudbury Neutrino Observatory, , SNOLAB researchers share the elevator with miners on their way to work in the Vale's Creighton nickel mine., The question of what happened to all the antimatter has remained unanswered.,   

    From University of Pennsylvania: “Answering big questions by studying small particles” 

    U Penn bloc

    From University of Pennsylvania

    April 8, 2019

    Erica K. Brockmeier-Writer
    Eric Sucar- Photographer

    A view inside the SNO detector, a 40-foot acrylic sphere that’s covered with thousands of photodetectors. The facility is located in SNOLAB, a research facility located 2km underground near in the Vale’s Creighton nickel mine, Sudbury, Canada (Photo credit: SNO+ Collaboration).

    Neutrinos are extremely lightweight subatomic particles that are produced during nuclear reactions both here on Earth and in the center of stars. But neutrinos aren’t harmful or radioactive: In fact, nearly 100 trillion neutrinos bombard Earth every second and usually pass through the world without notice.

    Joshua Klein is an experimental particle physicist who studies neutrinos and dark matter. His group, along with retired professor Eugene Beier, collaborates with the Sudbury Neutrino Observatory (SNO), an international research endeavor focused on the study of neutrinos. Klein and Beier’s groups previously designed and now maintain the electronics at SNOLAB that collect data on these subatomic particles.

    Klein is fascinated by neutrinos and how they could help answer fundamental questions about the nature of the universe. “They may explain why the universe is made up of matter and not equal parts matter and anti-matter, they may be responsible for how stars explode, they may even tell us something about the laws of physics at the highest energy scales,” says Klein.

    Previous research on neutrinos has already led to groundbreaking discoveries in particle physics. The SNO collaboration was awarded the 2016 Breakthrough Prize in Fundamental Physics for solving the “solar neutrino problem.” The problem was that the number of neutrinos being produced by the sun was only a third of what was predicted by theoretical physicists, a discrepancy that had puzzled researchers since the 1970s.

    To solve this, researchers went about 1.2 miles underground to study neutrinos in order to avoid the cosmic radioactive particles that could interfere with their minute and precise measurements. The SNOLAB facility in Sudbury, Canada, which houses a a 40-foot wide acrylic vessel surrounded by photodetectors, allowed physicists to measure the three different types of neutrinos at the same time. Physicists found that neutrinos were able to change from one type into another.

    The exterior of the SNO Detector as seen from the ground at SNOLAB (Photo credit: SNOLAB).

    Today, 15 years later, researchers are looking for an incredibly rare process involving neutrinos that, if found, could revolutionize the field of fundamental physics. “Now that we know that neutrinos can change form, along with the fact that neutrinos have mass but no charge, we can hypothesize that they can be their own antiparticle. If this is true, it could explain why the universe is made of only matter,” says Klein.

    The question of what happened to all the antimatter has remained unanswered since Paul Dirac won the Nobel Prize in 1933 after calculating that every particle in the universe must have a corresponding antiparticle. But the majority of the universe is made of ordinary matter, not equal parts matter and anti-matter, and scientists are trying to figure out why.

    The photodetectors at SNOLAB are now being upgraded as part of SNO+ [Physical Review D] in order to search for a rare type of radioactive decay known as a neutrinoless double beta decay, a never-before seen process that would prove that neutrinos and anti-neutrinos are actually the same particle. Witnessing a neutrinoless double-beta decay event is so rare, if it even exists, and would give off such a small signal that the only way to detect it is through the combination of powerful equipment, refined analyses, and a lot of patience.

    Instead of sitting around waiting for a rare event to happen, researchers are actively taking advantage of this state-of-the-art underground facility. “One of the selling points of SNO+ is that it’s a multipurpose detector,” says graduate student Eric Marzec. “A lot of detectors are produced with a singular goal, like detecting dark matter, but SNO+ has a lot of other interesting physics that it can probe.”

    Here at Penn, students from the Klein lab conduct key maintenance and repairs on the electronic components that are instrumental to the success of SNO+. They also conduct research on new materials that can help increase the sensitivity of the detector, providing more chances of seeing a rare neutrinoless double-beta decay event. (Four photos, no individual descriptions.)

    Marzec and Klein were part of a recent study using SNO+’s upgraded capabilities to collect new data on solar neutrinos [Physical Review D]. Before the detector vessel is filled with scintillator, a soap-like liquid that will help them detect rare radioactive decays, it was briefly filled with water. This enabled researchers to collect data on what direction the neutrinos came from, which then allowed them to focus their efforts on studying neutrinos that came from the Sun.

    The solar neutrino problem may be solved, but new data on solar neutrinos is still incredibly useful, especially since data from SNO+ have very low background signals from things like cosmic radiation. “There’s only a few experiments that have ever been able to measure neutrinos coming from the sun,” says Marzec. “People might someday want to look at whether the neutrino production of the sun varies over time, so it’s useful to have as many time points and as many measurements over the years as possible.”

    Marzec has spent a considerable amount of time working at the SNOLAB facility in northern Ontario. He describes a typical day as starting with a 6 a.m. underground elevator ride that travels more than a mile underground. SNOLAB researchers share the elevator with miners on their way to work in the Vale’s Creighton nickel mine. “All the miners get very dirty, but all the SNOLAB people are clean, so the difference between them is stark. It’s very obvious who is the nerd underground and who the miners are,” says Marzec.

    After traveling 6,800 floors underground, researchers walk more than half a mile through a series of tunnels to reach the entrance of SNOLAB (Photo credit: SNOLAB).

    After arriving at the –6,800th floor, researchers walk more than a half mile from the cage shaft to the SNOLAB through underground dirt tunnels. When they reach the lab, they have to shower and change into threadless uniforms to prevent any microscopic threads from getting inside the sensitive detector. After air quality checks are completed, the researchers are free to begin their work on the detector.

    When asked what it’s like to work more than a mile underground, Marzec comments that he got used to the strangeness after a few visits. “The first time, it feels very much like you’re underground because the pressure is very noticeable, and you feel exhausted at the end of the day.” Thankfully, Marzec and his colleagues don’t have to travel a mile underground every time they want to collect data from SNO+ since they can remotely collect and analyze the hundreds of terabytes of data generated by the detector.

    To do any repair work or cleaning inside the detector, researchers must be lowered into the 40 foot tall sphere using a harness (Photo credit: SNOLAB).

    As Marzec is in the final stages of preparing his Ph.D. thesis, he says he will miss his time working on SNO+. “It’s kind of monastic,” Marzec says about his time working at SNOLAB. “You go there and mediate on physics while you’re there. But it’s also kind of a social thing as well: There are a lot of people you know who are working on the same stuff.”

    Klein and his group, including four graduate students and two post-docs, recently returned from a SNOLAB collaboration meeting, where upwards of 100 physicists met to present and discuss recent results and the upcoming plans for the next phase of the project. Klein is excited, and, admittedly, a little bit nervous, to see how everything comes together. “Putting in the liquid scintillator will change everything—there’s never been a detector being converted from a water-based detector to a scintillator detector. Here at Penn, for us, it’s big because we designed upgrades to the electronics to handle the fact that we will be getting data at a rate that’s about 100 times higher,” says Klein.

    A scientist works inside the SNO+ detector while it is partially filled with deuterated water. Each one of the gold-colored circles is an individual photodetector (Photo credit: SNOLAB).

