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  • richardmitnick 10:50 am on September 16, 2014 Permalink | Reply
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    From New Scientist: “Curtain closing on Higgs boson photon soap opera” 

    NewScientist

    New Scientist

    15 September 2014
    Michael Slezak

    It was the daytime soap opera of particle physics. But the final episode of the first season ends in an anticlimax. The Higgs boson‘s decay into pairs of photons – the strongest yet most confusing clue to the particle’s existence – is looking utterly normal after all.

    Experiments don’t detect the Higgs boson directly – instead, its existence is inferred by looking at the particles left behind when it decays. One way it made itself known at CERN’s Large Hadron Collider near Geneva, Switzerland, two years ago was by decaying into pairs of photons. Right at the start, there were so many photons that physicists considered it a “deviant decay” – and a possible window into new laws of physics, which could help explain the mysteries of dark energy and the like.

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

    Even as other kinks in the data got ironed out, the excess of photons remained. At the time, physicists speculated that it could be due to a mysterious second Higgs boson being created, or maybe the supersymmetric partner of the top quark.

    Supersymmetry standard model
    Standard Model showing Supersymmetric Particles

    Identity crisis

    If unheard of particles and physical laws weren’t dramatic enough, six months later, the decay into photons was giving the Higgs an identity crisis. When physicists measured the Higgs mass by observing it decaying into another type of particle, called a Z boson, it appeared lighter than when doing a similar calculation using the decay into photons. “The results are barely consistent,” Albert de Roeck, one of the key Higgs hunters at CERN’s CMS experiment, said at the time.

    But over the past year, physicists at CERN have found that the Higgs boson is acting exactly as the incomplete standard model of particle physics predicts, leaving us with no clues about how to extend it.

    Now, in an anticlimactic summary on the two photon decay, both big experiments at the LHC have posted results showing the photons are, after all the fuss, also doing exactly what the standard model predicts.

    Powering up

    “This is probably the final word,” wrote CERN physicist Adam Falkowski on his blog.

    Ever the optimist, de Roeck thinks there’s still room in the data for the two photon decay channel to be caught misbehaving. Our present outlook is due to our relatively fuzzy view of the behaviour so far, he says. When the LHC is switched back on next year after an upgrade, it will be smashing protons together with double the previous energy.

    With that kind of power, the measurements will be more exact, and any small deviations from standard model predictions could emerge. “It is most likely the last word for run one of the LHC, but definitely not the last word,” de Roeck says. “I still believe ultimately we will find significant deviations or something unexpected in the Higgs sector. Then all hell will break loose.”

    See the full article here.

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  • richardmitnick 1:17 pm on September 3, 2014 Permalink | Reply
    Tags: , , CERN LHC,   

    From Symmetry: “Watching ‘the clock’ at the LHC” 

    Symmetry

    September 03, 2014
    Sarah Charley

    As time ticks down to the restart of the Large Hadron Collider, scientists are making sure their detectors run like clockwork.

    clock
    Photo by Antonio Saba, CERN

    For the last two years, the Large Hadron Collider at CERN has been quietly slumbering while engineers and technicians prime it for the next run of data-taking in the summer of 2015.

    But this has been anything but a break for researchers from the LHC experiments.

    “Two years seems like a long time, but it goes by really fast,” says Michael Williams, a researcher on the LHCb experiment and assistant professor of physics at the Massachusetts Institute of Technology. “I think now it’s becoming a reality that running is coming soon, and it’s exciting.”

    CERN LHCb New
    LHCb

    One of the biggest tasks the collaborations are confronting right now is calibrating all the individual components so that their timing is completely synchronized. This synchronization of the components—called “the clock”—allows physicists to reconstruct the flights of particles through the different parts of the detector to form a picture of the entire collision event.

    “The clock is the foundation on which everything stands. It’s the heartbeat of the detector,” says UCLA physicist and CMS run coordinator Greg Rakness. “If the clock isn’t working, then the data makes no sense.”

    CERN CMS New
    CMS

    The four largest LHC detectors—called ALICE, ATLAS, CMS and LHCb—each consist of dozens of smaller subdetectors, which in turn are supported by myriads of electronics and supporting subsystems. A huge challenge is ensuring that all of the subdetectors, electronics and supporting software are functioning as one single unit.

