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  • richardmitnick 9:54 am on February 12, 2018 Permalink | Reply
    Tags: , , , First high-precision measurement of the mass of the W boson at the LHC, FNAL Tevatron, , , ,   

    From CERN ATLAS : “First high-precision measurement of the mass of the W boson at the LHC” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    12th February 2018

    1
    Display of a candidate event for a W boson decaying into one muon and one neutrino from proton-proton collisions recorded by ATLAS with LHC stable beams at a collision energy of 7 TeV. (Image: ATLAS Collaboration/CERN).

    In a paper published today in the European Physical Journal C, the ATLAS Collaboration reports the first high-precision measurement at the Large Hadron Collider (LHC) of the mass of the W boson. This is one of two elementary particles that mediate the weak interaction – one of the forces that govern the behaviour of matter in our universe. The reported result gives a value of 80370±19 MeV for the W mass, which is consistent with the expectation from the Standard Model of Particle Physics, the theory that describes known particles and their interactions.

    The measurement is based on around 14 million W bosons recorded in a single year (2011), when the LHC was running at the energy of 7 TeV. It matches previous measurements obtained at Large Electron-Positron Collider[LEP] , the ancestor of the LHC at CERN, and at the Tevatron , a former accelerator at Fermilab [FNAL] in the United States, whose data made it possible to continuously refine this measurement over the last 20 years.

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    CERN LEP

    3
    FNAL Tevatron

    FNAL/Tevatron

    The W boson is one of the heaviest known particles in the universe. Its discovery in 1983 crowned the success of CERN’s Super Proton Synchrotron , leading to the Nobel Prize in physics in 1984. Although the properties of the W boson have been studied for more than 30 years, measuring its mass to high precision remains a major challenge.

    4
    Super Proton Synchrotron

    “Achieving such a precise measurement despite the demanding conditions present in a hadron collider such as the LHC is a great challenge,” said the physics coordinator of the ATLAS Collaboration, Tancredi Carli. “Reaching similar precision, as previously obtained at other colliders, with only one year of Run 1 data is remarkable. It is an extremely promising indication of our ability to improve our knowledge of the Standard Model and look for signs of new physics through highly accurate measurements.”

    The Standard Model is very powerful in predicting the behaviour and certain characteristics of the elementary particles and makes it possible to deduce certain parameters from other well-known quantities. The masses of the W boson, the top quark and the Higgs boson for example, are linked by quantum physics relations. It is therefore very important to improve the precision of the W boson mass measurements to better understand the Higgs boson, refine the Standard Model and test its overall consistency.

    Remarkably, the mass of the W boson can be predicted today with a precision exceeding that of direct measurements. This is why it is a key ingredient in the search for new physics, as any deviation of the measured mass from the prediction could reveal new phenomena conflicting with the Standard Model.

    The measurement relies on a thorough calibration of the detector and of the theoretical modelling of the W boson production. These were achieved through the study of Z boson events and several other ancillary measurements. The complexity of the analysis meant it took almost five years for the ATLAS team to achieve this new result. Further analysis with the huge sample of now-available LHC data, will allow even greater accuracy in the near future.

    See the full article here .

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    LHC at CERN

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  • richardmitnick 4:30 pm on December 19, 2017 Permalink | Reply
    Tags: , , CERN Large Hadron Collider, , FNAL Tevatron, , , Large Electron-Positron Collider, , , , , ,   

    From Symmetry: “Machine evolution” 

    Symmetry Mag
    Symmetry

    12/19/17
    Amanda Solliday

    1
    Courtesy of SLAC

    Planning the next big science machine requires consideration of both the current landscape and the distant future.

    Around the world, there’s an ecosystem of large particle accelerators where physicists gather to study the most intricate details of matter.

    These accelerators are engineering marvels. From planning to construction to operation to retirement, their lifespans stretch across decades.

    But to get the most out of their investments of talent and funding, laboratories planning such huge projects have to think even longer-term: What could these projects become in their next lives?

    The following examples show how some of the world’s big physics machines have evolved to stay at the forefront of science and technology.

    Same tunnel, new collisions

    Before CERN research center in Geneva, Switzerland, had its Large Hadron Collider, it had the Large Electron-Positron Collider. LEP was the largest electron-positron collider ever built, occupying a nearly 17-mile circular tunnel dug beneath the border of Switzerland and France. The tunnel took three years to completely excavate and build.