    Despite the numerous technical and logistical challenges ahead, researchers are enthusiastic about the potential that SNO+ can bring to particle physics research. Other areas of study include learning how neutrinos change form, studying low-energy neutrinos to figure out why the Sun seems to have less “heavy” elements than astronomers expect, and measuring geoneutrinos to figure out why Earth is hotter than other nearby planets like Mars.

    But for Klein, the prospect of finding a rare neutrinoless double beta decay event remains the most thrilling aspect of this research, which, if discovered, could turn the Standard Model of particle physics on its head. “After the question of what is dark energy and what is dark matter, the question of whether neutrinos are their own antiparticle is the most important question for particle physics to answer,” Klein says. “And if neutrinos are their own antiparticle, the simplest piece you can put into the equation [within the Standard Model] blows up: It doesn’t work, it’s mathematically inconsistent. And we don’t know how we would fix that. It is a completely experimental question, so that’s why we’re excited.”

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    U Penn campus

    Academic life at Penn is unparalleled, with 100 countries and every U.S. state represented in one of the Ivy League’s most diverse student bodies. Consistently ranked among the top 10 universities in the country, Penn enrolls 10,000 undergraduate students and welcomes an additional 10,000 students to our world-renowned graduate and professional schools.

    Penn’s award-winning educators and scholars encourage students to pursue inquiry and discovery, follow their passions, and address the world’s most challenging problems through an interdisciplinary approach.

  • richardmitnick 9:25 am on March 20, 2019 Permalink | Reply
    Tags: "Solving a 50-year-old beta decay puzzle with advanced nuclear model simulations", , , , Neutrinoless double beta decay, , Synthesis of heavy elements, Technische Universität Darmstadt, The electroweak force, , When protons inside atomic nuclei convert into neutrons or vice versa   

    From Lawrence Livermore National Laboratory and ORNL: “Solving a 50-year-old beta decay puzzle with advanced nuclear model simulations” 


    Oak Ridge National Laboratory

    From Lawrence Livermore National Laboratory

    March 19, 2019

    Anne M Stark

    First-principles calculations show that strong correlations and interactions between two nucleons slow down beta decays in atomic nuclei compared to what’s expected from the beta decays of free neutrons. This impacts the synthesis of heavy elements and the search for neutrinoless double beta decay. Image by Andy Sproles/Oak Ridge National Laboratory.

    For the first time, an international team including scientists at Lawrence Livermore National Laboratory (LLNL) has found the answer to a 50-year-old puzzle that explains why beta decays of atomic nuclei are slower than expected.

    The findings fill a long-standing gap in physicists’ understanding of beta decay (converting a neutron into a proton and vice versa), a key process stars use to create heavier elements. The research appeared in the March 11 edition of the journal Nature Physics.

    Using advanced nuclear model simulations, the team, including LLNL nuclear physicists Kyle Wendt (a Lawrence fellow), Sofia Quaglioni and twice-summer intern Peter Gysbers (UBC/TRIUMF), found their results to be consistent with experimental data showing that beta decays of atomic nuclei are slower than what is expected, based on the beta decays of free neutrons.

    “For decades, physicists couldn’t quite explain nuclear beta decay, when protons inside atomic nuclei convert into neutrons or vice versa, forming the nuclei of other elements,” Wendt said. “Combining modern theoretical tools with advanced computation, we demonstrate it is possible to reconcile, for a considerable number of nuclei, this long-standing discrepancy between experimental measurements and theoretical calculations.”

    Historically, calculations of beta decay rates have been much faster than what is seen experimentally. Nuclear physicists have worked around this discrepancy by artificially scaling the interaction of single nucleons with the electroweak force, a process referred to as “quenching.” This allowed physicists to describe beta decay rates, but not predict them. While nuclei near each other in mass would have similar quenching factors, the factors could differ dramatically for nuclei well separated in mass.

    Predictive calculations of beta decay require not just accurate calculations of the structure of both the mother and daughter nuclei, but also of how nucleons (both individually and as correlated pairs) couple to the electroweak force that drives beta decay. These pairwise interactions of nucleons with the weak force represented an extreme computational hurdle due to the strong nuclear correlations in nuclei.

    The team simulated beta decays from light to heavy nuclei, up to tin-100 decaying into indium-100, demonstrating their approach works consistently across the nuclei where ab initio calculations are possible. This sets the path toward accurate predictions of beta decay rates for unstable nuclei in violent astrophysical environments, such as supernova explosions or neutron star mergers that are responsible for producing most elements heavier than iron.

    “The methodology in this work also may hold the key to accurate predictions of the elusive neutrinoless double-beta decay, a process that if seen would revolutionize our understanding of particle physics,” Quaglioni said.

    Other institutions include Oak Ridge National Laboratory, TRIUMF and the Technische Universität Darmstadt Germany.

    Technische Universität Darmstadt campus

    Technische Universität Darmstadt

    The work was funded by the Laboratory Directed Research and Development Program.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    LLNL Campus

    Operated by Lawrence Livermore National Security, LLC, for the National Nuclear Security Administration
    Lawrence Livermore National Laboratory (LLNL) is an American federal research facility in Livermore, California, United States, founded by the University of California, Berkeley in 1952. A Federally Funded Research and Development Center (FFRDC), it is primarily funded by the U.S. Department of Energy (DOE) and managed and operated by Lawrence Livermore National Security, LLC (LLNS), a partnership of the University of California, Bechtel, BWX Technologies, AECOM, and Battelle Memorial Institute in affiliation with the Texas A&M University System. In 2012, the laboratory had the synthetic chemical element livermorium named after it.

    LLNL is self-described as “a premier research and development institution for science and technology applied to national security.” Its principal responsibility is ensuring the safety, security and reliability of the nation’s nuclear weapons through the application of advanced science, engineering and technology. The Laboratory also applies its special expertise and multidisciplinary capabilities to preventing the proliferation and use of weapons of mass destruction, bolstering homeland security and solving other nationally important problems, including energy and environmental security, basic science and economic competitiveness.

    The Laboratory is located on a one-square-mile (2.6 km2) site at the eastern edge of Livermore. It also operates a 7,000 acres (28 km2) remote experimental test site, called Site 300, situated about 15 miles (24 km) southeast of the main lab site. LLNL has an annual budget of about $1.5 billion and a staff of roughly 5,800 employees.

    LLNL was established in 1952 as the University of California Radiation Laboratory at Livermore, an offshoot of the existing UC Radiation Laboratory at Berkeley. It was intended to spur innovation and provide competition to the nuclear weapon design laboratory at Los Alamos in New Mexico, home of the Manhattan Project that developed the first atomic weapons. Edward Teller and Ernest Lawrence,[2] director of the Radiation Laboratory at Berkeley, are regarded as the co-founders of the Livermore facility.

    The new laboratory was sited at a former naval air station of World War II. It was already home to several UC Radiation Laboratory projects that were too large for its location in the Berkeley Hills above the UC campus, including one of the first experiments in the magnetic approach to confined thermonuclear reactions (i.e. fusion). About half an hour southeast of Berkeley, the Livermore site provided much greater security for classified projects than an urban university campus.

    Lawrence tapped 32-year-old Herbert York, a former graduate student of his, to run Livermore. Under York, the Lab had four main programs: Project Sherwood (the magnetic-fusion program), Project Whitney (the weapons-design program), diagnostic weapon experiments (both for the Los Alamos and Livermore laboratories), and a basic physics program. York and the new lab embraced the Lawrence “big science” approach, tackling challenging projects with physicists, chemists, engineers, and computational scientists working together in multidisciplinary teams. Lawrence died in August 1958 and shortly after, the university’s board of regents named both laboratories for him, as the Lawrence Radiation Laboratory.