    CERN ALICE New
    ALICE

    CERN ATLAS New
    ATLAS

    “We have 18 different detectors that make up ALICE, and we have several different detection techniques,” says Federico Ronchetti, a scientist associated with CERN and Italian laboratory INFN who serves as the ALICE experiment 2015 run coordinator. “You have to combine the different pieces of information to produce an event. This is an integration, one of the most critical parts of the overall detector commissioning.”

    As Rakness says: “In the end, it’s one detector.”

    In addition to being in time with themselves, the LHC detectors must be in time with the LHC. During this next run, high-energy bunches of protons accelerated inside the LHC will collide every 25 nanoseconds. If a detector’s timing is out of sync with the accelerator, scientists will have no way of accurately reconstructing the particle collisions.

    If the detector were out of sync with the LHC, it would mistakenly show large chunks of energy suddenly going missing—just what physicists expect would happen if a rarely interacting particle, such as a dark matter particle, passed through the detector.

    “What a better way to create a fake ‘new physics’ signal than if half the detector is out of sync?” Rakness says. “You’d have new physics all the time!”

    Even though the task is daunting, the LHC researchers charged with commissioning the detectors are confident that they and their detectors will be ready for the accelerator’s second run in early 2015.

    “We understand our detector much better now,” says Kendall Reeves, a researcher for the University of Texas, Dallas, who works on the ATLAS experiment. “We have the experience from Run 1 to help out—and having that experience is invaluable. We are in a much better position now then we were at the beginning of Run 1.”

    “Nothing is too complicated,” Rakness says. “In the end, this whole complicated chain breaks down to a step-by-step process. And then it ticks.”

    CERN LHC particles

    LHC Tube Graphic
    LHC Tunnel

    CERN LHC Map
    LHC at CERN

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.


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  • richardmitnick 4:33 pm on August 25, 2014 Permalink | Reply
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    From Livermore Lab: “Calculating conditions at the birth of the universe” 


    Lawrence Livermore National Laboratory

    08/25/2014
    Anne M Stark, LLNL, (925) 422-9799, stark8@llnl.gov

    Using a calculation originally proposed seven years ago to be performed on a petaflop computer, Lawrence Livermore researchers computed conditions that simulate the birth of the universe.

    When the universe was less than one microsecond old and more than one trillion degrees, it transformed from a plasma of quarks and gluons into bound states of quarks – also known as protons and neutrons, the fundamental building blocks of ordinary matter that make up most of the visible universe.

    The theory of quantum chromodynamics (QCD) governs the interactions of the strong nuclear force and predicts it should happen when such conditions occur.

    In a paper appearing in the Aug. 18 edition of Physical Review Letters, Lawrence Livermore scientists Chris Schroeder, Ron Soltz and Pavlos Vranas calculated the properties of the QCD phase transition using LLNL’s Vulcan, a five-petaflop machine. This work was done within the LLNL-led HotQCD Collaboration, involving Los Alamos National Laboratory, Institute for Nuclear Theory, Columbia University, Central China Normal University, Brookhaven National Laboratory and Universität Bielefed in Germany.

    vulcan
    A five Petaflop IBM Blue Gene/Q supercomputer named Vulcan

    This is the first time that this calculation has been performed in a way that preserves a certain fundamental symmetry of the QCD, in which the right and left-handed quarks (scientists call this chirality) can be interchanged without altering the equations. These important symmetries are easy to describe, but they are computationally very challenging to implement.

    “But with the invention of petaflop computing, we were able to calculate the properties with a theory proposed years ago when petaflop-scale computers weren’t even around yet,” Soltz said.

    The research has implications for our understanding of the evolution of the universe during the first microsecond after the Big Bang, when the universe expanded and cooled to a temperature below 10 trillion degrees.

    Below this temperature, quarks and gluons are confined, existing only in hadronic bound states such as the familiar proton and neutron. Above this temperature, these bound states cease to exist and quarks and gluons instead form plasma, which is strongly coupled near the transition and coupled more and more weakly as the temperature increases.

    “The result provides an important validation of our understanding of the strong interaction at high temperatures, and aids us in our interpretation of data collected at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory and the Large Hadron Collider at CERN.” Soltz said.

    Brookhaven RHIC
    RHIC at Brookhaven

    CERN LHC Grand Tunnel
    LHC at CERN

    Soltz and Pavlos Vranas, along with former colleague Thomas Luu, wrote an essay predicting that if there were powerful enough computers, the QCD phase transition could be calculated. The essay was published in Computing in Science & Engineering in 2007, “back when a petaflop really did seem like a lot of computing,” Soltz said. “With the invention of petaflop computers, the calculation took us several months to complete, but the 2007 estimate turned out to be pretty close.”

