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  • richardmitnick 10:01 am on August 17, 2016 Permalink | Reply
    Tags: , , , CERN: Facts & Figures, Higgs   

    From CERN: “Facts & Figures” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead


    The Large Hadron Collider (LHC) is the most powerful particle accelerator ever built. The accelerator sits in a tunnel 100 metres underground at CERN, the European Organization for Nuclear Research, on the Franco-Swiss border near Geneva, Switzerland.

    What is the LHC?

    The LHC is a particle accelerator that pushes protons or ions to near the speed of light. It consists of a 27-kilometre ring of superconducting magnets with a number of accelerating structures that boost the energy of the particles along the way.

    Why is it called the “Large Hadron Collider”?

    “Large” refers to its size, approximately 27km in circumference
    “Hadron” because it accelerates protons or ions, which belong to the group of particles called hadrons
    “Collider” because the particles form two beams travelling in opposite directions, which are made to collide at four points around the machine

    How does the LHC work?

    The CERN accelerator complex is a succession of machines with increasingly higher energies. Each machine accelerates a beam of particles to a given energy before injecting the beam into the next machine in the chain. This next machine brings the beam to an even higher energy and so on. The LHC is the last element of this chain, in which the beams reach their highest energies.

    The CERN accelerator complex (Image: CERN)

    Inside the LHC, two particle beams travel at close to the speed of light before they are made to collide. The beams travel in opposite directions in separate beam pipes – two tubes kept at ultrahigh vacuum. They are guided around the accelerator ring by a strong magnetic field maintained by superconducting electromagnets. Below a certain characteristic temperature, some materials enter a superconducting state and offer no resistance to the passage of electrical current. The electromagnets in the LHC are therefore chilled to ‑271.3°C (1.9K) – a temperature colder than outer space – to take advantage of this effect. The accelerator is connected to a vast distribution system of liquid helium, which cools the magnets, as well as to other supply services.

    What are the main goals of the LHC?

    The Standard Model of particle physics – a theory developed in the early 1970s that describes the fundamental particles and their interactions – has precisely predicted a wide variety of phenomena and so far successfully explained almost all experimental results in particle 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 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.

    But the Standard Model is incomplete. It leaves many questions open, which the LHC will help to answer.

    What is the origin of mass? The Standard Model does not explain the origins of mass, nor why some particles are very heavy while others have no mass at all. However, theorists Robert Brout, François Englert and Peter Higgs made a proposal that was to solve this problem. The Brout-Englert-Higgs mechanism gives a mass to particles when they interact with an invisible field, now called the “Higgs field”, which pervades the universe.
    Particles that interact intensely with the Higgs field are heavy, while those that have feeble interactions are light. In the late 1980s, physicists started the search for the Higgs boson, the particle associated with the Higgs field. In July 2012, CERN announced the discovery of the Higgs boson, which confirmed the Brout-Englert-Higgs mechanism.

    CERN ATLAS Higgs Event
    CERN ATLAS Higgs Event

    CERN CMS Higgs Event
    CERN CMS Higgs Event

    However, finding it is not the end of the story, and researchers have to study the Higgs boson in detail to measure its properties and pin down its rarer decays.

    Will we discover evidence for supersymmetry? The Standard Model does not offer a unified description of all the fundamental forces, as it remains difficult to construct a theory of gravity similar to those for the other forces. Supersymmetry – a theory that hypothesises the existence of more massive partners of the standard particles we know – could facilitate the unification of fundamental forces.

    Standard model of Supersymmetry DESY
    Standard model of Supersymmetry DESY

    What are dark matter and dark energy? The matter we know and that makes up all stars and galaxies only accounts for 4% of the content of the universe. The search is then still open for particles or phenomena responsible for dark matter (23%) and dark energy (73%).

    Why is there far more matter than antimatter in the universe? Matter and antimatter must have been produced in the same amounts at the time of the Big Bang, but from what we have observed so far, our Universe is made only of matter.

    How does the quark-gluon plasma give rise to the particles that constitute the matter of our Universe?

    Quark gluon plasma. Duke University
    Quark gluon plasma. Duke University

    For part of each year, the LHC provides collisions between lead ions, recreating conditions similar to those just after the Big Bang. When heavy ions collide at high energies they form for an instant the quark-gluon plasma, a “fireball” of hot and dense matter that can be studied by the experiments.

    How was the LHC designed?

    Scientists started thinking about the LHC in the early 1980s, when the previous accelerator, the LEP, was not yet running. In December 1994, CERN Council voted to approve the construction of the LHC and in October 1995, the LHC technical design report was published.

    Contributions from Japan, the USA, India and other non-Member States accelerated the process and between 1996 and 1998, four experiments (ALICE, ATLAS, CMS and LHCb) received official approval and construction work started on the four sites.

    LHC Run 2

    What are the detectors at the LHC?

    There are seven experiments installed at the LHC: ALICE, ATLAS, CMS, LHCb, LHCf, TOTEM and MoEDAL. They use detectors to analyse the myriad of particles produced by collisions in the accelerator. These experiments are run by collaborations of scientists from institutes all over the world. Each experiment is distinct, and characterized by its detectors.

    What is the data flow from the LHC experiments?

    The CERN Data Centre stores more than 30 petabytes of data per year from the LHC experiments, enough to fill about 1.2 million Blu-ray discs, i.e. 250 years of HD video. Over 100 petabytes of data are permanently archived, on tape.

    Costs for Run 1
    Exploitation costs of the LHC when running (direct and indirect costs) represent about 80% of the CERN annual budget for operation, maintenance, technical stops, repairs and consolidation work in personnel and materials (for machine, injectors, computing, experiments).
    The directly allocated resources for the years 2009-2012 were about 1.1 billion CHF.

    Costs for LS1
    The cost of the Long Shutdown 1 (22 months) is estimated at 150 Million CHF. The maintenance and upgrade works represent about 100 MCHF for the LHC and 50 MCHF for the accelerator complex without the LHC.

    What is the LHC power consumption?

    The total power consumption of the LHC (and experiments) is equivalent to 600 GWh per year, with a maximum of 650 GWh in 2012 when the LHC was running at 4 TeV. For Run 2, the estimated power consumption is 750 GWh per year.
    The total CERN energy consumption is 1.3 TWh per year while the total electrical energy production in the world is around 20000 TWh, in the European Union 3400 TWh, in France around 500 TWh, and in Geneva canton 3 TWh.

    What are the main achievements of the LHC so far?

    10 September 2008: LHC first beam (see press release)

    23 November 2009: LHC first collisions (see press release)

    30 November 2009: world record with beam energy of 1.18 TeV (see press release)

    16 December 2009: world record with collisions at 2.36 TeV and significant quantities of data recorded (see press release)

    March 2010: first beams at 3.5 TeV (19 March) and first high energy collisions at 7 TeV (30 March) (see press release)

    8 November 2010: LHC first lead-ion beams (see press release)

    22 April 2011: LHC sets new world record beam intensity (see press release)

    5 April 2012: First collisions at 8 TeV (see press release)

    4 July 2012: Announcement of the discovery of a Higgs-like particle at CERN (see press release)

    For more information about the Higgs boson:
    The Higgs boson
    CERN and the Higgs boson
    The Basics of the Higgs boson
    How standard is the Higgs boson discovered in 2012?
    Higgs update 4 July

    28 September 2012: Tweet from CERN: “The LHC has reached its target for 2012 by delivering 15 fb-1 (around a million billion collisions) to ATLAS and CMS ”

    14 February 2013: At 7.24 a.m, the last beams for physics were absorbed into the LHC, marking the end of Run 1 and the beginning of the Long Shutdown 1 (see press release)

    8 October 2013: Physics Nobel prize to François Englert and Peter Higgs “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN’s Large Hadron Collider” (see press release)

    See LHC Milestones.

    See the full article here.

