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  • richardmitnick 9:06 am on February 11, 2014 Permalink | Reply
    Tags: , , , , , Symmetry Breaking   

    From Symmetry: “Quarks in the looking glass” 

    February 10, 2014
    Kandice Carter

    A recent experiment at Jefferson Lab probed the mirror symmetry of quarks, determining that one of their intrinsic properties is non-zero—as predicted by the Standard Model.
    sm
    Standard Model of Particle Physics

    From matching wings on butterflies to the repeating six-point pattern of snowflakes, symmetries echo through nature, even down to the smallest building blocks of matter. Since the discovery of quarks, the building blocks of protons and neutrons, physicists have been exploiting those symmetries to study quarks’ intrinsic properties and to uncover what those properties can reveal about the physical laws that govern them.

    A recent experiment carried out at Jefferson Lab has provided a new determination of an intrinsic property of quarks that’s five times more precise than the previous measurement.

    jlab
    Courtesy of Jefferson Lab

    The result has also set new limits, in a way complementary to such as the Large Hadron Collider at CERN, for the energies that researchers would need to access physics beyond the Standard Model. The Standard Model is a well-tested theory that, excluding gravity, describes the subatomic particles and their interactions, and physicists believe that peering beyond the Standard Model may help resolve many unanswered questions about the origins and underlying framework of our universe. The result was published in the February 6 edition of Nature.

    CERN

    CERN LHC New
    LHC

    The experiment probed properties of the mirror symmetry of quarks. In mirror symmetry, the characteristics of an object remain the same even if that object is flipped as though it were reflected in a mirror.

    The mirror symmetry of quarks can be probed by gauging their interactions with other particles through fundamental forces. Three of the four forces that mediate the interactions of quarks with other particles—gravity, electromagnetism and the strong force—are mirror-symmetric. However, the weak force—the fourth force—is not. That means that the intrinsic characteristics of quarks that determine how they interact through the weak force (called the weak couplings) are different from, for example, the electric charge for the electromagnetic force, the color charge for the strong force, and the mass for gravity.

    jlab
    Info-Graphic by: Jefferson Lab

    In Jefferson Lab’s Experimental Hall A, experimenters measured the breaking of the mirror symmetry of quarks through the process of deep-inelastic scattering. A 6.067 billion-electronvolt beam of electrons was sent into deuterium nuclei, the nuclei of an isotope of hydrogen that contain one neutron and one proton each (and thus an equal number of up and down quarks).

    “When it’s deep-inelastic scattering, the momentum carried by the electron goes inside the nucleon and breaks it apart,” says Xiaochao Zheng, an associate professor of physics at the University of Virginia and a spokesperson for the collaboration that conducted the experiment.

    To produce the effect of viewing the quarks through a mirror, half of the electrons sent into the deuterium were set to spin along the direction of their travel (like a right-handed screw), and the other half were set to spin in the opposite direction. Researchers identified about 170,000 million electrons that interacted with quarks in the nuclei through both the electromagnetic and the weak forces over a two-month period of running.

    “This is called an inclusive measurement, but that just means that you only measure the scattered electrons. So, we used both spectrometers, but each detecting electrons independently from the other. The challenging part is to identify the electrons as fast as they come,” Zheng says.

    The experimenters found an asymmetry, or difference, in the number of electrons that interacted with the target when they were spinning in one direction versus the other. This asymmetry is due to the weak force between the electron and quarks in the target. The weak force experienced by quarks has two components. One is analogous to electric charge and has been measured well in previous experiments. The other component, related to the spin of the quark, has been clearly isolated for the first time in the Jefferson Lab experiment.

    Specifically, the present result led to a determination of the effective electron-quark weak coupling combination 2C2u–C2d that is five times more precise than previously determined. This particular coupling describes how much of the mirror-symmetry breaking in the electron-quark interaction originates from quarks’ spin preference in the weak interaction. The new result is the first to show that this combination is non-zero, as predicted by the Standard Model.

    The last experiment to access this coupling combination was E122 at SLAC National Accelerator Laboratory. Data from that experiment were used to establish the newly theorized Standard Model more than 30 years ago.

