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  • richardmitnick 12:55 pm on November 7, 2017 Permalink | Reply
    Tags: , Neutrinos, , The U Washington Majorana experiment   

    From SURF: “Deep Talks delves into MAJORANA results” 

    SURF logo
    Sanford Underground levels

    Sanford Underground Research facility

    November 3, 2017
    Constance Walter
    Communications Director
    Contact by email

    What do the results look like and what do they mean for the experiment? For science? For Sanford Lab?

    The Majorana experiment sits inside a six-layered shield. Matt Kapust

    U Washington Majorana Demonstrator Experiment at SURF

    The MAJORANA DEMONSTRATOR Collaboration recently released its first physics results at a neutrino conference. What do those results mean for the experiment? For science? For Sanford Lab?

    Join Dr. Vincente Guiseppe Thursday, Nov. 9, for “Released from the Depths: What do Majorana’s results look like and what do they mean?,” at the Sanford Lab Homestake Visitor Center, 160 W. Main Street, in Lead, S.D. Guiseppe, co-spokesperson for the collaboration, will take us on a journey deep inside the Majorana experiment, explaining the collaboration’s effort to build an extremely quiet experiment that could tell us more about the origins of our universe.

    “These initial results will give us a better understanding of the always-elusive neutrino and how it shaped the universe,” Guiseppe said.

    Collaborators with the Majorana Demonstrator built their experiment on the 4850 Level of the Sanford Lab to escape cosmic radiation that constantly bombards the earth. The experiment, which uses enriched germanium crystals to look for a rare form of radioactive decay called neutrinoless double-beta decay, is further protected by a six-layered shield. The collaboration hopes to answer one of the most challenging and important questions in physics: are neutrinos their own antiparticles? If the answer is yes, we could finally learn why matter is more abundant than antimatter and why we exist at all.

    Guiseppe, an assistant professor of physics and astronomy at the University of South Carolina, oversaw the design and construction of the shield. His experimental nuclear and astroparticle physics research focuses on neutrino physics and ultra-low background experiments conducted deep underground.

    Deep Talks begins at 5 p.m. with a social hour; the talk begins at 6 p.m. Free beer from Crow Peak Brewing Company in Spearfish is available for those 21 and older. Deep Talks is sponsored by Sanford Lab, the Sanford Lab Homestake Visitor Center, Crow Peak Brewing Company and First National Bank in Lead. The event is free to the public.

    Deep Talks is a lecture series created by the Sanford Underground Research Facility and the Sanford Lab Homestake Visitor Center. The event is held the second Thursday of each month, October through May. Deep Talks is free to the public. Donations to support community education are welcome.

    Sanford Lab is operated by the South Dakota Science and Technology Authority (SDSTA) with funding from the Department of Energy. Our mission is to advance compelling underground, multidisciplinary research in a safe work environment and to inspire and educate through science, technology, and engineering. Visit us at http://www.SanfordLab.org.

    Visit the Sanford Lab Homestake Visitor Center at http://sanfordlabhomestake.com

    See the full article here .

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    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.

    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

  • richardmitnick 8:41 am on November 1, 2017 Permalink | Reply
    Tags: , , , Neutrinos, ,   

    From FNAL: “Fermilab expands international partnerships” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    October 31, 2017
    Katie Yurkewicz

    The global neutrino physics community is coming together to develop a leading-edge, dual-site experiment for neutrino science called the Deep Underground Neutrino Experiment (DUNE), hosted at Fermilab in Batavia, Illinois.

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

    FNAL DUNE Argon tank at SURF

    Surf-Dune/LBNF Caverns at Sanford

    SURF building in Lead SD USA

    The facility required for this experiment, the Long-Baseline Neutrino Facility (LBNF), will comprise the world’s highest-intensity neutrino beam at Fermilab and the infrastructure necessary to support massive cryogenic detectors installed deep underground at the Sanford Underground Research Facility 1,300 kilometers away in Lead, South Dakota, as well as detectors at Fermilab.

    Scientists from more than 175 institutions in 31 countries make up the DUNE scientific collaboration, which is conducting R&D and designing the experiment’s massive detectors. Two large prototype liquid-argon detectors (called protoDUNEs) are under construction at CERN and will be tested with that lab’s particle beam in the fall of 2018.

    CERN Proto DUNE Maximillian Brice

    Inside ProtoDune – CERN

    And a high-level science and technology agreement was recently signed with the United Kingdom that supports participation by that country in LBNF/DUNE.

    In parallel, Fermilab and the Department of Energy’s Office of Science have been working with international partners to develop and execute agreements that pave the way towards greater scientific collaboration, from the exchange of personnel to the joint design and delivery of components for accelerators and detectors.

    In October 2016, Fermilab signed an agreement with the Australian Research Council’s Centre of Excellence in Particle Physics at the Terascale, a consortium of four universities.

    Since then, agreements that establish joint interest and activities in particle physics research have been signed by Fermilab with additional institutions including the Federal University of ABC in Brazil, the Johannes Gutenberg University of Mainz in Germany, the National Autonomous University of Mexico and the University of Colima in Mexico. A student exchange program was also established with the Instituto de Fisica Corpuscular in Spain.

    And the pace of the development of new partnerships continues to increase. Two agreements were recently signed in the same week: The first on Oct. 17 between Fermilab and Canada’s York University establishing a joint faculty position; and the second on Oct. 19 with France’s Institute for Nuclear and Particle Physics , part of the country’s National Center for Scientific Research.

    As construction continues for the laboratory’s Short-Baseline Neutrino program and ramps up for LBNF/DUNE, keep an eye on Fermilab’s website and Twitter feed for news of even more international agreements toward joint research in neutrino science.


    See the full article here .

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

  • richardmitnick 10:08 am on October 23, 2017 Permalink | Reply
    Tags: , , , , , , Neutrinos   

    From LBNL: “Experiment Provides Deeper Look into the Nature of Neutrinos” 

    Berkeley Logo

    Berkeley Lab

    October 23, 2017
    Glenn Roberts Jr.
    (510) 486-5582

    The first glimpse of data from the full array of a deeply chilled particle detector operating beneath a mountain in Italy sets the most precise limits yet on where scientists might find a theorized process to help explain why there is more matter than antimatter in the universe.

    This new result, submitted today to the journal Physical Review Letters, is based on two months of data collected from the full detector of the CUORE (Cryogenic Underground Observatory for Rare Events) experiment at the Italian National Institute for Nuclear Physics’ (INFN’s) Gran Sasso National Laboratories (LNGS) in Italy. CUORE means “heart” in Italian.

    The CUORE detector array, shown here in this rendering is formed by 19 copper-framed “towers” that each house a matrix of 52 cube-shaped crystals Credit CUORE collaboration

    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

    The Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) leads the U.S. nuclear physics effort for the international CUORE collaboration, which has about 150 members from 25 institutions. The U.S. nuclear physics program has made substantial contributions to the fabrication and scientific leadership of the CUORE detector.