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    Stem Education Coalition

    Meet CERN in a variety of places:

    Cern Courier




    CERN CMS New

    CERN LHCb New II


    CERN LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles

    Quantum Diaries

  • richardmitnick 2:02 pm on July 14, 2016 Permalink | Reply
    Tags: , , , Higgs   

    From FNAL: “Importance of multivariate analysis” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

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

    July 14, 2016
    Andy Beretvas
    Giorgio Chiarelli

    During the hunt for the Higgs boson, scientists had to investigate and study a number of predicted processes.

    Science proceeds step by step, looking for the unknown and the unexplored. Higgs production is rare, and as many different processes contribute to the background against which the Higgs signal must be distinguished, physicists have to reduce that background piece by piece to bring it to an acceptable level.

    The left plot show the distribution of the dijet mass. The right plot shows the neural network output. Both plots are for the one-tag candidates where events from all lepton categories are added together. The best fit to the data is shown.

    One of the ways in which the Higgs was hunted is through its associated production with W bosons.

    W boson properties are well known and provide a way to select events in which a Higgs boson can be searched through its decays into two b quarks.

    Unfortunately there are processes that can mimic our signal. One of them is the production of a W and a Z boson together, with the Z boson decaying into two heavy flavor quarks (two charm or two beauty quarks) and the W decaying into leptons (one charged and one neutral). A second is the production of a WW boson pair, in which the second W decays into heavy flavor quark.

    These processes are predicted in the Standard Model, but until now, they escaped a clear observation in this final state.

    Scientists at CDF have looked into the full data set collected during the 10 years of Tevatron Run II to identify these processes. During this search, they developed a number of techniques to disentangle events containing real W’s from events in which its presence was mimicked by other processes.

    The separation of signal and background is shown in the left plot of the above figure. Among the techniques used as part of this analysis was that of a neural network. Its output is shown on the right side of the figure. This technique is modeled on the central nervous system.

    CDF also looked for events containing a W or a Z decaying into heavy quarks, and we used the know-how developed in the Higgs experiment. The evidence for the Higgs boson was obtained in part thanks to an earlier version of this study.

    In the end, the measuring of WZ (W→lepton and neutrino; Z→bb or cc) and WW (W→lepton and neutrino; W→c or s) is an interesting check of the Standard Model prediction, with the two signals never measured separately so far at a hadron collider. CDF measured a production cross section for WW of 9.4 ± 4.2 picobarns and WZ of 3.7 +2.5 -2.2 picobarns with and evidence of 2.87 sigma for the first process and 2.12 for the second one.

    Learn more.

    See the full article here .

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    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. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

  • richardmitnick 3:27 pm on June 23, 2016 Permalink | Reply
    Tags: , Higgs, , Where are the bottom quarks?   

    From Symmetry: “The Higgs-shaped elephant in the room” 

    Symmetry Mag


    Sarah Charley

    Higgs bosons should mass-produce bottom quarks. So why is it so hard to see it happening?

    Maximilien Brice, CERN

    Higgs bosons are born in a blob of pure concentrated energy and live only one-septillionth of a second before decaying into a cascade of other particles. In 2012, these subatomic offspring were the key to the discovery of the Higgs boson.

    Higgs Boson Event

    So-called daughter particles stick around long enough to show up in the CMS and ATLAS detectors at the Large Hadron Collider. Scientists can follow their tracks and trace the family trees back to the Higgs boson they came from.

    CERN/CMS Detector

    CERN/ATLAS detector

    But the particles that led to the Higgs discovery were actually some of the boson’s less common progeny. After recording several million collisions, scientists identified a handful of Z bosons and photons with a Higgs-like origin. The Standard Model of particle physics predicts that Higgs bosons produce those particles 2.5 and 0.2 percent of the time.

    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 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

    Physicists later identified Higgs bosons decaying into W bosons, which happens about 21 percent of the time.

    According to the Standard Model, the most common decay of the Higgs boson should be a transformation into a pair of bottom quarks. This should happen about 60 percent of the time.

    The strange thing is, scientists have yet to discover it happening (though they have seen evidence).

    According to Harvard researcher John Huth, a member of the ATLAS experiment, seeing the Higgs turning into bottom quarks is priority No. 1 for Higgs boson research.

    “It would behoove us to find the Higgs decaying to bottom quarks because this is the largest interaction,” Huth says, “and it darn well better be there.”

    If the Higgs to bottom quarks decay were not there, scientists would be left completely dumbfounded.

    “I would be shocked if this particle does not couple to bottom quarks,” says Jim Olsen, a Princeton researcher and Physics Coordinator for the CMS experiment. “The absence of this decay would have a very large and direct impact on the relative decay rates of the Higgs boson to all of the other known particles, and the recent ATLAS and CMS combined measurements are in excellent agreement with expectations.”

    To be fair, the decay of a Higgs to two bottom quarks is difficult to spot.

    When a dying Higgs boson produces twin Z or W bosons, they each decay into a pair of muons or electrons. These particles leave crystal clear signals in the detectors, making it easy for scientists to spot them and track their lineage. And because photons are essentially immortal beams of light, scientists can immediately spot them and record their trajectory and energy with electromagnetic detectors.

    But when a Higgs births a pair of bottom quarks, they impulsively marry other quarks, generating huge unstable families which bourgeon, break and reform. This chaotic cascade leaves a messy ancestry.

    Scientists are developing special tools to disentangle the Higgs from this multi-generational subatomic soap opera. Unfortunately, there are no cheek swabs or Maury Povich to announce, Higgs, you are the father! Instead, scientists are working on algorithms that look for patterns in the energy these jets of particles deposit in the detectors.

    “The decay of Higgs bosons to bottom quarks should have different kinematics from the more common processes and leave unique signatures in our detector,” Huth says. “But we need to deeply understand all the variables involved if we want to squeeze the small number of Higgs events from everything else.”

    Physicist Usha Mallik and her ATLAS team of researchers at the University of Iowa have been mapping the complex bottom quark genealogies since shortly after the Higgs discovery in 2012.

    “Bottom quarks produce jets of particles with all kinds and colors and flavors,” Mallik says. “There are fat jets, narrow gets, distinct jets and overlapping jets. Just to find the original bottom quarks, we need to look at all of the jet’s characteristics. This is a complex problem with a lot of people working on it.”

    This year the LHC will produce five times more data than it did last year and will generate Higgs bosons 25 percent faster. Scientists expect that by August they will be able to identify this prominent decay of the Higgs and find out what it can tell them about the properties of this unique particle.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 11:19 am on November 22, 2015 Permalink | Reply
    Tags: , , , Higgs, , ,   

    From Nautilus: “Who Really Found the Higgs Boson” 2014 but Very Instructive 



    October 23, 2014
    By Neal Hartman Illustration by Owen Freeman


    To those who say that there is no room for genius in modern science because everything has been discovered, Fabiola Gianotti has a sharp reply. “No, not at all,” says the former spokesperson of the ATLAS Experiment, the largest particle detector at the Large Hadron Collider at CERN.

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

    “Until the fourth of July, 2012 we had no proof that nature allows for elementary scalar fields. So there is a lot of space for genius.”

    She is referring to the discovery of the Higgs boson two years ago—potentially one of the most important advances in physics in the past half century.

    Candidate Higgs boson events from collisions between protons in the LHC
    Date 17 November 2013

    It is a manifestation of the eponymous field that permeates all of space, and completes the standard model of physics: a sort of baseline description for the existence and behavior of essentially everything there is.

    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.

    By any standards, it is an epochal, genius achievement.

    What is less clear is who, exactly, the genius is. An obvious candidate is Peter Higgs, who postulated the Higgs boson, as a consequence of the Brout-Englert-Higgs mechanism, in 1964.