    The extremely computationally intensive calculation was made possible through a Grand Challenge allocation of time on the Vulcan Blue Gene/Q Supercomputer at Lawrence Livermore National Laboratory.

    See the full article here.

    Operated by Lawrence Livermore National Security, LLC, for the Department of Energy’s National Nuclear Security
    Administration
    DOE Seal
    NNSA
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  • richardmitnick 11:28 am on August 15, 2014 Permalink | Reply
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    Brian Cox on the LHC 

    Published on Dec 8, 2012

    A great video, a bit dated, by our freind Brian Cox

    “Rock-star physicist” Brian Cox talks about his work on the Large Hadron Collider at CERN. Discussing the biggest of big science in an engaging and accessible way, Cox brings us along on a tour of the massive project.

    Watch, enjoy and learn.

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  • richardmitnick 10:20 am on August 12, 2014 Permalink | Reply
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    From Fermilab: “From the Deputy Director – CMS excitement” 


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

    Tuesday, Aug. 12, 2014
    jl
    Joe Lykken

    When I joined the CMS collaboration seven years ago, I was motivated both by the exciting discovery potential of the Large Hadron Collider and by the fact that many of my friends from the Tevatron experiments were starting to move into leading roles for CMS. In the years leading up to the July 4, 2012, announcement of the Higgs boson discovery, I witnessed from the inside how the momentum carried over from the Tevatron era enabled, on many levels, the remarkable success of the CMS experiment.

    Fermilab Tevatron
    Tevatron rings

    CERN CMS New
    CMS at CERN’s LHC

    Fermilab DZero
    DZero at the Tevatron

    Fermilab CDF
    CDF at the Tevatron

    But wait — there’s more. The LHC will be turning on again early next year with both higher collision energy and higher “luminosity” — the rate at which collisions occur. This raises the prospects for many kinds of discoveries, including new heavy particles (perhaps the “superpartners” predicted by my favorite theory, supersymmetry), or unexpected properties of the Higgs boson. I have placed a friendly bet with Tom LeCompte, the former ATLAS collaboration physics coordinator and our Argonne neighbor, that superpartners will in fact be discovered by CMS and ATLAS during this next LHC run.

    CERN LHC Map
    LHC at CERN

    CERN ATLAS New
    ATLAS at CERN

    Supersymmetry standard model
    Standard Model of Supersymmetry

    Continued success of the CMS experiment requires significant upgrades to the CMS detector to meet the challenges of higher-luminosity running. The U.S. CMS collaboration has taken responsibility for upgrading three major subsystems in a Phase I upgrade project jointly funded by the Department of Energy and the National Science Foundation.

    Last week, this U.S. CMS project passed the simultaneous CD-2/CD-3 reviews, allowing these crucial upgrades to proceed. It was all smiles at the closeout last Thursday. This achievement reflects excellent work by the CMS Detector Upgrade Project team led by Steve Nahn, with deputies Aaron Dominguez and Lucas Taylor, involving CMS collaborators from many universities and labs and lots of talented people at Fermilab.

    A proud day for U.S. CMS, with many more to come.

    See the full article here.

    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

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  • richardmitnick 10:47 am on July 21, 2014 Permalink | Reply
    Tags: , , CERN LHC, , , , vLHC@home   

    vLHC@home Banner

    vLHC Logo

    vLHC@home project

    This is a project that utilizes the CERN-developed CernVM virtual machine and the BOINC virtualization layer to harness volunteer cloud computing power for full-fledged LHC event physics simulation on volunteer computers.

    The theory simulations that have been running as Test4Theory since 2011, were the first of a series of physics applications running on the LHC@home platform. Soon the theory simulations will be followed by more simulations from the LHC experiment collaborations. These applications exploit virtual machine technology, enabling volunteers to contribute to the huge computational task of searching for new fundamental particles and physics at CERN’s LHC.

    The Virtual LHC@home project (formerly known as Test4Theory) allows users to participate in running simulations of high-energy particle physics using their home computers.

    The results are submitted to a database which is used as a common resource by both experimental and theoretical scientists working on the Large Hadron Collider at CERN.

    Lots of volunteers around the world are connected to this project running vLHCathome simulations right now.

