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  • richardmitnick 7:58 am on August 10, 2017 Permalink | Reply
    Tags: , , , , , , T2K   

    From ScienceNews: “Neutrino experiment may hint at why matter rules the universe” 

    ScienceNews bloc

    ScienceNews

    1
    NEUTRINO CLUES The T2K experiment found clues that neutrinos may behave differently than their antimatter partners. In a possible sighting of an electron neutrino at the Super-Kamiokande detector in Hida, Japan (shown), colored spots represent sensors that observed light from the interacting neutrino. Kamioka Observatory/ICRR/The University of Tokyo

    A new study hints that neutrinos might behave differently than their antimatter counterparts. The result amplifies scientists’ suspicions that the lightweight elementary particles could help explain why the universe has much more matter than antimatter.

    In the Big Bang, 13.8 billion years ago, matter and antimatter were created in equal amounts. To tip that balance to the universe’s current, matter-dominated state, matter and antimatter must behave differently, a concept known as CP, or “charge parity,” violation.

    In neutrinos, which come in three types — electron, muon and tau — CP violation can be measured by observing how neutrinos oscillate, or change from one type to another. Researchers with the T2K experiment found that muon neutrinos morphed into electron neutrinos more often than expected, while muon antineutrinos became electron antineutrinos less often. That suggests that the neutrinos were violating CP, the researchers concluded August 4 at a colloquium at the High Energy Accelerator Research Organization, KEK, in Tsukuba, Japan.

    T2K scientists had previously presented a weaker hint [Physical Review Letters]of CP violation. The new result is based on about twice as much data, but the evidence is still not definitive. In physicist parlance, it is a “two sigma” measurement, an indicator of how statistically strong the evidence is. Physicists usually require five sigma to claim a discovery.

    Even three sigma is still far away — T2K could reach that milestone by 2026. A future experiment, DUNE, now under construction at the Sanford Underground Research Laboratory in Lead, S.D., may reach five sigma.

    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

    It is worth being patient, says physicist Chang Kee Jung of Stony Brook University in New York, who is a member of the T2K collaboration. “We are dealing with really profound problems.”

    See the full article here .

    Science News is edited for an educated readership of professionals, scientists and other science enthusiasts. Written by a staff of experienced science journalists, it treats science as news, reporting accurately and placing findings in perspective. Science News and its writers have won many awards for their work; here’s a list of many of them.

    Published since 1922, the biweekly print publication reaches about 90,000 dedicated subscribers and is available via the Science News app on Android, Apple and Kindle Fire devices. Updated continuously online, the Science News website attracted over 12 million unique online viewers in 2016.

    Science News is published by the Society for Science & the Public, a nonprofit 501(c) (3) organization dedicated to the public engagement in scientific research and education.

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  • richardmitnick 6:47 am on September 2, 2016 Permalink | Reply
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    From U Rochester: “Why neutrinos ‘matter’ in the early universe” 

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    University of Rochester

    August 30, 2016
    Monique Patenaude
    monique.patenaude@rochester.edu

    1
    T2K’s detector. (University of Tokyo photo / Kamioka Observatory, Institute for Cosmic Ray Research)

    Physicists love good symmetry—and that love is more than aesthetic appeal. One of the more important symmetries in all of science is the one between antimatter and matter.

    Energy in the early universe was transformed into equal parts of matter and antimatter. Barring anything else, those equal parts should have destroyed each other and left us with no matter with which to make stars and planets, and people and dogs.

    So physicists reason that something must have broken the matter-antimatter symmetry in the early universe, leaving us with a universe dominated by, well, stuff—one in which we (and dogs) can exist. The puzzle of how the matter-antimatter symmetry was broken is one of the great questions that particle physicists are trying to answer.

    University of Rochester graduate student, Konosuke (Ko) Iwamoto, updated the physics world on this question at the 38th biennial International Conference on High Energy Physics (ICHEP), in Chicago earlier this month.