    He was awarded the Nobel Prize in 2013 along with Francois Englert (Englert and his deceased colleague Robert Brout arrived at the same result independently). But does this mean that Higgs was a genius? Peter Jenni, one of the founders and the first “spokesperson” of the ATLAS Experiment Collaboration (one of the two experiments at CERN that discovered the Higgs particle), hesitates when I ask him the question.

    “They [Higgs, Brout and Englert] didn’t think they [were working] on something as grandiose as [Einstein’s relativity],” he states cautiously. The spontaneous symmetry breaking leading to the Higgs “was a challenging question, but [Albert Einstein] saw something new and solved a whole field. Peter Higgs would tell you, he worked a few weeks on this.”

    What, then, of the leaders of the experimental effort, those who directed billions of dollars in investment and thousands of physicists, engineers, and students from almost 40 countries for over three decades? Surely there must have been a genius mastermind directing this legion of workers, someone we can single out for his or her extraordinary contribution.

    “No,” says Gianotti unequivocally, which is rare for a physicist, “it’s completely different. The instruments we have built are so complex that inventiveness and creativity manifests itself in the day-by-day work. There are an enormous amount of problems that require genius and creativity to be spread over time and over many people, and all at the same level.”

    Scientific breakthroughs often seem to be driven by individual genius, but this perception belies the increasingly collaborative nature of modern science. Perhaps nothing captures this dichotomy better than the story of the Higgs discovery, which presents a stark contrast between the fame awarded to a few on the one hand, and the institutionalized anonymity of the experiments that made the discovery possible on the other.

    An aversion to the notion of exceptional individuals is deeply rooted within the ATLAS collaboration, a part of its DNA. Almost all decisions in the collaboration are approved by representative groups, such as the Institute Board, the Collaboration Board, and a plethora of committees and task forces. Consensus is the name of the game. Even the effective CEO, a role Gianotti occupied from 2009 to 2013, is named the “Spokesperson.” She spoke for the collaboration, but did not command it.

    Collectivity is crucial to ATLAS in part because it’s important to avoid paying attention to star personalities, so that the masses of physicists in the collaboration each feel they own the research in some way. Almost 3,000 people qualify as authors on the key physics papers ATLAS produces, and the author list can take almost as many pages as the paper itself.1

    The genius of crowds: Particle physics collaborations can produce academic papers with hundreds of authors. One 2010 paper was 40 pages long—with 10 pages devoted to the authors list, pictured here.1

    On a more functional level, this collectivity also makes it easier to guard against bias in interpreting the data. “Almost everything we do is meant to reduce potential bias in the analysis,” asserts Kerstin Tackmann, a member of the Higgs to Gamma Gamma analysis group during the time of the Higgs discovery, and recent recipient of the Young Scientist Prize in Particle Physics. Like many physicists, Tackmann verges on the shy, and speaks with many qualifications. But she becomes more forceful when conveying the importance of eliminating bias.

    “We don’t work with real data until the very last step,” she explains. After the analysis tools—algorithms and software, essentially—are defined, they are applied to real data, a process known as the unblinding. “Once we look at the real data,” says Tackmann, “we’re not allowed to change the analysis anymore.” To do so might inadvertently create bias, by tempting the physicists to tune their analysis tools toward what they hope to see, in the worst cases actually creating results that don’t exist. The ability of the precocious individual physicist to suggest a new data cut or filter is restricted by this procedure: He or she wouldn’t even see real data until late in the game, and every analysis is vetted independently by multiple other scientists.

    This collective discipline is one way that ATLAS tames the complexity of the data it produces, which in raw form is voluminous enough to fill a stack of DVDs that reaches from the earth to the moon and back again, 10 times every year. The data must be reconstructed into something that approximates an image of individual collisions in time and space, much like the processing required for raw output from a digital camera.

    But the identification of particles from collisions has become astoundingly more complex since the days of “scanning girls” and bubble chamber negatives, where actual humans sat over enlarged images of collisions and identified the lines and spirals as different particles. Experimentalists today need to have expert knowledge of the internal functioning of the different detector subsystems: pixel detector, silicon strip tracker, transition radiation tracker, muon system, and calorimeters, both hadronic and electromagnetic. Adjustments made to each subsystem’s electronics, such as gain or threshold settings, might cause the absence or inclusion of what looks like real data but isn’t. Understanding what might cause false or absent signals, and how they can be accounted for, is the most challenging and creative part of the process. “Some people are really clever and very good at this,” says Tackmann.

    The process isn’t static, either. As time goes on, the detector changes from age and radiation damage. In the end the process of perfecting the detector’s software is never-ending, and the human requirements are enormous: roughly 100 physicists were involved in the analysis of a single and relatively straightforward particle signature, the decay of the Higgs into two Gamma particles. The overall Higgs analysis was performed by a team of more than 600 physicists.

    The depth and breadth of this effort transform the act of discovery into something anonymous and distributed—and this anonymity has been institutionalized in ATLAS culture. Marumi Kado, a young physicist with tousled hair and a quiet zen-like speech that borders on a whisper, was one of the conveners of the “combined analysis” group that was responsible for finally reaching the level of statistical significance required to confirm the Higgs discovery. But, typically for ATLAS, he downplays the importance of the statistical analysis—the last step—in light of the complexity of what came before. “The final analysis was actually quite simple,” he says. “Most of the [success] lay in how you built the detector, how well you calibrated it, and how well it was designed from the very beginning. All of this took 25 years.”

    The deeply collaborative work model within ATLAS meant that it wasn’t enough for it to innovate in physics and engineering—it also needed to innovate its management style and corporate culture. Donald Marchand, a professor of strategy execution and information management at IMD Business School in Lausanne, describes ATLAS as following a collaborative mode of working that flies in the face of standard “waterfall”—or top down—management theory.

    Marchand conducted a case study on ATLAS during the mid-2000s, finding that the ATLAS management led with little or no formal authority.2 Most people in the collaboration work directly “for” someone who is in no way related to their home institute, which actually writes their paycheck. For example, during the construction phase, the project leader of the ATLAS pixel detector, one of its most data-intensive components, worked for a U.S. laboratory in California. His direct subordinate, the project engineer, worked for an institute in Italy. Even though he was managing a critical role in the production process, the project leader had no power to promote, discipline, or even formally review the project engineer’s performance. His only recourse was discussion, negotiation, and compromise. ATLAS members are more likely to feel that they work with someone, rather than for them.

    Similarly, funding came from institutes in different countries through “memorandums of understanding” rather than formal contracts. The collaboration’s spokesperson and other top managers were required to follow a politic of stewardship, looking after the collaboration rather than directing it. If collaboration members were alienated, that could mean the loss of the financial and human capital they were investing. Managers at all levels needed to find non-traditional ways to provide feedback, incentives, and discipline to their subordinates.

    The coffee chat was one way to do this, and became the predominant way to conduct the little daily negotiations that kept the collaboration running. Today there are cafés stationed all around CERN, and they are full from morning to evening with people having informal meetings. Many physicists can be seen camped out in the cafeteria for hours at a time, working on their laptops between appointments. ATLAS management also created “a safe harbor, a culture within the organization that allows [employees] to express themselves and resolve conflicts and arguments without acrimony,” Marchand says.

    The result is a management structure that is remarkably effective and flexible. ATLAS managers consistently scored in the top 5 percent of a benchmark scale that measures how they control, disseminate, and capitalize on the information capital in their organization.3 Marchand also found that the ATLAS management structure was effective at adapting to changing circumstances, temporarily switching to a more top-down paradigm during the core production phase of the experiment, when thousands of identical objects needed to be produced on assembly lines all over the world.

    This collaborative culture didn’t arise by chance; it was built into ATLAS from the beginning, according to Marchand. The original founders infused a collaborative ethic into every person that joined by eschewing personal credit, talking through conflicts face to face, and discussing almost everything in open meetings. But that ethic is codified nowhere; there is no written code of conduct. And yet it is embraced, almost religiously, by everyone that I spoke with.