    CUORE is considered one of the most promising efforts to determine whether tiny elementary particles called neutrinos, which interact only rarely with matter, are “Majorana particles” – identical to their own antiparticles. Most other particles are known to have antiparticles that have the same mass but a different charge, for example. CUORE could also help us home in on the exact masses of the three types, or “flavors,” of neutrinos – neutrinos have the unusual ability to morph into different forms.

    “This is the first preview of what an instrument this size is able to do,” said Oliviero Cremonesi, a senior faculty scientist at INFN and spokesperson for the CUORE collaboration. Already, the full detector array’s sensitivity has exceeded the precision of the measurements reported in April 2015 after a successful two-year test run that enlisted one detector tower. Over the next five years CUORE will collect about 100 times more data.

    Yury Kolomensky, a senior faculty scientist in the Nuclear Science Division at Lawrence Berkeley National Laboratory (Berkeley Lab) and U.S. spokesperson for the CUORE collaboration, said, “The detector is working exceptionally well and these two months of data are enough to exceed the previous limits.” Kolomensky is also a professor in the UC Berkeley Physics Department.

    The new data provide a narrow range in which scientists might expect to see any indication of the particle process it is designed to find, known as neutrinoless double beta decay.

    “CUORE is, in essence, one of the world’s most sensitive thermometers,” said Carlo Bucci, technical coordinator of the experiment and Italian spokesperson for the CUORE collaboration. Its detectors, formed by 19 copper-framed “towers” that each house a matrix of 52 cube-shaped, highly purified tellurium dioxide crystals, are suspended within the innermost chamber of six nested tanks.

    Cooled by the most powerful refrigerator of its kind, the tanks subject the detector to the coldest known temperature recorded in a cubic meter volume in the entire universe: minus 459 degrees Fahrenheit (10 milliKelvin).

    The detector array was designed and assembled over a 10-year period. It is shielded from many outside particles, such as cosmic rays that constantly bombard the Earth, by the 1,400 meters of rock above it, and by thick lead shielding that includes a radiation-depleted form of lead rescued from an ancient Roman shipwreck. Other detector materials were also prepared in ultrapure conditions, and the detectors were assembled in nitrogen-filled, sealed glove boxes to prevent contamination from regular air.

    “Designing, building, and operating CUORE has been a long journey and a fantastic achievement,” said Ettore Fiorini, an Italian physicist who developed the concept of CUORE’s heat-sensitive detectors (tellurium dioxide bolometers), and the spokesperson-emeritus of the CUORE collaboration. “Employing thermal detectors to study neutrinos took several decades and brought to the development of technologies that can now be applied in many fields of research.”

    Together weighing over 1,600 pounds, CUORE’s matrix of roughly fist-sized crystals is extremely sensitive to particle processes, especially at this extreme temperature. Associated instruments can precisely measure ever-slight temperature changes in the crystals resulting from these processes.

    Berkeley Lab and Lawrence Livermore National Laboratory scientists supplied roughly half of the crystals for the CUORE project. In addition, the Berkeley Lab team designed and fabricated the highly sensitive temperature sensors – called neutron transmutation doped thermistors – invented by Eugene Haller, a senior faculty scientist in Berkeley Lab’s Materials Sciences Division and a UC Berkeley faculty member.

    CUORE was assembled in this specially designed clean room to help protect it from contaminants. (Credit: CUORE collaboration)

    Berkeley Lab researchers also designed and built a specialized clean room supplied with air depleted of natural radioactivity, so that the CUORE detectors could be installed into the cryostat in ultraclean conditions. And Berkeley Lab scientists and engineers, under the leadership of UC Berkeley postdoc Vivek Singh, worked with Italian colleagues to commission the CUORE cryogenic systems, including a uniquely powerful cooling system called a dilution refrigerator.

    Former UC Berkeley postdoctoral students Tom Banks and Tommy O’Donnell, who also had joint appointments in the Nuclear Science Division at Berkeley Lab, led the international team of physicists, engineers, and technicians to assemble over 10,000 parts into towers in nitrogen-filled glove boxes. They bonded almost 8,000 gold wires, measuring just 25 microns in diameter, to 100-micron sized pads on the temperature sensors, and on copper pads connected to detector wiring.

    CUORE measurements carry the telltale signature of specific types of particle interactions or particle decays – a spontaneous process by which a particle or particles transform into other particles.

    In double beta decay, which has been observed in previous experiments, two neutrons in the atomic nucleus of a radioactive element become two protons. Also, two electrons are emitted, along with two other particles called antineutrinos.

    Neutrinoless double beta decay, meanwhile – the specific process that CUORE is designed to find or to rule out – would not produce any antineutrinos. This would mean that neutrinos are their own antiparticles. During this decay process the two antineutrino particles would effectively wipe each other out, leaving no trace in the CUORE detector. Evidence for this type of decay process would also help scientists explain neutrinos’ role in the imbalance of matter vs. antimatter in our universe.

    Neutrinoless double beta decay is expected to be exceedingly rare, occurring at most (if at all) once every 100 septillion (1 followed by 26 zeros) years in a given atom’s nucleus. The large volume of detector crystals is intended to greatly increase the likelihood of recording such an event during the lifetime of the experiment.

    There is growing competition from new and planned experiments to resolve whether this process exists using a variety of search techniques, and Kolomensky noted, “The competition always helps. It drives progress, and also we can verify each other’s results, and help each other with materials screening and data analysis techniques.”

    Lindley Winslow of the Massachusetts Institute of Technology, who coordinated the analysis of the CUORE data, said, “We are tantalizingly close to completely unexplored territory and there is great possibility for discovery. It is an exciting time to be on the experiment.”

    CUORE is supported jointly by the Italian National Institute for Nuclear Physics Istituto Nazionale di Fisica Nucleare (INFN) in Italy, and the U.S. Department of Energy’s Office of Nuclear Physics, the National Science Foundation, and the Alfred P. Sloan Foundation in the U.S. The CORE collaboration includes about 150 scientists from Italy, U.S., China, France, and Spain, and is based in the underground Italian facility called INFN Gran Sasso National Laboratories (LNGS) of the INFN.

    CUORE collaboration members include: Italian National Institute for Nuclear Physics (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 Center for Nuclear Science and Materials Science (CNRS/IN2P3) in France; and the Shanghai Institute of Applied Physics and Shanghai Jiao Tong University in China.

    The U.S.-CUORE team was lead by late Prof. Stuart Freedman until his untimely passing in 2012. Other current and former Berkeley Lab members of the CUORE collaboration not previously mentioned include US Contractor Project Manager Sergio Zimmermann (Engineering Division), former U.S. Contractor Project Manager Richard Kadel, staff scientists Jeffrey Beeman, Brian Fujikawa, Sarah Morgan, Alan Smith, postdocs Giovanni Benato, Raul Hennings-Yeomans, Ke Han, Yuan Mei, Bradford Welliver, Benjamin Schmidt, graduate students Adam Bryant, Alexey Drobizhev, Roger Huang, Laura Kogler, Jonathan Ouellet, and Sachi Wagaarachchi, and engineers David Biare, Luigi Cappelli, Lucio di Paolo, and Joseph Wallig.