    Iwamoto presented the highly anticipated findings from the Japan-based T2K neutrino experiment collaboration concerning the minute differences in the oscillations of subatomic particles called neutrinos and antineutrinos. (Almost every particle has an antimatter counterpart: a particle with the same mass but opposite charge.)

    T2K map
    T2K map

    The new results suggest that the matter-antimatter symmetry may have been broken by neutrinos. T2K’s experiments show that neutrinos and antineutrinos behave differently—the imbalance may have disrupted the matter/antimatter balance. Though the results are not conclusive—there is a 1-in-20 chance that their results are a fluke—but physicists are excited about the findings and further data gathering from T2K and other experiments is underway.

    “It is fabulous that Ko was chosen to present the findings of the T2K collaboration at ICHEP,” says Rochester professor of physics, Steven Manly. “ICHEP is the biggest international conference in particle physics and it was started in the 1950s by the then chair of Rochester’s physics department, Robert Marshak. Everyone still calls it the ‘Rochester conference.’”

    T2K is a large, international particle physics experiment operating in Japan. In this experiment, an intense beam of neutrinos is produced at the Japan Proton Accelerator Research Complex (J-PARC), which is located on the east coast of Japan, approximately 100 miles north of Tokyo. 185 miles away, the beam detector is located deep inside a mine in the mountains of western Japan. Physicists involved in the experiment measure how the neutrinos oscillate from one of three types, or “flavors,” to another during the transit across Japan.

    Japan Proton Accelerator Research Complex J-PARC
    Japan Proton Accelerator Research Complex J-PARC

    Professors Kevin McFarland and Manly lead the Rochester neutrino group on T2K. Members of the collaboration recently shared the 2016 Breakthrough Prize in Fundamental Physics “for the fundamental discovery and exploration of neutrino oscillations, revealing a new frontier beyond, and possibly far beyond, the standard model of particle physics.”

    See the full article here .

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    U Rochester Campus

    The University of Rochester is one of the country’s top-tier research universities. Our 158 buildings house more than 200 academic majors, more than 2,000 faculty and instructional staff, and some 10,500 students—approximately half of whom are women.

    Learning at the University of Rochester is also on a very personal scale. Rochester remains one of the smallest and most collegiate among top research universities, with smaller classes, a low 10:1 student to teacher ratio, and increased interactions with faculty.

     
  • richardmitnick 5:13 pm on August 23, 2016 Permalink | Reply
    Tags: , , , Hyper-Kamiokande, , , , T2K   

    From Physics Today: “Six reasons to get excited about neutrinos” 

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    Physics Today

    23 August 2016
    Andrew Grant

    Extra Dimensions: New results and upcoming experiments offer hope that neutrinos hold the key to expanding the standard model.

    The headlines from the recent International Conference on High Energy Physics (ICHEP) in Chicago trended sad, focused on the dearth of discoveries from the Large Hadron Collider. (See, for example, “Prospective particle disappears in new LHC data.”) Yet there was some optimism to be found in the Windy City, particularly among neutrino physicists. Here are six reasons to believe that neutrinos might provide the window into new physics that the LHC has not:

    Neutrinos are proof that the standard model is wrong. Sure, we know that dark matter and dark energy are missing from the standard model. But neutrinos are standard-model members, and the theoretical predictions are wrong. Prevailing theory says that neutrinos are massless; the Nobel-winning experiments at the Sudbury Neutrino Observatory and Super-Kamiokande demonstrated definitively that neutrinos oscillate between three flavors (electron, muon, and tau) and thus have mass. André de Gouvêa, a theoretical physicist at Northwestern University, deems neutrinos the “only palpable evidence of physics beyond the standard model.” Everything we learn about neutrinos in the coming years is new physics.

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    This signal from May 2014 denotes the detection of an electron neutrino by Fermilab’s NOvA experiment. Credit: NOvA Neutrino Experiment.