    Collaboration members are sceptical of attributing individual credit to anything. Every paper includes the entire author list, and all of ATLAS’s outreach material is signed “The ATLAS Collaboration.” People are suspicious of those that are perceived to take too much personal credit in the media. One famous member of the collaboration (as well as a former rock star and host of the highly successful BBC series, Horizon) is looked upon dubiously by many, who see him as drawing too much attention to himself through his association with the experiment.

    MIND THE GAP: Over 60 institutes collaborated to build and install a new detector layer inside a 9-millimeter gap between the beam pipe (the evacuated pipe inside of which protons circulate) and the original detector. ATLAS Experiment © 2014 CERN

    In searching for genius at ATLAS, and other experiments at CERN, it seems almost impossible to point at anything other than the collaborations themselves. More than any individual, including the theorists who suggest new physics and the founders of experimental programs, it is the collaborations that reflect the hallmarks of genius: imagination, persistence, open-mindedness, and accomplishment.

    The results speak for themselves: ATLAS has already reached its first key objective in just one-tenth of its projected lifetime, and continues to evolve in a highly collaborative way. This May, one of the first upgrades to the detector was installed. Called the Insertable B-Layer (IBL), it grew out of a task force formed near the end of ATLAS’s initial commissioning period, in 2008, with the express goal of documenting why inserting another layer of detector into a 9-millimeter clearance space just next to the beam pipe was considered impossible.

    Consummate opportunists, the task force members instead came up with a design that quickly turned into a new subproject. And though it’s barely larger than a shoebox, the IBL’s construction involved more than 60 institutes all over the world, because everyone wanted to be involved in this exciting new thing. When it came time to slide the Insertable B-layer sub-detector into its home in the heart of ATLAS earlier this year, with only a fraction of a millimeter of clearance over 7 meters in length, the task was accomplished in just two hours—without a hitch.

    Fresh opportunities for new genius abound. Gianotti singles out dark matter as an example: “96 percent of the universe is dark. We don’t know what it’s made of and it doesn’t interact with our instruments. We have no clue,” she says. “So there is a lot of space for genius.” But instead of coming from the wild-haired scientist holding a piece of chalk or tinkering in the laboratory, that genius may come from thousands of people working together.


    1. Aad, G. et al. Charged-particle multiplicities in pp interactions at sqrt(s) = 900 GeV measured with the ATLAS detector at the LHC. Physics Letters B 688, 21-42 (2010).

    2. IMD case study by Marchand, D.A. & Margery, P. The ATLAS and LHC Collaborations at CERN: Exploring the Big Bang, IMD-3-2015 (2009).

    3. Marchand, D., Kettinger, W., & Rollins, J. Information Orientation: The Link to Business Performance Oxford University Press (2001).

    See the full article here .

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    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

  • richardmitnick 7:32 pm on September 15, 2015 Permalink | Reply
    Tags: , , , , Higgs   

    From Symmetry: “Where the Higgs belongs” 


    September 15, 2015
    Sarah Charley

    The Higgs doesn’t quite fit in with the other particles of the Standard Model of particle physics.

    CERN CMS Event

    If you were Luke Skywalker in Star Wars, and you carried a tiny green Jedi master on your back through the jungles of Dagobah for long enough, you could eventually raise your submerged X-wing out of the swamp just by using the Force.

    But if you were a boson in the Standard Model of particle physics, you could skip the training—you would be the force.

    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.

    Bosons are particles that carry the four fundamental forces. These forces push and pull what would otherwise have been an unwieldy soup of particles into the beautiful mosaic of stars and galaxies that permeate the visible universe.

    The fundamental forces keep protons incredibly stable (the strong force holds them together), cause compasses to point north (the electromagnetic force attracts the needle), make apples fall off trees (gravity attracts the fruit to the ground), and keep the sun shining (the weak force allows nuclear fusion to occur).

    In 2012, the Higgs boson became an officially recognized member of this family of fundamental bosons.

    The Higgs is called a boson because of a quantum mechanical property called spin—which represents a particle’s intrinsic angular momentum and characterizes how a particle plays with its Standard Model friends.

    Bosons have an integer spin (0, 1, 2) which makes them the touchy-feely types. They have no need for personal space. Fermions, on the other hand, have a non-integer spin (1/2, 3/2, etc.), which makes them a bit more isolated; they prefer to keep their distance from other particles.

    The Higgs has a spin of 0, making it officially a boson.

    “Every boson is associated with one of the four fundamental forces,” says Kyle Cranmer, an associate professor of physics at New York University. “So if we discover a new boson, it seems natural that we should find a new force.”

    Scientists think that a Higgs force does exist. But it’s the Higgs boson’s relationship to that force that makes it a bit of a black sheep. It’s the reason that, when the Higgs is added to the Standard Model of particle physics, it’s often pictured apart from the rest of the boson family.

    What the Higgs is for

    The Higgs boson is an excitation of the Higgs field, which interacts with some of the fundamental particles to give them mass.

    “The way the Higgs field gives masses to particles is its own unique feature, which is different from all other known fields in the universe,” says Matt Strassler, a Harvard University theoretical physicist. “When the Higgs field turns on, it changes the environment for all particles; it changes the nature of empty space itself. The way particles interact with this field is based on their intrinsic properties.”

    There are three inherent qualifications required for a field to generate a force: The field must be able to switch on and off. It must have a preferred direction. And it must be able to attract or repel.

    Normally the Higgs field fails the first two requirements—it’s always on, with no preferred direction. But in the presence of a Higgs boson, the field is distorted, theoretically allowing it to generate a force.

    “We think that two particles can pull on each other using the Higgs field,” Strassler says. “The same equations we used to predict that the Higgs particle should exist, and how it should decay to other particles, also predict this force will exist.”

    Just what role that force might play in our greater understanding of the universe is still a mystery.

    “We know the Higgs field is essential in the formation of stable matter,” Strassler says. “But the Higgs force—as far as we know—is not.”

    The Higgs force could be important in some other way, Strassler says. It could be related to how much dark matter exists in the universe or the huge imbalance between matter and antimatter. “It’s too early to write it off,” he says.

    During this run of the Large Hadron Collider, physicists expect to produce roughly 10 times as many Higgs bosons as they did during the first run.

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

    This will enable scientists to examine the properties of this peculiar particle more deeply.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 10:42 am on July 31, 2015 Permalink | Reply
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    From FNAL- “Frontier Science Result: CMS Shedding light on the invisible Higgs” 

    FNAL II photo

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

    July 31, 2015
    Jim Pivarski

    Event recorded with the CMS detector in 2012 at a proton-proton center of mass energy of 8 TeV. The event shows characteristics expected from the decay of the Standard Model Higgs boson to a pair of photons (dashed yellow lines and green towers). The event could also be due to known standard model background processes..

    There are basically two types of detectors used in collider experiments: trackers, which are sensitive to any particles that interact electromagnetically, and calorimeters, which are sensitive to any particles that interact electromagnetically or through the strong force. That’s only two of the four forces — there’s also the weak force and gravity. Anything that interacts exclusively through the latter two forces would be invisible.

    This is not a speculative point. Neutrinos are effectively invisible in collider experiments. Even specialized neutrino detectors can detect only a small fraction of the neutrinos that pass through them. Dark matter is known purely through its gravitational effect on galaxies; no one even knows if it interacts via the weak force as well. Invisible particles could be slipping through detectors at the LHC right now.

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

    But if you can’t see them, how can you find them? Fortunately, physicists have developed a few tricks, mostly involving conservation laws. For instance, conservation of charge forces some particles and antiparticles to be produced in pairs, and one may be detected while the other decays invisibly. Conservation of momentum requires particles to be produced symmetrically around the beamline; if the observed distribution is highly asymmetric, that’s an indication of an unseen particle.