    The first particle beam traveled around the LEP circular collider in 1989. Long before then, the international group of CERN physicists and engineers were already thinking about what CERN’s next machine could be.

    “People were saying, ‘Well, if we do build LEP, then we should make it compatible with the [then-proposed] Large Hadron Collider,’” says James Gillies, a senior communications advisor and member of the strategic planning and evaluation unit at CERN. “If you want to have a future facility, you often have to engage the people who just finished designing one machine to start thinking about the next one.”

    LEP’s designers chose an energy for the collider that would mass-produce Z bosons, fundamental particles discovered by earlier experiments at CERN. The LHC would be a step up from LEP, reaching higher energies that scientists hoped could produce the Higgs boson. In the 1960s, theorists proposed the Higgs as a way to explain the origin of the mass of elementary particles. And the new machine to look for it could be built in the same 17-mile tunnel excavated for LEP.

    Engineers began working on the LHC while LEP was still running. The new machine required enlargements to underground areas—it needed bigger detectors and new experimental halls.

    “That was challenging because these caverns are huge. As they were being excavated, the pressure on the LEP tunnel was reduced and the LEP beamline needed realignment,” Gillies says. “So you constantly had to realign the collider for experiments as you were digging.”

    After LEP reached its highest energy in 2000, it was switched off. The tunnel remained the same, says Gillies, but there were many other changes. Only one of the LEP detectors, DELPHI, remains underground at CERN as a visitors’ point.

    In 2012, LHC scientists announced the discovery of the long-sought Higgs boson. The LHC is planned to continue running until at least 2035, gradually increasing the intensity of its particle collisions. The research and development into the accelerator’s successor is already happening. The possibilities include a higher energy LHC, a compact linear collider or an even larger circular collider.

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    Large Electron-Positron Collider
    Location: CERN—Geneva, Switzerland
    First beam: 1989
    Link to LEP Timeline: Timeline
    Courtesy of CERN

    LHC

    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    Large Hadron Collider
    Location: CERN—Geneva, Switzerland
    First beam: 2008
    Link to LHC Timeline: Timeline
    Courtesy of CERN

    High-powered science
    Decades before the LHC came into existence, a suburb of Chicago was home to the most powerful collider in the world: the Tevatron. A series of accelerators at Fermi National Accelerator Laboratory boosted protons and antiprotons to nearly the speed of light. In the final, 4-mile Tevatron ring, the particles reached record energy levels, and more than 1000 superconducting magnets steered them into collisions. Physicists used the Tevatron to make the first direct measurement of the tau neutrino and to discover the top quark, the last observed lepton and quark, respectively, in the Standard Model.

    The Tevatron shut down in 2011 after the LHC came up to speed, but the rest of Fermilab’s accelerator infrastructure was still hard at work powering research in particle physics—particularly on the abundant, mysterious and difficult-to-detect neutrino.

    Starting in 1999, a brand-new, 2-mile circular accelerator called the Main Injector was added to the Fermilab complex to increase the number of Tevatron particle collisions tenfold. It was joined in its tunnel by the Recycler, a permanent magnet ring that stored and cooled antiprotons.

    But before the Main Injector was even completed, scientists had identified a second purpose: producing powerful beams of neutrinos for experiments in Illinois and 500 miles away in Minnesota.

    FNAL/NOvA experiment map

    By 2005, the proton beam circulating in the Main Injector was doing double duty: sending ever-more-intense beams to the Tevatron collider and smashing into a target to produce neutrinos. Following the shutdown of the Tevatron, the Recycler itself was recycled to increase the proton beam power for neutrino research.

    “I’m still amazed at how we are able to use the Recycler. It can be difficult to transition if a machine wasn’t originally built for that purpose,” says Ioanis Kourbanis, the head of the Main Injector department at Fermilab.

    Fermilab’s high-energy neutrino beam is already the most intense in the world, but the laboratory plans to enhance it with future improvements to the Main Injector and the Recycler, and to build a brand-new neutrino beamline.

    Neutrinos almost never interact with matter, so they can pass straight through the Earth on their way to detectors onsite and others several hundred miles away. Scientists hope to learn more about neutrinos and their possible role in shaping our early universe.

    The new beamline will be part of the Long-Baseline Neutrino Facility, which will send neutrinos 800 miles underground to the massive, mile-deep detectors of the Deep Underground Neutrino Experiment.