    FNAL/NOvA experiment
    FNAL/NOvA experiment map

    Neutrinos’ ability to morph from one flavor to another is only now starting to be understood. Each of neutrinos’ three flavors is actually a quantum superposition of three different mass states. By understanding the interplay of the three mass states, characterized by parameters called mixing angles, physicists can pin down how neutrinos transform between flavors. Fresh data from the NOvA experiment at Fermilab near Chicago suggest that neutrino mixing may not be as simple as most theories predict.

    Neutrinos may exhibit charge conjugation–parity (CP) violation. All known examples of CP violation, in which particle decays proceed differently with matter than with antimatter, take place in processes involving quark-containing particles like kaons and B mesons. But at the Neutrino 2016 meeting in London and at ICHEP, the T2K experiment offered fresh data hinting at matter–antimatter asymmetry for neutrinos.

    T2K Experiment
    Super-Kamiokande
    T2K map
    T2K Experiment

    After firing beams of muon neutrinos and antineutrinos at the Super-Kamiokande detector in Japan, scientists expected to detect 23 electron neutrinos and 7 electron antineutrinos; instead they have spotted 32 and 4, respectively. T2K isn’t anywhere close to achieving a 5 σ result, but the evidence for CP violation seems to be growing as the experiment acquires more data.

    Neutrinos may be the first fundamental particles that are Majorana fermions. Because the neutrino is the only fermion that is electrically neutral, it is also the only one that could be a Majorana fermion, a particle that is identical to its antiparticle. Learning whether neutrinos are Majorana particles or typical Dirac fermions would provide invaluable insight as to how neutrinos acquired mass at the dawn of the universe, de Gouvêa says. To determine the nature of neutrinos, physicists are hunting for a process called neutrinoless double beta decay. In typical double beta decay, two neutrons transform into protons and emit a pair of antineutrinos. If those antineutrinos are Majorana particles, they could annihilate each other. A 16 August paper from the KamLAND-Zen experiment in Japan reports the most stringent limits for the rate of neutrinoless double beta decay, further constraining the possibility that neutrinos are Majorana particles.

    Another neutrino flavor may be waiting to be discovered. The discovery of a fourth neutrino flavor, the sterile neutrino, would make every particle physicist forget about the LHC’s particle drought. Such a neutrino could enable physicists to explain dark matter or the absence of antimatter in the universe. The Antarctic detector IceCube just reported a negative result in the hunt for a sterile neutrino, but results from prior experiments still leave some wiggle room for the particle’s existence.

    Multiple powerful neutrino experiments are on the horizon. The NOvA experiment is up and running and delivering data that, at least so far, seem to complement T2K’s hints of CP violation. Fermilab scientists are already excited about the Deep Underground Neutrino Experiment, which should come on line around 2025.

    FNAL LBNF/DUNE from FNAL to SURF
    FNAL LBNF/DUNE from FNAL to SURF

    Hyper-Kamiokande, a megadetector in Japan with a million-ton tank of water for neutrino detection, should start operations around the same time.

    See the full article here .

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    “Our mission

    The mission of Physics Today is to be a unifying influence for the diverse areas of physics and the physics-related sciences.

    It does that in three ways:

    • by providing authoritative, engaging coverage of physical science research and its applications without regard to disciplinary boundaries;
    • by providing authoritative, engaging coverage of the often complex interactions of the physical sciences with each other and with other spheres of human endeavor; and
    • by providing a forum for the exchange of ideas within the scientific community.”

     
  • richardmitnick 2:56 pm on August 8, 2016 Permalink | Reply
    Tags: , , , , T2K   

    From ICL: “Evidence mounts that neutrinos are the key to the universe’s existence” 

    Imperial College London
    Imperial College London

    06 August 2016
    Hayley Dunning

    T2K Experiment
    T2K map
    T2K Experiment; T2K map

    1
    The T2K near detector. No image credit

    New experimental results show a difference in the way neutrinos and antineutrinos behave, which could explain why matter persists over antimatter.

