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  • richardmitnick 9:38 am on April 9, 2015 Permalink | Reply
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    From FNAL- “Frontier Science Result: CDF – Happy hunting grounds 

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

    April 9, 2015
    Fabrizio Margaroli and Andy Beretvas

    1
    This artistic view of a Feynman diagram shows the process of proton colliding with an antiproton, producing a W’, which then decays into a top quark and an antibottom quark.

    We understand nature in terms of elementary particles interacting through a set of well-known forces, which are mediated by other particles. These are the graviton (mediator of gravity), the photon (mediator of electromagnetism), the gluon (mediator of the strong force), the W and Z bosons (mediators of the weak force) and the Higgs boson. We produce and detect these particles (except the graviton) in large numbers at colliders around the world.

    But is that all the universe is made of — a handful of different types of particles? We have good reasons to believe that this is not the case. New forces can exist, and the corresponding mediating particles could be seen at colliders. However, such particles have been hunted extensively at the Large Hadron Collider without success so far.

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

    If new forces are hiding so well from physicists’ determination to discover them, either they would have to be mediated by very massive bosons or these bosons would have to interact very weakly with ordinary stuff.

    The W and Z boson serve as a good model for this kind of exotic stuff: In fact they are both very heavy compared to their peers and interact weakly with ordinary matter. They live very shortly before decaying into more “mundane” particles, most of the time quarks. If new forces were to exist with such properties, then the LHC would not be the best hunting ground because of its enormous production rate of quarks from ordinary forces.

    A new analysis of Tevatron data performed by the CDF collaboration searches for the existence of new electrically charged, massive particles (a W’ boson) decaying into a top and a bottom quark. Top and bottom quarks leave striking signatures in the detector; W’ events would resemble ordinary production of such quarks if not for the extra energy provided by the decay of the parent particle.

    FNAL Tevatron
    FNAL Tevatron machine
    Tevatron

    FNAL CDF
    CDF part of the Tevatron

    The search for a W’ with data from the CDF experiment turns out to be the most sensitive for such a heavy particle with mass below 650 GeV (approximately 700 times the proton mass). Unfortunately, no surprise turned out from CDF data. The ball is now again in the hands of the LHC experiments!

    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 7:40 am on April 4, 2015 Permalink | Reply
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    From FNAL: “New magnet at Fermilab achieves high-field milestone” 

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

    April 3, 2015
    Emanuela Barzi, Technical Division

    1
    This magnet recently achieved an important milestone, reaching its design field of 11.5 Tesla. It is the first successful niobium-3-tin, twin-aperture accelerator magnet in the world. Photo: Sean Johnson, TD

    Last month, a new superconducting magnet developed and fabricated at Fermilab reached its design field of 11.5 Tesla at a temperature nearly as cold as outer space. It is the first successful twin-aperture accelerator magnet made of niobium-3-tin in the world.

    The advancements in niobium-3-tin, or Nb3Sn, magnet technology and the ongoing U.S. collaboration with CERN on the development of these and other Nb3Sn magnets are enabling the use of this innovative technology for future upgrades of the Large Hadron Collider (LHC).

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

    They may also provide the cornerstone for future circular machines of interest to the worldwide high-energy physics community. Because of the exceptional challenges — Nb3Sn is brittle and requires high-temperature processing — this important milestone was achieved at Fermilab after decades of worldwide R&D efforts both in the Nb3Sn conductor itself and in associated magnet technologies.

    Superconducting magnets are at the heart of most particle accelerators for fundamental science as well as other scientific and technological applications. Superconductivity is also being explored for use in biosensors and quantum computing.

    Thanks to Nb3Sn’s stronger superconducting properties, it enables magnets of larger field than any in current particle accelerators. As a comparison, the niobium-titanium dipole magnets built in the early 1980s for the Tevatron particle collider produced about 4 Tesla to bend the proton and antiproton beams around the ring. The most powerful niobium-titanium magnets used in the LHC operate at roughly 8 Tesla. The new niobium-3-tin magnet creates a significantly stronger field.