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


    FNAL DUNE Argon tank at SURF


    Surf-Dune/LBNF Caverns at Sanford



    SURF building in Lead SD USA

    Scientists from around the world will use the DUNE data to answer questions about neutrinos, thanks to the repurposed pieces of the Fermilab accelerator complex.

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    FNAL Tevatron

    FNAL/Tevatron map


    FNAL/Tevatron DZero detector


    FNAL/Tevatron CDF detector

    Tevatron
    Location: Fermilab—Batavia, Illinois
    First beam: 1983
    Link to Tevatron Timeline: Timeline
    Courtesy of Fermilab

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    Neutrinos at the Main Injector (NuMI) beam
    Location: Fermilab—Batavia, Illinois
    First beam: 2004
    Link to Fermilab Timeline: Timeline
    Courtesy of Fermilab

    A monster accelerator

    When physicists first came up with the idea to build a two-mile linear accelerator at what is now called SLAC National Accelerator Laboratory, managed by Stanford University, they called it “Project M” for “Monster.” Engineers began building it from hand-drawn designs. Once completed, the machine was able to accelerate electrons to near the speed of light, producing its first particle beam in May 1966.

    SLAC Campus

    The accelerator’s scientific purpose has gone through several iterations of particle physics experiments over the decades, from fixed-target experiments to the Stanford Linear Collider (the only electron-positron linear collider ever built) to an injector for a circular collider, the Positron-Electron Project.

    These experiments led to the discovery that protons are made of quarks, the first evidence that the charm quark existed (through observations of the J/psi particle, co-discovered with researchers at MIT) and the discovery of the tau lepton.

    In 2009, the lab used the accelerator as the backbone for a different type of science machine—an X-ray free-electron laser, the Linac Coherent Light Source.

    “Looking around, SLAC was the only place in the world with a linear accelerator capable of driving a free-electron laser,” says Claudio Pellegrini, a distinguished professor emeritus of physics at the University of California, Los Angeles and a visiting scientist and consulting professor at SLAC. Pellegrini first proposed the idea to transform SLAC’s linear accelerator.

    The new machine, a DOE Office of Science user facility, would be the world’s first laser of its kind that could produce extremely bright hard X-rays, the high-energy X-rays that let scientists take snapshots of atoms and molecules.

    “Much of the physics and many of the tools learned and developed during the operation of the Stanford Linear Collider were directly applicable to the free electron laser,” says Lia Merminga, head of the accelerator directorate at SLAC. “This was a big factor in the LCLS being commissioned in record time. Without the Stanford Linear Collider experience, this significant body of work would have to be reinvented and reproduced almost from scratch.”

    Little about the accelerator itself needed to change. But to create a free-electron laser, scientists needed to design a new part: an electron gun, a device that generates electrons to be injected into the accelerator. A collaboration of several national labs and UCLA created a new type of electron gun for LCLS, while other national labs helped build undulators, a series of magnets that would wiggle the electrons to create X-rays.

    LCLS used only the last third of SLAC’s original linear accelerator. In part of the remaining section, scientists are developing plasma wakefield and other new particle acceleration techniques.

    For the X-ray laser’s next iteration, LCLS-II, scientists are aiming for an even brighter laser that will fire 1 million pulses per second, allowing them to observe rare and exceptionally transient events.

    SLAC/LCLS II

    To do this, they will need to replace the original copper structures with superconducting technology. The technology is derived from designs for a large International Linear Collider [ILC] proposed to be built in Japan.

    ILC schematic

    “I’m in awe of the foresight of the original builders of SLAC’s linear accelerator,” Merminga adds. “We’ve been able to do so much with this machine, and the end is not yet in sight.”

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    Fixed target and collider experiments

    Location: SLAC—Menlo Park, California
    First beam: 1966
    Link to SLAC Timeline: Timeline
    Courtesy of SLAC

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    Linac Coherent Light Source
    Location: SLAC—Menlo Park, California
    First beam: 2009
    Link to SLAC Timeline: Timeline
    Courtesy of SLAC

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 10:22 am on October 24, 2017 Permalink | Reply
    Tags: A new chapter in Fermilab’s electron lens legacy, , , , , FNAL Tevatron, Scientists at Fermilab invented and developed one novel collider component 20 years ago: the electron lens   

    From FNAL: “A new chapter in Fermilab’s electron lens legacy” 

    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.