    In a recent study, CMS physicists used the latter technique to determine how often Higgs bosons decay into invisible particles and also a photon.

    CERN CMS Detector
    CMS in the LHC at CERN

    This is interesting because Higgs bosons have been observed only in a few of their predicted decay modes — the rest could be wildly different from expectations. In particular, Higgs bosons could interact with new phenomena like dark matter or supersymmetry, and most of these particles would be invisible.

    Supersymmetry standard model
    Standard Model of Supersymmetry

    One of the ways supersymmetry might be hiding is by decaying into gravitinos (gravity only), neutralinos (gravity and weak only) and a visible photon.

    Through this analysis, the mostly invisible signature has been partially ruled out: At most 7 to 13 percent of Higgs bosons might decay this way, if any at all. Before the measurement, it could have been as much as 57 percent. That’s a lot for one bite!

    See the full article here.

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    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. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

  • richardmitnick 2:54 pm on June 1, 2015 Permalink | Reply
    Tags: , , Higgs,   

    From Quanta: “A New Theory to Explain the Higgs Mass” 

    Quanta Magazine
    Quanta Magazine

    May 27, 2015
    Natalie Wolchover

    Skip Sterling for Quanta Magazine

    Three physicists who have been collaborating in the San Francisco Bay Area over the past year have devised a new solution to a mystery that has beleaguered their field for more than 30 years. This profound puzzle, which has driven experiments at increasingly powerful particle colliders and given rise to the controversial multiverse hypothesis, amounts to something a bright fourth-grader might ask: How can a magnet lift a paperclip against the gravitational pull of the entire planet?

    Despite its sway over the motion of stars and galaxies, the force of gravity is hundreds of millions of trillions of trillions of times weaker than magnetism and the other microscopic forces of nature. This disparity shows up in physics equations as a similarly absurd difference between the mass of the Higgs boson, a particle discovered in 2012 that controls the masses and forces associated with the other known particles, and the expected mass range of as-yet-undiscovered gravitational states of matter.

    In the absence of evidence from Europe’s Large Hadron Collider (LHC) supporting any of the theories previously proposed to explain this preposterous mass hierarchy — including the seductively elegant “supersymmetry” — many physicists have come to doubt the very logic of nature’s laws.

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

    Increasingly, they worry that our universe might just be a random, rather bizarre permutation among uncountable other possible universes — an effective dead end in the quest for a coherent theory of nature.

    This month, the LHC launched its eagerly anticipated second run at nearly double its previous operating energy, continuing its pursuit of new particles or phenomena that would solve the hierarchy problem. But the very real possibility that no new particles lie around the corner has left theoretical physicists facing their “nightmare scenario.” It has also gotten them thinking.

    “It is in moments of crisis that new ideas develop,” said Gian Giudice, a theoretical particle physicist at the CERN laboratory near Geneva, which houses the LHC.

    The new proposal offers a possible way forward. The trio is “super excited,” said David Kaplan, 46, a theoretical particle physicist from Johns Hopkins University in Baltimore, Md., who developed the model during a West Coast sabbatical with Peter Graham, 35, of Stanford University and Surjeet Rajendran, 32, of the University of California, Berkeley.

    David Kaplan of Johns Hopkins University. Will Kirk

    Their solution traces the hierarchy between gravity and the other fundamental forces back to the explosive birth of the cosmos, when, their model suggests, two variables that were evolving in tandem suddenly deadlocked. At that instant, a hypothetical particle called the “axion” locked the Higgs boson into its present-day mass, far below the scale of gravity. The axion has appeared in theoretical equations since 1977 and is deemed likely to exist. Yet no one, until now, noticed that axions could be what the trio calls “relaxions,” solving the hierarchy problem by “relaxing” the value of the Higgs mass.

    “It’s a very, very clever idea,” said Raman Sundrum, a theoretical particle physicist at the University of Maryland in College Park who was not involved in developing it. “Possibly some version of that is the way the world works.”

    In the weeks since the trio’s paper appeared online, it has opened up “a new playground” populated with researchers eager to revise its weaknesses and take its basic premise in different directions, said Nathaniel Craig, a theoretical physicist at the University of California, Santa Barbara.

    “This just seems like a pretty simple possibility,” Rajendran said. “We’re not standing on our heads to do something crazy here. It just wants to work.”

    However, as several experts noted, in its current form the idea has shortcomings that will need to be carefully considered. And even if it survives this scrutiny, it could take more than a decade to test experimentally. For the time being, experts said, the relaxion is shaking up longheld views and encouraging some physicists to see the hierarchy problem in a new light. The lesson, said Michael Dine, a physicist at the University of California, Santa Cruz, and a veteran of the hierarchy problem, is “not to just give up and assume that we won’t be able to figure it out.”

    An Unnatural Balance

    For all the revelry surrounding the 2012 discovery of the Higgs boson, which completed the “Standard Model” of particle physics and earned Peter Higgs and François Englert the 2013 Nobel Prize in physics, it came as little surprise; the particle’s existence and measured mass of 125 giga-electron volts (GeV) agreed with years of indirect evidence.

    Standard Model of Particle Physics. The diagram shows the elementary particles of the Standard Model (the Higgs boson, the three generations of quarks and leptons, and the gauge bosons), including their names, masses, spins, charges, chiralities, and interactions with the strong, weak and electromagnetic forces. It also depicts the crucial role of the Higgs boson in electroweak symmetry breaking, and shows how the properties of the various particles differ in the (high-energy) symmetric phase (top) and the (low-energy) broken-symmetry phase (bottom).

    It’s what wasn’t found at the LHC that left experts baffled. Nothing showed up that could reconcile the Higgs mass with the predicted mass scale associated with gravity, which lies beyond experimental reach at 10,000,000,000,000,000,000 GeV.

    The mass-energy scale associated with gravity (right) lies 17 orders of magnitude beyond the scale of the known particles (left), where 1 GeV = 1,000 MeV. The tendency of particle masses to equalize in calculations makes this a puzzling hierarchy. Nelson Hsu for Quanta Magazine

    “The issue is that in quantum mechanics, everything influences everything else,” Giudice explained. The super-heavy gravitational states should mingle quantum mechanically with the Higgs boson, contributing huge factors to the value of its mass. Yet somehow, the Higgs boson ends up lightweight. It’s as if all the gargantuan factors affecting its mass — some positive, others negative, but all dozens of digits long — have magically canceled out, leaving an extraordinarily tiny value behind. The improbably fine-tuned cancellation of these factors seems “suspicious,” Giudice said. “You think, well, there must be something else behind it.”

    Experts often compare the finely tuned Higgs mass to a pencil standing on its lead tip, nudged this way and that by powerful forces like air currents and table vibrations that have somehow struck a perfect balance. “It is not a state of impossibility; it is a state of extremely small likelihood,” said Savas Dimopoulos of Stanford. If you came across such a pencil, he said, “you would first move your hand over the pencil to see if there was any string holding it from the ceiling. [Next] you would look at the tip to see if there is chewing gum.”

    Physicists have similarly sought a natural explanation for the hierarchy problem since the 1970s, confident that the search would lead them toward a more complete theory of nature, perhaps even turning up the particles behind “dark matter,” the invisible substance that permeates galaxies. “Naturalness has really been the leitmotif of that research,” Giudice said.

    Surjeet Rajendran of the University of California, Berkeley. Sarah Wittmer

    Since the 1980s, the most popular proposal has been supersymmetry. It solves the hierarchy problem by postulating a yet-to-be-discovered twin for each elementary particle: for the electron, a hypothetical “selectron,” for each quark, a “squark,” and so on. Twins contribute opposite terms to the mass of the Higgs boson, rendering it immune to the effects of super-heavy gravity particles (since they are nullified by the effects of their twins).