    The good agreement between the new 2C2u–C2d result and the Standard Model also indicates that experimenters must reach higher energy limits in order to potentially find new interactions beyond the Standard Model with respect to the violation of mirror symmetry due to the spin of the quarks. The new limits, 5.8 and 4.6 trillion electronvolts, are within reach of the Large Hadron Collider at CERN, but the spin feature provided by this experiment cannot be identified cleanly in collider experiments.

    In the meantime, the researchers plan to extend this experiment in the next era of research at Jefferson Lab. In a bid to further refine the knowledge of quarks’ mirror-symmetry breaking, experimenters will use Jefferson Lab’s upgraded accelerator to nearly double the energy of the electron beam, reducing their experimental errors and improving the precision of the measurement by five to 10 times the current value. The experiment will be scheduled following completion of the upgrade in 2017.

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.



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  • richardmitnick 7:15 pm on March 20, 2012 Permalink | Reply
    Tags: , , , , Symmetry Breaking   

    From Symmetry/Breaking: “More physics for your funding” 

    Sarah Charley
    March 20, 2012

    “The decommissioning of the Tevatron represented the end of an era, but it also is ushering in the next generation of physics by providing valuable equipment to other experiments.

    ‘We don’t have enough funding to buy things new, so when we want to improve our experiments, we must search for and reuse equipment,’ said Bogdan Wojtsekhowski, a staff scientist at Jefferson Lab. ‘Scientists share equipment all the time. It’s the best way to get more physics for your budget.’

    Fermilab’s CDF experiment is donating photomultiplier tubes, computers, electronics racks and other equipment to experiments located all over the world,’ said Jonathan Lewis of Fermilab’s Particle Physics Division, who is organizing the decommissioning of the detector.

    ‘These computers are going to a lab in Korea,’ Lewis said during a tour of the building. ‘And we’re sending those electronics racks to Italy.’

    Jefferson Lab received more than 600 of the Tevatron experiment’s photomultiplier tubes for an experiment measuring the charge distribution inside protons. New, these photomultiplier tubes would have cost $700,000, but because they came from Fermilab, J-Lab had to pay only roughly $1,000 for disassembly and shipping costs.

    ‘We could not have afforded these photomultiplier tubes new, so we are very appreciative that we could get them from Fermilab,’ Wojtsekhowski said. ‘They will significantly enhance this experiment’s detection capabilities – by 30 percent, which means we will get more accurate data for the same beam time and stay within our budget. It was amazing luck.’

    The equipment swap is not limited to just national labs. Many universities, which often have tight research budgets, have placed claims on old Tevatron material.”

    See the article here.

    Symmetrybreaking is a joint Fermilab/SLAC publication

     
  • richardmitnick 10:35 am on January 24, 2012 Permalink | Reply
    Tags: , , , , , , , Symmetry Breaking   

    From ALICE at CERN via Symmetry/Breaking: “Scientists finish installation of 80-ton ‘particle thermometer’ at ALICE detector” 

    “Scientists on the ALICE experiment at the Large Hadron Collider just completed the installation of a crucial component for tracking high-energy particle jets. Without it, physicists would be lacking crucial tools to select which events out of billions to store and analyze.

    Engineers and physicists around the world worked intensively over five years to complete the electromagnetic calorimeter, or EMCal. The United States, supported by the Department of Energy’s Nuclear Physics Office, contributed 70 percent of the project costs. Scientists installed the last two pieces of the 80-ton device on Jan. 18.

    The EMCal’s heft comes from its many sheets of lead absorbers, which it needs to stop particles coming from collisions in the detector in order to measure their energy. “The calorimeter measures the energy of individual photons and electrons,” said ALICE physicist Peter Jacobs. “It’s a sort of particle thermometer.”

    EMCal

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    Scientists install the electromagnetic calorimeter at the ALICE detector. Image: CERN

    See the full post here.

     
  • richardmitnick 10:11 am on December 15, 2011 Permalink | Reply
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    From The Sanford Undergorund Laboratory via Symmetry/Breaking: “First physics experiments soon to move into former Homestake mine” 

    December 15, 2011
    Bill Harlan, Sanford Underground Laboratory
    Guest author

    “Construction of a 12,000-square-foot research campus a mile underground is nearing completion in the Black Hills of South Dakota, and scientists will begin to move the first physics experiments underground this spring.

