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  • richardmitnick 11:32 am on August 14, 2017 Permalink | Reply
    Tags: , ATLAS sees first direct evidence of light-by-light scattering at high energy, , , HEP, ,   

    From ATLAS at CERN: “ATLAS sees first direct evidence of light-by-light scattering at high energy” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    14th August 2017
    Katarina Anthony

    1
    A light-by-light scattering candidate event measured in the ATLAS detector. (Image: ATLAS Collaboration/CERN).

    Physicists from the ATLAS experiment at CERN have found the first direct evidence of high energy light-by-light scattering, a very rare process in which two photons – particles of light – interact and change direction. The result, published today in Nature Physics , confirms one of the oldest predictions of quantum electrodynamics (QED).

    “This is a milestone result: the first direct evidence of light interacting with itself at high energy,” says Dan Tovey (University of Sheffield), ATLAS Physics Coordinator. “This phenomenon is impossible in classical theories of electromagnetism; hence this result provides a sensitive test of our understanding of QED, the quantum theory of electromagnetism.”

    Direct evidence for light-by-light scattering at high energy had proven elusive for decades – until the Large Hadron Collider’s second run began in 2015. As the accelerator collided lead ions at unprecedented collision rates, obtaining evidence for light-by-light scattering became a real possibility. “This measurement has been of great interest to the heavy-ion and high-energy physics communities for several years, as calculations from several groups showed that we might achieve a significant signal by studying lead-ion collisions in Run 2,” says Peter Steinberg (Brookhaven National Laboratory), ATLAS Heavy Ion Physics Group Convener.

    Heavy-ion collisions provide a uniquely clean environment to study light-by-light scattering. As bunches of lead ions are accelerated, an enormous flux of surrounding photons is generated. When ions meet at the centre of the ATLAS detector, very few collide, yet their surrounding photons can interact and scatter off one another. These interactions are known as ‘ultra-peripheral collisions’.

    Studying more than 4 billion events taken in 2015, the ATLAS collaboration found 13 candidates for light-by-light scattering. This result has a significance of 4.4 standard deviations, allowing the ATLAS collaboration to report the first direct evidence of this phenomenon at high energy.

    “Finding evidence of this rare signature required the development of a sensitive new ‘trigger’ for the ATLAS detector,” says Steinberg. “The resulting signature — two photons in an otherwise empty detector — is almost the diametric opposite of the tremendously complicated events typically expected from lead nuclei collisions. The new trigger’s success in selecting these events demonstrates the power and flexibility of the system, as well as the skill and expertise of the analysis and trigger groups who designed and developed it.”

    ATLAS physicists will continue to study light-by-light scattering during the upcoming LHC heavy-ion run, scheduled for 2018. More data will further improve the precision of the result and may open a new window to studies of new physics. In addition, the study of ultra-peripheral collisions should play a greater role in the LHC heavy-ion programme, as collision rates further increase in Run 3 and beyond.

    See the full article here .

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  • richardmitnick 11:02 am on August 7, 2017 Permalink | Reply
    Tags: , , , , HEP, ,   

    From BNL: “MicroBooNE Produces Clearest Images of Neutrino Interactions Yet” 

    Brookhaven Lab

    August 7, 2017
    Kelsey Harper
    kharper@bnl.gov

    With updates to its electronics, the state-of-the-art neutrino detector now boasts impressive “signal to noise” sensitivity.

    1
    A 3D reconstruction of various particles, including neutrinos, interacting with the argon atoms inside MicroBooNE’s time projection chamber (TPC). This reconstruction is based off of when and where electrons produced by such interactions hit the plane of wires at one end of the TPC.

    FNAL/MicrobooNE

    A U.S.-based international collaboration studying “ghost-like” fundamental particles called neutrinos at an experiment known as MicroBooNE has produced the clearest images of neutrino interactions yet. The U.S. Department of Energy’s Brookhaven National Laboratory contributed to the design of this experiment from the beginning, and recently designed novel low-noise “cold electronics” for the detector, which is located at DOE’s Fermi National Accelerator Laboratory (Fermilab).

    A U.S.-based international collaboration studying “ghost-like” fundamental particles called neutrinos at an experiment known as MicroBooNE has produced the clearest images of neutrino interactions yet. The U.S. Department of Energy’s Brookhaven National Laboratory contributed to the design of this experiment from the beginning, and recently designed novel low-noise “cold electronics” for the detector, which is located at DOE’s Fermi National Accelerator Laboratory (Fermilab). With implementation of sophisticated noise-filtering software and updates to the detector hardware, the MicroBooNE collaboration has produced new clean images that make it easier for researchers to spot and study different types of neutrinos. A paper published in the Journal of Instrumentation illustrates the electronic challenges and solutions that led to this advance.

    “These innovations will naturally be included in the next generation of neutrino detector design,” said Brookhaven physicist Xin Qian, the leader of Brookhaven’s MicroBooNE physics group.

    The next generation is a big deal, literally: four 17,000-ton neutrino detectors (compared to MicroBooNE’s “small” 170-ton detector) are planned for a future Deep Underground Neutrino Experiment (DUNE).