    October 18, 2017
    Leah Poffenberger

    Sending bunches of protons speeding around a circular particle collider to meet at one specific point is no easy feat. Many different collider components work keep proton beams on course — and to keep them from becoming unruly.

    Scientists at Fermilab invented and developed one novel collider component 20 years ago: the electron lens. Electron lenses are beams of electrons formed into specific shapes that modify the motion of other particles — usually protons — that pass through them.

    The now retired Tevatron, a circular collider at Fermilab, and the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory have both benefited from electron lenses, a concept originally developed at Fermilab.

    FNAL Tevatron

    FNAL/Tevatron map


    FNAL/Tevatron DZero detector


    FNAL/Tevatron CDF detector

    BNL RHIC Campus

    BNL/RHIC Star Detector

    BNL RHIC PHENIX

    “Electron lenses are like a Swiss Army knife for accelerators: They’re relatively simple and inexpensive, but they can be applied in a wide variety of ways,” said Alexander Valishev, a Fermilab scientist who co-authored a recent study for a new electron lens application, which could be crucial to forthcoming colliders.

    The innovation is detailed in an article published on Sept. 27 in Physical Review Letters. (The article was also recently selected for presentation in the Physics Central’s Physics Buzz Blog.)

    “This little breakthrough in the physics of beams and accelerators is kind of a beginning of a bigger invention — it’s a new thing,” said Fermilab’s Vladimir Shiltsev, an author of the published paper. Shiltsev also played a major role in the origination of electron lenses in 1997. “Fermilab is known for inventions and developments that are, first, exciting, and then, functional. That’s what national labs are built for, and that’s what we’ve achieved.”

    1
    An electron lens introduces differences in the movement of particles that constitute a particle bunch. In the illustration, the perspective is looking down the beam pipe — down the path of the particle bunch. The bunch is seen as approaching the viewer (as the circle increases in size). Left: the particle bunch, represented as a uniformly blue circle, contains particles that all behave in the same way. Because the constituent particles follow the exact same trajectory, the bunch is more susceptible to wild deviations from its path, resulting from electromagnetic wake-fields. Right: Treated by an electron lens, the particle bunch, represented by red and blue, contains particles that move slightly differently from one another. For example, particles closer to the interior of the bunch move differently from those closer to the outside. This variegation helps confine the particle bunch to the more desirable straightforward path. Illustration: Diana Brandonisio

    A lens into the future

    This new type of electron lens, called the Landau damping lens, will be a critical part of a huge, prospective project in particle physics research: the Future Circular Collider at CERN.

    CERN Future Circular Collider

    The FCC would push the boundaries of traditional collider design to further study the particle physics beyond the Higgs boson, a fundamental particle discovered only five years ago.

    The proposed FCC has to be a high-luminosity machine: Its particle beams will need to be compact and densely packed. Compared with CERN’s Large Hadron Collider, the beams will also have a dramatic increase in energy — 50 trillion electronvolts, compared with the LHC’s beam energy of 7 trillion electronvolts. That involves an equally dramatic increase in the size of the accelerator. With a planned circumference of 100 kilometers, the FCC would dwarf the 27-kilometer LHC.

    LHC

    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    These high-energy, high-luminosity supercolliders all experience a problem, regardless of size: An intense beam of protons packed into the width of human hair traveling over a long distance can become unstable, especially if all the protons travel in exactly the same way.

    In a collider, particles arrive in packets called bunches — roughly foot-long streams packed with hundreds of billions of particles. A particle beam is formed of dozens, hundreds or thousands of these bunches.

    Imagine a circular collider as a narrow racetrack, with protons in a bunch as a tight pack of racecars. A piece of debris suddenly appears in the middle of the track, disrupting the flow of traffic. If every car reacts in the same way, say, by veering sharply to the left, it could lead to a major pileup.

    Inside the collider, it’s not a matter of avoiding just one bump on the track, but adjusting to numerous dynamic obstacles, causing the protons to change their course many times over. If an anomaly, such as a kink in the collider’s magnetic field, occurs unexpectedly, and if the protons in the beam all react to it in the same way at the same time, even a slight change of course could quickly go berserk.