    FNALTevatron
    FNAL Tevatron machine
    Fermilab CDF
    FNAL DZero
    Tevatron at FNAL

    Because the Tevatron accelerated positively charged protons and negatively charged antiprotons, its magnets had only one aperture. By contrast, the LHC uses two proton beams. This requires two-aperture magnets with fields in opposite directions. And because the LHC collides beams at higher energies, it requires larger magnetic fields.

    In the process of upgrading the LHC and in conceiving future particle accelerators and detectors, the high-energy physics community is investing as never before in high-field magnet technologies. This creative process involves the United States, Europe, Japan and other Asian countries. The latest strategic plan for U.S. high-energy physics, the 2014 report by the Particle Physics Project Prioritization Panel, endorses continued U.S. leadership in superconducting magnet technology for future particle physics programs. The U.S. LHC Accelerator Research Program (LARP), which comprises four DOE national laboratories — Berkeley Lab, Brookhaven Lab, Fermilab and SLAC — plays a key role in this strategy.

    The 15-year investment in Nb3Sn technology places the Fermilab team led by scientist Alexander Zlobin at the forefront of this effort. The Fermilab High-Field Magnet Group, in collaboration with U.S. LARP and CERN, built the first reproducible series in the world of single-aperture 10- to 12-Tesla accelerator-quality dipoles and quadrupoles made of Nb3Sn, establishing a strong foundation for the LHC luminosity upgrade at CERN.

    The laboratory has consistently carried out in parallel an assertive superconductor R&D program as key to the magnet success. Coordination with industry and universities has been critical to improve the performance of the next generation of high-field accelerator magnets.

    The next step is to develop 15-Tesla Nb3Sn accelerator magnets for a future very high-energy proton-proton collider. The use of high-temperature superconductors is also becoming a realistic prospect for generating even larger magnetic fields. An ultimate goal is to develop magnet technologies based on combining high- and low-temperature superconductors for accelerator magnets above 20 Tesla.

    The robust and versatile infrastructure that was developed at Fermilab, together with the expertise acquired by the magnet scientists and engineers in design and analysis tools for superconducting materials and magnets, makes Fermilab an ideal setting to look to the future of high-field magnet research.

    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 11:13 am on March 30, 2015 Permalink | Reply
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    From FNAL: “Superconducting test accelerator achieves first electron beam” 

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

    March 30, 2015
    Diana Kwon

    1
    Last week the first SRF cavities of Fermilab’s superconducting test accelerator propelled their first electrons. Photo: Reidar Hahn

    2
    The superconducting test accelerator team celebrates first beam in the operations center at NML. Vladimir Shiltsev, left, is pointing to an image of the beam. Photo: Pavel Juarez, AD

    The newest particle accelerators and those of the future will be built with superconducting radio-frequency (SRF) cavities, and institutions around the world are working hard to develop this technology. Fermilab’s advanced superconducting test accelerator was built to take advantage of SRF technology accelerator research and development.

    On Friday, after more than seven years of planning and building by scientists and engineers, the accelerator has delivered its first beam.

    The Fermilab superconducting test accelerator is a linear accelerator (linac) with three main components: a photoinjector that includes an RF gun coupled to an ultraviolet-laser system, several cryomodules and a beamline. Electron bunches are produced when an ultraviolet pulse generated by the laser hits a cathode located on the back plate of the gun. Acceleration continues through two SRF cavities inside the cryomodules. After exiting the cryomodules, the bunches travel down a beamline, where researchers can assess them.

    Each meter-long cavity consists of nine cells made from high-purity niobium. In order to become superconductive, the cavities sit in a vessel filled with superfluid liquid helium at temperatures close to absolute zero.

    As RF power pulses through these cavities, it creates an oscillating electric field that runs through the cells. If the charged particles meet the oscillating waves at the right phase, they are pushed forward and propelled down the accelerator.

    The major advantage of using superconductors is that the lack of electrical resistance allows virtually all the energy passing through to be used for accelerating particle beams, ultimately creating more efficient accelerators.

    “It’s more bang for the buck,” said Elvin Harms, one of the leaders of the commissioning effort.