    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

    This massive project will attempt to solve some of the biggest mysteries about neutrinos and their role in our universe.

    Tracking elusive particles

    Trillions of neutrinos—abundant yet elusive particles created in the nuclear reactions powering stars—stream from our sun to Earth every second. But because these particles so rarely interact with matter (which is why we don’t feel them passing through us), the detectors built to spot them must be extremely large and sensitive. To study neutrinos, scientists often also turn to more intense and easily understood sources of these particles: nuclear reactors and particle accelerators. The MicroBooNE collaboration studies neutrinos generated by the Booster proton accelerator at Fermilab, and collects detailed images of their interactions with a detector called a liquid-argon time projection chamber (LArTPC).

    3
    MicroBooNE’s time projection chamber—where the neutrino interactions take place—during assembly at Fermilab. The chamber measures ten meters long and two and a half meters high. Photo credit: Fermilab

    Although a ‘time projection chamber’ may sound like something from a Michael Crichton novel, it’s a very real technology that has transformed neutrino physics. It’s one of the few types of detectors that can see most of what happens when a neutrino interacts inside.

    Neutrinos come in three different “flavors”—electron, muon, and tau. As these neutrinos sail through the LArTPC’s school bus-sized tank of argon, kept liquid at a biting -303 degrees Fahrenheit, they occasionally interact with one of the argon atoms. This interaction produces charged and neutral particles, with a charged particle sometimes corresponding to the type of neutrino involved. The charged particles shoot through the bath, kicking electrons off the argon atoms they pass. These electrons get caught in the tank’s strong electric field and zip toward one end, eventually striking an array of wires. Based on the time and placement of each signal generated when an electron strikes a wire, scientists can figure out where the neutrino collision took place and what it looked like, allowing them to determine the type and energy of the neutrino detected.

    Trouble arises, however, when the little currents produced by the kicked-off electrons are muffled by electronic “noise.” Much like static on a radio, noise can drown out the signals of a neutrino collision, making the reconstructed paths blurry and difficult to analyze. According to Jyoti Joshi, a Brookhaven Lab post-doctoral fellow and the leader of the MicroBooNE detector physics working group, the challenge with LArTPC electronics is that “the signal we’re dealing with is so small that we need a very, very sensitive detector to amplify the signal so we can see it. But then, of course, you amplify anything, including noise.”

    4
    Brookhaven Lab physicist Hucheng Chen holding a replica of one of the 50 cold electronics boards installed in MicroBooNE. He is standing next to a mock-up of one of MicroBooNE’s 11 signal feedthroughs—the part of the detector where electronic signals from the cold electronics of the time projection chamber are carried to the warm electronics outside the cryostat.

    To try to minimize noise, MicroBooNE researchers worked with the engineers and scientists at Fermilab and in Brookhaven Lab’s Instrumentation Division who had pioneered the development of “cold electronics” for the experiment. Placing the electronics inside the detector tank reduces noise by shortening the path each signal has to travel before getting amplified. But because the tank is filled with liquid argon, these electronics had to be designed to thrive at temperatures hundreds of degrees below zero, long past the range where conventional electronics, like those in your smartphone, can function.

    The researchers expected the cold electronics installed at MicroBooNE to produce relatively clean signals and a good picture of the neutrino collisions. But “there are always some surprises,” said Mary Bishai, a senior physicist at Brookhaven Lab. “We had all this excess noise, and at the beginning people blamed the newest technology, the cold electronics.”

    After a year of collecting data, the researchers had enough information to pinpoint three sources of excess noise.

    “The noise was nearly all from the conventional electronics outside the argon tank,” said Mike Mooney, a Brookhaven Lab post-doctoral fellow and a key contributor in the effort to identify sources of noise.

    Most of the noise came from the external power supply for the electronics inside the bath, and from small fluctuations in the high voltage that creates the tank’s electric field. The third and least significant source of noise was an unusual burst that appeared only at a certain frequency, but the team has yet to determine where this final source comes from.

    The collaboration initially reduced the excess noise by developing a software program to sift out the desired electron signals. This initial solution allowed them to collect higher-quality data while addressing the actual sources of noise. “We demonstrated that software could remove certain types of noise from the data without losing the very small signals we want to see” said Brian Kirby, the BNL post-doc leading the evaluation of the software fix.

    5
    A comparison of particle interaction signals before and after MicroBooNE researchers removed the excess noise.

    With the software in place, the researchers could make the necessary changes to the detector’s hardware. They tackled the power supply noise by replacing the part that, just like your laptop charger, converts a higher voltage to a stable lower voltage that the cold electronics require. To combat the noise associated with generating the tank’s electric field, the researchers added a filter that would stabilize the high voltage. They eliminated more than eighty percent of the original noise with these hardware changes alone, and reduced it even further by then reapplying the software filters.

    The reconstructed neutrino paths are now sharply clear, like the burst of a small firework that was previously obscured by fog. These clean tracks are absolutely vital as the MicroBooNE team is implementing pattern recognition software to “train” a computer to pick out different types of neutrino collisions.

