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

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

    MIT News

    MIT Widget

    MIT News

    March 26, 2018
    Jennifer Chu

    1
    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 10:08 am on October 23, 2017 Permalink | Reply
    Tags: , , CUORE collaboration, , , ,   

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

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    Berkeley Lab

    October 23, 2017
    Glenn Roberts Jr.
    geroberts@lbl.gov
    (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.

    2
    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 4:35 pm on September 2, 2016 Permalink | Reply
    Tags: , CUORE collaboration, , Seach for neutrinoless double beta decay,   

    From Symmetry: “CUORE almost ready for first cool-down” 

    Symmetry Mag

    Symmetry

    09/02/16
    Ricarda Laasch

    1
    CUORE collaboration

    The refrigerator that will become the coldest cubic meter in the universe is fully loaded and ready to go.

    Deep within a mountain in Italy, scientists have finished the assembly of an experiment more than one decade in the making. The detector of CUORE, short for Cryogenic Underground Observatory for Rare Events, is ready to be cooled down to its operating temperature for the first time.

    Ettore Fiorini, the founder of the collaboration, proposed the use of low temperature detectors to search for rare events in 1984 and started creating the first prototypes with his group in Milano. What began as a personal project involving a tiny crystal and a small commercial cooler has grown to a collaboration of 165 scientists loading almost one ton of crystals and several tons of refrigerator and shields.

    The CUORE experiment is looking for a rare process that would be evidence that almost massless particles called neutrinos are their own antiparticles, something that would give scientists a clue as to how our universe came to be.

    Oliviero Cremonesi, current spokesperson of the CUORE collaboration, joined the quest in 1988 and helped write the first proposal for the experiment. At first, funding agencies in Italy and the United States approved a smaller version: Cuoricino.

    “We had five exciting years of measurements from 2003 to 2008 on this machine, but we knew that we wanted to go bigger. So we kept working on CUORE,” Cremonesi says.

    In 2005 the collaboration got approval for the big detector, which they called CUORE. That started them on a whole new journey involving growing crystals in China, bringing them to Italy by boat, and negotiating with archeologists for the right to use 2000-year-old Roman lead as shielding material.

    “I imagine climbing Mount Everest is a little bit like this,” says Lindley Winslow, a professor at the Massachusetts Institute of Technology and group leader of the MIT activities on CUORE. “We can already see the top, but this last part is the hardest. The excitement is high, but also the fear that something goes wrong.”

    The CUORE detector, assembled between 2012 and 2014, consists of 19 fragile copper towers that each host 52 tellurium oxide crystals connected by wires and sensors to measure their temperature.

    For this final stage, scientists built a custom refrigerator from extremely pure materials. They shielded and housed it inside of a mountain at Gran Sasso, Italy.

    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO
    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, Italy

    At the end of July, scientists began moving the detector to its new home. After a brief pause to ensure the site had not been affected by the 6.2-magnitude earthquake that hit central Italy on August 24, they finished the job on August 26.

    The towers now reside in the largest refrigerator used for a scientific purpose. By the end of October, they will be cooled below 10 millikelvin (negative 460 Fahrenheit), colder than outer space.

    Everything has to be this cold because the scientists are searching for minuscule temperature changes caused by an ultra-rare process. It is predicted to occur only once every trillion trillion years and is called neutrinoless double beta decay.

    During a normal beta decay, one atom changes from one chemical element into its daughter element and sends out one electron and one antineutrino. For the neutrinoless double beta decay, this would be different: The element would change into its granddaughter. Instead of one electron and one neutrino sharing the energy of the decay, only two electrons would leave, and an observer would see no neutrinos at all.

    This would only happen if neutrinos were their own antiparticles. In that case, the two neutrinos would cancel each other out, and it would seem like they never existed in the first place.

    If scientists measure this decay, it would change the current scientific thinking about the neutrino and give scientists clues about why there is so much more matter than anti-matter in the universe.

    “We are excited to start the cool-down, and if everything works according to plan, we can start measuring at the beginning of next year,” Winslow says.

    See the full article here .

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  • richardmitnick 1:17 pm on April 23, 2015 Permalink | Reply
    Tags: , CUORE collaboration, ,   

    From Symmetry: “Extreme cold and shipwreck lead” 

    Symmetry

    April 23, 2015
    Lauren Biron

    Scientists have proven the concept of the CUORE experiment, which will study neutrinos with the world’s coldest detector and ancient lead.