    Hopefully, these explanations can help give an idea of why the computing resources made available by volunteers in this way can be crucial for improving our understanding of what is really happening inside the beam pipe of the Large Hadron Collider. Soon, other types of simulations from the LHC experiments will be added to this project.

    If you would like to participate in this project, downlod and install the BOINC and CERN VM software. Then attach to the project. While you are at BOINC, look over the other projects to find some that might be of interest.

    BOINC

    CERN LHC Map
    LHC map

    CERN LHC particles


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  • richardmitnick 10:58 am on July 15, 2014 Permalink | Reply
    Tags: , , CERN LEP, CERN LHC, , ,   

    From CERN: “The Large Electron-Positron Collider” 

    CERN New Masthead

    No Date
    No Writer Credit

    With its 27-kilometre circumference, the Large Electron-Positron (LEP) collider was – and still is – the largest electron-positron accelerator ever built. The excavation of the LEP tunnel was Europe’s largest civil-engineering project prior to the Channel Tunnel. Three tunnel-boring machines started excavating the tunnel in February 1985 and the ring was completed three years later.

    lep

    In its first phase of operation, LEP consisted of 5176 magnets and 128 accelerating cavities. CERN’s accelerator complex provided the particles and four enormous detectors, ALEPH, DELPHI, L3 and OPAL, observed the collisions.

    LEP was commissioned in July 1989 and the first beam circulated in the collider on 14 July. The collider’s initial energy was chosen to be around 91 GeV, so that Z bosons could be produced. The Z boson and its charged partner the W boson, both discovered at CERN in 1983, are responsible for the weak force, which drives the Sun, for example. Observing the creation and decay of the short-lived Z boson was a critical test of the Standard Model. In the seven years that LEP operated at around 100 GeV it produced around 17 million Z particles.

    sm
    The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    In 1995 LEP was upgraded for a second operation phase, with as many as 288 superconducting accelerating cavities added to double the energy so that the collisions could produce pairs of W bosons. The collider’s energy eventually topped 209 GeV in 2000.

    During 11 years of research, LEP’s experiments provided a detailed study of the electroweak interaction. Measurements performed at LEP also proved that there are three – and only three – generations of particles of matter. LEP was closed down on 2 November 2000 to make way for the construction of the Large Hadron Collider in the same tunnel.

    CERN LHC Grand Tunnel
    LHC

    CERN LHC Map
    LHC map

    See the full article here.

    Meet CERN in a variety of places:

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New
    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries


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  • richardmitnick 8:21 am on July 15, 2014 Permalink | Reply
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    From Brookhaven Lab: “Physicists Detect Process Even Rarer than the Long-Sought Higgs Particle” 

    Brookhaven Lab

    July 15, 2014
    Karen McNulty Walsh

    New stringent test of the Standard Model and the mechanism by which the Higgs imparts mass to other particles

    Scientists running the ATLAS experiment at the Large Hadron Collider (LHC), the world’s largest and most powerful “atom smasher,” report the first evidence of a process that can be used to test the mechanism by which the recently discovered Higgs particle imparts mass to other fundamental particles. More rare than the production of the Higgs itself, this process—a scattering of two same-charged particles called W bosons off one another—also provides a new stringent test of the Standard Model of particle physics. The findings, which so far are in agreement with predictions of the Standard Model, are reported in a paper just accepted by Physical Review Letters.

    sm
    The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    CERN ATLAS New
    CERN/ATLAS

    CERN LHC Grand Tunnel
    LHC Tunnel

    CERN LHC Map
    LHC map

    “By measuring this process we can check whether the Higgs particle we discovered does its job the way we expect it to.”

    Brookhaven Lab/ATLAS physicist Marc-André Pleier

    “Only about one in 100 trillion proton-proton collisions would produce one of these events,” said Marc-André Pleier, a physicist at the U.S. Department of Energy’s Brookhaven National Laboratory who played a leadership role in the analysis of this result for the ATLAS collaboration. Complicating matters further, finding one such rare event is not enough. “You need to observe many to see if the production rate is above or on par with predictions,” Pleier said. “We looked through billions of proton-proton collisions produced at the LHC for a signature of these events—decay products that allow us to infer like Sherlock Holmes what happened in the event.”