    “This is a really big deal in terms of pushing the field forward,” says Qian. “The lessons we learned will feed back to the next generation of technology development. For this kind of technology, there’s no way we can do it ‘just right’ the first time. We need to try it and improve it, try it and improve it.”

    The MicroBooNE collaboration will continue doing just that, trying and improving, as it lays the groundwork for DUNE, the biggest neutrino experiment ever attempted.

    Brookhaven’s work on MicroBooNE was funded by the DOE Office of Science (HEP) and the National Science Foundation.

    See the full article here .

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    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
    i1

     
  • richardmitnick 12:20 pm on August 4, 2017 Permalink | Reply
    Tags: , , , HEP, ,   

    From CERN ALPHA: “The ALPHA experiment explores the secrets of antimatter” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    CERN

    3 Aug 2017
    Stefania Pandolfi

    1
    Alpha Experiment (Image: Maximilien Brice/CERN)

    In a paper published today in Nature, the ALPHA experiment at CERN’s Antiproton Decelerator reports the first observation of the hyperfine structure of antihydrogen, the antimatter counterpart of hydrogen. These findings point the way to ever more detailed analyses of the structure of antihydrogen and could help understand any differences between matter and antimatter.

    The researchers conducted spectroscopy measurements on homemade antihydrogen atoms, which drive transitions between different energy states of the anti-atoms. They could in this way improve previous measurements by identifying and measuring two spectral lines of antihydrogen. Spectroscopy is a way to probe the internal structure of atoms by studying their interaction with electromagnetic radiation.

    In 2012, the ALPHA experiment demonstrated for the first time the technical ability to measure the internal structure of atoms of antimatter. In 2016, the team reported the first observation of an optical transition of antihydrogen. By exposing antihydrogen atoms to microwaves at a precise frequency, they have now induced hyperfine transitions and refined their measurements. The team were able to measure two spectral lines for antihydrogen, and observe no difference compared to the equivalent spectral lines for hydrogen, within experimental limits.

    “Spectroscopy is a very important tool in all areas of physics. We are now entering a new era as we extend spectroscopy to antimatter,” said Jeffrey Hangst, Spokesperson for the ALPHA experiment. “With our unique techniques, we are now able to observe the detailed structure of antimatter atoms in hours rather than weeks, something we could not even imagine a few years ago.”

    With their trapping techniques, ALPHA are now able to trap a significant number of antiatoms – up to 74 at a time – thereby facilitating precision measurements. With this new result, the ALPHA collaboration has clearly demonstrated the maturity of its techniques for probing the properties of antimatter atoms.

    The rapid progress of CERN’s experiments at the unique Antiproton Decelerator facility is very promising for ever more precise measurements to be carried out in the near future.

    CERN Antiproton Decelerator

    See the full article here.

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  • richardmitnick 8:25 am on August 3, 2017 Permalink | Reply
    Tags: 5 fundamental parameters from top quark decay, , , HEP, ,   

    From ATLAS: “5 fundamental parameters from top quark decay” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    3rd August 2017
    ATLAS Collaboration

    Number 4 may shock you!

    1
    Figure 1: The radiation of decay products from a polarized top quark follows patterns like those shown here. An analysis of the radiation is used to measure top quark properties in a new analysis. (Image: ATLAS Collaboration/CERN)

    For many physicists, discovering “new physics” means bringing to light a new particle. Another path to discovery lies in carefully measuring the properties of known particles and the interactions between them. The ATLAS experiment has now released new results on the top quark’s interaction with the charged intermediate vector boson.

    While the Higgs boson, which escaped observation until as recently as 2012, is certainly the most intriguing elementary particle, the top quark is arguably second. Heavier than even the Higgs boson, the top quark packs as much mass as a gold nucleus into a single point like constituent. Precise measurements of the top quark have taken a great leap forward at the Large Hadron Collider (LHC), where the production rate is high and the backgrounds are low.

    In the recent paper [JHEP], the ATLAS collaboration presents results obtained from decays of polarized top quarks. The polarization occurs when top quarks are produced singly through the parity-violating weak interaction, rather than in pairs through the parity-conserving strong interaction. Singly-produced top quarks have only recently become an important tool for discovery.

    2
    Figure 2: The plot shows the strength of each of the decay patterns such as those shown in Figure 1. The red solid line is the Standard Model expectation. The data points are the measurement. The measurement is in very good agreement with the Standard Model. (Image: ATLAS Collaboration/CERN)

    Nine distinct decay patterns, examples of which are shown in Figure 1, can be discerned in these decays, similar to antennae patterns. These patterns depend upon five fundamental constants (called f1, f1+,f0+,δ-, and P) governing the interaction between the top, its partner the bottom quark, and the charged weak boson (W±). Current understanding of physics holds that the top quark couplings should be “left-handed” like those of the other quarks, and that they should be identical between the top quarks and its antiparticle, the top antiquark. The new measurements put that understanding to the test.