    Historically, the Berkeley and Livermore laboratories have had very close relationships on research projects, business operations, and staff. The Livermore Lab was established initially as a branch of the Berkeley laboratory. The Livermore lab was not officially severed administratively from the Berkeley lab until 1971. To this day, in official planning documents and records, Lawrence Berkeley National Laboratory is designated as Site 100, Lawrence Livermore National Lab as Site 200, and LLNL’s remote test location as Site 300.[3]

    The laboratory was renamed Lawrence Livermore Laboratory (LLL) in 1971. On October 1, 2007 LLNS assumed management of LLNL from the University of California, which had exclusively managed and operated the Laboratory since its inception 55 years before. The laboratory was honored in 2012 by having the synthetic chemical element livermorium named after it. The LLNS takeover of the laboratory has been controversial. In May 2013, an Alameda County jury awarded over $2.7 million to five former laboratory employees who were among 430 employees LLNS laid off during 2008.[4] The jury found that LLNS breached a contractual obligation to terminate the employees only for “reasonable cause.”[5] The five plaintiffs also have pending age discrimination claims against LLNS, which will be heard by a different jury in a separate trial.[6] There are 125 co-plaintiffs awaiting trial on similar claims against LLNS.[7] The May 2008 layoff was the first layoff at the laboratory in nearly 40 years.[6]

    On March 14, 2011, the City of Livermore officially expanded the city’s boundaries to annex LLNL and move it within the city limits. The unanimous vote by the Livermore city council expanded Livermore’s southeastern boundaries to cover 15 land parcels covering 1,057 acres (4.28 km2) that comprise the LLNL site. The site was formerly an unincorporated area of Alameda County. The LLNL campus continues to be owned by the federal government.


    DOE Seal

  • richardmitnick 2:03 pm on February 5, 2019 Permalink | Reply
    Tags: A new source for Majorana calibration, , Cobalt-56 is an ideal source-Cobalt-56 has a really short half-life only 77 days, Neutrinoless double beta decay, , , , The collaboration has been using its thorium source for five years- the signatures it produces are at a slightly higher energy level than that at which neutrinoless double-beta decay is expected to oc, Thorium lasts for years. Indeed the collaboration has been using its thorium source for five years,   

    From Sanford Underground Research Facility: “A new source for Majorana calibration” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    February 4, 2019
    Erin Broberg

    Researchers recently got a special delivery: a hundred million atoms of Cobalt-56, an ideal calibration source.

    A string of germanium detectors inside a cleanroom glovebox on the 4850 Level of Sanford Lab, before they were installed in the Majorana Demonstrator in 2016.
    Photo by Matthew Kapust

    U Washington Majorana Demonstrator Experiment at SURF

    Researchers have not seen the copper glow of the Majorana Demonstrator’s internal detector since 2016. Sealed behind six layers, including 5,200 lead bricks and two heavy copper shields, the Majorana Demonstrator has recorded a steady stream of data that will inform the next-generation neutrinoless double-beta decay experiments. But how do researchers know if the information they’re receiving is accurate? How do they know something hasn’t gone amiss deep inside?

    Simple. They use an advanced calibration system that allows them to monitor the performance of the germanium detectors that make up the heart of the demonstrator. Ralph Massarczyk, staff scientist at Los Alamos National Laboratory, designed and created the calibration system used by the Majorana Demonstrator collaboration.

    “In a typical detector,” Massarczyk explains, “there is enough natural background that you can easily calibrate a detector. But with Majorana, you have a very minimal background, which is not enough to determine its performance.”

    Without substantial background data, researchers don’t know if the background is stable or not. The detector could be reporting events at inaccurate energy levels or even missing them completely. So, to calibrate this extremely sensitive detector, a calibration source is used to produce a standard set of well-known physics events that researchers can use to understand detector performance.

    Typically, the collaboration uses thorium, a naturally occurring, slightly radioactive material that creates signatures the Majorana Demonstrator can easily read. The only problem with this source is that the signatures it produces are at a slightly higher energy level than that at which neutrinoless double-beta decay is expected to occur.

    For a more ideal calibration, Massarczyk and his team got a special delivery: a hundred million atoms of Cobalt-56, a slightly radioactive isotope created in particle accelerators and used mostly in the medical field. The source underwent several “swipe tests” to ensure no leaks had occurred.

    “Cobalt-56 is an ideal source. It produces a lot of events, and those events are at the exact energy where we expect to see a neutrinoless double-beta decay event,” Massarczyk said.

    If it is such a perfect indicator, why don’t researchers use it every time?

    “Cobalt-56 has a really short half-life, only 77 days,” said Massarczyk. “This means that at the end of 77 days, only one-half of the source will be left. After waiting another 77 days, only one-fourth will be left. After a year, the source is gone.”

    Thorium, on the other hand, lasts for years. Indeed, the collaboration has been using its thorium source for five years, Massarczyk said.

    Delivery methods

    To deliver a calibration source to the detector modules behind layers of shielding, Massarczyk designed a “line source.” In this system, a 5-meter long, half-inch thick plastic tube is inserted into a track from the outside of the shield. The tube, which carries the calibration source, is pushed along the “grooves” on the outside of each detector module, snaking its way around twice.

    “It sort of resembles a helix,” Massarczyk said. “This way, the signals are distributed evenly, rather than coming from one point, allowing each detector within the modules to see activity from the same source.”

    The normal rate for the Majorana Demonstrator is a few signature counts per hour. When a radioactive calibration source is included, researchers see a few thousand events per second. During its weekly calibration run, the Majorana Demonstrator sees more events in 3 hours than it would otherwise detect in the span of 120 years.

    “If, while this source is inside, the demonstrator creates signals that correspond with known data, then we know the demonstrator is well-calibrated and on track,” Massarczyk said.

    Looking to the future

    The Majorana Demonstrator is expected to run for a few more years, so the short half-life of Cobalt-56 means it is not a sustainable calibration option for the team. That’s why this week’s calibration was so important. The data collected has been sent to analysts for interpretation.

    “The main purpose for this data is to double-check the data analysis we do in the energy region 2MeV, where we expect the neutrinoless double-beta decay events to occur,” Massarczyk said.

    The information gained from these tests also is of interest to collaborators with LEGEND (Large Enriched Germanium Experiment for Neutrinoless ββ Decay), who are trying to perfect the next-generation neutrinoless double-beta decay experiment.

    Legend Collaboration UNC Chapel Hill

    “As they plan a ton-scale experiment, researchers want to know if the materials are clean enough, if the shielding is working and how far underground they need to go,” said Massarczyk. “Understanding the backgrounds gives us important information to make those decisions.”

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.
    LUX/Dark matter experiment at SURFLUX/Dark matter experiment at SURF

    In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    LUX’s mission was to scour the universe for WIMPs, vetoing all other signatures. It would continue to do just that for another three years before it was decommissioned in 2016.

    In the midst of the excitement over first results, the LUX collaboration was already casting its gaze forward. Planning for a next-generation dark matter experiment at Sanford Lab was already under way. Named LUX-ZEPLIN (LZ), the next-generation experiment would increase the sensitivity of LUX 100 times.

    SLAC physicist Tom Shutt, a previous co-spokesperson for LUX, said one goal of the experiment was to figure out how to build an even larger detector.
    “LZ will be a thousand times more sensitive than the LUX detector,” Shutt said. “It will just begin to see an irreducible background of neutrinos that may ultimately set the limit to our ability to measure dark matter.”
    We celebrate five years of LUX, and look into the steps being taken toward the much larger and far more sensitive experiment.