    1
    Courtesy of the CUORE collaboration

    Scientists on an experiment in Italy are looking for a process so rare, it is thought to occur less than once every trillion, trillion years. To find it, they will create the single coldest cubic meter in the universe.

    The experiment, the Cryogenic Underground Observatory for Rare Events, will begin by the end of the year, scientists recently announced after a smaller version demonstrated the feasibility of the design.

    The project, based at Gran Sasso National Laboratory, will examine a property of ghostly neutrinos by looking for a process called neutrinoless double beta decay. If scientists find it, it could be a clue as to why there is more matter than antimatter in the universe–and show that neutrinos get their mass in a way that’s different from all other particles.

    The full CUORE experiment requires 19 towers of tellurium dioxide crystals, each made of 52 blocks just smaller than a Rubik’s cube. Physicists will place these towers into a refrigerator called a cryostat and cool it to 10 millikelvin, barely above absolute zero. The cryostat will eclipse even the chill of empty space, which registers a toasty 2.7 Kelvin (minus 455 degrees Fahrenheit).

    CUORE uses the cold crystals to search for a small change in temperature caused by these rare nuclear decays. Unlike ordinary beta decays, in which electrons and antineutrinos share energy, the neutrinoless double beta decay produces two electrons, but no neutrinos at all. It is as if the two antineutrinos that should have been produced annihilate one another inside the nucleus.

    “This would be really cool because it would mean that the neutrino and the antineutrino are the same particle, and most of the time we just can’t tell the difference,” says Lindley Winslow, a professor at MIT and one of over 160 scientists working on CUORE.

    Neutrinos could be the only fundamental particles of matter to have this strange property.

    For the past two years, scientists collected data on just one of the crystal towers housed in a smaller cryostat, a project called CUORE-0. The most recent result establishes the most sensitive limits for seeing neutrinoless beta decay in tellurium crystals. In addition, the researchers verified that the techniques developed to construct CUORE work well and reduce background radiation prior to the full experiment coming online.

    “It’s a great result for Te-130, We are also very excited that we were able to demonstrate that what’s coming online with CUORE is what we hoped it would be,” says Reina Maruyama, professor of physics at Yale University and a member of the CUORE Physics Board. “We look forward to shattering our own result from CUORE-0 once CUORE comes to life”

    Avoiding radioactive contamination and shielding the experiment from outside sources that might mimic the telltale energy signature CUORE is searching for is a priority. The mountains at Gran Sasso will provide one layer of shielding from cosmic bombardment, but the CUORE cryostat will also get a second layer of protection against the minor radiation of the mountain itself. Ancient Roman lead ingots, salvaged from a shipwreck that occurred more than 2000 years ago, have been melted down into a shield that will cocoon the crystal towers.

    Lead excels at blocking radiation but can itself become slightly radioactive when hit by cosmic rays. The ingots that sat at the bottom of the sea for two millennia have been spared cosmic bombardment and provide very clean, if somewhat exotic, shielding material.

    The next step for CUORE will be to finish commissioning the powerful refrigerator, the largest of its kind. The cryostat must remain stable even with the tons of material inside. After the detector is installed and the cryostat cooled, it will likely take between six months and a year to find the ultimate sensitivity, measure contamination (if there is any), and show that the detector works perfectly, says Yury Kolomensky, professor of physics at the University of California, Berkeley, and the US spokesperson for the CUORE collaboration. Then it will take data for five years.

    “And then we hope to come back with either a discovery [of neutrinoless double beta decay]–or not. And if not, that means we have shrunk the size of the haystack by a factor of 20,” Kolomensky says.

    If CUORE goes well, it could find itself a contender for the next generation of neutrinoless double beta decay experiments, something Kolomensky says the nuclear physics community plans to decide over the next two to three years. CUORE uses tellurium, a plentiful isotope that has good energy resolution, meaning scientists can tell precisely where the peak is and what caused it. Other large-scale neutrinoless double beta decay experiments use germanium or xenon instead.

    “The worldwide community is looking at all the technologies very carefully,” Kolomensky says. “If our detector works as advertised at this scale, we’ll be in a very strong position to build an even better detector.”

    CUORE’s journey has already been more than 30 years in the making, according to Oliviero Cremonesi, spokesperson for the collaboration.