    By studying the full multidimensional decay patterns, ATLAS measures many properties of the top-bottom-W interaction at the same time and without some of the assumptions that have been made in the past. The analysis is known for both its complexity and its power. Results are shown in Figure 2. Five fundamental constants are determined from the decay. The fourth one, δ–, quantifies the matter-antimatter asymmetry in top quark decays. It is consistent with zero and consistent with the current understanding of fundamental physics. Shocking? Maybe – but physicists are slowly getting used to the idea that the Standard Model is an excellent description of nature.

    The analysis uses proton–antiproton collisions at 8 TeV, data collected at the LHC in 2012. Investigators are now applying even more refined techniques to collisions at a higher centre-of-mass energy of 13 TeV now being collected at CERN. Future measurements at higher precision may finally observe deviations from the Standard Model.

    Links:

    Analysis of the Wtb vertex from the measurement of triple-differential angular decay rates of single top quarks produced in the t-channel at s√ = 8 TeV with the ATLAS detector (arXiv:1707.05393) [Above].
    EPS 2017 presentation by Susana Cabrera Urban: Anomalous couplings in single top and searches for rare top quark couplings with the ATLAS detector
    See also the full lists of ATLAS Conference Notes and ATLAS Physics Papers.

    See the full article here .

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  • richardmitnick 12:05 pm on July 20, 2017 Permalink | Reply
    Tags: , , , HEP, ,   

    From CERN: “HIE-ISOLDE: Nuclear physics gets further energy boost” 

    Cern New Bloc

    Cern New Particle Event

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    CERN

    17 July 2017
    Harriet Kim Jarlett

    CERN ISOLDE


    This is the Miniball germanium array, which is using the first HIE-ISOLDE beams for the experiments described below (Image: Julien Ordan /CERN)

    For the first time in 2017, the HIE- ISOLDE linear accelerator began sending beams to an experiment, marking the start of ISOLDE’s high-energy physics programme for this year.

    The HIE-ISOLDE (High-Intensity and Energy upgrade of ISOLDE) project incorporates a new linear accelerator (Linac) into CERN’s ISOLDE facility (which stands for the Isotope mass Separator On-Line). ISOLDE is a unique nuclear research facility, which produces radioactive nuclei (ones with too many, or too few, neutrons) that physicists use to research a range of topics, from studying the properties of atomic nuclei to biomedical research and to astrophysics.

    Although ISOLDE has been running since April, when the accelerator chain at CERN woke up from its technical stop over winter, HIE-ISOLDE had to wait until now as new components, specifically a new cryomodule, needed to be installed, calibrated, aligned and tested.

    Each cryomodule contains five superconducting cavities used to accelerate the beam to higher energies. With a third module installed, HIE-ISOLDE is able to accelerate the nuclei up to an average energy of 7.5 MeV per nucleon, compared with the 5.5 MeV per nucleon reached in 2016.

    This higher energy also allows physicists to study the properties of heavier isotopes – ones with a mass up to 200, with a study of 206 planned later this year, compared to last year when the heaviest beam was 142. From 2018, the HIE-ISOLDE Linac will contain four of these cryomodules and be able to reach up to 10 MeV per nucleon.

    “Each isotope we study is unique, so each experiment either studies a different isotope or a different property of that isotope. The HIE-ISOLDE linac gives us the ability to tailor make a beam for each experiment’s energy and mass needs,” explains Liam Gaffney, who runs the Miniball station where many of HIE-ISOLDE’s experiments are connected.

    The HIE-ISOLDE beams will be available until the end of November, with thirteen experiments hoping to use the facility during that time – more than double the number that took data last year. The first experiment, which begins today, will study the electromagnetic interactions between colliding nuclei of the radioactive isotope Selenium 72 and a platinum target. With this reaction they can measure whether or not the nuclei is more like a squashed disc or stretched out, like a rugby ball; or some quantum mechanical mixture of both shapes.

    See the full article here.

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  • richardmitnick 12:18 pm on July 16, 2017 Permalink | Reply
    Tags: Ask Ethan: How close are we to a Theory of Everything?, , , , , Electromagnetic and weak and strong and gravitational forces are the four fundamental forces known to exist in this Universe, , Formulation of the Standard Model in 1968, HEP, It’s not even a certainty that there even is a theory of everything, , , The Standard Model can be written as a single equation but all the forces within are not unified   

    From Ethan Siegel: “Ask Ethan: How close are we to a Theory of Everything?” 

    Ethan Siegel
    July 15, 2017

    1
    The idea that the forces, particles and interactions that we see today are all manifestations of a single, overarching theory is an attractive one, requiring extra dimensions and lots of new particles and interactions. Image credit: Wikimedia Commons user Rogilbert.

    “Those who begin coercive elimination of dissent soon find themselves exterminating dissenters. Compulsory unification of opinion achieves only the unanimity of the graveyard.” -Robert Jackson

    Since well before Einstein, it was the dream of those who study the Universe to find a single equation to govern as many phenomena as possible. Rather than have a separate law for each and every physical property the Universe has, we could unify these laws into a single, overarching framework. All the laws of electric charge, magnetism, electric currents, induction and more were unified into a single framework by James Clerk Maxwell in the mid-1800s. Ever since, physicists have dreamed of a Theory of Everything: a single equation governing all the laws of the Universe. What progress have we made? That’s the question of Paul Harding, who wants to know:

    “Has science made any progress with regards to the Grand Unified Theory and the Theory of Everything? And could you elaborate on what it would mean if we did find a unified equation?”