    The superconducting test accelerator’s photoinjector gun first produced electrons in June 2013. In the current run, electrons are being shot through one single-cavity cryomodule, with a second, upgraded model to be installed in the next few months. Future plans call for accelerating the electron beam through an eight-cavity cryomodule, CM2, which was the first to reach the specifications of the proposed International Linear Collider (ILC).

    Fermilab is one of the few facilities that provides space for advanced accelerator research and development. These experiments will help set the stage for future superconducting accelerators such as SLAC’s Linac Coherent Light Source II, of which Fermilab is one of several partner laboratories.

    “The linac is similar to other accelerators that exist, but the ability to use this type of setup to carry out accelerator science experiments and train students is unique,” said Philippe Piot, a physicist at Fermilab and professor at Northern Illinois University leading one of the first experiments at the test accelerator. A Fermilab team has designed and is beginning to construct the Integrable Optics Test Accelerator ring, a storage ring that will be attached to the superconducting test accelerator in the years to come.

    “This cements the fact that Fermilab has been building up the infrastructure for mastering SRF technology,” Harms said. “This is the crown jewel of that: saying that we can build the components, put them together, and now we can accelerate a beam.”

    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 12:53 pm on March 27, 2015 Permalink | Reply
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    From CMS at CERN/LHC: “CMS is never idle” 

    CERN New Masthead

    2015-03-27
    André David and Dave Barney

    CERN CMS New II

    1
    Before proton collisions take place again at the LHC, the CMS detector has been looking at the result of collisions of cosmic particles high up in the atmosphere. This event display shows the track of a muon that reached the CMS detector 100 m underground and passed through the muon chambers (in red) and the silicon tracker (in yellow). Muons as this one are used to calibrate the detector in advance of proton collisions.

    CMS is eager to see the first collisions of the LHC Run2. The recent news that the LHC restart may be delayed because of a hardware issue gives us extra time to prepare for those collisions. Far from being idle waiting for collisions, CMS is busy taking advantage of other types of collision.

    CMS is never idle. Without beams, the data-taking does not stop: collisions of cosmic particles high up in the atmosphere produce showers of particles, including muons. Some of these muons have high enough energies to penetrate through the 100 m of ground over the CMS detector and traverse it, leaving behind a trail of dots in our detectors. By connecting the dots, we can learn where the different detector components are inside the huge volume (~3700m3) of CMS to better than a millimetre. This is very important because the whole detector was taken apart and put back together in preparation for Run2. With the cosmic ray muons, we can also synchronise the different detectors down to one hundred-millionth of a second, given that cosmic muons interact with many detectors as they cross the experiment. After a long shutdown, we are also coming back to operating the experiment 24 hours a day, 7 days a week. There is always a shift crew operating and monitoring the experiment, an larger crew of experts that stand ready to intervene in case issues arise, and an even larger community that checks the quality of the data collected. So we exploit this cosmic debris to understand out detectors to the needed precision to later find again the Higgs boson and possibly new, as-yet undiscovered, particles; the more cosmic muon signals we record and analyse, the better prepared we will be to tackle proton collisions at 13 TeV.

    See the full article here.

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    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
    CERN LHC Grand Tunnel

    LHC particles

    Quantum Diaries

     
  • richardmitnick 10:51 am on March 27, 2015 Permalink | Reply
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    From FNAL- “Frontier Science Result: CMS Rule of three 

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

    March 27, 2015
    Jim Pivarski

    CERN CMS New
    CMS

    1
    The three-fold symmetry of electrons, muons and taus may be broken by Higgs decays. (Design adapted from a neolithic spiral and the flag of Sicily.)

    In Rendezvous with Rama, Arthur C. Clarke imagined an artifact built by aliens who have three arms with three fingers each, so everything about it has a three-fold symmetry. One could argue that our fondness for bilateral symmetries (in the design of cars, planes, cathedrals, etc.) comes from the ubiquity of this shape in life on Earth, and creatures from other worlds might have developed differently. However, it is more surprising to find such a pattern imprinted on the universe itself.

    All particles of matter appear in threes: three generations of leptons and three generations of quarks. The second generation is a complete copy of the first with heavier masses, and the third generation is yet another copy. For instance, a muon is a heavy version of an electron, and a tau is a heavy muon. No one knows why matter comes in triplicate like this.