    Supersymmetry standard model
    Standard Model of Supersymmetry

    But no evidence for supersymmetry or for any competing ideas — such as “technicolor” and “warped extra dimensions” — turned up during the first run of the LHC from 2010 to 2013. When the collider shut down for upgrades in early 2013 without having found a single “sparticle” or any other sign of physics beyond the Standard Model, many experts felt they could no longer avoid contemplating a stark alternative. What if the Higgs mass, and by implication the laws of nature, are unnatural? Calculations show that if the mass of the Higgs boson were just a few times heavier and everything else stayed the same, protons could no longer assemble into atoms, and there would be no complex structures — no stars or living beings. So, what if our universe really is as accidentally fine-tuned as a pencil balanced on its tip, singled out as our cosmic address from an inconceivably vast array of bubble universes inside an eternally frothing “multiverse” sea simply because life requires such an outrageous accident to exist?

    This multiverse hypothesis, which has loomed over discussions of the hierarchy problem since the late 1990s, is seen as a bleak prospect by most physicists. “I just don’t know what to do with it,” Craig said. “We don’t know what the rules are.” Other bubbles of the multiverse, if they exist, lie beyond the boundaries of light communication, forever limiting theories about the multiverse to what we can observe from within our lonely bubble. With no way to tell where our data point lies on the vast spectrum of possibilities in a multiverse, it becomes difficult or impossible to construct multiverse-based arguments about why our universe is the way it is. “I don’t know at what point we would ever be convinced,” Dine said. “How would you settle it? How would you know?”

    The Higgs and the Relaxion

    Kaplan visited the Bay Area last summer to collaborate with Graham and Rajendran, whom he knew because all three had worked at various times under Dimopoulos, who was one of the key developers of supersymmetry. Over the past year the trio split their time between Berkeley and Stanford — and the various coffee shops, lunch spots and ice cream parlors bordering both campuses — exchanging “embryonic bits of the idea,” Graham said, and gradually developing a new origin story for the laws of particle physics.

    Inspired by a 1984 attempt by Larry Abbott to address a different naturalness problem in physics, they sought to recast the Higgs mass as an evolving parameter, one that could dynamically “relax” to its tiny value during the birth of the cosmos rather than starting out as a fixed, seemingly improbable constant. “Though it took six months of dead ends and really stupid models and very baroque, complicated things, we ended up landing on this very simple picture,” Kaplan said.

    In their model, the Higgs mass depends on the numerical value of a hypothetical field that permeates space and time: an axion field. To picture it, “we think of the totality of space as being this 3-D mattress,” Dimopoulos said. The value at each point in the field corresponds to how compressed the mattress springs are there. It has long been recognized that the existence of this mattress — and its vibrations in the form of axions — could solve two deep mysteries: First, the axion field would explain why most interactions between protons and neutrons run both forward and backward, solving what’s known as the “strong CP” problem. And axions could make up dark matter. Solving the hierarchy problem would be a third impressive achievement.

    The story of the new model begins when the cosmos was an energy-infused dot. The axion mattress was extremely compressed, which made the Higgs mass enormous. As the universe expanded, the springs relaxed, as if their energy were spreading through the springs of the newly created space. As the energy dissipated, so did the Higgs mass. When the mass fell to its present value, it caused a related variable to plunge past zero, switching on the Higgs field, a molasseslike entity that gives mass to the particles that move through it, such as electrons and quarks. Massive quarks in turn interacted with the axion field, creating ridges in the metaphoric hill that its energy had been rolling down. The axion field got stuck. And so did the Higgs mass.

    Peter Graham of Stanford University. Courtesy of Peter Graham

    In what Sundrum called a radical break from past models, the new one shows how the modern-day mass hierarchy might have been sculpted by the birth of the cosmos. “The fact that they’ve put equations to this in a realistic sense is really remarkable,” he said.

    Dimopoulos remarked on the striking minimalism of the model, which employs mostly pre-established ideas. “People like myself who have invested quite a bit on these other approaches to the hierarchy problem were very happily surprised that you don’t have to look very far,” he said. “In the backyard of the Standard Model, the solution was there. It took very clever young people to realize that.

    “This elevates the stock price of the axion,” he added. Recently, the Axion Dark Matter eXperiment at the University of Washington in Seattle began looking for the rare conversions of dark matter axions into light inside strong magnetic fields.

    Axion Dark Matter eXperiment

    Now, Dimopoulos said, “We should look even harder to find it.”

    However, like many experts, Nima Arkani-Hamed of the Institute for Advanced Study in Princeton, N.J., noted that it’s early days for this proposal. While “it’s definitely clever,” he said, its current implementation is far-fetched. For example, in order for the axion field to have gotten stuck on the ridges created by the quarks rather than rolling past them, cosmic inflation must have progressed much more slowly than most cosmologists have assumed. “You add 10 billion years of inflation,” he said. “You have to wonder why all of cosmology arranges itself just to make this happen.”

    And even if the axion is discovered, that alone wouldn’t prove it is the “relaxion” — that it relaxes the value of the Higgs mass. As Kaplan’s stay in the Bay Area winds down, he, Graham and Rajendran are beginning to develop ideas for how to test that aspect of their model. It might eventually be possible to oscillate an axion field, for example, to see whether this affects the masses of nearby elementary particles, by way of the Higgs mass. “You would see the electron mass wiggling,” Graham said.

    These tests of the proposal will not happen for many years. (The model doesn’t predict any new phenomena that the LHC would detect.) And realistically, several experts said, it faces long odds. So many clever proposals have failed over the years that many physicists are reflexively skeptical. Still, the intriguing new model is delivering a timely dose of optimism.

    “We thought we had thought of everything and there was nothing new under the sun,” Sundrum said. “What this shows is that humans are pretty smart and there’s still room for new breakthroughs.”

    See the full article here.

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    Formerly known as Simons Science News, Quanta Magazine is an editorially independent online publication launched by the Simons Foundation to enhance public understanding of science. Why Quanta? Albert Einstein called photons “quanta of light.” Our goal is to “illuminate science.” At Quanta Magazine, scientific accuracy is every bit as important as telling a good story. All of our articles are meticulously researched, reported, edited, copy-edited and fact-checked.

  • richardmitnick 12:10 pm on March 3, 2015 Permalink | Reply
    Tags: , , Higgs,   

    From BBC: “New Higgs detection ‘closes circle’” 


    3 March 2015
    Jonathan Webb

    The low energy work is separate from studies at the Large Hadron Collider

    Physicists who detected a version of the Higgs Boson in a superconductor say their discovery closes a “historical circuit”.

    They also stressed that the low-energy work was “completely separate” from the famous evidence gathered by the Large Hadron Collider.

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

    Superconductivity was the field of study where the idea for the Higgs originated in the 1960s. But the particle proved impossible to witness because it decays so fast. This new signature was glimpsed as very thin, chilled layers of metal compounds were pushed very close to the boundary of their superconducting state. This process creates a “mode” in the material that is analogous to the Higgs Boson but lasts much longer.

    Rather than the study of particles, it belongs in the field known condensed matter physics; it also uses much less energy than experiments at the LHC, where protons are smashed together at just under the speed of light. It was at the LHC in 2012 that the Higgs Boson, believed to give all the other subatomic particles their mass, was detected for the very first time.

    The new superconductor discovery was presented amid much discussion at this week’s March Meeting of the American Physical Society in San Antonio, Texas. It also appeared in the journal Nature Physics in January. Speaking at the meeting, Prof Aviad Frydman from Bar Ilan University in Israel responded in no uncertain terms to the suggestion that his work could substitute for the LHC. “That’s complete nonsense,” he told the BBC. “In fact it’s kind of embarrassing.”

    The team used superconducting films made from compounds of niobium (pictured here as a fibre) and indium

    Prof Frydman said the convergence of results from “two extremes of physics” was the most striking aspect of his findings, which were the fruit of a collaboration spanning Israel, Germany, Russia, India and the USA. “You take the high energy physics, which works in gigaelectronvolts. And then you take superconductivity, which is low energy, low temperature, one millivolt. “You have 10 to the 15 (one quadrillion) orders of magnitude between them, and the same physics governs both! That is the nice thing.”