    Yes, we’ve made progress, but we’re not there yet. Not only that, but it’s not even a certainty that there even is a theory of everything.

    2
    The electromagnetic, weak, strong and gravitational forces are the four fundamental forces known to exist in this Universe. Image credit: Maharishi University of Management.

    The laws of nature, as we’ve discovered them so far, can be broken down into four fundamental forces: the force of gravity, governed by General Relativity, and the three quantum forces that govern particles and their interactions, the strong nuclear force, the weak nuclear force, and the electromagnetic force. The earliest attempts at a unified theory of everything came shortly after the publication of General Relativity, before we understood that there were fundamental laws to govern nuclear forces. These ideas, known as Kaluza-Klein theories, sought to unify gravitation with electromagnetism.

    3
    The idea of unifying gravitation with electromagnetism goes all the way back to the early 1920s, and the work of Theodr Kaluza and Oskar Klein. Image credit: SLAC National Accelerator Laboratory.

    SLAC Campus

    By adding an extra spatial dimension to Einstein’s General Relativity, a fifth dimension overall (in addition to the standard three space and one time) gave rise to Einstein’s gravity, Maxwell’s electromagnetism, and a new, extra scalar field. The extra dimension would need to be small enough to avoid interfering with the laws of gravity, and the details were such that the extra scalar field needed to have no discernible effects on the Universe. Since there was no way to formulate a quantum theory of gravity with this, the discovery of quantum physics and the nuclear forces — which this attempt at unification couldn’t account for — caused this to fall out of favor.

    4
    The quarks, antiquarks, and gluons of the standard model have a color charge, in addition to all the other properties like mass and electric charge. The Standard Model can be written as a single equation, but all the forces within are not unified. Image credit: E. Siegel.

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

    However, the strong and weak nuclear forces led to the formulation of the Standard Model in 1968, which brought the strong, weak, and electromagnetic forces under the same overarching umbrella. Particles and their interactions were all accounted for, and a slew of new predictions were made, including a big one about unification. At high energies of around 100 GeV (the energy required to accelerate a single electron to a potential of 100 billion volts), a symmetry unifying the electromagnetic and the weak forces would be restored. New, massive bosons were predicted to exist, and with the discovery of the W and Z bosons in 1983, this prediction was confirmed. The four fundamental forces were reduced down to three.

    5
    The idea of unification holds that all three of the Standard Model forces, and perhaps even gravity at higher energies, are unified together in a single framework. Image credit: © ABCC Australia 2015 http://www.new-physics.com.

    Unification was already an interesting idea, but models took off. People assumed that at higher energies still, the strong force would unify with the electroweak; that was where the idea of Grand Unification Theories (GUTs) came from. Some assumed that at even higher energies, perhaps around the Planck scale, the gravitational force would unify as well; this is one of the main motivations for string theory. What’s very interesting about these ideas, however, is that if you want to have unification, you need to restore symmetries at higher energies. And if the Universe has symmetries at high energies that are broken today, that translates into something observable: new particles and new interactions.

    6
    The Standard Model particles and their supersymmetric counterparts. This spectrum of particles is an inevitable consequence of unifying the four fundamental forces in the context of String Theory. Image credit: Claire David.

    So what new particles and interactions are predicted? This depends on which variant of unification theories you go for, but include:

    Heavy, neutral, dark-matter-like particles,
    supersymmetric partner particles,
    magnetic monopoles,
    heavy, charged, scalar bosons,
    multiple Higgs-like particles,
    and particles that mediate proton decay.

    Although we can be certain, from indirect observations, that there is some origin to our Universe’s dark matter, none of these particles or predicted decays have been observed to exist.

    7
    In 1982, an experiment running under the leadership of Blas Cabrera, one with eight turns of wire, detected a flux change of eight magnetons: indications of a magnetic monopole. Unfortunately, no one was present at the time of detection, and no one has ever reproduced this result or found a second monopole. Image credit: Cabrera B. (1982). First Results from a Superconductive Detector for Moving Magnetic Monopoles, Physical Review Letters, 48 (20) 1378–1381.

    This is a pity, in many regards, because we’ve searched, and hard. In 1982, one of the experiments searching for magnetic monopoles registered a single positive result, spawning many copycats which attempted to discover large numbers of others. Unfortunately, that one positive result was anomalous, and no one has ever replicated it. Also in the 1980s, people began building giant tanks of water and other atomic nuclei, searching for evidence of proton decay. While those tanks eventually wound up being repurposed as neutrino detectors, not a single proton has ever been observed to decay. The proton lifetime is now constrained to be greater than 1035 years: some 25 orders of magnitude greater than the age of the Universe.

    8
    The water-filled tank at Super Kamiokande, which has set the most stringent limits on the lifetime of the proton. In later years, detectors set up in this fashion have made outstanding neutrino observatories, but have yet to detect a single proton decay. Image credit: Kamioka Observatory, ICRR, University of Tokyo.