    For quarks, the symmetry isn’t perfect because W bosons can turn quarks of one generation into quarks of another generation. Something else transforms generations of neutrinos. But charged leptons — electrons, muons and taus — appear to be rigidly distinct. Some physicists suspect that we simply haven’t found the particle that mixes them yet.

    Or perhaps we have: Theoretically, the Higgs boson could mix lepton generations the way that the W boson mixes quarks. The Higgs decay modes haven’t all been discovered yet, so it’s possible that a single Higgs could decay into two generations of leptons at once, such as one muon and one tau. CMS scientists searched for muon-tau pairs with the right amount of energy to have come from a Higgs boson, and the results were surprising.

    They saw an excess of events. That is, they considered all the ways that other processes could masquerade as Higgs to muon-tau decays, estimated how many of these spurious events they should expect to find, and found slightly more. The word “slightly” should be emphasized — it is on the border of statistical significance, and other would-be discoveries at this level of significance (and stronger) have been shown to be flukes. On the other hand, if the effect is real, it would start as a weak signal until enough data confirm it.

    Naturally, the physics community is eager to see how this develops. The LHC, which is scheduled to restart soon at twice the energy of the first run, has the potential to produce Higgs bosons at a much higher rate — perhaps enough to determine whether this three-fold symmetry of leptons is broken or not.

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

    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 1:02 pm on March 26, 2015 Permalink | Reply
    Tags: Accelerator Science, , J-PARC, ,   

    From AAAS: “Shuttered Japanese proton accelerator nears restart” 

    AAAS

    AAAS

    25 March 2015
    Dennis Normile

    Idled after a radiation leak in May 2013, the Japan Proton Accelerator Research Complex (J-PARC) in Tokaimura took a step toward resuming full operations yesterday when the governor of Ibaraki Prefecture accepted a set of countermeasures aimed at preventing another accident. If the facility passes a final inspection by Japan’s Nuclear Regulation Authority, J-PARC could resume normal operations by the end of next month.

    Japan Proton Accelerator Research Complex J-PARC
    J-PARC

    It has been a long slog. An independent investigative panel convened by J-PARC concluded that the accident resulted from a combination of equipment malfunction and human error. In J-PARC’s Hadron Experimental Facility, a proton beam from a 50-GeV synchrotron strikes a target to produce a variety of secondary subatomic particles, including kaons, pions, and muons for use in experiments to determine their characteristics and interactions. On 23 May 2013, a malfunction sent a brief, unexpectedly high intensity beam at a gold target and vaporized radioactive material leaked into the experiment hall. Unaware of what had happened, researchers and staff inhaled contaminated air and also vented it outside the building. J-PARC took 34 hours to notify local and national authorities of the accident. All experiments were halted pending an investigation.

    The expert panel later determined that 34 people had inhaled the vapors and received slight internal radiation exposure that wasn’t deemed harmful and that the release outside the building posed no threat to area residents or the environment. Nonetheless, J-PARC, operated jointly by the High Energy Accelerator Research Organization and the Japan Atomic Energy Agency, then had to convince local and national authorities they could resume operating the facility without endangering staff or the community.

    The countermeasures developed over the past 2 years include upgrading schemes to minimize the impact of equipment glitches, making key experimental chambers airtight, fitting ventilation equipment with filters, and upgrading radiation monitoring and alarm systems. Researchers and staff have received safety training. Designated, trained emergency response personnel will be on hand at all times during operations and J-PARC will conduct accident drills several times annually.

    Experiments resumed at J-PARC’s Materials and Life Science Experimental Facility in February 2014 and at the Neutrino Experimental Facility last May after reviews and strengthening of safety programs.

    J-PARC Neutrino Experimental Facility
    J-PARC Neutrino Experimental Facility Tunnel
    J-PARC Neutrino Experimental Facility

    But more extensive work was needed in the hadron facility. The upgrades were accepted by the prefecture’s own panel of experts earlier this month. Yesterday’s presentation to the governor was largely symbolic. Starting next week, J-PARC officials will explain their strengthened safety measures at three public meetings in nearby towns. The final green light must come from the Nuclear Regulation Authority, which will inspect the facility next month.