    See the full article here .

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  • richardmitnick 8:09 pm on October 13, 2017 Permalink | Reply
    Tags: , Baby MIND, , , , Neutrinos, ,   

    From CERN: “Baby MIND born at CERN now ready to move to Japan” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead


    13 Oct 2017
    Stefania Pandolfi

    Baby MIND under test on the T9 beamline at the Proton Synchrotron experimental hall in the East Area, summer 2017 (Image: Alain Blondel/University of Geneva)

    A member of the CERN Neutrino Platform family of neutrino detectors, Baby MIND, is now ready to be shipped from CERN to Japan in 4 containers to start the experimental endeavour it has been designed and built for. The containers are being loaded on 17 and 18 October and scheduled to arrive by mid-December.

    Baby MIND is a 75-tonne neutrino detector prototype for a Magnetised Iron Neutrino Detector (MIND). Its goal is to precisely identify and track positively or negatively charged muons – the product of muon neutrinos from the (Tokai to Kamioka) beam line, interacting with matter in the WAGASCI neutrino detector, in Japan.

    T2K map, T2K Experiment, Tokai to Kamioka, Japan

    The more detailed the identification of the muon that crosses the Baby MIND detector, the more we can learn about the original neutrino, in view of contributing to a more precise understanding of the neutrino oscillations phenomenon*.

    The journey of these muon neutrinos starts from the Japan Proton Accelerator Research Complex (J-PARC) in Tokai. They travel all the way to the Super-Kamiokande Detector in Kamioka, some 295 km away.

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

    On their journey, the neutrinos pass through the near detector complex building, located 280 m downstream from Tokai, where the WAGASCI + Baby MIND suite of detectors are. Baby MIND aims to measure the velocity and charge of muons produced by the neutrino interactions with matter in the WAGASCI detector. Muons precise tracking will help testing our ability to reconstruct important characteristics of their parent neutrinos. This, in turn, is important because in studying muon neutrino oscillations on their journey from Tokai to Kamioka, it is crucial to know how strongly and how often they interact with matter.

    Born from prototyping activities launched within the AIDA project, since its approval in December 2015 by the CERN Research Board, the Baby MIND collaboration – comprising CERN, University of Geneva, the Institute of Nuclear research in Moscow, the Universities of Glasgow, Kyoto, Sofia, Tokyo, Uppsala and Valencia – has been busy designing, prototyping, constructing and testing this detector. The magnet construction phase, which lasted 6 months, was completed in mid-February 2017, two weeks ahead of schedule.

    The fully assembled Baby MIND detector was tested on a beam line (link sends e-mail) at the experimental zone of the Proton Synchrotron in the East Hall during Summer 2017. These tests showed that the detector is working as expected and, therefore, ready to go.

    Baby MIND under test on the T9 beamline at the Proton Synchrotron experimental hall in the East Area, summer 2017 (Image: Alain Blondel/University of Geneva)

    *Neutrino oscillations

    Neutrinos are everywhere. Each second, several billion of these particles coming from the Sun, the Earth and our galaxy, pass through our bodies. And yet, they fly past unnoticed. Indeed, despite their cosmic abundance and ubiquity, neutrinos are extremely difficult to study because they hardly interact with matter. For this reason, they are among the least understood particles in the Standard Model (SM) of particle physics.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    What we know is that they come in three types or ‘flavours’ – electron neutrino, muon neutrino and tau neutrino. Since their first detection in 1956, and until the late 1990s neutrinos were thought to be massless, in line with the SM predictions. However, a few years later, the Super-Kamiokande experiment in Japan and then the Sudbury Neutrino Observatory in Canada independently demonstrated that neutrinos can change (oscillate) from one flavour to another spontaneously.

    Sudbury Neutrino Observatory, , no longer operating

    This is only possible if neutrinos have masses, however small, and the probability of changing flavour is proportional to their difference in mass and the distance they travel. This ground-breaking discovery was awarded with the 2015 Physics Nobel Prize.

    See the full article here.

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  • richardmitnick 8:25 pm on October 9, 2017 Permalink | Reply
    Tags: , , , , , Neutrinos, The Prospect of Neutrinos with Gravitational Waves,   

    From AAS NOVA: “The Prospect of Neutrinos with Gravitational Waves” 


    American Astronomical Society

    9 October 2017
    Susanna Kohler

    Gamma ray burst artist depiction Credit NASA Swift Mary Pat Hrybyk-Keith and John Jones

    Artist’s impression of a gamma-ray burst, a powerful flash of gamma-rays that may be emitted from the merger of a neutron star with another compact object. [ESO/A. Roquette]

    With the first detection of gravitational waves in 2015, scientists celebrated the opening of a new window to the universe.

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation

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

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    ESA/eLISA the future of gravitational wave research

    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    But multi-messenger astronomy — astronomy based on detections of not just photons, but other signals as well — was not a new idea at the time: we had already detected tiny, lightweight neutrinos emitted from astrophysical sources. Will we be able to combine observations of neutrinos and gravitational waves in the future to provide a deeper picture of astrophysical events?

    Artist’s impression of the first stage of a binary neutron star merger. [NASA, ESA, and A. Feild (STScI)]

    Signs of a Merger

    If the answer is yes, the key will probably be short gamma-ray bursts (SGRBs). Theory predicts that when a neutron star merges with another compact object (either another neutron star or a black hole), a number of signals may be observable. These include:

    gravitational waves as the binary spirals inward,
    a brief burst of gamma rays at merger (this is the SGRB),
    high-energy neutrino emission during the SGRB,
    optical and infrared emission after the merger in the form of a kilonova, and
    radio afterglows of the merger remnants.

    While we’ve observed the various electromagnetic components of this picture, the multi-messenger part is lacking: gravitational-wave detections haven’t been made in conjunction with electromagnetic counterparts thus far, and the only confirmed astrophysical sources of neutrinos are the Sun and Supernova 1987A.

    Remnant of SN 1987A seen in light overlays of different spectra. ALMA data (radio, in red) shows newly formed dust in the center of the remnant. Hubble (visible, in green) and Chandra (X-ray, in blue) data show the expanding shock wave.

    Predicted neutrino fluxes during different stages of emission in an SGRB. [Kimura et al. 2017]

    Can we expect this to change in the future? A team of authors led by Shigeo Kimura (Pennsylvania State University) has now explored the likelihood that we’ll be able to detect high-energy neutrinos in association with future gravitational-wave events.

    Detecting the SGRB Neutrinos

    Kimura and collaborators first estimate the flux of high-energy neutrinos expected during various emission phases of an SGRB. They show that a period of late-time emission, known as the “extended emission” phase, may produce high-energy neutrinos more efficiently than the other phases. But would we be able to see these neutrinos?