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    Rick Labahn, project engineer (left) and Ben Sayler, director of education and outreach at Sanford Lab, check out the almost-finished Davis Cavern, located about a mile underground in the former Homestake mine. Photo by Matt Kapust, Sanford Underground Laboratory

    ‘We’re on schedule for occupancy in March 2012, but it’s quite a little process,’ said Project Engineer Rick Labahn, understating the complexity of his job. Labahn is directing the outfitting of the Davis Campus, which comprises two large underground halls at the 4,850-foot level of the Sanford Underground Laboratory in the former Homestake gold mine. Early next spring researchers will begin installing two experiments there—both of them at the leading edge of 21st-century physics. The Large Underground Xenon experiment, which already is taking test run data in a building on the surface, aims to become the world’s most sensitive detector to look for a mysterious substance called dark matter. Thought to comprise 80 percent of all the matter in the universe, dark matter remains undetected so far. The second experiment, the Majorana Demonstrator, will search for one of the rarest forms of radioactive decays—neutrinoless double-beta decay. Majorana could help determine whether subatomic particles called neutrinos can act as their own anti-particles, a discovery that could help physicists better explain how the universe evolved.”

    See the full article here.

     
  • richardmitnick 7:25 am on November 18, 2011 Permalink | Reply
    Tags: , , , , , , Symmetry Breaking   

    From Symmetry/Breaking – Hey, Higgs, Come Out, Come Out, Wherever You Are 

    Favored Higgs hiding spot remains after most complete search yet

    Kathryn Grim
    November 18, 2011

    “The CMS and ATLAS experiments at the Large Hadron Collider have backed the Standard Model Higgs boson, if it exists, into a corner with their first combined Higgs search result.

    The study, made public today, eliminates several hints the individual experiments saw in previous analyses but leaves in play the favored mass range for the Higgs boson, between 114 and 141 GeV. ATLAS and CMS ruled out at a 95 percent confidence level a Higgs boson with a mass between 141 and 476 GeV.

    The new result combines eight studies of predicted decays of the Higgs boson using data the experiments collected up to July. Physicists expected to be able to rule out an even wider mass range, between 125 and 500 GeV, based on the amount of data used and the sensitivities of the different search modes. But small excesses that could be the result of statistical fluctuations or could indicate the presence of a hidden particle reduced the range of masses that could be excluded.

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    The Standard Model Higgs boson is excluded at a 95 percent confidence level everywhere the thick black line drops below the red line. Image: ATLAS and CMS experiments

    ‘I think it could be an interesting message the data is telling us,’ said physicist Eilam Gross of the Weizmann Institute of Science, who shares leadership of the ATLAS experiment’s Higgs group. ‘Any discovery starts with the inability to exclude.”

    Several related measurements indirectly suggest a Standard Model Higgs boson exists at the lower end of the mass range.’ “

    See the full article here.

    Symmetrybreaking is a joint Fermilab/SLAC publication

     
  • richardmitnick 3:32 pm on November 15, 2011 Permalink | Reply
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    More on Heavy Ion Physics from Symmetry/Beaking 

    The making and tending of heavy ion beams for the LHC

    November 15, 2011
    Amy Dusto

    “This week the Large Hadron Collider began heavy ion physics, the process of colliding lead ions to learn about conditions in the primordial universe.

    The accelerator is expected to perform five to 10 times better than it did in its first run of these collisions last November. Although the heavy ion program will last only from now until CERN’s annual winter shutdown just after the first week of December, operators started preparations months in advance. Here symmetry breaking examines what it really takes to put lead beams in the LHC.

    The source

    Making heavy ions is more complicated than preparing the protons used in regular LHC collisions, which come from hydrogen gas. Since hydrogen atoms have only one proton and one electron each, applying a voltage to them is sufficient to rip off their electrons, leaving a load of beam-ready, positively charged protons. But the source for heavy ions, enriched lead, starts with 82 electrons. Physicists do not have miracle flypaper to grab that many subatomic particles at once, so the process takes a few steps.