    “It’s very emotional for me. We started in the ‘80s with milligram prototypes, and now we have a ton-size detector and a unique cryogenic system,” Cremonesi says. “Even more exciting is the knowledge that this adventure could continue in the future.”

    See the full article here.

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  • richardmitnick 1:10 pm on April 9, 2015 Permalink | Reply
    Tags: , CUORE collaboration, ,   

    From LBL: “For Ultra-cold Neutrino Experiment, a Successful Demonstration” 

    Berkeley Logo

    Berkeley Lab

    April 9, 2015
    Kate Greene

    1
    Bottom view of a CUORE tower. Credit: CUORE Collaboration

    2
    The CUORICINO Tower during the construction, before the installation of the copper shields. The 13 layers of TeO2 detectors are visible. Credit: CUORE Collaboration

    Today an international team of nuclear physicists announced the first scientific results from the Cryogenic Underground Observatory for Rare Events (CUORE) experiment. CUORE, located at the INFN Gran Sasso National Laboratories in Italy, is designed to confirm the existence of the Majorana neutrino, which scientists believe could hold the key to why there is an abundance of matter over antimatter. Or put another way: why we exist in this universe.

    The results of the experiment, called CUORE-0, were announced at INFN Gran Sasso Laboratories (LNGS) in Italy, the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), and at other institutions in the US.

    The findings are twofold. First, the CUORE-0 results place some of the most sensitive constraints on the mass of the elusive Majorana neutrino to date. With these new constraints, the CUORE team is essentially shrinking the size of the haystack that hides the Majorana needle, making it much more likely to be found.

    Second, the experiment, successfully demonstrates the performance of CUORE’s novel design—a detector made of towers of Rubik’s cube-sized crystals of tellurium dioxide. These towers are placed in a high-tech refrigerator that has been painstakingly decontaminated, shielded from cosmic rays, and cooled to near absolute zero.

    Today’s results represent data collected over two years from just one tower of tellurium dioxide crystals. By the end of the year, all 19 towers, each containing 52 crystals, will be online, increasing CUORE’s sensitivity by a factor of 20.

    “CUORE-0 is so far the largest detector operating at a temperature very close to absolute zero,” says Dr. Oliviero Cremonesi of INFN-Milano Bicocca, spokesperson for the CUORE collaboration. “CUORE is presently in its final stages of construction, and when completed, it will study the nuclear processes associated with the Majorana neutrino with unprecedented sensitivity.”

    “With the CUORE-0 results, we’ve proven that our experimental design, materials, and processes, which include extremely clean surfaces, pure materials, and precision assembly, are paying off,” says Yury Kolomensky, senior faculty scientist in the Physics Division at Berkeley Lab, professor of physics at UC Berkeley, and U.S. spokesperson for the CUORE collaboration.

    Annihilations in the Early Universe

    To pin down the Majorana neutrino, the researchers are looking for a telltale indicator, a rare nuclear process called neutrinoless double-beta decay. This process is expected to occur infrequently, if at all: less than once every septillion (a trillion trillion, or, a 1 followed by 24 zeros) years per nucleus.

    Unlike regular double-beta decay, which emits two anti-neutrinos, neutrinoless double-beta decay emits no neutrinos at all. It’s as if one of the anti-neutrinos has transformed into a neutrino and cancelled—or annihilated—its sibling inside the nucleus.

    “In 1937, Ettore Majorana predicted that neutrinos and anti-neutrinos could be two manifestations of the same particle – in modern language, they are called Majorana particles,” says Reina Maruyama, assistant professor of physics at Yale University, and a member of the CUORE Physics Board, which guided the analysis of the data. “Detecting neutrinoless double-beta decay would lead us directly to the Majorana particle, and give us hints as to why the universe has so much more matter than antimatter.”

    Known laws of physics forbid such matter-antimatter transformations for normal electrically charged particles like electrons and protons. But neutrinos, which are electrically neutral, may be a special kind of matter with special capabilities.

    The proposed matter-antimatter transitions, while extraordinarily rare now, if they happen at all, may have been common in the universe just after the big bang. The remainder of existence, then, after all the annihilations, would be the matter-full universe we see today.