    “It’s not that our experiment can replace the LHC. It’s completely separate.”

    Superconductors are materials that, when under critical conditions including temperatures near absolute zero (-273C), allow electrons to move with complete freedom. It was attempts to understand this property that ultimately led to Peter Higgs and others proposing the now-famous boson. “In the 1960s there were two distinct, basic problems. One was superconductivity and one was the mass of particles,” Prof Frydman explained.

    “People like Phil Anderson developed this mechanism for understanding superconductivity. And the guys from high energy saw this kind of solution, and applied it to high energy physics. That’s where the Higgs actually came from.” So the detection of a superconducting Higgs, he added, is “closing a historical circuit”. This closure was a long time coming. Detecting the Higgs in a superconductor had seemed almost impossible. This was because the energy required to excite (and detect) the Higgs mode – even though vastly less than that needed to generate its analogous particle inside the LHC – would destroy the very property of superconductivity. The Higgs mode would vanish almost before it arose. But when Prof Frydman and his colleagues held their thin films in conditions very close to the “critical transition” between being a superconductor and an insulator, they created a longer-lived, lower-energy Higgs mode.

    Other claims of a superconducting Higgs have been made in the past, including one in 2014. They have all faced criticism. Indeed, Prof Frydman’s conference presentation was also greeted with intense questions from others in the field. “Like any physical finding, there are different interpretations,” he said. “The Cern experiment is also being contested.”

    See the full article here.

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  • richardmitnick 5:18 pm on January 23, 2015 Permalink | Reply
    Tags: , Higgs,   

    From Wired: “How Three Guys With $10K and Decades-Old Data Almost Found the Higgs Boson First” An Absolutely Great Story 

    Wired logo


    The Large Electron-Positron collider’s ALEPH detector was disassembled in 2001 to make room for the Large Hadron Collider. ALEPH collaboration/CERN

    On a fall morning in 2009, a team of three young physicists huddled around a computer screen in a small office overlooking Broadway in New York. They were dressed for success—even the graduate student’s shirt had buttons—and a bottle of champagne was at the ready. With a click of the mouse, they hoped to unmask a fundamental particle that had eluded physicists for decades: the Higgs boson.

    Of course, these men weren’t the only physicists in pursuit of the Higgs boson. In Geneva, a team of hundreds of physicists with an $8 billion machine called the Large Hadron Collider, and the world’s attention, also was in the hunt. But shortly after starting for the first time, the LHC had malfunctioned and was offline for repairs, opening a window three guys at NYU hoped to take advantage of.

    The key to their strategy was a particle collider that had been dismantled in 2001 to make room for the more powerful LHC. For $10,000 in computer time, they would attempt to show that the Large Electron-Positron collider had been making dozens of Higgs bosons without anybody noticing.

    “Two possible worlds stood before us then,” said physicist Kyle Cranmer, the leader of the NYU group. “In one, we discover the Higgs and a physics fairy tale comes true. Maybe the three of us share a Nobel prize. In the other, the Higgs is still hiding, and instead of beating the LHC, we have to go back to working on the LHC.”

    Cranmer had spent years working on both colliders, beginning as a graduate student at the Large Electron-Positron collider. He had been part of a 100-person statistical team that combed through terabytes of LEP data for evidence of new particles. “Everyone thought we had been very thorough,” he said. “But our worldview was colored by the ideas that were popular at the time.” A few years later, he realized the old data might look very different through the lens of a new theory.

    So, like detectives poring through evidence in a cold case, the researchers aimed to prove that the Higgs, and some supersymmetric partners in crime, had been at the scene in disguise.

    Dreaming up the Higgs

    The Higgs boson is now viewed as an essential component of the Standard Model of physics, a theory that describes all known particles and their interactions. But back in the 1960s, before the Standard Model had coalesced, the Higgs was part of a theoretical fix for a radioactive problem.

    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.

    Here’s the predicament they faced. Sometimes an atom of one element will suddenly transform into an atom of a different element in a process called radioactive decay. For example, an atom of carbon can decay into an atom of nitrogen by emitting two light subatomic particles. (The carbon dating of fossils is a clever use of this ubiquitous process.) Physicists trying to describe the decay using equations ran into trouble—the math predicted that a sufficiently hot atom would decay infinitely quickly, which isn’t physically possible.

    To fix this, they introduced a theoretical intermediate step into the decay process, involving a never-before-seen particle that blinks into existence for just a trillionth of a trillionth of a second. As if that weren’t far-fetched enough, in order for the math to work, the particle—called the W boson—would need to weigh 10 times as much as the carbon atom that kicked off the process.
    “Figuring out what happened in a collider is like trying to figure out what your dog ate at the park yesterday. You can find out, but you have to sort through a lot of shit to do it.”

    To explain the bizarrely large mass of the W boson, three teams of physicists independently came up with the same idea: a new physical field. Just as your legs feel sluggish and heavy when you wade through deep water, the W boson seems heavy because it travels through what became known as the Higgs field (named after physicist Peter Higgs, who was a member of one of the three teams). The waves kicked up by the motion of this field, by way of a principle known as wave-particle duality, become particles called Higgs bosons.

    Their solution boiled down to this: Radioactive decay requires a heavy W boson, and a heavy W boson requires the Higgs field, and disturbances in the Higgs field produce Higgs bosons. “Explaining” radioactive decay in terms of one undetected field and two undiscovered particles may seem ridiculous. But physicists are conspiracy theorists with a very good track record.

    Forensic physics

    How do you find out if a theoretical particle is real? By the time Cranmer came of age, there was an established procedure. To produce evidence of new particles, you smash old ones together really, really hard. This works because E = mc2 means energy can be exchanged for matter; in other words, energy is the fungible currency of the subatomic world. Concentrate enough energy in one place and even the most exotic, heavy particles can be made to appear. But, they explode almost immediately. The only way to figure out they were there is to catch and analyze the detritus.

    How particle detectors work

    The innermost layer of a modern detector is made of thin silicon strips, like in a camera. A zooming particle, such as an electron, leaves a track of activated pixels. The track curves slightly, thanks to a magnetic field, and the degree of curvature reveals the electron’s momentum. Next the electron enters a series of chambers of excitable gas, where it ionizes little trails behind it. An electric field pulls the charged trails over to an array of wire sensors. Finally, the electron enters an iron or steel calorimeter which slows the particle to a halt, gathering and recording all of it’s energy.

    Modern particle accelerators like the LEP and LHC are like high-tech surveillance states. Thousands of electronic sensors, photoreceptors, and gas chambers monitor the collision site. Particle physics has become a forensic science.

    It’s also a messy science. “Figuring out what happened in a collider is like trying to figure out what your dog ate at the park yesterday,” said Jesse Thaler, the MIT physicist who first told me of Cranmer’s quest. “You can find out, but you have to sort through a lot of shit to do it.”

    The situation may be even worse than that. To reason backward from the particles that live long enough to detect to the short-lived undetected ones, requires detailed knowledge of each intermediate decay—almost like an exact description of all the chemical reactions in the dog’s gut. Complicating matters further, small changes in the theory you’re working with can affect the whole chain of reasoning, causing big changes in what you conclude really happened.
    The fine-tuning problem

    While the LEP was running, the Standard Model was the theory used to interpret its data. A panoply of particles were made, from the beauty quark to the W boson, but Cranmer and others had found no sign of a Higgs. They started to get worried: If the Higgs wasn’t real, how much of the rest of the Standard Model was also a convenient fiction?