    See the full article here.

    The American Association for the Advancement of Science is an international non-profit organization dedicated to advancing science for the benefit of all people.

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  • richardmitnick 2:29 pm on March 19, 2015 Permalink | Reply
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    From LC Newsline: “Updating the physics case for the ILC” 

    Linear Collider Collaboration header
    Linear Collider Collaboration

    19 March 2015

    3
    Hitoshi Yamamoto

    Director’s Corner

    1

    The physics case of the ILC has been studied intensively for many years, culminating in the physics volume of the Technical Design Report (TDR).

    ILC schematic
    ILC

    It was followed by efforts to compare various machines such as the European Strategy studies and the Snowmass studies. Still, the scientific and political environments surrounding the ILC keep changing. On the scientific front, the LHC has found the Higgs particle and placed limits on new physics.

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

    The LHC is now upgrading the energy and a new run is about to start. On the political side, the committees of the MEXT in Japan are evaluating the case for the ILC both technically and scientifically. It is thus important that we continue to update the physics case for the ILC and communicate it to relevant people.

    The task of updating the physics case for the ILC largely lies on the shoulders of the physics working group of the LCC. With the members of the MEXT committees as audience in mind, they have produced a document called Precis of the Physics Case for the ILC. This turned out to be an extremely useful document for newcomers such as incoming graduate students to learn about the physics of the ILC. It was, however, a little too technical for the audience originally intended. To fill the gap, it was followed by a shorter document intended really for general public – Scientific Motivations for the ILC. This latter document is now mostly ready for distribution. The content of these documents are used by members of those committees in their discussions.

    When evaluating the competitiveness of the ILC, we need to consider circular electron-positron colliders as well as a luminosity-upgraded LHC. At present, there are two studies on next-generation circular electron-positron collider: one at CERN and another in China. The one at CERN is called the FCC (Future Circular Collider) study the main part of which is a proton-proton collider with an optional electron-positron collider to start with. It would start after the LHC ends around 2035. The stated timing of the Chinese circular electron-positron collider, called CEPC, is earlier and about the same as that of the ILC. The CEPC is a Higgs factory with the design luminosity per collision point is about three times that of the baseline ILC running as a Higgs factory. It should be noted, however, that the upgraded ultimate ILC luminosity as a Higgs factory is four times that of the baseline. A merit of a circular collider is that multiple collisions points can be arranged. The CEPC would run with two collision points. All in all, the ILC
    as a Higgs factory is quite similar in luminosity to the CEPC. The wall plug power for the ultimate ILC Higgs factory is 187 MW, which is about the same as the current LHC, while that of CEPC is more than twice as much.

    2
    LC, LHC and the Chinese CEPC in overview

    At the latest LCB (Linear Collider Board) meeting, the way to communicate the physics case of the ILC to public was one of the topics intensively discussed. The LCB has then agreed that we need a short bulleted list of the physics case for the ILC. Several of us then sat down and came up with three points. Here they are with some editing:

    Important properties are the interaction strength between Higgs and other particles. ILC can measure them 3 to 10 times more accurately then the ultimate LHC. This means that the ILC is equivalent to 10 to 100 ultimate LHCs running simultaneously.

    The LHC can reach higher energy than the ILC, but can miss important phenomena.

    At the Tevatron collider, which is similar to the LHC, more than 10,000 Higgs particles were created but no clear signal was detected. At the ILC, about 100 Higgs particles are enough.

    FNAL Tevatron
    Fermilab CDF
    Fermilab DZero
    Tevatron at FNAL

    Circular electron-positron colliders have fundamental limits for energy increase due to synchrotron radiation.

    In the Standard Model of particle physics, the Higgs particle is the key particle and top quark is the heaviest particle.

    5
    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).

    Higgs-Higgs, Higgs-top interactions cannot be directly measured at the circular electron colliders since they cannot reach high enough energy. When a new particle sits at just above the energy limit, the ILC could be upgraded to reach the energy by making it longer or using higher accelerating gradient while it is difficult for a circular collider.

    See the full article here.