    A comparison of IceCube’s detection capabilities (top) to those of the planned IceCube-Gen2 (bottom), for different models of neutrino emission during an SGRB. [Kimura et al. 2017]

    U Wisconsin ICECUBE neutrino detector at the South Pole

    U Wisconsin IceCube Gen-2

    To answer this, the authors calculate the probability of detection for neutrinos coming from a distance of ~300 Mpc — the predicted sensitivity range of advanced LIGO for gravitational-wave detection from a face-on neutron-star binary. They find that the IceCube Neutrino Observatory could detect neutrinos from around 10% of average extended-emission events — or perhaps up to half in the most optimistic scenario. The planned next iteration of the detector, IceCube-Gen2, should do better, however: Kimura and collaborators estimate that a quarter of the extended emission events will be detectable in the general case, and up to three quarters of them may be seen in the optimistic case.

    The authors’ calculations suggest that within several years of operation of IceCube-Gen2, there is a good chance that we’ll be able to simultaneously detect gamma rays, neutrinos, and gravitational waves from bright SGRBs. This will provide us with powerful tools for learning about the physics of these energetic events.


    Shigeo S. Kimura et al 2017 ApJL 848 L4. doi:10.3847/2041-8213/aa8d14

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    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

  • richardmitnick 11:29 am on September 25, 2017 Permalink | Reply
    Tags: , , , , Neutrinos, ,   

    From U Wisconsin IceCube: “Looking for new physics in the neutrino sector” 

    U Wisconsin IceCube South Pole Neutrino Observatory

    25 Sep 2017
    Sílvia Bravo

    ICECUBE neutrino detector

    Neutrinos are intriguing in more ways than one. And although the fact that they have such tiny mass explains their quirky behavior, their allure remains intact. The issue is that neutrino masses are not predicted by the Standard Model; thus, on its own, the existence of a neutrino with mass is an indication of new physics. And that’s what scientists around the world, including at IceCube, want to learn: what type of new physics are neutrinos pointing to?

    New physics could appear in the form of a new type of neutrino or it could help us understand the nature of dark matter. The possibilities are endless. In a new search for nonstandard neutrino interactions, the IceCube Collaboration has tested theories that introduce heavy bosons, such as some Grand Unified Theories. These heavy bosons would explain, for example, why neutrinos have masses much smaller than their lepton partners. The study resulted in new constraints on these models, which are among the world’s best limits for nonstandard interactions in the muon-tau neutrino sector. These results have just been submitted to Physical Review D.

    Confidence limits from this analysis are shown as solid vertical red lines. The light blue and light green vertical lines show previous limits by Super-Kamiokande and another study using IceCube data at higher energy. Credit: IceCube Collaboration.

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

    The flavor of neutrinos oscillates as they travel through matter or empty space, a quantum effect on macroscopic scales that proves that they have mass. When atmospheric neutrinos reach IceCube after crossing the Earth, they have often morphed from muon into tau neutrinos. If TeV-scale bosons predicted by nonstandard theories exist, they will modify the probability that a given type of neutrino oscillates into other types. The result is that the disappearance pattern of muon neutrinos in IceCube will change, with effects that span a large range of energies.

    In IceCube, for studies using atmospheric neutrinos that sail through the Earth, these nonstandard interactions (NSIs) can be parametrized in terms of the strength of muon neutrino to tau neutrino morphing due to an NSI, a parameter called .

    IceCube researchers have analyzed three years of data, using the same neutrino sample used for a recent measurement of the neutrino oscillation parameters, but with an additional selection criterion to improve the signal purity. The remaining 4,625 candidate neutrino events were used to fit the oscillation parameters, including the NSI contribution.

    The best fit of muon to tau NSI oscillations was consistent with no nonstandard interactions. “Even though no new physics was shown by this study, it narrows in on the possible existence of new neutrino interactions with regular matter” says Carlos Argüelles, an IceCube researcher from MIT. “It also showcases the advantages of having a very broad energy range, so experiments like IceCube can look for new oscillation physics with neutrinos, which are 10 to 1000 times more energetic than the average proton.”

    The 90% confidence level upper limit on the NSI parameter is consistent with previous measurements by Super-Kamiokande, which at that time had set the world’s best limits. The new IceCube measurement slightly improves Super-Kamiokande’s measurements, also extending the energy range. A more recent study using published IceCube data at even higher energies has also set limits on the parameter, which in turn were slightly more stringent than the ones of the present study.

    Albrecht Karle, a professor of physics at UW–Madison, comments that “the results shown here are based on only a relatively small set of muon neutrinos available.” IceCube is collecting more than 100,000 muon neutrinos per year, which are yet to be mined for physics beyond the Standard Model. “With almost a million atmospheric neutrinos, IceCube has an incredible data set for investigating even small deviations from Standard Model physics.”

    And keeping in mind that it’s not all about the detector, Melanie Day, another IceCube researcher and co-author on this paper, adds, “Not enough is said about the value of teamwork and collaboration over individual contributions to scientific results. But without that, this result would not have been possible.”

    See the full article here .

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

  • richardmitnick 3:19 pm on September 22, 2017 Permalink | Reply
    Tags: , , Neutrinos, ,   

    From ORNL via CERN Courier: “Miniature detector first to spot coherent neutrino-nucleus scattering” 


    Oak Ridge National Laboratory

    CERN Courier

    Detector placement. No image credit

    The COHERENT collaboration at Oak Ridge National Laboratory (ORNL) in the US has detected coherent elastic scattering of neutrinos off nuclei for the first time. The ability to harness this process, predicted 43 years ago, offers new ways to study neutrino properties and could drastically reduce the scale of neutrino detectors.

    Neutrinos famously interact very weakly, requiring very large volumes of active material to detect their presence. Typically, neutrinos interact with individual protons or neutrons inside a nucleus, but coherent elastic neutrino-nucleus scattering (CEνNS) occurs when a neutrino interacts with an entire nucleus. For this to occur, the momentum exchanged must remain significantly small compared to the nuclear size. This restricts the process to neutrino energies below a few tens of MeV, in contrast to the charged-current interactions by which neutrinos are usually detected. The signature of CEνNS is a low-energy nuclear recoil with all nucleon wavefunctions remaining in phase, but until now the difficulty in detecting these low-energy nuclear recoils has prevented observations of CEνNS – despite the predicted cross-section for this process being the largest of all low-energy neutrino couplings.

    The COHERENT team, comprising 80 researchers from 19 institutions, used ORNL’s Spallation Neutron Source (SNS), which generates the most intense pulsed neutron beams in the world while simultaneously creating a significant yield of low-energy neutrinos.

    ORNL Spallation Neutron Source

    Approximately 5 × 1020 protons are delivered per day, each returning roughly 0.08 isotropically emitted neutrinos per flavour. The researchers placed a detector, a caesium-iodide scintillator crystal doped with sodium, 20 m from the neutrino source with shielding to reduce background events associated with the neutron-induced nuclear recoils produced from the SNS. The results favour the presence of CEνNS over its absence at the 6.7σ level, with 134±22 events observed versus 173±48 predicted.

    Crucially, the result was achieved using the world’s smallest neutrino detector, with a mass of 14.5 kg. This is a consequence of the large nuclear mass of caesium and iodine, which results in a large CEνNS cross-section.