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    Fermilab LBNE

    U Washington Majorana Demonstrator Experiment at SURF

    The MAJORANA DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment in the Sanford Underground Research Facility (SURF) in Lead, SD. The goal of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge 0νββ Q-value at 2039 keV. MAJORANA plans to collaborate with GERDA for a future tonne-scale 76Ge 0νββ search.

    LBNL LZ project at SURF, Lead, SD, USA


    CASPAR is a low-energy particle accelerator that allows researchers to study processes that take place inside collapsing stars.

    The scientists are using space in the Sanford Underground Research Facility (SURF) in Lead, South Dakota, to work on a project called the Compact Accelerator System for Performing Astrophysical Research (CASPAR). CASPAR uses a low-energy particle accelerator that will allow researchers to mimic nuclear fusion reactions in stars. If successful, their findings could help complete our picture of how the elements in our universe are built. “Nuclear astrophysics is about what goes on inside the star, not outside of it,” said Dan Robertson, a Notre Dame assistant research professor of astrophysics working on CASPAR. “It is not observational, but experimental. The idea is to reproduce the stellar environment, to reproduce the reactions within a star.”

  • richardmitnick 10:24 am on April 2, 2018 Permalink | Reply
    Tags: , , , Neutrinoless double beta decay, , , ,   

    From CNN: “Why the universe shouldn’t exist at all” 


    April 1, 2018

    FNAL’s Don Lincoln

    Don Lincoln, a senior physicist at Fermilab, does research using the Large Hadron Collider. He is the author of The Large Hadron Collider: The Extraordinary Story of the Higgs Boson and Other Stuff That Will Blow Your Mind, and produces a series of science education videos. Follow him on Facebook. The opinions expressed in this commentary are his.

    Why is there something, rather than nothing?” could be the oldest and deepest question in all of metaphysics. Long exclusively the province of philosophy, in recent years this question has become one that can be addressed by scientific methods. What’s more, a new scientific advance has made it more likely that we will finally be able to answer this cosmic conundrum. This is a big deal, because the simplest scientific answer to that question is “We shouldn’t exist at all.”

    Obviously, we know that there must be something, because we’re here. If there were nothing, we couldn’t ask the question. But why? Why is there something? Why is the universe not a featureless void? Why does our universe have matter and not only energy? It might seem surprising, but given our current theories and measurements, science cannot answer those questions.

    However, give some scientists 65 pounds of a rare isotope of germanium, cool it to temperatures cold enough to liquify air, and place their equipment nearly a mile underground in an abandoned gold mine, and you’ll have the beginnings of an answer. Their project is called the Majorana Demonstrator and it is located at the Sanford Underground Research Facility, near Lead, South Dakota.

    U Washington Majorana Demonstrator Experiment at SURF

    Science paper om Majorana Demonstrator project
    Initial Results from the Majorana Demonstrator
    Journal of Physics: Conference Series

    SURF-Sanford Underground Research Facility

    SURF Above Ground

    SURF Out with the Old

    SURF An Empty Slate

    SURF Carving New Space

    SURF Shotcreting

    SURF Bolting and Wire Mesh

    SURF Outfitting Begins

    SURF circular wooden frame was built to form a concrete ring to hold the 72,000-gallon (272,549 liters) water tank that would house the LUX dark matter detector

    SURF LUX water tank was transported in pieces and welded together in the Davis Cavern

    SURF Ground Support

    SURF Dedicated to Science

    SURF Building a Ship in a Bottle

    SURF Tight Spaces

    SURF Ready for Science

    SURF Entrance Before Outfitting

    SURF Entrance After Outfitting

    SURF Common Corridior

    SURF Davis

    SURF Davis A World Class Site

    SURF Davis a Lab Site

    SURF DUNE LBNF Caverns at Sanford Lab

    FNAL DUNE Argon tank at SURF

    U Washington LUX Xenon experiment at SURF

    SURF Before Majorana

    U Washington Majorana Demonstrator Experiment at SURF

    To grasp why science has trouble explaining why matter exists — and to understand the scientific achievement of Majorana — we must first know a few simple things. First, our universe is made exclusively of matter; you, me, the Earth, even distant galaxies. All of it is matter.

    However, our best theory for explaining the behavior of the matter and energy of the universe contradicts the realities that we observe in the universe all around us. This theory, called the Standard Model, says that the matter of the universe should be accompanied by an identical amount of antimatter, which, as its name suggests, is a substance antagonistic to matter. Combine equal amounts of matter and antimatter and it will convert into energy.

    And the street goes both ways: Enough energy can convert into matter and antimatter. (Fun fact: Combining a paper clip’s worth of matter and antimatter will result in the same energy released in the atomic explosion at Hiroshima. Don’t worry though; since antimatter’s discovery in 1931, we have only been able to isolate enough of it to make about 10 pots of coffee.)

    An enigma about the relative amounts of matter and antimatter in the universe arises when we think about how the universe came to be. Modern cosmology says the universe began in an unimaginable Big Bang — an explosion of energy. In this theory, equal amounts of matter and antimatter should have resulted.

    So how is our universe made exclusively of matter? Where did the antimatter go?

    The simplest answer is that we don’t know. In fact, it remains one of the biggest unanswered problems of modern physics.

    Just because the question of missing antimatter is unanswered doesn’t mean that scientists are completely clueless. Beginning in 1964 and continuing through to the present day, physicists have studied the problem and we have found out that early in the universe there was a slight asymmetry in the laws of nature that treated matter and antimatter differently.

    Very approximately, for every billion antimatter subatomic particles that were made in the Big Bang, there were a billion-and-one matter particles. The billion matter and antimatter particles were annihilated, leaving the small amount of leftover matter (the “one”) that went on to make up the universe we see around us. This is accepted science.

    However, we don’t know the process whereby the asymmetry in the laws of the universe arose. One possible explanation revolves around a class of subatomic particles called leptons.

    The most well-known of the leptons is the familiar electron, found around atoms. However, a less known lepton is called the neutrino. Neutrinos are emitted in a particular kind of nuclear radiation, called beta decay. Beta decay occurs when a neutron in an atom decays into a proton, an electron, and a neutrino.

    Neutrinos are fascinating particles. They interact extremely weakly; a steady barrage of neutrinos from the nuclear reactions in the sun pass through the entire Earth essentially without interacting. Because they interact so little, they are very difficult to detect and study. And that means that there are properties of neutrinos that we still don’t understand.

    Still a mystery to scientists is whether there is a difference between neutrino matter and neutrino antimatter. While we know that both exist, we don’t know if they are different subatomic particles or if they are the same thing. That’s a heavy thought, so perhaps an analogy will help.

    Imagine you have a set of twins, with each twin standing in for the matter and antimatter neutrinos. If the twins are fraternal, you can tell them apart, but if they are identical, you can’t. Essentially, we don’t know which kind of twins the neutrino matter/antimatter pair are.

    If neutrinos are their own antimatter particle, it would be an enormous clue in the mystery of the missing antimatter. So, naturally, scientists are working to figure this out.

    The way they do that is to look first for a very rare form of beta decay, called double beta decay. That’s when two neutrons in the nucleus of an atom simultaneously decay. In this process, two neutrinos are emitted. Scientists have observed this kind of decay.