    One could avoid the problem by thinning the particle beam from the get-go. By using lower-density proton beams, you provide less opportunity for protons to go off course. But that would mean removing protons and so missing out on potential for scientific discovery.

    Another, better way to address the problem is to introduce differences into the beam so that not all the protons in the bunches behave the same way.

    To return to the racetrack: If the drivers all react to the piece of debris different ways —some moving slightly to the right, others slightly to the left, one brave driver just skips over the top — the cars can all merge back together and continue the race, no accidents.

    Creating differentiations within a proton bunch would do essentially the same thing. Each proton follows its own, ever-so-slightly different course around the collider. This way, any departure from the course is isolated, rather than compounded by protons all misbehaving in concert, minimizing harmful beam oscillations.

    “Particles at the center of the bunch will move differently than particles around the outside,” Shiltsev said. “The protons will all be kind of messed up, but that’s what we want. If they all move together, they become unstable.”

    These differences are usually created with a special type of magnet called octupoles. The Tevatron, before its decommissioning in 2011, had 35 octupole magnets, and the LHC now has 336.

    But as colliders get larger and achieve greater energies, they need exponentially higher numbers of magnets: The FCC will require more than 10,000 octupole magnets, each a meter long, to achieve the same beam-stabilizing results as previous colliders.

    That many magnets take up a lot of space: as much as 10 of the FCC’s 100 kilometers.

    “That seems ridiculous,” Shiltsev said. “We’re looking for a way to avoid that.”

    The scientific community recognizes the Landau damping nonlinear lens as a likely solution to this problem: A single one-meter-long electron lens could replace all 10,000 octupole magnets and possibly do a better job keeping beams stable as they speed toward collision, without introducing any new problems.

    “At CERN they’ve embraced the idea of this new electron lens type, and people there will be studying them in further detail for the FCC,” Valishev said. “Given what we know so far about the issues that the future colliders will face, this would be a device of extremely high criticality. This is why we’re excited.”

    Electron Legos

    The Landau damping lens will join two other electron lens types in the repertoire of tools physicists have to modify or control beams inside a collider.

    “After many years of use, people are very happy with electron lenses: It’s one of the instruments used for modern accelerators, like magnets or superconducting cavities,” Shiltsev said. “Electron lenses are just one of the building blocks or Lego pieces.”

    Electron lenses are a lot like Legos: Lego pieces are made of the same material and can be the same color, but a different shape determines how they can be used. Electron lenses are all made of clouds of electrons, shaped by magnetic fields. The shape of the lens dictates how the lens influences a beam of protons.

    Scientists developed the first electron lens at Fermilab in 1997 for use to compensate for so-called beam-beam effects in the Tevatron, and a similar type of electron lens is still in use at the Brookhaven’s RHIC.

    In circular colliders, particle beams pass by each other, going in opposing directions inside the collider until they are steered into a collision at specific points. As the beams buzz by one another, they exert a small force on each other, which causes the proton bunches to expand slightly, decreasing their luminosity.

    That first electron lens, called the beam-beam compensation lens, was created to combat the interaction between the beams by squeezing them back to their original, compact state.

    After the success of this electron lens type in the Tevatron, scientists realized that electron beams could be shaped a second way to create another type of electron lens.

    Scientists designed the second lens to be shaped like a straw, allowing the proton beam to pass through the inside unaffected. The occasional proton might try to leave its group and stray from the center of the beam. In the LHC, losing even one-thousandth of the total number of protons in an uncontrolled way could be dangerous. The electron lens acts as a scraper, removing these rogue particles before they could damage the collider.

    “It’s extremely important to have the ability to scrape these particles because their energy is enormous,” Shiltsev said. “Uncontrolled, they can drill holes, break magnets or produce radiation.”

    Both types of electron lens have made their mark in collider design as part of the success of the Tevatron, RHIC and the LHC. The new Landau damping lens may help usher in the next generation of colliders.

    “The electron lens is an example of something that was invented here at Fermilab 20 years ago,” Shiltsev said. “This is a one of the rare technologies that wasn’t just brought to perfection at Fermilab: It was invented, developed and perfected and still continues to shine.”