    This is also too bad, because Grand Unification offers a clean and elegant path to generating the matter/antimatter asymmetry in the Universe. At very early times, the Universe is hot enough to produce matter-and-antimatter pairs of all the particles that can possibly exist. In most GUTs, two of those particles that exist are superheavy X-and-Y bosons, which are charged, and contain both quark and lepton couplings. There’s expected to be an asymmetry in the way the matter versions and the antimatter versions decay, and they can give rise to a leftover presence of matter over antimatter, even if there was none initially. Unfortunately, again, we have yet to find any positive evidence for such particles and/or interactions.

    9
    An equally-symmetric collection of matter and antimatter (of X and Y, and anti-X and anti-Y) bosons could, with the right GUT properties, give rise to the matter/antimatter asymmetry we find in our Universe today. Image credit: E. Siegel / Beyond The Galaxy.

    Ethan Siegel Beyond the Galaxy

    Some physicists contend that the Universe must have these symmetries, and the evidence must simply lie at energies too high for even the LHC to probe.

    LHC

    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    But others are coming around to a more uncomfortable possibility: perhaps nature doesn’t unify. Perhaps there is no Grand Unified Theory that describes our physical reality; perhaps a quantum theory of gravity doesn’t unify with the other forces; perhaps the problems of baryogenesis and dark matter have other solutions that aren’t rooted in these ideas. After all, the ultimate arbiter of what the Universe is like isn’t our ideas about it, but rather the results of experiment and observations. We can only ask the Universe what it’s like; it’s up to us to listen to what it tells us and go from there.

    6
    The Standard Model Lagrangian is a single equation encapsulating the particles and interactions of the Standard Model. It has five independent parts: the gluons (1), the weak bosons (2), how matter interacts with the weak force and the Higgs field (3), the ghost particles that subtract the Higgs-field redundancies (4), and the Fadeev-Popov ghosts, which affect the weak interaction redundancies (5). Neutrino masses are not included. Image credit: Thomas Gutierrez, who insists there is one ‘sign error’ in this equation.

    Although we can write the Standard Model as a single equation, it isn’t really a unified entity in the sense that there are multiple, separate, independent terms to govern different components of the Universe. The various parts of the Standard Model don’t interact with each other, as color charge doesn’t affect the electromagnetic or weak forces, and there are unanswered questions about why interactions that should occur, like CP-violation in the strong force, don’t.

    7
    When symmetries are restored (at the top of the potential), unification occurs. However, the breaking of symmetries, at the bottom of the hill, corresponds to the Universe we have today, complete with new species of massive particles. Image credit: Luis Álvarez-Gaumé & John Ellis, Nature Physics 7, 2–3 (2011).

    It’s the hope of many that unification holds the answer to these questions, and will solve many of the open problems and puzzles in physics today. However, any sort of additional symmetries — symmetries which are restored at high energies but are broken today — lead to new particles, new interactions, and new physical rules that the Universe plays by. We’ve tried to reverse-engineer some predictions using what rules we’d need for things to work out, yet the particles and unifications we were hoping to find never materialized. Unification won’t help you derive emergent properties like chemistry, biology, geology, or consciousness, but will help us better understand the origin of where everything came from, and how.

    8
    The cosmic history of the entire known Universe shows that we owe the origin of all the matter within it, and all the light, ultimately, to the end of inflation and the beginning of the Hot Big Bang. Image credit: E. Siegel / ESA and the Planck Collaboration.

    ESA/Planck

    Of course, there is the other possibility: that the Universe simply doesn’t unify. That the multiple different laws and rules we have are there for a reason: these symmetries that we’ve invented are simply our own mathematical inventions, and not descriptive of the physical Universe. For every elegant, beautiful, compelling physical theory that’s out there, there’s an equally elegant, beautiful, and compelling physical theory that is wrong. In these matters, as in all scientific matters, it’s up to humanity to ask the right questions. But it’s up to the Universe to tell us the answers. Whatever they are, that’s the Universe we have. It’s up to us to figure out what those answers mean.

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 10:22 pm on July 15, 2017 Permalink | Reply
    Tags: , , , , , HEP, , MEET SURF, , , , U Washington Majorana   

    Meet SURF-Sanford Underground Research Facility, South Dakota, USA 

    SURF logo
    Sanford Underground levels

    THIS POST IS DEDICATED TO CONSTANCE WALTER, Communications Director, fantastic writer, AND MATT KAPUST Creative Services Developer, master photogropher, FOR THEIR TIRELESS EFFORTS IN KEEPING US INFORMED ABOUT PROGRESS FOR SCIENCE IN SOUTH DAKOTA, USA.