    However, if neutrinos are their own antiparticle, an even rarer thing can occur called “neutrinoless double beta decay.” In this process, the neutrinos are absorbed before they get outside of the nucleus. In this case, no neutrinos are emitted. This process has not been observed and this is what scientists are looking for. The observation of a single, unambiguous neutrinoless double beta decay would show that matter and antimatter neutrinos were the same.

    If indeed neutrinoless double beta decay exists, it’s very hard to detect and it’s important that scientists can discriminate between the many types of radioactive decay that mimic that of a neutrino. This requires the design and construction of very precise detectors.

    So that’s what the Majorana Demonstrator scientists achieved. They developed the technology necessary to make this very difficult differentiation. This demonstration paints a way forward for a follow-up experiment that can, once and for all, answer the question of whether matter and antimatter neutrinos are the same or different. And, with that information in hand, it might be possible to understand why our universe is made only of matter.

    For millennia, introspective thinkers have pondered the great questions of existence. Why are we here? Why is the universe the way it is? Do things have to be this way? With this advance, scientists have taken a step forward in answering these timeless questions.

    See the full article here .

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  • richardmitnick 12:53 pm on March 29, 2018 Permalink | Reply
    Tags: , Gran Sasso National Laboratories (LNGS), Is the neutrino is its own antiparticle?, , Neutrinoless double beta decay   

    From MIT News: “Scientists report first results from CUORE neutrino experiment” 

    MIT News

    MIT Widget

    MIT News

    March 26, 2018
    Jennifer Chu

    Researchers working on the cryostat. Image: CUORE Collaboration

    Data could shed light on why the universe has more matter than antimatter.

    This week, an international team of physicists, including researchers at MIT, is reporting the first results from an underground experiment designed to answer one of physics’ most fundamental questions: Why is our universe made mostly of matter?

    According to theory, the Big Bang should have produced equal amounts of matter and antimatter — the latter consisting of “antiparticles” that are essentially mirror images of matter, only bearing charges opposite to those of protons, electrons, neutrons, and other particle counterparts. And yet, we live in a decidedly material universe, made mostly of galaxies, stars, planets, and everything we see around us — and very little antimatter.

    Physicists posit that some process must have tilted the balance in favor of matter during the first moments following the Big Bang. One such theoretical process involves the neutrino — a particle that, despite having almost no mass and interacting very little with other matter, is thought to permeate the universe, with trillions of the ghostlike particles streaming harmlessly through our bodies every second.

    There is a possibility that the neutrino may be its own antiparticle, meaning that it may have the ability to transform between a matter and antimatter version of itself. If that is the case, physicists believe this might explain the universe’s imbalance, as heavier neutrinos, produced immediately after the Big Bang, would have decayed asymmetrically, producing more matter, rather than antimatter, versions of themselves.

    One way to confirm that the neutrino is its own antiparticle, is to detect an exceedingly rare process known as a “neutrinoless double-beta decay,” in which a stable isotope, such as tellurium or xenon, gives off certain particles, including electrons and antineutrinos, as it naturally decays. If the neutrino is indeed its own antiparticle, then according to the rules of physics the antineutrinos should cancel each other out, and this decay process should be “neutrinoless.” Any measure of this process should only record the electrons escaping from the isotope.

    The underground experiment known as CUORE, for the Cryogenic Underground Observatory for Rare Events, is designed to detect a neutrinoless double-beta decay from the natural decay of 988 crystals of tellurium dioxide.

    CUORE experiment,at the Italian National Institute for Nuclear Physics’ (INFN’s) Gran Sasso National Laboratories (LNGS) in Italy,a search for neutrinoless double beta decay

    In a paper published this week in Physical Review Letters, researchers, including physicists at MIT, report on the first two months of data collected by CUORE (Italian for “heart”). And while they have not yet detected the telltale process, they have been able to set the most stringent limits yet on the amount of time that such a process should take, if it exists at all. Based on their results, they estimate that a single atom of tellurium should undergo a neutrinoless double-beta decay, at most, once every 10 septillion (1 followed by 25 zeros) years.

    Taking into account the massive number of atoms within the experiment’s 988 crystals, the researchers predict that within the next five years they should be able to detect at least five atoms undergoing this process, if it exists, providing definitive proof that the neutrino is its own antiparticle.

    “It’s a very rare process — if observed, it would be the slowest thing that has ever been measured,” says CUORE member Lindley Winslow, a member of the Laboratory for Nuclear Science, and the Jerrold R. Zacharias Career Development Assistant Professor of Physics at MIT, who led the analysis. “The big excitement here is that we were able to run 998 crystals together, and now we’re on a path to try and see something.”

    The CUORE collaboration includes some 150 scientists primarily from Italy and the U.S., including Winslow and a small team of postdocs and graduate students from MIT.

    Coldest cube in the universe

    The CUORE experiment is housed underground, in the Italian National Institute for Nuclear Physics’ (INFN) Gran Sasso National Laboratories, buried deep within a mountain in central Italy, in order to shield it from external stimuli such as the constant bombardment of radiation from sources in the universe.

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

    The heart of the experiment is a detector consisting of 19 towers, each containing 52 cube-shaped crystals of tellurium dioxide, totaling 988 crystals in all, with a mass of about 742 kilograms, or 1,600 pounds. Scientists estimate that this amount of crystals embodies around 100 septillion atoms of the particular tellurium isotope. Electronics and temperature sensors are attached to each crystal to monitor signs of their decay.

    The entire detector resides within an ultracold refrigerator, about the size of a vending machine, which maintains a steady temperature of 6 millikelvin, or -459.6 degrees Fahrenheit. Researchers in the collaboration have previously calculated that this refrigerator is the coldest cubic meter that exists in the universe.

    The experiment needs to be kept exceedingly cold in order to detect minute changes in temperature generated by the decay of a single tellurium atom. In a normal double-beta decay process, a tellurium atom gives off two electrons, as well as two antineutrinos, which amount to a certain energy in the form of heat. In the event of a neutrinoless double-beta decay, the two antineutrinos should cancel each other out, and only the energy released by the two electrons would be generated. Physicists have previously calculated that this energy must be around 2.5 megaelectron volts (Mev).

    In the first two months of CUORE’s operation, scientists have essentially been taking the temperature of the 988 tellurium crystals, looking for any miniscule spike in energy around that 2.5 Mev mark.

    “CUORE is like a gigantic thermometer,” Winslow says. “Whenever you see a heat deposit on a crystal, you end up seeing a pulse that you can digitize. Then you go through and look at these pulses, and the height and width of the pulse corresponds to how much energy was there. Then you zoom in and count how many events were at 2.5 Mev, and we basically saw nothing. Which is probably good because we weren’t expecting to see anything in the first two months of data.”

    The heart will go on

    The results more or less indicate that, within the short window in which CUORE has so far operated, not one of the 1,000 septillion tellurium atoms in the detector underwent a neutrinoless double-beta decay. Statistically speaking, this means that it would take at least 10 septillion years, or years, for a single atom to undergo this process if a neutrino is in fact its own antiparticle.

    “For tellurium dioxide, this is the best limit for the lifetime of this process that we’ve ever gotten,” Winslow says.

    CUORE will continue to monitor the crystals for the next five years, and researchers are now designing the experiment’s next generation, which they have dubbed CUPID — a detector that will look for the same process within an even greater number of atoms. Beyond CUPID, Winslow says there is just one more, bigger iteration that would be possible, before scientists can make a definitive conclusion.

    “If we don’t see it within 10 to 15 years, then, unless nature chose something really weird, the neutrino is most likely not its own antiparticle,” Winslow says. “Particle physics tells you there’s not much more wiggle room for the neutrino to still be its own antiparticle, and for you not to have seen it. There’s not that many places to hide.”