    3
    Tower assembly. Credit: CUORE Collaboration

    Crystal Clarity

    The CUORE crystals of tellurium dioxide are packed with more than 50 septillion nuclei of tellurium-130, a naturally occurring isotope that can produce double-beta decay and possibly neutrinoless double-beta decay. For the experiment, the crystal towers sit in an extremely cold refrigerator called a cryostat that’s cooled to about 10 milliKelvin or -273.14 degrees Celsius. Last year, the CUORE cryostat set a record for being the coldest volume of its size.

    In the very cold CUORE crystals, presence of both nuclear processes would produce small but precisely measured temperature rises, observable by highly sensitive temperature detectors within the cryostat. These temperature increases correspond to spectra—essentially the amount of energy given off—from the nuclear event. Two-neutrino double-beta decay produces a broad spectrum. In contrast, neutrinoless double-beta decay would create a characteristic peak at the energy of 2528 kiloelectron-volts. This peak is what the researchers are looking for.

    The CUORE experiment sits about a kilometer beneath the tallest mountain of the Apennine range in Italy, where rock shields it from cosmic rays. This location, as well as the experimental design, enables the sensitivity required to detect neutrinoless double-beta decay.

    “The sensitivity demonstrated by the results today is outstanding,” says Stefano Ragazzi, director of the INFN Gran Sasso National Laboratories. “The INFN Gran Sasso Laboratories offers a worldwide unique environment to search for ultra-rare interactions of Majorana neutrinos and dark matter particles and is proud to host the most sensitive experiments in these fields of research.”

    “While there’s no direct evidence of the Majorana neutrino yet, our team is optimistic that CUORE is well positioned to find it,” says Ettore Fiorini, professor emeritus of physics at the University of Milano-Bicocca and founding spokesperson emeritus of the experiment. “There is a competition of sorts, with other experiments using complementary techniques to CUORE turning on at about the same time. The next few years will be tremendously exciting.”

    CUORE is supported jointly by the Italian National Institute for Nuclear Physics Istituto Nazionale di Fisica Nucleare (INFN) in Italy, and the Department of Energy’s Office of Science and the National Science Foundation in the US. The CUORE collaboration is made of 157 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.

    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 US Contractor Project Manager Richard Kadel (Physics Division, retired), Prof. Eugene Haller (UCB and Materials Science Division), staff scientists Jeffrey Beeman (MSD), Brian Fujikawa (Nuclear Science Division), Sarah Morgan (Engineering), Alan Smith (EH&S), postdocs Jacob Feintzeig (NSD). Raul Hennings-Yeomans (UCB and NSD), Ke Han (NSD, now Yale), Yuan Mei (NSD), and Vivek Singh (UCB and NSD), graduate students Alexey Drobizhev and Sachi Wagaarachchi (UCB and NSD), and engineers David Biare, Lucio di Paolo (NSD and LNGS), and Joseph Wallig (Engineering). Researcher Thomas Banks, postdoc Thomas O’Donnell, graduate student Jonathan Ouellet, all at physics department at UC Berkeley and NSD, NSD staff member Brian Fujikawa, and a former NSD postdoc Ke Han (now at Yale) made especially significant contributions to the analysis of CUORE-0 data and preparation of the results for the publication.

    See the full article here.

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  • richardmitnick 4:05 pm on October 28, 2014 Permalink | Reply
    Tags: , CUORE collaboration,   

    From LBL: “Creating the Coldest Cubic Meter in the Universe” 

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    Berkeley Lab

    October 28, 2014
    Kate Greene 510-486-4404

    In an underground laboratory in Italy, an international team of scientists has created the coldest cubic meter in the universe. The cooled chamber—roughly the size of a vending machine—was chilled to 6 milliKelvin or -273.144 degrees Celsius in preparation for a forthcoming experiment that will study neutrinos, ghostlike particles that could hold the key to the existence of matter around us.

    cube
    Scientist inspect the cryostat of the of the Cryogenic Underground Observatory for Rare Events. Credit: CUORE collaboration

    The collaboration responsible for the record-setting refrigeration is called the Cryogenic Underground Observatory for Rare Events (CUORE), supported jointly by the Istituto Nazionale di Fisica Nucleare (INFN) in Italy, and the Department of Energy’s Office of Science and National Science Foundation in the US. Lawrence Berkeley National Lab (Berkeley Lab) manages the CUORE project in the US. The CUORE collaboration is made of 157 scientists from the U.S., Italy, China, Spain, and France, and is based in the underground Italian facility called Laboratori Nazionali del Gran Sasso (LNGS) of the INFN.