    The results, from the T2K experiment in Japan, show that the degree to which neutrinos change their type differs from their antineutrino counterparts. This is important because if all types of matter and antimatter behave the same way, they should have obliterated each other shortly after the Big Bang.

    So far, when scientists have looked at matter-antimatter pairs of particles, no differences have been large enough to explain why the universe is made up of matter – and exists – rather than being annihilated by antimatter.

    Neutrinos and antineutrinos are one of the last matter-antimatter pairs to be investigated since they are difficult to produce and measure, but their strange behaviour hints that they could be the key to the mystery.

    Flavour change

    Neutrinos (and antineutrinos) come in three ‘flavours’ of tau, muon and electron, each of which can spontaneously change into the other as the neutrinos travel over long distances.

    The latest results, announced today by a team of researchers including physicists from Imperial College London, show more muon neutrinos changing into electron neutrinos than muon antineutrinos changing into electron antineutrinos.

    This difference in muon-to-electron changing behaviour between neutrinos and antineutrinos means they would have different properties, which could have prevented them from destroying each other and allow the universe to exist.

    To explore the (anti)neutrino flavour changes, known as osciallations, the T2K experiment fires a beam of (anti)neutrinos from the J-PARC laboratory at Tokai Village on the eastern coast of Japan.

    It then detects them at the Super-Kamiokande detector, 295 km away in the mountains of the north-western part of the country. Here, the scientists look to see if the (anti)neutrinos at the end of the beam matched those emitted at the start.

    Very intriguing

    The latest results were concluded from relatively few data points, meaning there is still a one in 20 chance that the results are due to random chance, rather than a true difference in behaviour. However, the result is still exciting for the scientists involved.

    Dr Morgan Wascko, international co-spokesperson for the T2K experiment from the Department of Physics at Imperial said: “This is an important first step towards potentially solving one of the biggest mysteries in science.

    “T2K is the first experiment that is able to study neutrino and antineutrino oscillation under the same conditions, and the disparity we have observed is, while not yet statistically significant, very intriguing.”

    Dr Yoshi Uchida, also from the Department of Physics at Imperial and a principal investigator at T2K, added: “More data is needed to prove conclusively that neutrinos and antineutrinos behave differently, but this result is an indication that neutrinos will continue to provide breakthroughs in our understanding of the universe.

    Upgrades to the equipment that produces (anti)neutrinos, as well as to the detector that measures them, are expected to add more data within the next decade, and determine whether the difference is in fact real.

    See the full article here .

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    Imperial College London

    Imperial College London is a science-based university with an international reputation for excellence in teaching and research. Consistently rated amongst the world’s best universities, Imperial is committed to developing the next generation of researchers, scientists and academics through collaboration across disciplines. Located in the heart of London, Imperial is a multidisciplinary space for education, research, translation and commercialisation, harnessing science and innovation to tackle global challenges.

     
  • richardmitnick 7:58 pm on July 11, 2016 Permalink | Reply
    Tags: , , , , T2K   

    From New Scientist: “Neutrinos hint at why antimatter didn’t blow up the universe” 

    NewScientist

    New Scientist

    4 July 2016
    Lisa Grossman

    1
    Super-Kamiokande: a huge detector looking out for tiny particles. Kamioka Observatory/ICRR(Institute for Cosmic Ray Research)/The University of Tokyo

    It could all have been so different. When matter first formed in the universe, our current theories suggest that it should have been accompanied by an equal amount of antimatter – a conclusion we know must be wrong, because we wouldn’t be here if it were true. Now the latest results from a pair of experiments designed to study the behaviour of neutrinos – particles that barely interact with the rest of the universe – could mean we’re starting to understand why.

    Neutrinos and their antimatter counterparts, antineutrinos, each come in three types, or flavours: electron, muon and tau. Several experiments have found that neutrinos can spontaneously switch between these flavours, a phenomenon called oscillating.