    The intense scintillation of this material for low-energy nuclear recoils, combined with the large neutrino flux of the SNS, also contributed to the success of the measurement. In effect, CEνNS allows the same detection rates as conventional neutrino detectors that are 100 times more massive.

    “It is a nearly ideal detector choice for coherent neutrino scattering,” says lead designer Juan Collar of the University of Chicago. “However, other new coherent neutrino-detector designs are appearing over the horizon that look extraordinarily promising in order to further reduce detector mass, truly realising technological applications such as reactor monitoring.”

    Yoshi Uchida of Imperial College London, who was not involved in the study, says that detecting neutrinos via the neutral-current process as opposed to the usual charged-current process is a great advantage because it is “blind” to the type of neutrino being produced and is sensitive at low energies. “So in combination with other types of detection, it could tell us a lot about a particular neutrino source of interest.” However, he adds that the SNS set-up is very specific and that, outside such ideal conditions, it might be difficult to scale a similar detector in a way that would be of practical use. “The fact that the COHERENT collaboration already has several other target nuclei (and detection methods) being used in their set-up means there will be more to come on this subject in the near future.”

    See the full article here .

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    ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.


  • richardmitnick 12:15 pm on September 22, 2017 Permalink | Reply
    Tags: , groundwork for additional collaboration between the U.S. DOE its national laboratories (including Fermilab) and the UK Science and Technology Facilities Council, Neutrinos, UK labs and universities were important partners in the main Tevatron experiments CDF and DZero, UK Minister of State for Universities Science Research and Innovation Jo Johnson, UK science   

    From FNAL: “UK science minister announces $88 million for LBNF/DUNE, visits Fermilab” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Jo Johnson learns about accelerator technologies at Fermilab. From left: Fermilab Chief Strategic Partnerships Officer Alison Markovitz; Fermilab scientist Anna Grassellino; Andrew Price of the UK Science and Innovation Network; DUNE co-spokesperson Mark Thomson; STFC Chief Executive Brian Bowsher; UK Minister of State for Universities, Science, Research and Innovation Jo Johnson. Photo: Reidar Hahn

    UK minister Jo Johnson traveled to the United States this week to sign the first ever umbrella science and technology agreement between the two nations and to announce approximately $88 million in funding for the international Long-Baseline Neutrino Facility and Deep Underground Neutrino Experiment.

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

    FNAL DUNE Argon tank at SURF

    Surf-Dune/LBNF Caverns at Sanford

    SURF building in Lead SD USA

    On Thursday, he visited the host laboratory for LBNF/DUNE, the U.S. Department of Energy’s Fermi National Accelerator Laboratory, emphasizing the importance of the project and the strong scientific partnership between the two countries.

    Johnson, the UK minister of state for universities, science, research and innovation, signed the agreement on Wednesday in Washington, D.C. Signing for the United States was Judith G. Garber, acting assistant secretary of state for oceans and international environmental and scientific affairs.

    This new agreement lays the groundwork for additional collaboration between the U.S. DOE, its national laboratories (including Fermilab) and the UK Science and Technology Facilities Council. STFC funds research in particle physics, nuclear physics, space science and astronomy in the United Kingdom. The U.S. DOE is the largest supporter of basic research in the physical sciences in the United States.

    “Our continued collaboration with the U.S. on science and innovation benefits both nations,” said Johnson, “and this agreement will enable us to share our expertise to enhance our understanding of many important topics that have the potential to be world changing.”

    LBNF/DUNE will be a world-leading international neutrino experiment based in the United States. Fermilab’s powerful particle accelerators will create the world’s most intense beam of neutrinos and send it 800 miles through Earth to massive particle detectors, which will be built a mile underground at the Sanford Underground Research Facility in South Dakota.

    The UK research community is already a major contributor to the DUNE collaboration, providing expertise and components to the facility and the experiment. UK contributions range from the high-power neutrino production target to the data acquisition systems to the software that reconstructs particle interactions into visible 3-D readouts.

    DUNE will be the first large-scale experiment hosted in the United States that runs as a truly international project, with more than 1,000 scientists and engineers from 31 countries building and operating the facility. Its goal is to learn more about ghostly particles called neutrinos, which may provide insight into why we live in a matter-dominated universe that survived the Big Bang.

    The UK delegation visits the Fermilab underground neutrino experimental area. UK Minister Jo Johnson stands in the center. Immediately to his left is Fermilab Director Nigel Lockyer. Photo: Reidar Hahn

    In addition to Johnson, the UK delegation to Fermilab included Brian Bowsher, chief executive of STFC; Andrew Price of the UK Science and Innovation Network; and Martin Whalley, deputy consul general from the Great Britain Consulate in Chicago.

    They toured several areas of the lab, including the underground cavern that houses the NOvA neutrino detector, and the Cryomodule Test Facility, where components of the accelerator that will power DUNE are being tested. The UK will contribute world-leading expertise in particle accelerators to the upgrade of Fermilab’s neutrino beam and accelerator complex.

    “This investment is part of a long history of UK research collaboration with the U.S.,” said Bowsher. “International partnerships are the key to building these world-leading experiments, and I am looking forward to seeing our scientists work with our colleagues in the U.S. in developing this experiment and the exciting science that will happen as a result.”

    UK institutions have been a vital part of Fermilab’s 50-year history, from the earliest days of the laboratory. UK labs and universities were important partners in the main Tevatron experiments, CDF and DZero, in the 1980s and 1990s. UK institutions have been involved with accelerator research and development, are partners in Fermilab’s muon experiments and are at the forefront of Fermilab’s focus on neutrino physics.

    Sixteen UK institutions (14 universities and two STFC-funded labs) are contributors to the DUNE collaboration, the U.S.-hosted centerpiece for a world-class neutrino experiment. The collaboration is led by Mark Thomson, professor of experimental particle physics at the University of Cambridge, and Ed Blucher, professor and chair of the Department of Physics at the University of Chicago.

    “Our colleagues in the United Kingdom have been critical partners for Fermilab, for LBNF/DUNE and for the advancement of particle physics around the world,” said Fermilab Director Nigel Lockyer. “We look forward to the discoveries that these projects will bring.”

    See the full article here.

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    Fermilab Campus

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

  • richardmitnick 10:28 am on September 18, 2017 Permalink | Reply
    Tags: Alex Himmel of Fermilab, , , Chao Zhang of BNL, Congratulations to two award-winning DUNE collaborators, , , Neutrinos,   

    From NUS TO SURF: “Congratulations to two award-winning DUNE collaborators” 



    “It is great news that the US DOE has recognized the talents of two early career DUNE scientists — both Alex and Chao have made invaluable contributions to DUNE and are both deserving recipients of these prestigious funding awards.”
    — DUNE spokespersons Mark Thomson and Ed Blucher

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

    FNAL DUNE Argon tank at SURF

    Surf-Dune/LBNF Caverns at Sanford

    SURF building in Lead SD USA

    Chao Zhang of BNL. Credit: BNL

    Exerpted and adapted from Three Brookhaven Lab Scientists Selected to Receive Early Career Research Program Funding, BNL Newsroom, 15 Aug 2017.