    Sanford Underground Research facility

    The SURF story in pictures:

    SURF-Sanford Underground Research Facility


    SURF Above Ground

    SURF Out with the Old


    SURF An Empty Slate


    SURF Carving New Space


    SURF Shotcreting


    SURF Bolting and Wire Mesh


    SURF Outfitting Begins


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


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


    SURF Ground Support


    SURF Dedicated to Science


    SURF Building a Ship in a Bottle


    SURF Tight Spaces


    SURF Ready for Science


    SURF Entrance Before Outfitting


    SURF Entrance After Outfitting


    SURF Common Corridior


    SURF Davis


    SURF Davis A World Class Site


    SURF Davis a Lab Site


    SURF DUNE LBNF Caverns at Sanford Lab


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


    FNAL DUNE Argon tank at SURF

    U Washington LUX Xenon experiment at SURF


    SURF Before Majorana


    U Washington Majorana Demonstrator Experiment at SURF

    This is the full article here .

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

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

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

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

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

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

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

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

    Fermilab LBNE
    LBNE

     
  • richardmitnick 12:01 pm on July 9, 2017 Permalink | Reply
    Tags: , , , HEP, , , Probing physics beyond the Standard Model with heavy vector bosons   

    From ATLAS: “Probing physics beyond the Standard Model with heavy vector bosons” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    8th July 2017
    ATLAS Collaboration

    1
    Figure 1: The reconstructed mass of the selected candidate events decaying to WW or ZZ bosons, with the qqqq final state. The black markers represent the data. The blue and green curves represent the hypothesized signal for two different masses. The red curve represents the Standard Model processes. (Image: ATLAS Collaboration/CERN)

    Although the discovery of the Higgs boson by the ATLAS and CMS Collaborations in 2012 completed the Standard Model, many mysteries remain unexplained. For instance, why is the mass of the Higgs boson so much lighter than one would expect and why is gravity so weak?

    CERN CMS Higgs Event


    CERN ATLAS Higgs Event

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

    Numerous models beyond the Standard Model attempt to explain these mysteries. Some explain the apparent weakness of gravity by introducing additional dimensions of space in which gravity propagates. One model goes beyond that, and considers the real world as a higher-dimensional universe described by warped geometry, which leads to strongly interacting massive graviton states. Other models propose, for example, additional types of Higgs bosons.

    All these models predict the existence of new heavy particles that can decay into pairs of massive weak bosons (WW, WZ or ZZ). The search for such particles has benefited greatly from the increase in the proton–proton collision energy during Run 2 of the Large Hadron Collider (LHC).

    _______________________________________________________________________
    The search for new heavy particles has benefited greatly from the LHC’s increase in proton–proton collision energy.
    _______________________________________________________________________

    2
    Figure 2: The limit on the cross-section times branching ratio of hypothetical particle described by one of the models for the different final states. (Image: ATLAS Collaboration/CERN)

    The W and Z bosons are carrier particles that mediate the weak force. They decay into other Standard Model particles, like charged leptons (l), neutrinos (ν) and quarks (q). These particles are reconstructed differently in the detector. Quarks, for instance, are reconstructed as localized sprays of hadrons, denoted jets. The two bosons could yield several combinations of these particles in the final states. The ATLAS Collaboration has released results on searches involving all relevant decays of the boson pair: ννqq, llqq, lνqq and qqqq (where the lepton is an electron or muon).

    What do these searches have in common? In each of these, at least one of the bosons decays into a pair of quarks. When the sought-after particle is very massive, the two bosons from its decay are ejected with such large momenta that their respective decay products are collimated and the pair of quarks merge into a single large jet. This phenomenon provides a powerful means to distinguish the new physics signal from strong-interaction Standard Model processes. As some exemplary results of the searches, Figure 1 shows the distributions of the reconstructed mass of the candidate particle. Figure 2 shows the limit on the cross-section times branching ratio of a hypothetical particle described by one of the models.

    So far, no evidence of a new particle has been observed. The search continues with increased sensitivity as ATLAS collects more data.

    Links:
    See the full article for further references with links.

    See the full article here .

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

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    CERN Courier

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    Quantum Diaries

     
  • richardmitnick 10:10 am on July 9, 2017 Permalink | Reply
    Tags: , , CERN LHC LHCb, CERN Physicists Find a Particle With a Double Dose of Charm, , HEP, , ,   

    From NYT: “CERN Physicists Find a Particle With a Double Dose of Charm” 

    New York Times

    The New York Times

    JULY 6, 2017
    KENNETH CHANG

    3
    The new particle, awkwardly known as Xi-cc++ (pronounced ka-sigh-see-see-plus-plus)

    1
    The Vertex Locator detector is part of an experiment at CERN’s Large Hadron Collider that discovered a particle that contains two charm quarks. Credit CERN

    Physicists have discovered a particle that is doubly charming.

    Researchers reported on Thursday that in debris flying out from the collisions of protons at the CERN particle physics laboratory outside Geneva, they had spotted a particle that has long been predicted but not detected until now.

    The new particle, awkwardly known as Xi-cc++ (pronounced ka-sigh-see-see-plus-plus), could provide new insight into how tiny, whimsically named particles known as quarks, the building blocks of protons and neutrons, interact with each other.

    Protons and neutrons, which account for the bulk of ordinary matter, are made of two types of quarks: up and down. A proton consists of two up quarks and one down quark, while a neutron contains one up quark and two down quarks. These triplets of quarks are known as baryons.