    “We’ve been building this experiment for almost ten years,” says Yury Kolomensky, senior faculty scientist in the Physics Division of Berkeley Lab, professor of physics at UC Berkeley, and U.S. spokesperson for the CUORE collaboration. “This is a tremendous feat of cryogenics. We’ve exceeded our goal of 10 milliKelvin. Nothing in the universe this large has ever been as cold.”

    The chamber, technically called a cryostat, was designed and built in Italy, and maintained the ultra-cold temperature for more than two weeks. An international team of physicists, including students and postdoctoral scholars from Italy and the US, worked for over two years to assemble the cryostat, iron out the kinks, and demonstrate its record-breaking performance. The claim that no other object of similar size and temperature – either natural or man-made – exists in the universe was detailed in a recent paper by Jonathan Ouellet, Berkeley Lab Nuclear Science staff and UC Berkeley graduate student.

    In order to achieve such a low-temperature cryostat, the team used a multi chamber design that looks something like Russian nesting dolls: six chambers in total, each becoming progressively smaller and colder.

    dolls
    An illustration of the cross-section of the cryostat with a human figure for scale. Credit: CUORE collaboration

    The chambers are evacuated, isolating the insides from the room temperature, like in a thermos. The outer chambers are cooled to the temperature of liquid helium with mechanical coolers called pulse tubes – which do not require expensive cryogenic liquids. The innermost chamber is cooled using a process similar to traditional refrigeration in which a fluid evaporates and takes heat along with it. The only fluid that operates at such cold temperatures, however, is liquid helium. The researchers use a mixture of Helium-3 and Helium-4 that continuously circulates in a specialized cryogenic unit called dilution refrigerator, removing any remnant heat energy from the smallest chamber. The CUORE dilution refrigerator, built by Leiden Cryogenics in Netherlands, is one of the most powerful in the world. “It’s a Mack truck of dilution refrigerators,” Kolomensky says.

    The ultimate purpose for the coldest cubic meter in the universe is to house a new ultra-sensitive detector. The goal of CUORE is to observe a hypothesized rare process called neutrinoless double-beta decay. Detection of this process would allow researchers to demonstrate, for the first time, that neutrinos are their own antiparticles, thereby offering a possible explanation for the abundance of matter over anti-matter in our universe —in other words, why the galaxies, stars, and ultimately people exist in the universe at all.

    To detect neutrinoless double-beta decay, the team is using a detector made of 19 independent towers of tellurium dioxide (TeO2) crystals. Fifty-two crystals, each a little smaller than a Rubik’s cube, make up each tower. The team expects that they would be able to see evidence of the rare radioactive process within these cube-shaped crystals because the phenomenon would produce a barely detectable temperature rise, picked up by highly sensitive temperature sensors.

    Berkeley Lab, with Lawrence Livermore National Lab, has supplied roughly half the crystals for the CUORE project. In addition, Berkeley Lab designed and fabricated the highly sensitive temperature sensors – Neutron Transmutation Doped thermistors invented by Eugene Haller, UC Berkeley faculty and senior faculty scientist in the Material Science Division.

    UC postdocs Tom Banks and Tommy O’Donnell, who also have joint appointments with the Nuclear Science Division at Berkeley Lab, led the international team of physicists, engineers, and technicians to assemble over ten thousand parts into towers in nitrogen-filled glove boxes, including and bonding almost 8000 25-micron gold wires to 100-micron sized pads on the temperature sensors and on copper pads connected to detector wiring.

    The last of the 19 towers has recently been completed; all towers are now safely stored underground at LNGS, waiting to occupy the record-breaking vessel. The coldest cubic meter in the known universe is not just the feat of engineering; it will become a premier science instrument next year.

    US-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 US Contractor Project Manager Richard Kadel (Physics Division, retired), staff scientists Jeffrey Beeman (Materials Science Division), Brian Fujikawa (Nuclear Science Division), Sarah Morgan (Engineering), Alan Smith (EH&S), postdocs Raul Hennings-Yeomans (UCB and NSD), Ke Han (NSD, now Yale), and Yuan Mei (NSD), graduate students Alexey Drobizhev and Sachi Wagaarachchi (UCB and NSD), and engineers David Biare, Lucio di Paolo (NSD and LNGS), and Joseph Wallig (Engineering).

    For more information: CUORE collaboration news release here.

    See the full article here.

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