    Brookhaven Lab physicist and DUNE collaborator Chao Zhang was selected by DOE’s Office of High Energy Physics to receive funding for a project titled Optimization of Liquid Argon TPCs for Nucleon Decay and Neutrino Physics. Liquid Argon TPCs form the heart of many large-scale particle detectors designed to explore fundamental mysteries in particle physics.

    Chao’s aim is to optimize the performance of the DUNE far detector LArTPCs to fully realize their potential to track and identify particles in three dimensions, with a particular focus on making them sensitive to rare proton decays.

    His team at Brookhaven Lab will establish a hardware calibration system to ensure the experiment’s ability to extract subtle signals using specially designed cold electronics that will sit within the detector. They will also develop software to reconstruct the three-dimensional details of complex events, and analyze data collected at a prototype experiment (ProtoDUNE, located at Europe’s CERN laboratory) to verify that these methods are working, before incorporating any needed adjustments into the design of the detectors for DUNE.

    “I am honored and thrilled to receive this distinguished award,” said Chao. “With this support, my colleagues and I will be able to develop many new techniques to enhance the performance of LArTPCs, and we are excited to be involved in the search for answers to one of the most intriguing mysteries in science, the matter-antimatter asymmetry in the universe.”

    Read full article.

    Alex Himmel of Fermilab. Credit: Fermilab

    This article is excerpted and adapted from a Fermilab news article, 14 September 2017.

    Fermilab’s Alex Himmel expects to spend a large chunk of his career working on the Deep Underground Neutrino Experiment (DUNE), the flagship experiment of the U.S. particle physics community. That is incentive, he says, to lay the groundwork now to ensure its success.

    The Department of Energy has selected Himmel, a Wilson fellow, for a 2017 DOE Early Career Research Award to do just that. He will receive $2.5 million over five years to build a team and optimize software that will measure the flashes of ultraviolet light generated in neutrino collisions in a way that will determine the energy of the neutrino more precisely than is currently possible.

    Photons released from neutrino collisions will arrive at their detectors deteriorated and distorted due to scattering and reflections; the light measured is not the same as what was given off.

    “What we want to know is, given an amount of energy deposited in the argon, how much light do we see, taking out all the other things we know about how the light moves inside the detector,” he explained.

    Researchers are already looking forward to the long-term, positive impact of Himmel’s research.

    “Alex has been a true leader in understanding the physics potential of scintillation light in liquid-argon detectors,” said Ed Blucher. “His plan to develop techniques to make the most effective use of photon detection will help to enable the best and broadest possible physics program for DUNE.”

    Himmel has deep ties with Fermilab and neutrinos, starting with his first job as a summer student at Fermilab when he was 16. In 2012, he won the Universities Research Association Thesis Award for his research on muon antineutrino oscillations at Fermilab’s MINOS experiment.

    Read full article.

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  • richardmitnick 9:10 am on September 18, 2017 Permalink | Reply
    Tags: , , Neutrinos, , ,   

    From Stanford: “What ‘Ghost Particles’ Might Tell Us About Our Origins” EXO-200 Experiment 

    Stanford University Name
    Stanford University

    Daisy Yuhas


    Stanford physicists hope an elusive subatomic particle will help us answer big questions, such as ‘Why is our universe dominated by matter?’

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

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

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

    The stars were still faintly visible on the morning four years ago that Scott Kravitz first drove out to the salt mines in southeastern New Mexico. Then a second-year graduate student in physics, Kravitz was preparing to journey half a mile below the Earth’s surface.

    When he arrived at the facility, Kravitz passed through security, donned coveralls and safety equipment (including a portable air purifier in case of fire), and boarded a mesh-walled container called the cage. The double-decker structure — which fits no more than six people on each level — is the only method for descending to the tunnels below.

    It was unlike any elevator Kravitz had ridden. Within seconds, he and his fellow passengers were swallowed by darkness. No one spoke. No one turned on a headlamp. The soft sounds of air whistling past and the rattling of the cage were all he could hear.


    “It was like a meditation,” Kravitz recalls. The trip felt longer than its five-minute duration. Kravitz was eager to disembark, but not out of nervousness. More than anything, he was excited about what lay below.

    When the doors opened, a wave of hot, stale air thick with salt dust greeted him. Headlamps and overhead lighting illuminated the excavated rose-gray walls and floor of the 250-million-year-old mineral reserve.

    What brought Kravitz to this remote spot beneath the desert was neither geology nor earth science. Nor was it waste disposal — though the nearly impermeable salt bed is primarily used for that purpose, housing drums of radioactive refuse. Kravitz, PhD ’17, had come as a member of Stanford physics professor Giorgio Gratta’s research team, which studies elusive subatomic particles called neutrinos. Down in the mines, the scientists are trying to detect an unusual event that could unlock mysteries about the makeup of everything around us.

    Little Neutral Ones

    The neutrino is a fundamental (or indivisible) particle of matter, significantly smaller than an atom. It is just one of 17 fundamental particles that physicists have discovered to date. Others include the electron, familiar from high school chemistry class, and the photon, or particle of light, which is the only fundamental particle our eyes can detect.

    Each of these particles has special properties, and the neutrino is no exception. For one, it is the most abundant particle of matter. Its name comes from the Italian for “little neutral one,” encapsulating both the fact that it is very tiny — even for a fundamental particle — and that it has no positive or negative electric charge.

    “Neutrinos are the particles that we understand the least,” says theoretical physicist André de Gouvêa. “And they are important for understanding a lot of natural phenomena.” A professor at Northwestern University, de Gouvêa has spent much of his career studying neutrinos and developing models to explain how they fit into our understanding of the rest of the universe.

    Neutrinos are born when the nucleus of an atom changes in some way. That change could come about when atoms in a radioactive material break down. But it could also happen when atomic nuclei join together (fusion) or split apart (fission), two of the most energetically intense events known to humankind.

    In a trailer-like clean room in the depths of the mine, Gratta’s team monitors the breakdown of a radioactive form of the element xenon. Radioactive material is inherently unstable. As the xenon decays, the nuclei within its atoms may release other particles. Gratta and others want to see whether neutrinos emerge and then annihilate each other.

    Certain theories predict such a find. But if the interaction exists, it will be tough to spot. “You are dealing with very rare processes,” Gratta explains.

    The salt mines offer an ideal location for their project. On Earth’s surface, we are constantly bombarded by subatomic particles that would be difficult to disentangle from an experiment’s data set. Deep underground, the layers of salt and earth create a shield that blocks most unwanted phenomena from the scientists’ detector.

    At the moment, the experiment — called EXO-200 — is in a race, of sorts, with several other particle physics experiments that have the same end goal.

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

    FNAL DUNE Argon tank at SURF

    Surf-Dune/LBNF Caverns at Sanford

    SURF building in Lead SD USA


    About EXO-200…
    The Enriched Xenon Observatory is an experiment in particle physics aiming to detect “neutrino-less double beta decay” using large amounts of xenon isotopically enriched in the isotope 136. A 200-kg detector using liquid Xe is currently being installed at the Waste Isolation Pilot Plant (WIPP) near Carlsbad, New Mexico. Many research and development efforts are underway for a ton-scale experiment, with the goal of probing new physics and the mass of the neutrino.