    The analysis efforts started two years ago and were carried out in particular by groups from Brookhaven, Lawrence Berkeley National Laboratory, Michigan State University, and Technische Universität Dresden, Germany. Preliminary results were presented by Pleier at the “Rencontres de Moriond – QCD and High Energy Interactions” conference in March 2014. Now finalized based on a total of 34 observed events, the measured interaction rate is in good agreement with that predicted by the Standard Model, a theory describing all known fundamental particles and their interactions.

    “The Standard Model has so far survived all tests, but we know that it is incomplete because there are observations of dark matter, dark energy, and the antimatter/matter asymmetry in the universe that can’t be explained by the Standard Model,” Pleier said. So physicists are always looking for new ways to test the theory, to find where and how it might break down.

    “This process of W boson interactions is one we could never test,” Pleier said, “because we didn’t have enough energy or large enough data sets needed to see this very rare process—until we built the LHC.”

    Now with the LHC data in hand, the measured rate agrees with the prevailing theory’s predictions and establishes a signal at a significance level of 3.6 sigma—strong evidence, according to Pleier. “The probability for this measurement to be a mere background fluctuation is very small—about one in 6000,” he said. But the physicists would like to be more certain by collecting more data to reduce uncertainties and increase the level of significance.

    image
    Candidate event for WW → WW scattering

    There’s another reason for continuing the quest: “By measuring this process we can check whether the Higgs particle we discovered does its job the way we expect it to,” Pleier said. “A wealth of models in addition to the Higgs mechanism exists to try to explain how fundamental particles get their mass. Measurements of such scattering processes can thus be both a fundamental test of the Standard Model and a window to new physics.”

    To test the Higgs mechanism, the scientists compare distributions of decay products of the W scattering process—how often they observe particular products at a particular energy and geometrical configuration.

    “It’s like a fingerprint,” Pleier said.“We have a predicted fingerprint and we have the fingerprint we measure. If the fingerprints match, we know that the Higgs does its job of mass generation the way it should. But if it deviates, we know that some other physics mechanism is helping out because the Higgs alone is not doing what we expect.”

    Again, so far, the data indicate that the Higgs is working as expected.

    “For the first time, we can rule out certain models or predictions that we could not before,” Pleier said. “To complete the job, we need more data, at higher energy, so we can see the fingerprint more clearly.”

    The LHC will resume data taking at increased collision energies—13 tera-electronvolts (TeV) instead of 8 TeV—in spring of 2015. The datasets collected will be up to 150 times the size of the currently available data and will allow for a detailed behind-the-scenes look at the Higgs at work.

    The ATLAS experiment at LHC is supported by DOE’s Office of Science and the National Science Foundation.

    Brookhaven National Laboratory serves as the U.S. host laboratory for the ATLAS experiment at the LHC, and plays multiple roles in this international collaboration, from construction and project management to data storage, distribution, and analysis, funded by the DOE Office of Science (HEP). For more information about Brookhaven’s role, see: http://www.bnl.gov/ATLAS/

    DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

    See the full article here.

    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.

    DOE Office of Science


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  • richardmitnick 9:01 am on July 10, 2014 Permalink | Reply
    Tags: , , CERN LHC, , ,   

    From BBC: “LHC scientists to search for ‘fifth force of Nature'” 

    BBC

    10 July 2014
    Pallab Ghosh

    The next couple of years will be make or break for the next big theory in physics called supersymmetry – SUSY for short. It might make way for a rival idea which predicts the existence of a ‘fifth force’ of nature.

    Next Spring, when the Large Hadron Collider (LHC) resumes its experiments, scientists will be looking for evidence of SUSY. It explains an awful lot that the current theory of particle physics does not. But there is a growing problem, provocatively expressed by Nobel Laureate George Smoot: “supersymmetry has got symmetry and it’s super but there is no experimental data to suggest it is correct.”

    CERN LHC Grand Tunnel
    LHC tunnel

    CERN LHC New
    LHC map

    According to the simplest versions of the theory, supersymmetric particles should have been discovered at the LHC by now. One set of null results prompted Prof Chris Parkes, of the LHCb to quip: “Supersymmetry may not be dead but these latest results have certainly put it into hospital”.

    But other forms of the theory are still very much in play.

    Next year will be an important year for SUSY. The LHC will be smashing atoms together at almost twice the energy it did in its first run. Even those who are still strong advocates of SUSY, such as Cern’s revered professor of theoretical physics, John Ellis, agree that if LHC scientists do not find super particles in the LHC’s second run, it might be time for the hospital patient to be moved to the mortuary.