    This research is supported by the National Institute for Nuclear Physics (INFN) in Italy, the National Science Foundation, the Alfred P. Sloan Foundation, and the U.S. Department of Energy.

    See the full article here .

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  • richardmitnick 1:05 pm on March 26, 2018 Permalink | Reply
    Tags: Gan Sasso Laboratory, , , , Neutrinoless double beta decay,   

    From LBNL: “Underground Neutrino Experiment Could Provide Greater Clarity on Matter-Antimatter Imbalance” 

    Berkeley Logo

    Berkeley Lab

    March 26, 2018
    Glenn Roberts Jr.
    (510) 486-5582

    Stacks of lead bricks (gray) and a copper chamber make up the innermost layers of the MAJORANA DEMONSTRATOR’s multilayered shield. The shielding materials weigh about 57 tons. (Credit: Matthew Kapust/Sanford Underground Research Facility)

    By Dawn Levy

    If equal amounts of matter and antimatter had formed in the Big Bang more than 13 billion years ago, one would have annihilated the other upon meeting, and today’s universe would be full of energy – but no matter – to form stars, planets, and life.

    So the very existence of matter suggests something is wrong with Standard Model equations describing symmetry between subatomic particles and their antiparticles.

    In a study published March 26 in Physical Review Letters, nuclear physicists from the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and other institutions working on the MAJORANA DEMONSTRATOR experiment have shown that they can shield a sensitive, scalable, 44-kilogram germanium detector array from background radioactivity. The experiment is led by Oak Ridge National Laboratory (ORNL).

    This accomplishment is critical to developing and proposing a much larger future experiment – with approximately a ton of detectors – to study the nature of neutrinos. These electrically neutral particles interact only weakly with matter, making their detection exceedingly difficult.

    “We’re trying to figure out the really basic question: Are neutrinos their own antiparticles?” said Alan Poon, the detector group leader for the MAJORANA DEMONSTRATOR. “Another goal is to demonstrate that we can actually build a bigger detector.”

    John Wilkerson, a nuclear physicist from ORNL and the University of North Carolina at Chapel Hill who led the construction of the experiment, said, “The excess of matter over antimatter is one of the most compelling mysteries in science.” The collaboration involves 129 researchers from 27 institutions and 6 nations.

    The experiment seeks to observe a phenomenon in atomic nuclei called “neutrinoless double-beta decay.” This observation would prove that neutrinos are their own antiparticles. The existence of this type of decay would have “profound implications for our understanding of the universe,” Wilkerson added. These measurements could also provide a better understanding of neutrino mass.

    Berkeley Lab was responsible for fashioning a specially prepared form of germanium crystals into working detectors for the experiment, and building the detector array’s front-end electronics that sit very close to the detectors. Decades ago, Berkeley Lab pioneered the technique for making high-purity germanium detectors and invented the type of germanium detectors that were adapted for the MAJORANA DEMONSTRATOR experiment.

    Poon noted that the electronics and other components surrounding the detectors are made of ultrapure materials to reduce background “noise,” or unwanted signals from naturally occurring radiation. “They are the lowest-radioactivity front-end electronics in the world,” he said.

    A researcher works on the delicate wiring of a MAJORANA cryostat, which is like a thermos under vacuum that chills the detectors at the heart of the experiment. The experiment’s two cryostats each house 29 germanium detectors. Berkeley Lab fashioned a specialized form of germanium crystals into working detectors for the experiment. (Credit: Matthew Kapust/Sanford Underground Research Facility)

    The collaboration also used Berkeley Lab’s National Energy Research Scientific Computing Center (NERSC) to process and analyze data from the experiment. NERSC will be the principal site for data processing and analyses throughout the course of the experiment.

    NERSC Cray XC40 Cori II supercomputer

    LBL NERSC Cray XC30 Edison supercomputer

    The Genepool system is a cluster dedicated to the DOE Joint Genome Institute’s computing needs. Denovo is a smaller test system for Genepool that is primarily used by NERSC staff to test new system configurations and software.


    PDSF is a networked distributed computing cluster designed primarily to meet the detector simulation and data analysis requirements of physics, astrophysics and nuclear science collaborations.

    In a 2015 report of the U.S. Nuclear Science Advisory Committee to the Department of Energy and the National Science Foundation, a U.S.-led ton-scale experiment to detect neutrinoless double-beta decay was deemed a top priority for the nuclear physics community. Nearly a dozen experiments have sought neutrinoless double-beta decay, and as many future experiments have been proposed. One of their keys to success depends on avoiding background radiation that could mimic the signal of neutrinoless double-beta decay.

    That was the key accomplishment of the MAJORANA DEMONSTRATOR. Its implementation was completed in South Dakota in September 2016, nearly a mile underground at the Sanford Underground Research Facility.

    SURF-Sanford Underground Research Facility

    SURF Above Ground

    SURF Out with the Old

    SURF An Empty Slate

    SURF Carving New Space

    SURF Shotcreting

    SURF Bolting and Wire Mesh

    SURF Outfitting Begins

    SURF circular wooden frame was built to form a concrete ring to hold the 72,000-gallon (272,549 liters) water tank that would house the LUX dark matter detector

    SURF LUX water tank was transported in pieces and welded together in the Davis Cavern

    SURF Ground Support

    SURF Dedicated to Science

    SURF Building a Ship in a Bottle

    SURF Tight Spaces

    SURF Ready for Science

    SURF Entrance Before Outfitting

    SURF Entrance After Outfitting

    SURF Common Corridior

    SURF Davis

    SURF Davis A World Class Site

    SURF Davis a Lab Site

    SURF DUNE LBNF Caverns at Sanford Lab

    FNAL DUNE Argon tank at SURF

    U Washington LUX Xenon experiment at SURF

    SURF Before Majorana

    U Washington Majorana Demonstrator Experiment at SURF

    Siting the experiment under nearly a mile of rock was the first of many steps collaborators took to reduce interference from background levels of radiation. Other steps included a cryostat made of the world’s purest copper and a complex six-layer shield to eliminate interference from cosmic rays, radon, dust, fingerprints, and naturally occurring radioactive isotopes.

    “If you’re going to search for neutrinoless double-beta decay, it’s critical to know that radioactive background is not going to overwhelm the signal you seek,” said ORNL’s David Radford, a lead scientist in the experiment.

    There are many ways for an atomic nucleus to fall apart. A common decay mode happens when a neutron inside the nucleus emits an electron (called a “beta”) and an antineutrino to become a proton. In two-neutrino double-beta decay, two neutrons decay simultaneously to produce two protons, two electrons, and two antineutrinos. This process has been observed. The MAJORANA Collaboration seeks evidence for a similar decay process that has never been observed, in which no neutrinos are emitted.

    Conservation of the number of leptons – subatomic particles such as electrons, muons, or neutrinos that do not take part in strong interactions – was written into the Standard Model of particle physics. “There is no really good reason for this, just the observation that it appears that’s the case,” said Radford. “But if lepton number is not conserved, when added to processes that we think happened during the very early universe, that could help explain why there is more matter than antimatter.”

    Many theorists believe that the lepton number is not conserved: that the neutrino and the antineutrino – which were assumed to have opposite lepton numbers – are really the same particle spinning in different ways. Italian physicist Ettore Majorana introduced that concept in 1937, predicting the existence of particles that are their own antiparticles.