    The T2K experiment in Japan watches for these oscillations as neutrinos travel between the J-PARC accelerator in Tokai and the Super-Kamiokande neutrino detector in Kamioka, 295 kilometres away.

    T2K map
    T2K map

    It began operating in February 2010, but had to shut down for several years after Japan was rocked by a magnitude-9 earthquake in 2011.

    Puff of radiation

    In 2013, the team announced that 28 of the muon neutrinos that took off from J-PARC had become electron neutrinos by the time they reached Super-Kamiokande, the first true confirmation that the metamorphosis was happening.

    They then ran the experiment with muon antineutrinos, to see if there was a difference between how the ordinary particles and their antimatter counterparts oscillate. An idea called charge-parity (CP) symmetry holds that these rates should be the same.

    CP symmetry is the notion that physics would remain basically unchanged if you replaced all particles with their respective antiparticles. It appears to hold true for nearly all particle interactions, and implies that the universe should have produced the same amount of matter and antimatter in the big bang.

    Matter and antimatter destroy one another, so if CP symmetry holds, both should have mostly vanished in a puff of radiation early on in the universe’s history, well before matter was able to congeal into solid stuff. That’s clearly not what happened, but we don’t know why. Any deviation from CP symmetry we observe could help explain this discrepancy.

    “We know in order to create more matter than antimatter in the universe, you need a process that violates CP symmetry,” says Patricia Vahle, who works on NoVA, a similar experiment to T2K that sends neutrinos between Illinois and Minnesota.

    FNAL/NOvA experiment
    FNAL/NOvA experiment

    “So we’re going out and looking for any process that can violate this CP symmetry.”

    Flavour changers

    We already know of one: the interactions of different kinds of quarks, the constituents of protons and neutrons in atoms. But their difference is not great enough to explain why matter dominated so completely in the modern universe. Neutrino oscillations are another promising place to look for deviations.

    This morning at the Neutrino conference in London, UK, we got our first signs of such deviations. Hirohisa Tanaka of the University of Toronto, Canada, reported the latest results from T2K. They have now seen 32 muon neutrinos morphing into the electron flavour, compared to just 4 muon antineutrinos becoming the anti-electron variety.

    This is more matter and less antimatter than they expected to see, assuming CP symmetry holds. Although the number of detections in each experiment is small, the difference is enough to rule out CP symmetry holding at the 2 sigma level – in other words, there is only around a 5 per cent chance that T2K would see such differences if CP symmetry is preserved in this process.

    Particle physicists normally wait until things reach the 3 sigma level before getting excited, and won’t consider it a discovery until 5 sigma, so it’s early days for neutrinos breaking CP symmetry. But at the same conference, Vahle presented the latest results from NoVA that revealed the two experiments were in broad agreement about the possibility.

    The extent of CP violation rests on a key parameter called delta-CP, which ranges from 0 to 2π. Both teams found that their results were best explained by setting the value equal to 1.5π. “Their data really does prefer the same value that T2K does,” says Asher Kaboth, who works on T2K. “All of the preferences for the delta-CP stuff are pointing in the same direction.”

    NoVA plans to run its own antineutrino experiments next year, which will help firm up the results, and both teams are continuing to gather more data. It’s too soon to say definitively, but one of the mysteries of why we are here could be on the road to getting solved

    See the full article here .

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  • richardmitnick 8:23 am on July 11, 2016 Permalink | Reply
    Tags: , , , T2K, T2K presents first CP violation search result   

    From T2K: “T2K presents first CP violation search result” 

    T2K Experiment
    T2K Experiment, Japan

    T2K

    July 4, 2016

    New data support growing hint of different oscillation probabilities for neutrinos and antineutrinos.