    “If it is not found in LHC run two then there will be relatively few corners it could hide,” he told BBC News.

    “I know that at that point the community may decide that the guys who predicted supersymmetry are dying off like flies and that young guys will be interested in different types of theories and supersymmetry may be forgotten. But I don’t think we are at that point yet.”
    LHC Tunnel Engineers have spent more than a year upgrading the LHC’s systems. The hope is that this will allow a new realm of physics to be opened up

    One of those young guys is Thibaut Mueller, a 24-year-old PhD student at Cambridge University. He is already checking out alternatives to SUSY.

    “A few years ago we thought it was a case of who will be first to find supersymmetry,” he said.

    “Now there is less and less focus on it and more people are starting to branch out into other models.”

    Mr Mueller’s PhD looks at an alternative to supersymmetry called the composite Higgs model. This idea has been around for decades but is undergoing a resurgence as some researchers raise questions over supersymmetry. Physicists will be looking for evidence for it in the next run of the LHC in 2015.

    Thibault’s colleague Dr Ben Gripaios believes that the Composite Higgs theory is now a serious alternative to supersymmetry.
    Continue reading the main story

    “SUSY was regarded by many people as the perfect theory. We have been looking really hard for it for a long time and we have not found it and so possibly there is a different explanation. For me the most compelling alternative is the Composite Higgs. It is just as plausible as supersymmetry,” he told BBC News.

    The current theory to explain the forces of nature was developed in the 1960s and is called the Standard Model. It elegantly explains how 13 particles, including the Higgs, interact to create three of the four forces of nature: electromagnetism, and the nuclear strong and weak forces.

    sm
    The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    But the Standard Model does not explain how gravity works, nor can it account for the [dark] matter and [dark] energy that makes up 95% of the Universe – referred to by physicists as the “Dark Universe”.

    Supersymmetry is an extension of the Standard Model and is an attempt to explain some of the things the current theory can’t.
    Super particles The stage has been set for some years for the detection of super particles. But so far they have been a no show.

    It predicts the existence of so-called superparticles which account for much of the missing mass and energy of the Universe.

    Supersymmetry standard model
    Supersymmetry standard model

    Supersymmetry also neatly solves what physicists describe as the “fine tuning problem”. In very crude terms, all subatomic particles can be thought to have two values for their mass: Their mass in isolation which is called their “bare” mass, and their experimental mass, which includes interactions with other sub-atomic particles.

    For all particles the two masses are about the same, except for the Higgs, whose bare mass must be many times larger than its experimental mass.

    Going from such a relatively big number to a small number is an unlikely occurrence, rather like a skydiver landing on the head of a pin each time they jump out of a plane. It can only happen if there is an overarching force guiding the skydiver on to the pin head – something that physicists call “fine tuning”.

    The existence of superparticles interacting with their normal counterparts fine tunes the Higgs’s two masses perfectly. The drawback though is that there is no evidence of SUSY, at least not yet.

    The composite Higgs theory also solves the fine tuning problem, albeit less elegantly and, just as with SUSY, there is no experimental evidence for it. It supposes that the Higgs is not a fundamental particle, but is instead made up of other fundamental particles bound together by a hitherto unseen fifth force of nature. This is similar to what is already known to happen with the strong nuclear force, which binds quarks together to produce nuclear particles like protons and neutrons.

    Scientists at the LHC hope to detect evidence for one or other theory when they resume their experiments in April. In effect, the starting gun goes off in an invisible two-horse race where the winner emerges only at the finish line. Supersymmetry is still the favourite in the minds of most particle physicists, but Thibaut Mueller thinks that the likelihood of finding evidence for composite Higgs theory is not far behind.

    Why then is this promising youngster gambling his still early career on the outsider?

    High risk

    “This is a high risk, high gain game,” he explained. “If we find either (SUSY or the composite Higgs) this would be the biggest revolution in particle physics and possibly the whole of physics since quantum mechanics in the the 1940s.

    “Even if we do not find evidence for SUSY or composite Higgs, we will still have learned important facts about the Standard Model, which will guide us to new theories”.

    Of course, the researchers may see neither, which raises the possibility that no fine tuning is needed to turn the big Higgs into the little Higgs.

    That would mean that we live in a Universe where the dice are loaded to ensure that the Higgs experimental mass will always improbably land neatly on its bare mass each and every time.