    There are also heavier quarks with even quirkier names — strange, charm, top, bottom — and baryons containing permutations of heavier quarks also exist.

    An experiment at CERN, within the behemoth Large Hadron Collider, counted more 300 Xi-cc++ baryons, each consisting of two heavy charm quarks and one up quark.

    LHC

    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    The discovery fits with the Standard Model, the prevailing understanding of how the smallest bits of the universe behave, and does not seem to point to new physics.

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

    “The existence of these particles has been predicted by the Standard Model,” said Patrick Spradlin, a physicist at the University of Glasgow who led the research. “Their properties have also been predicted.”

    Dr. Spradlin presented the findings on Thursday at a European Physical Society conference in Venice, and a paper describing them has been submitted to the journal Physical Review Letters.

    Up and down quarks have almost the same mass, so in protons and neutrons, the three quarks swirl around each other in an almost uniform pattern. In the new particle, the up quark circulates around the two heavy charm quarks at the center. “You get something far more like an atom,” Dr. Spradlin said.

    Quark interactions are complex and difficult to calculate, and the structure of the new particles will enable physicists to check the assumptions and approximations they use in their calculations. “It’s a new regime in quark-quark dynamics,” said Jonathan L. Rosner, a retired theoretical physicist at the University of Chicago.

    The mass of the Xi-cc++ is about 3.8 times that of a proton. The particle is not stable. Dr. Spradlin said the scientists had not yet figured out its lifetime precisely, but it falls apart after somewhere between 50 millionths of a billionth of a second and 1,000 millionths of a billionth of a second.

    For Dr. Rosner, the CERN results appear to match predictions that he and Marek Karliner of Tel Aviv University made.

    What is less clear is how the new particle fits in with findings from 2002, when physicists working at Fermilab outside Chicago made the first claim of a doubly charmed baryon, one consisting of two charm quarks plus a down quark (instead of the up quark seen in the CERN experiment).

    FNAL Tevatron

    FNAL/Tevatron map


    FNAL/Tevatron DZero detector


    FNAL/Tevatron CDF detector

    The two baryons should be very close in mass, but the Fermilab one was markedly lighter than what the CERN researchers found for Xi-cc++, and it appeared to decay instantaneously, in less than 30 millionths of a billionth of a second.

    Theorists like Dr. Rosner had difficulty explaining the behavior of the Fermilab particle within the Standard Model. “I didn’t have an honest alternative to allow me to believe that result,” he said.

    Peter S. Cooper, a deputy spokesman for the Fermilab experiment, congratulated the CERN researchers on their discovery. “That paper smells sweet,” he said. “From an experimental point of view, there’s nothing wrong. They definitely have something.”

    But he said the Fermilab findings still stood, too. He acknowledged that the two results do not readily make sense together.

    “I consider this a problem for my theoretical brethren to work out,” Dr. Cooper said. He added that it was a textbook example of the scientific method: “Our theoretical colleagues make a prediction. We go out and make a measurement and see if it’s right. If it isn’t, they go back and think harder.”

    It is possible one of the experiments is wrong. Researchers at other laboratories, including at CERN, have sought to detect the Fermilab baryon without success. Dr. Spradlin said he and his colleagues are searching the same data that revealed the Xi-cc++ for the baryon with two charm quarks and one down quark. That could confirm the Fermilab findings or reveal a mass closer to theorists’ expectations.

    “We should be able to see it with the data we have,” Dr. Spradlin said. “I think we are very close to resolving this controversy.”

    I presented an earlier post from LHCb, but it contained no reference to the paper in Physical Review Letters.

    See the full article here .

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  • richardmitnick 8:51 am on July 7, 2017 Permalink | Reply
    Tags: , , CERN Data Centre passes the 200-petabyte milestone, HEP, ,   

    From CERN: “CERN Data Centre passes the 200-petabyte milestone” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    CERN

    6 July 2017
    Mélissa Gaillard

    1
    CERN’s Data Centre (Image: Robert Hradil, Monika Majer/ProStudio22.ch)

    On 29 June 2017, the CERN DC passed the milestone of 200 petabytes of data permanently archived in its tape libraries. Where do these data come from? Particles collide in the Large Hadron Collider (LHC) detectors approximately 1 billion times per second, generating about one petabyte of collision data per second. However, such quantities of data are impossible for current computing systems to record and they are hence filtered by the experiments, keeping only the most “interesting” ones. The filtered LHC data are then aggregated in the CERN Data Centre (DC), where initial data reconstruction is performed, and where a copy is archived to long-term tape storage. Even after the drastic data reduction performed by the experiments, the CERN DC processes on average one petabyte of data per day. This is how the the milestone of 200 petabytes of data permanently archived in its tape libraries was reached on 29 June.

    2
    This map shows the routes for the three 100 Gbit/s fibre links between CERN and the Wigner RCP. The routes have been chosen carefully to ensure we maintain connectivity in the case of any incidents. (Image: Google)

    See the full article here.

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    Meet CERN in a variety of places:

    Quantum Diaries
    QuantumDiaries

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New

    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles

    Quantum Diaries

     
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