    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 3:26 pm on October 23, 2017 Permalink | Reply
    Tags: , ATLAS and CMS join forces to tackle top-quark asymmetry, , FNAL Tevatron, , ,   

    From CERN: “ATLAS and CMS join forces to tackle top-quark asymmetry” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    CERN

    20 Oct 2017
    Matthew Chalmers
    Henry Bennie

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    Event display of a tt̄ event candidate in the 2015 data (Image: ATLAS/CERN)

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    All matter around us is made of elementary particles called quarks and leptons. Each group consists of six particles, which are related in pairs, or “generations” – the up quark and the down quark form the first, lightest and most stable generation, followed by the charm quark and strange quark, then the top quark and bottom (or beauty) quark, the heaviest and least stable generation. (Image: Daniel Dombinguez/CERN)

    In their hunt for new particles and phenomena lurking in LHC collisions, the ATLAS and CMS experiments have joined forces to investigate the top quark. As the heaviest of all elementary particles, weighing almost as much as an atom of gold, the top quark is less well understood than its lighter siblings. With the promise of finding new physics hidden amongst the top quark’s antics, ATLAS and CMS have combined their top-quark data for the first time.

    There were already hints that the top quark didn’t play by the rules in data collected at the Tevatron collider at Fermilab in the US (the same laboratory that discovered the particle in 1995).

    FNAL Tevatron

    FNAL/Tevatron map


    FNAL/Tevatron DZero detector


    FNAL/Tevatron CDF detector

    Around a decade ago, researchers found that, when produced in pairs from the Tevatron’s proton-antiproton collisions, top quarks tended to be emitted in the direction of the proton beam, while anti-tops aligned in the direction of the antiproton beam. A small forward-backward asymmetry is predicted by the Standard Model, but the data showed the measured asymmetry to be tantalisingly bigger than expected, potentially showing that new particles or forces are influencing top-quark pair production.

    “As physicists, when we see something like this, we get excited,” says ATLAS researcher Frederic Deliot. If the asymmetry is much larger than predicted, it means “there could be lots of new physics to discover.”

    The forward-backward asymmetry measured at the Tevatron cannot be seen at the LHC because the LHC collides protons with protons, not antiprotons. But a related charge asymmetry, which causes top quarks to be produced preferentially in the centre of the LHC’s collisions, can be measured. The Standard Model predicts the effect to be small (around 1%) but, as with the forward-backward asymmetry, it could be made larger by new physics. The ATLAS and CMS experiments both measured the asymmetry by studying differences in the angular distributions of top quarks and antiquarks produced at the LHC at energies of 7 and 8 TeV.

    Alas, individually and combined, their results show no deviation from the latest Standard Model calculations.

    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.

    These calculations have in fact recently been improved, and show that the predicted asymmetry is slightly higher than previously thought. This, along with improvements in data analysis, even brings the earlier Tevatron result into line with the Standard Model.

    ATLAS and CMS will continue to subject the heavyweight top quark to tests at energies of 13 TeV to see if it deviates from its expected behaviour, including precision measurements of its mass and interactions with other Standard Model particles. But measuring the asymmetry will get even tougher, because the effect is predicted be half as big at a higher energy. “It’s going to be difficult,” says Deliot. “It will be possible to explore using the improved statistics at higher energy, but it is clear that the space for new physics has been severely restricted.”

    The successful combination of the charge-asymmetry measurements was achieved within the LHC top-quark physics working group, where scientists from ATLAS and CMS and theory experts work together intensively towards improving the interplay between theory and the two experiments, explains CMS collaborator Thorsten Chwalek. “Although the combination of ATLAS and CMS charge asymmetry results didn’t reveal any hints of new physics, the exercise of understanding all the correlations between the measurements was very important and paved the way for future ATLAS+CMS combinations in the top-quark sector.”

    See the full article here.

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    THE FOUR MAJOR PROJECT COLLABORATIONS

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    CERN CMS New

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

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

    New York Times

    The New York Times

    JULY 6, 2017
    KENNETH CHANG

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

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

    Physicists have discovered a particle that is doubly charming.

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

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

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

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

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

    LHC

    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

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

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

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

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

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

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

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

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

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

    FNAL Tevatron

    FNAL/Tevatron map


    FNAL/Tevatron DZero detector


    FNAL/Tevatron CDF detector

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

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

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

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

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

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

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

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

    See the full article here .