    In the absence of evidence for either theory, this anthropic principle might seem like a tempting option. But it’s one that those on the front line of research vehemently resist.

    According to Thibault Mueller that view is a “conversation stopper”.

    “It says that ‘we are special because we as humans are here to observe it and so we exist’. If we accept that then we might as well give up science altogether.

    “We (have established) that we as a species are not special, the Earth is not special, our Solar System is not special. Now we are saying: ‘Ah! Our Universe is not that special either’.”

    Prof Rolf Dieter Heuer, the director-general of the European Centre for Nuclear Research (Cern) recently told researchers at the International Conference on High Energy Physics (ICHEP) in Valencia, that there was “a lot at stake” for the LHC’s second run starting next year.

    Indeed there is: careers, reputations and deeply cherished ideas.

    But whatever the outcome, physicists are preparing themselves for the ride of their lives. As Prof Heuer told the physics community: “There’s much more to be discovered in the Dark Universe”.

    See the full article here.


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  • richardmitnick 5:34 am on July 5, 2014 Permalink | Reply
    Tags: , , CERN LHC, , ,   

    From Symmetry: “What’s next for Higgs boson research?” 

    Symmetry

    July 04, 2014
    Sarah Charley

    On July 4, 2012, physicists announced an amazing discovery—they had identified a new particle that looked very much like the predicted Higgs boson.

    higgs
    One of many depictions of Higgs

    Two years later, physicists have pinned down the traits of this particle and confirmed its identity. But the story doesn’t end there.

    This week, physicists presented their most recent measurements of the properties of the Higgs boson at the International Conference on High Energy Physics in Valencia, Spain (and celebrated with chocolate cake). Among the highlights are new precision measurements of the Higgs mass, characterizations of its quantum mechanical properties, an exploration of its decay patterns and new measurements of its lifetime.

    “In just two years, our knowledge of this particle has improved dramatically,” says Gabriella Sciolla, an ATLAS physicist and professor at Brandeis University. “For instance, we now know the mass of this particle with a precision better than half a gigaelectronvolt—which is remarkable since just two years ago, we had no idea what this mass could be.”

    CERN ATLAS New
    ATLAS at CERN

    But there is still more work to be done, she says.

    CERN LHC Grand Tunnel
    LHC Tunnel

    “The measurements of the Higgs boson’s couplings [to other particles] are just in their infancy,” she says. “Much more accurate measurements will be possible in the future. They will allow us to really probe deeper into the Higgs properties and hopefully answer the main question that is on our mind: Is the Higgs really what the Standard Model predicts, or is there more to it?”

    sm
    The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    The Higgs is a totally new sector of physics, says Michael Peskin, a professor of theoretical physics at SLAC National Accelerator Laboratory. “It is a particle that is not related to any other particles we know about… There’s lots left to explore.”

    Since the 1970s, the Higgs boson has been a cornerstone of the Standard Model of particle physics—our best understanding of matter at its most fundamental level. Its discovery in 2012 bolstered physicists’ confidence in the model, but it also surfaced deep, structural questions about what else might be hiding just out of reach.

    “The mass of the Higgs boson tells us something, but theorists are having a big debate about what it tells us,” Peskin says. “We need more research to see how this Higgs fits into our theories and models exactly.”

    Thus far, the measured properties of the Higgs boson have matched up with the Standard Model’s predictions quite nicely. But Peskin notes that there are still many small gaps that leave room for new physics.

    “The presence of new, heavier particles would only affect the Higgs boson slightly,” Peskin says. “If there are heavier, new particles, the measurements of the Higgs will deviate only slightly from the Standard Model’s predictions—maybe about 5 percent.”

    These heavier particles could even be new types of Higgs bosons.

    “If this is just the lightest Higgs of many other Higgs bosons, we need precision measurements to look for these slight deviations from the Standard Model,” Peskin says. “And we’re just not there yet.”

    The first run of the LHC gave scientists 14,000 Higgs bosons to study. The next run will give physicists five to 10 times more, which will let physicists make the precision measurements necessary to thoroughly examine this Higgs boson and see what else it might be hiding.

    CERN LHC Map
    LHC at CERN

    “The discovery itself was impressive,” Peskin says, “and two years later, I still think it is very impressive, but new discoveries are coming. Knowing the Higgs exists is an important milestone, but now we need to move to the next step.”

    See the full article here.

    CERN LHC particles

    Symmetry is a joint Fermilab/SLAC publication.



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