    The MAJORANA DEMONSTRATOR uses germanium crystals as both the source of double-beta decay and the means to detect it. Germanium-76 (Ge-76) decays to become selenium-76, which has a smaller mass. When germanium decays, mass gets converted to energy that is carried away by the electrons and the antineutrinos. “If all that energy goes to the electrons, then none is left for neutrinos,” Radford said. “That’s a clear identifier that we found the event we’re looking for.”

    The scientists distinguish two-neutrino vs. neutrinoless decay modes by their energy signatures. “It’s a common misconception that our experiments detect neutrinos,” said Jason Detwiler of the University of Washington, who is a co-spokesperson for the MAJORANA Collaboration and a former Glenn T. Seaborg Postdoctoral Fellow at Berkeley Lab. “It’s almost comical to say it, but we are searching for the absence of neutrinos. In the neutrinoless decay, the released energy is always a particular value. In the two-neutrino version, the released energy varies but is always smaller than it is for neutrinoless double-beta decay.”

    The MAJORANA DEMONSTRATOR has shown that the neutrinoless double-beta decay half-life of Ge-76 is at least 1025 years – 15 orders of magnitude longer than the age of the universe. So it’s impossible to wait for a single germanium nucleus to decay. “We get around the impossibility of watching one nucleus for a long time by instead watching on the order of 1026 nuclei for a shorter amount of time,” explained co-spokesperson Vincente Guiseppe of the University of South Carolina.

    Chances of spotting a neutrinoless double-beta decay in Ge-76 are rare – no more than 1 for every 100,000 two-neutrino double-beta decays, Guiseppe said. Using detectors containing large amounts of germanium atoms increases the probability of spotting the rare decays. Between June 2015 and March 2017, the scientists observed no events with the energy profile of neutrinoless decay, the process that has not yet been observed. (This was expected given the small number of germanium nuclei in the detector). However, they were encouraged to see many events with the energy profile of two-neutrino decays, verifying the detector could spot the decay process that has been observed.

    Strings of MAJORANA detectors are shown here. Each cylindrical “string” features stacks of germanium crystals separated by ultrapure copper components. (Credit: Matthew Kapust/Sanford Underground Research Facility).

    The MAJORANA Collaboration’s results coincide with new results from a competing experiment in Italy called GERDA (for GERmanium Detector Array), which takes a complementary approach to studying the same phenomenon.

    MPG GERmanium Detector Array (GERDA) at Gran Sasso, Italy

    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in L’Aquila, Italy

    “The MAJORANA DEMONSTRATOR and GERDA together have the lowest background of any neutrinoless double-beta decay experiment,” said Radford.

    The DEMONSTRATOR was designed to lay the groundwork for a ton-scale experiment by demonstrating that backgrounds can be low enough to justify building a larger detector. Just as bigger telescopes collect more light and enable viewing of fainter objects, increasing the mass of germanium allows for a greater probability of observing the rare decay. With 30 times more germanium than the current experiment, the planned one-ton experiment would be able to spot the neutrinoless double-beta decay of just one germanium nucleus per year.

    The MAJORANA DEMONSTRATOR is planned to continue taking data for two or three years. Meanwhile, a merger with GERDA is in the works to develop a possible one-ton detector called LEGEND, planned to be built in stages at an as-yet-to-be-determined site.

    Poon said, “Our data demonstrates that the background signals are low enough that we can actually build a bigger detector.”

    LEGEND 200, the LEGEND demonstrator, represents a step toward a possible future ton-scale experiment that will be a combination of GERDA, MAJORANA, and new detectors. Scientists hope to start on the first stage of LEGEND 200 by 2021. A ton-scale experiment, LEGEND 1000, would be the next stage, if approved.

    “This merger leverages public investments in the MAJORANA DEMONSTRATOR and GERDA by combining the best technologies of each,” said LEGEND Collaboration co-spokesperson (and long-time MAJORANA spokesperson up until last year) Steve Elliott of Los Alamos National Laboratory.

    Funding came from the U.S. Department of Energy Office of Science and the U.S. National Science Foundation. The Russian Foundation for Basic Research and Laboratory Directed Research and Development programs of DOE’s Los Alamos, Lawrence Berkeley, and Pacific Northwest national laboratories provided support. The research used resources of the Oak Ridge Leadership Computing Facility and NERSC, which are DOE Office of Science User Facilities at ORNL and Berkeley Lab, respectively. Sanford Underground Research Facility hosted and collaborated on the experiment.

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  • richardmitnick 10:06 am on February 26, 2018 Permalink | Reply
    Tags: , , Neutrinoless double beta decay,   

    From ScienceNews: “The quest to identify the nature of the neutrino’s alter ego is heating up” 


    February 26, 2018
    Emily Conover

    Physicists are trying to see if the particle’s matter and antimatter versions are the same.

    ANTIMATTER MYSTERY Physicists suspect that the neutrino may be its own antiparticle. Experiments such as GERDA (shown) are attempting to determine whether that hunch is correct by searching for a rare type of nuclear decay. K. Freund/GERDA collaboration

    Galaxies, stars, planets and life, all are formed from one essential substance: matter.

    But the abundance of matter is one of the biggest unsolved mysteries of physics. The Big Bang, 13.8 billion years ago, spawned equal amounts of matter and its bizarro twin, antimatter. Matter and antimatter partners annihilate when they meet, so an even-stephen universe would have ended up full of energy — and nothing else. Somehow, the balance tipped toward matter in the early universe.

    A beguiling subatomic particle called a neutrino may reveal how that happened. If neutrinos are their own antiparticles — meaning that the neutrino’s matter and antimatter versions are the same thing — the lightweight particle might point to an explanation for the universe’s glut of matter.

    So scientists are hustling to find evidence of a hypothetical kind of nuclear decay that can occur only if neutrinos and antineutrinos are one and the same. Four experiments have recently published results showing no hint of the process, known as neutrinoless double beta decay (SN: 7/6/02, p. 10). But another attempt, set to begin soon, may have a fighting chance of detecting this decay, if it occurs. Meanwhile, planning is under way for a new generation of experiments that will make even more sensitive measurements.

    “Right now, we’re standing on the brink of what potentially could be a really big discovery,” says Janet Conrad, a neutrino physicist at MIT not involved with the experiments.

    A league of its own

    Each matter particle has an antiparticle, a partner with the opposite electric charge. Electrons have positrons as partners; protons have antiprotons. But it’s unclear how this pattern applies to neutrinos, which have no electric charge.

    Rather than having distinct matter and antimatter varieties, neutrinos might be the lone example of a theorized class of particle dubbed a Majorana fermion (SN: 8/19/17, p. 8), which are their own antiparticles. “No other particle that we know of could have this property; the neutrino is the only one,” says neutrino physicist Jason Detwiler of the University of Washington in Seattle, who is a member of the KamLAND-Zen and Majorana Demonstrator neutrinoless double beta decay experiments.

    Neutrinoless double beta decay is a variation on standard beta decay, a relatively common radioactive process that occurs naturally on Earth. In beta decay, a neutron within an atom’s nucleus converts into a proton, releasing an electron and an antineutrino. The element thereby transforms into another one further along the periodic table.

    Beta decays

    The standard type of beta decay (left) occurs when a neutron in an atom’s nucleus converts into a proton and releases an electron (blue, e-) and an antineutrino (red). For certain species of atoms, two such decays can happen at once (middle). If the neutrino is its own antiparticle, those double beta decays could also occur without any emitted antineutrinos (right).