    Our Collaboration:

    University of Alabama
    Universität Bern
    Carleton University
    Colorado State University
    Drexel University
    Duke University
    Indiana University
    UC Irvine
    Institute of Basic Science (Republic of Korea)
    ITEP (Moscow)
    Laurentian University
    McGill University
    University of Erlangen-Nuremberg
    University of Illinois at Urbana-Champaign
    University of Maryland
    University of Massachusetts – Amherst
    University of North Carolina Wilmington
    University of South Dakota
    SLAC National Accelerator Laboraotory
    Stanford University
    Stony Brook University
    Technische Universität München
    Yale University


    Neutrinoless Double Beta Decay

    Neutrinoless double beta decay is a special case of beta decay. Beta decay is a common form of nuclear decay which occurs when a neutron in an unstable nucleus emits an electron and an antineutrino and becomes a proton.

    Double beta decay occurs when a nucleus is energetically or spin forbidden to decay through single beta decay. While it has been predicted to exist for a long time, the long half-life makes it difficult to observe. Double beta decay was only first observed in 1986. Many isotopes undergo double beta decay, including xenon 136. EXO-200 was the first experiment to observe this decay in xenon. In normal double beta decay, two electrons and two antineutrinos are ejected from the nucleus when two neutrons become protons. The half-lives of double beta decay isotopes are very long, above 1020 years. This is more than a billion times longer than the age of the universe! So if you started with 8 billion atoms that can undergo double beta decay at the beginning of the universe, you would expect about 1 to have decayed by now. 0nbb

    Neutrinoless double beta decay has not yet been seen, but some theories predict it. It is like normal double beta decay, but because of special properties of the neutrino, no neutrinos would be emitted from the nucleus. The electrons would carry all the energy of the decay, unlike normal double beta decay, in which the antineutrinos carry away energy. Thus, neutrinoless double beta decay has a unique, observable signature. In order for this to occur, the neutrino would have to be its own antiparticle. If neutrinos are their own antiparticles, which are known as “Majorana” particles, then this admits many elegant theories to explain how neutrinos acquire mass and why their mass is so much smaller than any other particle we know.

    We want to see neutrinoless double beta decay for two reasons. First, we don’t know if the neutrino is its own antiparticle or not, and seeing it would answer this question for sure. Second, we don’t know the exact mass of the neutrino and a measurement of the neutrinoless double beta decay half life would allow us to measure the neutrino mass. Even if we don’t see neutrinoless double beta decay, a limit on the half life places a limit on the neutrino mass.

    If you’re still curious, Physics World has a nice article on neutrinoless double beta decay that is more detailed, but still accessible to a lay person.

    EXO-200 is a prototype to develop techniques for working with liquid xenon in a time projection chamber (TPC). One possibility for tonne-scale EXO is a liquid TPC, so familiarity with EXO-200 technologies will contribute to the design of tonne-scale EXO. Additionally, EXO-200 provides a testing ground for developing and procuring extremely radiopure materials and removing backgrounds. EXO-200 has provided fundamental measurement of the double beta decay of xenon 136 and will provide improved limits on the rate of (or perhaps observation of) neutrinoless double beta decay.


    We are using 200 kg of liquid xenon (LXe) enriched to 80% of the 136 isotope for EXO-200. The LXe fills our TPC vessel. When a particle deposits energy in the liquid xenon, it ionizes the xenon atoms, knocking electrons off. We apply an electric field to the xenon, which pushes many of the electrons to wire grids where they are collected. The grid position provides a 2D location, and the number of electrons is related to the event’s energy. But some xenon ions recombine with the electrons before they can drift away. This puts the xenon atoms into excited states. When the excited atoms relax, they release ultraviolet light, known as scintillation, which we collect on avalanche photodiodes (APDs). The time between the light signal (which comes nearly instantaneously) and the ionization signal (which must drift and takes microsecond to arrive) allows us to reconstruct the full 3D location of the event when combined with the 2D position from the wire grids. Furthermore, the amount of light is also related to the event’s energy. Combining the ionization and light signals allows a better energy measurement than using either signal on its own.


    The TPC vessel is contained within a cryostat system to help keep the xenon at liquid temperature. The vessel is contained in a volume of HFE-7000, a synthetic fluid that is liquid from room temperature down to LXe temperatures. The HFE is within a large copper cryostat, which is then inside another coper cryostat with a vacuum gap in between for insulation. The cryostat is shielded with lead and contained in a class-100 cleanroom located 2150 ft underground at the Department of Energy’s Waste Isolation Pilot Plant. All of this is necessary to shield from radioactive backgrounds and cosmic rays. On top of that, materials contained within the lead have been extensively counted for radiopurity. The materials are low in radioactive isotopes and contamination. The majority of the material is ultrapur, copper, teflon, phosphorbronze, and acrylic.

    The stakes for their search are high. If neutrinos truly can cancel each other out, they could be the key to explaining one of the mysteries of how we came to be. Physicists recognize that when two particles of equal mass but opposite charge meet, they can collide and leave nothing but energy behind. When such an event occurs, it means that one particle was the other’s antiparticle. Antiparticles together make antimatter, and the existence of antimatter raises some uncomfortable questions. Nearly all particles of matter have antimatter counterparts, and because nature tends to favor balance, many scientists suspect that matter and antimatter were created equally at the dawn of time. But if that were the case, one might expect the two would simply destroy each other. Instead, we exist in a universe dominated by matter.

    If neutrinos can behave as their own antiparticles, that could help scientists decipher how matter particles came to outnumber their antimatter counterparts. Thus far, the search has come up empty. But the EXO-200 team is not discouraged. Regardless of whether they see this strange antimatter process, Gratta, Kravitz and their colleagues have already begun providing insight into an enigmatic particle. “Neutrinos have a number of peculiarities,” Gratta says. They have surprised scientists many times before and are bound to surprise them again.

    WHAT’S INSIDE: The EXO-200 experiment’s detector is composed of two parts — a central copper drum (bottom), which will be filled with xenon, and a large cooling system to keep the element in its liquid form. The detector enables Gratta and his team to study neutrinos. (Photos: Courtesy the EXO-200 Collaboration)


    Every second, trillions of neutrinos pass through you, but over a lifetime, only one or two may actually hit another particle in your body. They are small enough that they rarely bump into other particles, and because of their neutrality, they do not respond to the forces of electricity and magnetism. As a result, they can travel uninterrupted for long distances, and they are extremely difficult to catch. Stanford emeritus professor of physics Stan Wojcicki, another neutrino aficionado, explains that these particles have other curious properties. For example, the neutrino can come in any one of three types, or “flavors,” called electron, muon and tau. “As they travel across the atmosphere, they morph into another flavor,” Wojcicki says. From the late ’90s into the 2000s, Wojcicki studied those transformations.