    The model had at least one troubling feature beyond a missing Higgs: For matter to be capable of forming planets and stars, for the fundamental forces to be strong enough to hold things together but weak enough to avoid total collapse, an absurdly lucky cancellation (where two equivalent units of opposite sign combine to make zero) had to occur in some foundational formulas. This degree of what’s known as “fine-tuning” has a snowball’s chance in hell of happening by coincidence, according to physicist Flip Tanedo of the University of California, Irvine. It’s like a snowball never melting because every molecule of scorching hot air whizzing through hell just happens to avoid it by chance.

    So Cranmer was quite excited when he got wind of a new model that could explain both the fine-tuning problem and the hiding Higgs. The Nearly-Minimal Supersymmetric Standard Model has a host of new fundamental particles. The cancellation which seemed so lucky before is explained in this model by new terms corresponding to some of the new particles. Other new particles would interact with the Higgs, giving it a covert way to decay that would have gone unnoticed at the LEP.

    Supersymmetry standard model
    Standard Model of Supersymmetry

    If this new theory was correct, evidence for the Higgs boson was likely just sitting there in the old LEP data. And Cranmer had just the right tools to find it: He had experience with the old collider, and he had two ambitious apprentices. So he sent his graduate student James Beacham to retrieve the data from magnetic tapes sitting in a warehouse outside Geneva, and tasked NYU postdoctoral researcher Itay Yavin with working out the details of the new model. After laboriously deciphering dusty FORTRAN code from the original experiment and loading and cleaning information from the tapes, they brought the data back to life.

    This is what the team hoped to see evidence of in the LEP data:

    First, an electron and positron smash into each other, and their energy converts into the matter of a Higgs boson. The Higgs then decays into two ‘a’ particles—predicted by supersymmetry but never before seen—which fly in opposite directions. After a fraction of a second, each of the two ‘a’ particles decays into two tau particles. Finally each of the four tau particles decays into lighter particles, like electrons and pions, which survive long enough to strike the detector.

    As light particles hurtled through the detector’s many layers, detailed information on their trajectory was gathered (see sidebar). A tau particle would appear in the data as a common origin for a few of those trails. Like a firework shot into the sky, a tau particle can be identified by the brilliant arcs traced by its shrapnel. A Higgs, in turn, would appear as a constellation of light particles indicating the simultaneous explosion of four taus.

    Unfortunately, there are almost guaranteed to be false positives. For example, if an electron and a positron collide glancingly, they could create a quark with some of their energy. The quark could explode into pions, mimicking the behavior of a tau that came from a Higgs.

    A computer simulation of a Higgs decaying into more elementary particles. The colored tracks show what the detector would see. ALEPH Collaboration/CERN

    To claim that a genuine Higgs had been made, rather than a few impostors, Beacham and Yavin needed to be extremely careful. Electronics sensitive enough to measure a single particle will often misfire, so there are countless decisions about which events to count and which to discard as noise. Confirmation bias makes it too dangerous to set those thresholds while looking at actual data from the LEP, as Beachem and Yavin would have been tempted to shade things in favor of a Higgs discovery. Instead, they decided to build two simulations of the LEP. In one, collisions took place in a universe governed by the Standard Model; in the other, the universe followed the rules of the Nearly-Minimal Supersymmetric Model. After carefully tuning their code on the simulated data, the team concluded that they had enough power to proceed: If the Higgs had been made by the LEP, they would detect significantly more four-tau events than if it had not.
    Moment of theoretical truth

    The team was hopeful and nervous as the moment of truth approached. Yavin had hardly been sleeping, checking and re-checking the code. A bottle of champagne was ready. With one click, the count of four-tau events at the LEP would come onscreen. If the Standard Model was correct, there would be around six, an expected number of false positives. If the Nearly-Minimal Supersymmetric Standard Model was correct, there would be around 30, a big enough excess to conclude that there really had been a Higgs.

    “I had done my job,” Cranmer said. “Now it was up to nature.”

    Kyle Cranmer clicks for the Higgs! Also pictured: Itay Yavin (standing), James Beacham (sitting), and Veuve Clicquot (boxed). Courtesy Particle Fever

    There were just two tau quartets.

    “Honey, we didn’t find the Higgs,” Cranmer told his wife on the phone. Yavin collapsed in his chair. Beacham was thrilled the code had worked at all, and drank the champagne anyway.

    If Cranmer’s little team had found the Higgs boson before the multi-billion-dollar LHC and unseated the Standard Model, if the count had been 32 instead of 2, their story would have been front-page news. Instead, it was a typical success for the scientific method: A theory was carefully developed, rigorously tested, and found to be false.

    “With one keystroke, we rendered over a hundred theory papers null and void,” Beacham said.

    Three years later, a huge team of physicists at the LHC announced they had found the Higgs and that it was entirely consistent with the Standard Model. This was certainly a victory—for massive engineering projects, for international collaborations, for the theorists who dreamt up the Higgs field and boson 50 years ago. But the Standard Model probably won’t stand forever. It still has problems with fine-tuning and with integrating general relativity, problems that many physicists hope some new model will resolve. The question is, which one?

    “There are a lot of possibilities for how nature works,” said physicist Matt Strassler, a visiting scholar at Harvard University. “Once you go beyond the Standard Model, there are a gazillion ways to try to fix the fine-tuning problem.” Each proposed model has to be tested against nature, and each test invariably requires months or years of labor to do right, even if you’re cleverly reusing old data. The adrenaline builds until the moment of truth—will this be the new law of physics? But the vast number of possible models means that almost every test ends with the same answer: No. Try again.

    See the full article here.

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  • richardmitnick 11:21 am on July 25, 2014 Permalink | Reply
    Tags: , , , Higgs, ,   

    From Fermilab: “The Higgs gives mass to matter, too” 

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

    Friday, July 25, 2014
    Jim Pivarski

    Nearly 50 years before its discovery, the Higgs field was proposed as a way to explain why particles have mass. The Standard Model would be internally inconsistent if particles could have mass on their own (that is, as an intrinsic property like charge), but it would not be inconsistent to propose a new field that gives them an effective mass by interacting with them. That new field has come to be known as the Higgs field, and particles of this field are called Higgs bosons.

    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.

    Higgs Field simulation

    This story is well known, and it was told in many ways when the Higgs boson was discovered in 2012. What is less well known is that the problem of mass was not a single problem. The reason that force particles (such as W and Z bosons) cannot have intrinsic mass is different from the reason that matter particles (such as electrons and quarks) cannot have intrinsic mass. The effective mass of force particles and matter particles could come from different sources. There could be two Higgs fields, one that only interacts with and gives mass to force particles, the other to matter particles, or perhaps the mechanisms themselves could be completely different.

    higgs cms
    CMS depiction of the higgs boson

    Many physicists expected that a single Higgs field would pull double duty and give mass to all the particles. This, however, was a hypothesis, based on the expectation that nature is simple and elegant.

    As it turns out, nature seems to be simple and elegant. CMS scientists recently published a study of Higgs boson decays to matter particles, complementing its discovery, which was through its decays to force particles. The same Higgs field interacts with both types of particles in the expected way.

    Specifically, the study focused on Higgs to tau pairs (tau is a heavy cousin of the electron) and Higgs to b quarks (the b quark is a heavy cousin of the quarks found in the protons and neutrons of an atom). Since this interaction is responsible for mass, it is stronger for more massive particles. Both of these decay products are hard to distinguish from backgrounds, especially the b quarks, so the statistical significance is weak (3.8 sigma, equivalent to a one in 14,000 chance that the combined observation is spurious). However, these decays and all the decays to force particles point back to a single Higgs boson. The basic principles of physics may yet be simple enough to fit on the front of a T-shirt.

    The quark structure of the proton. (The color assignment of individual quarks is not important, only that all three colors are present.)

    The quark structure of the neutron. (The color assignment of individual quarks is not important, only that all three colors are present.)

    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.

    ScienceSprings is powered by MAINGEAR computers

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