    The T2K Collaboration presented new results on neutrino and antineutrino oscillations at the 27th International Conference on Neutrino Physics and Astrophysics (Neutrino 2016) at Imperial College London. T2K’s new data continue to prefer maximal mixing in the atmospheric angle (θ23), a value of the CP violating phase (δCP) near the maximally violating value -π/2, and the normal ordering of the neutrino mass hierarchy.

    With nearly twice the antineutrino data in 2016 compared to their 2015 result, T2K has performed a new analysis of all data, as shown in Fig 1, fitting both neutrino and antineutrino modes simultaneously. If CP violation occurs in neutrinos, it will manifest itself as a difference in the oscillation probabilities of neutrinos and antineutrinos. T2K’s observed electron antineutrino appearance event rate is lower than would be expected based on the electron neutrino appearance event rate, assuming that CP symmetry is conserved.

    When analyzed in a full framework of three neutrino and antineutrino flavors, and combined with measurements of electron antineutrino disappearance from reactor experiments, the size of the expected T2K 90% confidence interval for δCP with the current statistics ranges from approximately 2π (ie. the full range of δCP) to 1π depending on the true value of δCP and the true mass ordering. The actual T2K data yield a 90% confidence interval for δCP of [–3.02; –0.49] ([–1.87 ; –0.98]) for the normal (inverted) mass ordering, as shown in Fig 2. The CP conserving values (δCP=0 and δCP= π) lie outside of this interval.

    This new result is based on a data set of 1.44×1021 protons on target (POT), which is 20% of the POT exposure that T2K is set to receive. The full T2K exposure of 7.8×1021 POT is expected to come by ~2021, thanks to planned upgrades to the J-PARC Main Ring accelerator and the neutrino beamline. Moreover, T2K is proposing a run extension that will lead to a full exposure of 20×1021 POT, with 3σ sensitivity to CPV observation, by ~2025, when the next generation experiments are expected to begin operations.

    Violation of CP symmetry could hold the key to one of the most profound questions in science, which is: why is the universe comprised of matter today even though the Big Bang produced equal parts matter and antimatter? Although the new T2K result is not yet statistically significant, it is nevertheless an intriguing hint that the neutrino will continue to provide new breakthroughs in our understanding of the universe.

    More details on the new T2K result, as well as prospects for future running of the experiment, can be found in the presentation file from the London Neutrino 2016 conference.

    1
    Figure 1. Neutrino(top) and antineutrino(bottom) event distributions at the T2K far detector (Super-K), for both muon (left) and electron (right) flavors. In each figure, the black points show T2K (anti)neutrino data, the black curves show the expectations for the case of no neutrino oscillation, and the blue curves show the expectation for the best fit oscillation parameter values.

    2
    Figure 2. Negative log likelihood values as a function of the CP violating phase parameter δCP; The black (red) curves show the case for the normal (inverted) mass ordering; the black (red) vertical lines with hatch marks show the 90% CL allowed regions for the normal (inverted) mass ordering. This figure shows the result for T2K neutrino and antineutrino data, combined with reactor antineutrino results. The CP conserving values (δCP =0 and δCP= π) lie outside the 90% region.

    See the full article here .

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    T2K map
    T2K map

    T2K (Tokai to Kamioka) is a long-baseline neutrino experiment in Japan, and is studying neutrino oscillations. Neutrinos are elementary particles which come in three “flavours”: electron, muon, and tau. They only interact through the weak force, and are very difficult to detect as they rarely interact with matter. Electron neutrinos are produced in large numbers in the Sun, and solar neutrinos can pass all the way through the Earth without interacting.

    T2K has made a search for oscillations from muon neutrinos to electron neutrinos, and announced the first experimental indications for them in June 2011. These oscillations had never been observed by any previous experiment. T2K is also making measurements of oscillations from muon neutrinos to tau neutrinos (which have been seen by previous experiments). It will make the most accurate measurements to date of the probability of these oscillations and of the difference between the masses of two of the neutrinos (to be precise, T2K measures the difference between the squares of these masses).

     
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