    Shape-shifting is not unheard of among fundamental particles, but it was unexpected in neutrinos. Such changes are possible only through a quantum mechanical process that requires the particles involved to have mass. Yet, “the current theory of particle physics as a whole predicts that the mass of the neutrino should be zero,” de Gouvêa says. If scientists knew the precise mass, theoretical physicists could rework the existing models to build new, more comprehensive theories.

    The EXO-200 experiment could be well-positioned to resolve that quandary. If scientists succeed in their quest to see neutrinos behave as their own antimatter particles, Gratta explains, they will be “automatically measuring the mass of the particles involved.” That’s because physicists have worked out a relationship between the rate at which materials decay and the mass of the neutrinos present. Heavier neutrinos, for example, would be involved in more frequent decays than lighter neutrinos.

    More broadly, the EXO-200 experiment is testing two competing theories from the early 20th century about the nature of neutrinos. In one, proposed by a theoretical physicist named Paul Dirac, all particles can appear in one of four states that relate to their charge and how they move. But because neutrinos are neutral, another theorist, Ettore Majorana, suggested that each neutrino type might have just two variants. If so, he predicted that the two variants would have opposite qualities and therefore the same particle could cancel itself out — implying that the neutrino is its own antiparticle. (In July, physicists at Stanford and UC-Irvine demonstrated that they could create situations in which particle-like bundles of energy behave as both particle and antiparticle, adding extra heft to Majorana’s ideas.) “So, that’s what we’re after,” Gratta says. “We’re trying to detect whether neutrinos are Majorana particles.”

    Questions about the mass and variety of neutrinos are not merely academic. By better understanding their traits and behavior, scientists can also advance the study of the phenomena that produce them. Neutrinos from the sun, for example, are the product of fiery processes happening at that star’s core; by detecting those neutrinos, scientists have proof of a reaction they cannot otherwise observe (see sidebar, “Where Do Neutrinos Come From?”).

    Ghosts in the Machine

    Tucked within a corner of the salt mine, far from the waste storage, are metal containers set up by EXO-200 physicists to house their bright white, ultrasterilized “clean room.” The contrast between dark, gritty tunnel and hospital-esque experimental space is stark.

    As soon as they arrive, the scientists crowd into the clean room, three at a time, to change from miner gear into special Tyvek coveralls called bunny suits. This uniform prevents dirt, oil, hair and other detritus from dirtying their instruments. A large lead wall between the physicists and the detector itself forms an added radiation barrier. Without it, even a scientist’s sack lunch could significantly alter the detector’s readings.

    The EXO-200 detector was assembled at Stanford and moved into the mines in 2007, thanks to a collaborative effort among scientists that now spans 25 institutions in seven countries. EXO is an acronym for Enriched Xenon Observatory, and at its heart is a 200-kilogram (440-pound) tank filled with xenon. Radioactive xenon decays so slowly that the detector may only pick up data from a few events each year. To boost these numbers, the xenon is “enriched” to increase the odds of observing interesting decays. That means the scientists remove isotopes they won’t need while preserving the ones they expect to produce a neutrinoless decay.

    The task of neutrino hunting has been all about probability from the start. In 1930, the Austrian theoretical physicist Wolfgang Pauli first proposed the neutrino’s existence. At the time, he and his colleagues were puzzled. Several experiments had shown that radioactive elements decay and release electrons with much less energy than expected, given the materials involved. That finding might be explained, Pauli suggested, if another particle — incredibly small and without any charge — was also emerging from the decay.

    He figured the odds were so slim that anyone would be able to find this tiny neutral particle that he bet a case of Champagne against it. He is said to have remarked: “I have committed the cardinal sin of a theorist. I made a prediction which can never be tested.”

    Nonetheless, in the 1950s, American physicists Fred Reines and Clyde Cowan, based at the Los Alamos laboratory in New Mexico, took up the challenge. In honor of the strange ghostlike ability of their quarry, they named the experiment Project Poltergeist.

    Reines and Cowan built a giant detector for its time, 1 cubic meter in size. Because the neutrino only rarely touches other particles, the reasoning went — and still goes — that physicists need to monitor a very large amount of material for a very long time to increase the likelihood of spotting a neutrino in action. In 1956, Reines and Cowan confirmed that they had seen a neutrino interact with protons in tanks of cadmium chloride.

    Typically, “a neutrino comes into a detector and most of the time you don’t see it,” Stan Wojcicki says. “But very, very seldom, it will satisfy your curiosity and interact.” When that happens, depending on the materials involved, light, heat or even sound can be produced and measured.

    Researchers have built many kinds of neutrino detectors in the past half century — uncovering, in the process, the three flavors and the fact that neutrinos transform from one form into another. Today, there are essentially two types of detector. One catches particles that journey into the experiment from disparate sources, such as stars and power plants. Scientists on the Super-Kamiokande experiment in Japan, for example, observe neutrinos from the sun and atmosphere as they interact with particles within a detector that contains 50,000 tons of water and is situated beneath a mountain.

    The other class of detectors, which includes EXO-200, references the experiments that first inspired Pauli; they produce neutrinos within the detector using radioactive material and then measure the energy of particles such as electrons created during the decay. Using that information, the EXO-200 team can then determine whether neutrinos are present — or, as many hope, absent. Seeing a neutrinoless decay would indicate “a totally new process,” says Kravitz. “It implies that there are other particles out there that we don’t know about.”

    The Next Generation

    To date, there is still no confirmation that neutrinos serve as their own antiparticles. But Gratta’s team has made some interesting finds. In 2011, the researchers observed a rare pattern of decay in which a nucleus from an atom of xenon broke down to release two electrons and two neutrinos. The discovery is evidence of one of the slowest decay processes ever studied; it would ultimately take sextillions of years for their total sample to break down in this manner, longer than our universe has existed to date.

    In addition, the researchers have advanced the quest to ascertain the neutrino’s mass. Based on the languid rates of decay they have seen, the EXO-200 physicists can conclude that the neutrino is at least 3.5 million times lighter than an electron.

    To learn more, the scientists say it’s time for a new detector. EXO-200 will only continue to collect data for another year and a half, at which point the researchers believe they will have learned as much as they’re able to with that equipment. The proposed successor, dubbed NEXO, would contain a tank 25 times larger than the one in EXO-200’s detector. Able to accommodate about five tons of liquid xenon, NEXO would give the researchers significantly more decay data to study, accelerating the rate at which they can learn about these particles and enabling them to capitalize on what they’ve learned so far.

    In the meantime, the physicists have gained a certain fondness for their salt mine. “In many ways, it’s much more pleasant than other mines that I’ve been to,” Gratta says. Whereas some sites leave scientists mired in mud, he notes, “salt is very healthy.”

    Admittedly, it presents its challenges. When asked to provide a photograph from the tunnels, Gratta explains that salt dust and flash photography don’t mix — the images are speckled with bright white dots. “They look like stars,” he observes. The visual is a curious reminder of all the motes and particles we otherwise never see.

    “We were the first of these experiments to turn on,” Gratta says. “And hopefully, by this summer, we will be ahead.”

    See the full article here .

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