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    The Linear Collider Collaboration is an organisation that brings the two most likely candidates, the Compact Linear Collider Study (CLIC) and the International Liner Collider (ILC), together under one roof. Headed by former LHC Project Manager Lyn Evans, it strives to coordinate the research and development work that is being done for accelerators and detectors around the world and to take the project linear collider to the next step: a decision that it will be built, and where.

    Some 2000 scientists – particle physicists, accelerator physicists, engineers – are involved in the ILC or in CLIC, and often in both projects. They work on state-of-the-art detector technologies, new acceleration techniques, the civil engineering aspect of building a straight tunnel of at least 30 kilometres in length, a reliable cost estimate and many more aspects that projects of this scale require. The Linear Collider Collaboration ensures that synergies between the two friendly competitors are used to the maximum.

    Linear Collider Colaboration Banner

     
  • richardmitnick 12:28 pm on March 17, 2015 Permalink | Reply
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    From Symmetry: “Experiments combine to find mass of Higgs” 

    Symmetry

    March 17, 2015
    Sarah Charley

    1
    Illustration by Thomas McCauley and Lucas Taylor, CERN

    The CMS and ATLAS experiments at the Large Hadron Collider joined forces to make the most precise measurement of the mass of the Higgs boson yet.

    CERN CMS New II
    CMS

    CERN ATLAS New
    ATLAS

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC

    On the dawn of the Large Hadron Collider restart, the CMS and ATLAS collaborations are still gleaning valuable information from the accelerator’s first run. Today, they presented the most precise measurement to date of the Higgs boson’s mass.

    “This combined measurement will likely be the most precise measurement of the Higgs boson’s mass for at least one year,” says CMS scientist Marco Pieri of the University of California, San Diego, co-coordinator of the LHC Higgs combination group. “We will need to wait several months to get enough data from Run II to even start performing any similar analyses.”

    The mass is the only property of the Higgs boson not predicted by the Standard Model of particle physics—the theoretical framework that describes the interactions of all known particles and forces in the universe.

    3
    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).

    The mass of subatomic particles is measured in GeV, or giga-electronvolts. (A proton weighs about 1 GeV.) The CMS and ATLAS experiments measured the mass of the Higgs to be 125.09 GeV ± 0.24. This new result narrows in on the Higgs mass with more than 20 percent better precision than any previous measurements.

    Experiments at the LHC measure the Higgs by studying the particles into which it decays. This measurement used decays into two photons or four electrons or muons. The scientists used data collected from about 4000 trillion proton-proton collisions.

    By precisely pinning down the Higgs mass, scientists can accurately calculate its other properties—such as how often it decays into different types of particles. By comparing these calculations with experimental measurements, physicists can learn more about the Higgs boson and look for deviations from the theory—which could provide a window to new physics.

    “This is the first combined publication that will be submitted by the ATLAS and CMS collaborations, and there will be more in the future,” says deputy head of the ATLAS experiment Beate Heinemann, a physicist from the University of California, Berkeley, and Lawrence Berkeley National Laboratory.

    ATLAS and CMS are the two biggest Large Hadron Collider experiments and designed to measure the properties of particles like the Higgs boson and perform general searches for new physics. Their similar function allows them to cross check and verify experimental results, but it also inspires a friendly competition between the two collaborations.

    “It’s good to have competition,” Pieri says. “Competition pushes people to do better. We work faster and more efficiently because we always like to be first and have better results.”

    Normally, the two experiments maintain independence from one another to guarantee their results are not biased or influenced by the other. But with these types of precision measurements, working together and performing combined analyses has the benefit of strengthening both experiments’ results.

    “CMS and ATLAS use different detector technologies and different detailed analyses to determine the Higgs mass,” says ATLAS spokesperson Dave Charlton of the University of Birmingham. “The measurements made by the experiments are quite consistent, and we have learnt a lot by working together, which stands us in good stead for further combinations.”

    It also provided the unique opportunity for the physicists to branch out from their normal working group and learn what life is like on the other experiment.

    “I really enjoyed working with the ATLAS collaboration,” Pieri says. “We normally always interact with the same people, so it was a real pleasure to get to know better the scientists working across the building from us.”