    Meet Detlef Kuchler, a heavy-ion expert who tends the lead source, the first part of the heavy-ion acceleration process, by hand. He helped develop the method of extracting lead ions decades ago and can explain from memory its hundreds of associated, unlabeled diagrams. Although several people work on the source, a flowchart of what to do when things go wrong at this stage dead-ends everywhere with, ‘Call the expert.’ It may as well say, ‘Call Detlef.’ He spends a lot of nights and weekends at CERN during heavy ion season.”

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    Heavy-ion expert Detlef Kuchler holds a container of lead. Image: CERN

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    Kuchler prepares the oven. Image: Amy Dusto

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    Operators test beams of lead ions in this linear accelerator. Image: CERN

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    Operators declared “stable beams” today, which means the LHC is ready for heavy ion physics. Image: John Jowett

    See the full article here.

     
  • richardmitnick 4:07 pm on November 14, 2011 Permalink | Reply
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    From Symmetry/Breaking: “LHCb uses charm to find asymmetry” 

    Antonella Del Rosso at CERN Bulletin

    “According to theory, matter and antimatter should have been created in equal parts during the big bang. But somehow, the balance of the two skewed in the universe’s first moments. Now, matter dominates nature.

    Scientists from the LHCb collaboration at CERN recently saw curious possible evidence [take the time to look at this very cool piece] of this asymmetry: The difference between the decay rates of certain particles in their detector, D and anti-D charm mesons, was higher than expected.

    This anomaly is evidence of charge-parity violation, a more precise descriptor of nature’s preference for matter. Other LHC experiments have seen such symmetry breaking, but this is a first sighting in these charm particles.

    ‘CP violation is expected to be very small in charm physics,’ LHCb member Bolek Pietrzyk said. ‘This is a really surprising result.’

    The preliminary findings, which the collaboration presented Monday night in Paris, have a significance measured at 3.5 sigmas. Statistically speaking, this indicates an interesting observation. But scientists will need more certainty before they can declare a discovery.

    In this study, the group used data they collected in the first half of 2011. LHCb’s next steps will be to look at the rest of the 2011 data and see whether they can make sense of the observations within the Standard Model theory, or if they’ll need a new explanation.

    View the presentation about the LHCb result [same link as above, so you have another chance if you skipped by the first link].

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    7 TeV collision event seen by the LHCb detector. The LHCb experiment at the LHC will be well-placed to explore the mystery of antimatter. Image courtesy CERN

    Symmetrybreaking is a joint Fermilab/SLAC publication

     
  • richardmitnick 9:14 am on September 20, 2011 Permalink | Reply
    Tags: , , , Symmetry Breaking   

    From SLAC News Center via SymmetryBreaking: “How Slow is Slow? EXO Knows!” 

    September 8, 2011
    by Lori Ann White

    “Cooks think of watched pots. Handymen grumble about drying paint. Kids dread the endless night before Christmas morning.

    Turns out physicists have their own expression to convey the concept of “slow,” and now, thanks to the Enriched Xenon Observatory (EXO), they know how slow “slow” really is: The flurry of activity during the 13.75 billion years from the Big Bang to us was positively hasty in comparison.

    The expression is “2nubb” and it stands for two-neutrino double-beta decay, a rare type of particle decay undergone by certain forms of radioactive elements. In this type of decay, two neutrons, the neutral subatomic particles in the nucleus of an atom, spontaneously decay into two protons, two electrons, and two antineutrinos, which are the antimatter twins of the tiny, nearly massless mystery particles called neutrinos. The EXO team announced yesterday at a conference in Munich that, according to their measurements of two-neutrino double-beta decay in Xe-136, an isotope of xenon, the half-life of the process clocks in at 2.11 x 10^21 years. In other words, it would take 100 billion times longer than the universe has even existed for half of a sample of this radioactive isotope to decay via the 2nubb decay pathway.