    In certain isotopes of particular elements — species of atoms characterized by a given number of protons and neutrons — two beta decays can occur simultaneously, emitting two electrons and two antineutrinos. Although double beta decay is exceedingly rare, it has been detected. If the neutrino is its own antiparticle, a neutrino-free version of this decay might also occur: In a rarity atop a rarity, the antineutrino emitted in one of the two simultaneous beta decays might be reabsorbed by the other, resulting in no escaping antineutrinos.

    Such a process “creates asymmetry between matter and antimatter,” says physicist Giorgio Gratta of Stanford University, who works on the EXO-200 neutrinoless double beta decay experiment.

    SLAC EXO-200 Enriched Xenon Observatory near Carlsbad, New Mexico

    In typical beta decay, one matter particle emitted — the electron — balances out the antimatter particle — the antineutrino. But in neutrinoless double beta decay, two electrons are emitted with no corresponding antimatter particles. Early in the universe, other processes might also have behaved in a similarly asymmetric way.

    On the hunt

    To spot the unusual decay, scientists are building experiments filled with carefully selected isotopes of certain elements and monitoring the material for electrons of a particular energy, which would be released in the neutrinoless decay.

    If any experiment observes this process, “it would be a huge deal,” says particle physicist Yury Kolomensky of the University of California, Berkeley, a member of the CUORE neutrinoless double beta decay experiment. “It is a Nobel Prize‒level discovery.”

    CUORE experiment UC Berkeley, experiment at the Italian National Institute for Nuclear Physics’ (INFN’s) Gran Sasso National Laboratories (LNGS), a search for neutrinoless double beta decay

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

    Unfortunately, the latest results won’t be garnering any Nobels. In a paper accepted in Physical Review Letters, the GERDA experiment spotted no signs of the decay. Located in the Gran Sasso underground lab in Italy, GERDA looks for the decay of the isotope germanium-76. (The number indicates the quantity of protons and neutrons in the atom’s nucleus.) Since there were no signs of the decay, if the process occurs it must be extremely rare, the scientists concluded, and its half-life must be long — more than 80 trillion trillion years.

    Three other experiments have also recently come up empty. The Majorana Demonstrator experiment, located at the Sanford Underground Research Facility in Lead, S.D., which also looks for the decay in germanium, reported no evidence of neutrinoless double beta decay in a paper accepted in Physical Review Letters.

    U Washington Majorana Demonstrator Experiment at SURF

    Meanwhile, EXO-200, located in the Waste Isolation Pilot Plant, underground in a salt deposit near Carlsbad, N.M., reported no signs of the decay in xenon-136 in a paper published in the Feb. 16 Physical Review Letters.

    Likewise, no evidence for the decay materialized in the CUORE experiment, in results reported in a paper accepted in Physical Review Letters. Composed of crystals containing tellurium-130, CUORE is also located in the Gran Sasso underground lab.

    The most sensitive search thus far comes from the KamLAND-Zen neutrinoless double beta decay experiment located in a mine in Hida, Japan, which found a half-life longer than 100 trillion trillion years for the neutrinoless double beta decay of xenon-136.

    KamLAND at the Kamioka Observatory in located in a mine in Hida, Japan

    That result means that, if neutrinos are their own antiparticles, their mass has to be less than about 0.061 to 0.165 electron volts depending on theoretical assumptions, the KamLAND-Zen collaboration reported in a 2016 paper in Physical Review Letters. (An electron volt is particle physicists’ unit of energy and mass. For comparison, an electron has a much larger mass of half a million electron volts.)

    Neutrinos, which come in three different varieties and have three different masses, are extremely light, but exactly how tiny those masses are is not known. Mass measured by neutrinoless double beta decay experiments is an effective mass, a kind of weighted average of the three neutrino masses. The smaller that mass, the lower the rate of the neutrinoless decays (and therefore the longer the half-life), and the harder the decays are to find.

    KamLAND-Zen looks for decays of xenon-136 dissolved in a tank of liquid. Now, KamLAND-Zen is embarking on a new incarnation of the experiment, using about twice as much xenon, which will reach down to even smaller masses, and even rarer decays. Finding neutrinoless double beta decay may be more likely below about 0.05 electron volts, where neutrino mass has been predicted to lie if the particles are their own antiparticles.

    Supersizing the search

    KamLAND-Zen’s new experiment is only a start. Decades of additional work may be necessary before scientists clinch the case for or against neutrinos being their own antiparticles. But, says KamLAND-Zen member Lindley Winslow, a physicist at MIT, “sometimes nature is very kind to you.” The experiment could begin taking data as early as this spring, says Winslow, who is also a member of CUORE.

    To keep searching, experiments must get bigger, while remaining extremely clean, free from any dust or contamination that could harbor radioactive isotopes. “What we are searching for is a decay that is very, very, very rare,” says GERDA collaborator Riccardo Brugnera, a physicist at the University of Padua in Italy. Anything that could mimic the decay could easily swamp the real thing, making the experiment less sensitive. Too many of those mimics, known as background, could limit the ability to see the decays, or to prove that they don’t occur.

    In a 2017 paper in Nature, the GERDA experiment deemed itself essentially free from background — a first among such experiments. Reaching that milestone is good news for the future of these experiments. Scientists from GERDA and the Majorana Demonstrator are preparing to team up on a bigger and better experiment, called LEGEND, and many other teams are also planning scaled-up versions of their current detectors.

    Antimatter whodunit

    If scientists conclude that neutrinos are their own antiparticles, that fact could reveal why antimatter is so scarce. It could also explain why neutrinos are vastly lighter than other particles. “You can kill multiple problems with one stone,” Conrad says.

    Theoretical physicists suggest that if neutrinos are their own antiparticles, undetected heavier neutrinos might be paired up with the lighter neutrinos that we observe. In what’s known as the seesaw mechanism, the bulky neutrino would act like a big kid on a seesaw, weighing down one end and lifting the lighter neutrinos to give them a smaller mass. At the same time, the heavy neutrinos — theorized to have existed at the high energies present in the young universe — could have given the infant cosmos its early preference for matter.

    Discovering that neutrinos are their own antiparticles wouldn’t clinch the seesaw scenario. But it would provide a strong hint that neutrinos are essential to explaining where the antimatter went. And that’s a question physicists would love to answer.

    “The biggest mystery in the universe is who stole all the antimatter. There’s no bigger theft that has occurred than that,” Conrad says.


    J.B. Albert et al. Search for neutrinoless double-beta decay with the upgraded EXO-200 detector. Physical Review Letters. Vol. 120, February 16, 2018, p. 072701. doi: 10.1103/PhysRevLett.120.072701.

    C.E. Aalseth et al. Search for zero-neutrino double beta decay in 76Ge with the Majorana demonstrator. Physical Review Letters, in press, 2018.

    M. Agostini et al. Improved limit on neutrinoless double beta decay of 76Ge from GERDA Phase II. Physical Review Letters, in press, 2018.

    CUORE Collaboration. First results from CUORE: a search for lepton number violation via 0νββ decay of 130Te. Physical Review Letters, in press, 2018.

    KamLAND-Zen Collaboration. Search for majorana neutrinos near the inverted mass hierarchy region with KamLAND-Zen. Physical Review Letters. Vol. 117, August 19, 2017, p. 082503. doi:10.1103/PhysRevLett.117.082503.

    The GERDA Collaboration. Background-free search for neutrinoless double-β decay of 76Ge with GERDA. Nature. Vol. 544, April 6, 2017, p. 47. doi:10.1038/nature21717.

    See the full article here .

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