    With this groundwork for cross-experimental collaboration laid and with the LHC restart on the horizon, physicists from both collaborations look forward to working together to increase their experimental sensitivity. This will enable them not only to make more precise measurements in the future, but also to look beyond the Standard Model into the unknown.

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 1:20 pm on March 12, 2015 Permalink | Reply
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    From Don Lincoln at FNAL: The Detectors at the LHC 

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

    The Large Hadron Collider or LHC is the world’s biggest particle accelerator, but it can only get particles moving very quickly. To make measurements, scientists must employ particle detectors. There are four big detectors at the LHC: ALICE, ATLAS, CMS, and LHCb. In this video, Fermilab’s Dr. Don Lincoln introduces us to these detectors and gives us an idea of each one’s capabilities.

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    ALICE

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    ATLAS

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    CMS

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    LHCb

    See the full article here.

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    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 10:25 am on March 12, 2015 Permalink | Reply
    Tags: Accelerator Science, , , , ,   

    From FNAL- “Frontier Science Result: CDF and DZero Joining forces to test the Higgs boson’s spin and parity” 

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

    Thursday, March 12, 2015
    Tom Junk

    1
    This plot shows the observed and expected upper limits at the 95 percent credibility level on the fraction of exotic boson production for two cases (spin zero with negative parity and spin two with positive parity). A signal scale of one corresponds to the Standard Model.

    The Higgs boson caused a lot of excitement when the ATLAS and CMS collaborations announced its discovery in 2012.

    CERN ATLAS New
    ATLAS

    CERN CMS New
    CMS

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

    Everyone was bursting with questions: How much does it weigh? How is it made? How does it decay? Does it have any spin, and if so, how much? Does it look the same in a mirror or not (the question of “parity”)?

    The Standard Model predicts the answers to all of these questions, although some depend on the Higgs boson mass, which ATLAS and CMS have measured precisely.

    2
    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).

    So far, the new particle observed at the LHC is consistent with all of the Standard Model’s predictions. In particular, ATLAS and CMS’s measurements of the spin and parity allowed them to confidently identify the new particle as a Higgs boson.

    The Tevatron experiments, CDF and DZero, also found evidence for a Higgs boson in 2012, looking at events in which two bottom-flavored jets recoiled from a vector boson — either a Z or a W.

    FNALTevatron
    Tevatron

    FNAL CDF
    CDF

    FNAL DZero
    DZero

    All the same questions come up, as some models predict that one may observe a mixture of Higgs particles at the Tevatron different from what was observed at the LHC due to the different mixtures of production and decay modes that provide the most sensitivity.

    At the Tevatron, the Higgs boson’s properties were found to be consistent with those predicted for the Standard Model Higgs boson. Theorists provided a clever way to test some models of the Higgs boson’s spin and parity using Tevatron data: Higgs bosons with exotic spin and parity would be produced with more energy than the Standard Model version. CDF and DZero looked at the energies and angles of particles produced in Higgs boson events to check. But most events at the Tevatron are non-Higgs-boson background events, so a lot of hard work went in to test the models.

    Both DZero and CDF modified their Higgs boson analyses to search for the new particles, if they are present in addition to the Standard Model Higgs boson, or if they replace it entirely. Neither experiment found evidence for the exotic states, and the data prefer the Standard Model interpretation.

    But a much stronger statement can be made when CDF and DZero join forces and combine their results, using the same techniques used in the Standard Model Higgs search combinations. The signal strength of exotic Higgs bosons in the JP=0- and 2+ states is no more than 0.36 times that predicted for the Standard Model Higgs boson. Given a choice between the Standard Model Higgs boson, which has JP=0+, and one of the two exotic models replacing it with the same signal strength, the Tevatron data disfavors the exotic models with a significance of 5.0 standard deviations for 0- and 4.9 standard deviations for 2+.

    The figure above shows limits on the fraction of exotic Higgs boson production as functions of the total signal rate, assuming that the Higgs signal is a mixture of the Standard Model Higgs boson and one of the exotic kinds. The particle for which the Tevatron experiments reported evidence in 2012 is consistent with having the spin and parity predicted by the Standard Model.

    —Tom Junk

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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.

     
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