    ‘This represents the slowest Standard Model process ever measured,’ said Giorgio Gratta, Stanford University physicist and member of the joint SLAC-Stanford Kavli Institute for Particle Astrophysics and Cosmology , who leads the team. The Standard Model is the best description scientists have for the way all the building blocks of matter, like the aforementioned neutrons, protons and electrons, fit together, and why two-neutrino double-beta decay happens in the first place.”

    See the full article here.

    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science. i1

     
  • richardmitnick 5:23 pm on July 26, 2011 Permalink | Reply
    Tags: , , , Symmetry Breaking   

    From SymmetryBreaking: “More than one way to search for SUSY” 

    July 26, 2011 | 11:44 am
    Kathryn Grim

    “Experiments at the Large Hadron Collider have yet to find signs of supersymmetric particles, scientists announced at the European Physical Society conference this week in Grenoble.

    But physicists will significantly improve their knowledge of SUSY in the coming year through indirect methods, which could include the discovery of the Higgs boson.

    ‘ For supersymmetry, this is a decisive moment in time,’ said theorist Lars Bergstrom of Stockholm University.

    Supersymmetry is a model that solves some significant problems of the Standard Model of particle physics. SUSY doubles the zoo of elementary particles by adding a partner for each of the particles we already know. It handily relates different types of particles in the Standard Model and offers an appealing candidate for dark matter. So far, scientists have found no evidence of SUSY particles at the LHC.

    Discovering the mass of the Higgs boson, which scientists could do by next year, will reveal something about the likelihood that supersymmetry exists. Members of the ATLAS and CMS collaborations both displayed at the EPS conference tiny hints of a Higgs boson with a mass within the interval of 115-150 GeV.

    ‘ If it were higher than 140 GeV, you would have to twist things in weird ways to make supersymmetry work,’ Bergstrom said. He added, ‘ But one should never underestimate theorists.’ “

    Symmetrybreaking is a joint Fermilab/SLAC publication

     
  • richardmitnick 11:37 am on June 30, 2011 Permalink | Reply
    Tags: , , , , , Symmetry Breaking   

    From Fermilab via SymmetryBreaking: “New Tevatron collider result may help explain the matter-antimatter asymmetry in the universe” 

    • Don Lincoln

    June 30, 2011

    “About a year ago, the DZero collaboration at Fermilab published a tantalizing result in which the universe unexpectedly showed a preference for matter over antimatter. Now the collaboration has more data, and the evidence for this effect has grown stronger.

    The result is extremely exciting: The question of why our universe should exist solely of matter is one of the burning scientific questions of our time. Theory predicts that matter and antimatter was made in equal quantities. If something hadn’t slightly favored matter over antimatter, our universe would consist of a bath of photons and little else. Matter wouldn’t exist.

    The Standard Model predicts a value near zero for one of the parameters that is associated with the difference between the production of muons and antimuons in B meson decays. The DZero results from 2010 and 2011 differ from zero and are consistent with each other. The vertical bars of the measurements indicate their uncertainty.

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    The Standard Model of elementary particles, with the gauge bosons in the rightmost column

    The 2010 measurement looked at muons and antimuons emerging from the decays of neutral mesons containing bottom quarks, which is a source that scientists have long expected to be a fruitful place to study the behavior of matter and antimatter under high-energy conditions. DZero scientists found a 1 percent difference between the production of pairs of muons and pairs of antimuons in B meson decays at Fermilab’s Tevatron collider. Like all measurements, that measurement had an uncertainty associated with it. Specifically, there was about a 0.07 percent chance that the measurement could come from a random fluctuation of the data recorded. That’s a tiny probability, but since DZero makes thousands of measurements, scientists expect to see the occasional rare fluctuation that turns out to be nothing.

    During the last year, the DZero collaboration has taken more data and refined its analysis techniques. In addition, other scientists have raised questions and requested additional cross-checks. One concern was whether the muons and antimuons are actually coming from the decay of B mesons, rather than some other source.”

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    The Standard Model predicts a value near zero for one of the parameters that is associated with the difference between the production of muons and antimuons in B meson decays. The DZero results from 2010 and 2011 differ from zero and are consistent with each other. The vertical bars of the measurements indicate their uncertainty.

    See the full article here.

     
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