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  • richardmitnick 12:11 pm on June 10, 2017 Permalink | Reply
    Tags: , , FNAL Tevatron, , , , Tevatron first accelerator to use electron lens   

    From FNAL: “Tevatron first accelerator to use electron lens” 

    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.

    accelerator to use electron lens

    June 10, 2017
    Troy Rummler
    1

    Tevatron is the first accelerator to use an electron lens

    Fermilab’s Tevatron was the first particle accelerator to make use of an electron lens, a technique that allowed the machine to compensate for destabilizing forces unavoidably generated by the colliding beams. Proposed in 1997, the lenses were installed in 2001 and 2004 in the Tevatron, where they demonstrated beam-beam compensation. They were also used in the removal of unwanted particles. The innovation earned Fermilab scientist Vladimir Shiltsev a European Physical Society Accelerator Prize.

    FNAL Tevatron

    FNAL/Tevatron map


    FNAL/Tevatron DZero detector


    FNAL/Tevatron CDF detector

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    FNAL Icon
    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 3:46 pm on May 24, 2017 Permalink | Reply
    Tags: , , Early days, FNAL Tevatron, , ,   

    From FNAL: “Early Tevatron design days” 

    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.

    May 24, 2017
    Tom Nicol

    1
    Fermilab technicians assemble a magnet spool piece for the Tevatron. Photo: Fermilab

    When I started at the lab in December 1977, work on the dipole magnets for the Tevatron was well under way in what was then called the Energy Doubler Department in the Technical Services Section.

    My first project was to work on the quadrupole magnets and spools, which hadn’t really been started yet. The spool is a special unit that attaches to each quadrupole and the adjacent dipole. It contains what we used to call “the stuff that wouldn’t fit anywhere else” – correction magnets and their power leads, quench stoppers to dump the energy from all the magnets, beam position monitors, relief valves, things like that.

    At the time, we were located in the Village in the old director’s complex, which now houses the daycare center. We had a large open area where the engineers, designers and drafters worked and a small conference room where we kept up-to-date models of some of the things we were working on.

    2
    A team tests a magnet spool piece. Photo: Fermilab

    For several weeks we worked feverishly on the design of the quadrupole and spool combination — we in the design room and the model makers in the model shop on their full-scale models. We would work all week, then have a meeting with the lab director, Bob Wilson. Dr. Wilson would come out to see how we were doing, but more importantly to see what our designs looked like.

    It turns out he was very interested in that and very fussy that things — even those buried in the tunnel — looked just so.

    After every one of those meetings we’d walk back into the design room and tell everyone to tear up what we’d been working on and start over. The same would hold for the model makers. This went on for several weeks until Dr. Wilson was happy. We began to really dread going into those meetings, but in the end they served us very well.

    FNAL Tevatron

    FNAL/Tevatron map


    FNAL/Tevatron DZero detector


    FNAL/Tevatron CDF detector

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    FNAL Icon
    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 1:55 pm on May 24, 2017 Permalink | Reply
    Tags: , , Charm mesons and baryons, FNAL Tevatron, , , ,   

    From FNAL: ” Fermilab measures lifetimes and properties of charm mesons and baryons” 

    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.

    properties of charm mesons and baryons

    May 24, 2017
    Troy Rummler

    1

    Heavy quarks produced in high-energy collisions decay within a tiny fraction of a second, traveling less than a few centimeters from the collision point. To study properties of these particles, Fermilab began using microstrip detectors in the late 1970s. These detectors are made of thin slices of silicon and placed close to the interaction point in order to take advantage of the microstrip’s tremendous position resolution. Over time, Fermilab developed this technology, improving our understanding of silicon’s capabilities and adapting the technology to other detectors, including those at CDF and DZero.

    FNAL Tevatron

    FNAL/Tevatron map


    FNAL/Tevatron DZero detector


    FNAL/Tevatron CDF detector

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    FNAL Icon
    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 11:11 am on May 24, 2017 Permalink | Reply
    Tags: , , , , FNAL Tevatron, , Our failure in resolve,   

    From FNAL: “Fermilab scientists set upper limit for Higgs boson mass” 

    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.

    In 1977, theoretical physicists at Fermilab — Ben Lee and Chris Quigg, along with Hank Thacker — published a paper setting an upper limit for the mass of the Higgs boson. This calculation helped guide the design of the Large Hadron Collider by setting the energy scale necessary for it to discover the particle. The Large Hadron Collider turned on in 2008, and in 2012, the LHC’s ATLAS and CMS discovered the long-sought Higgs boson — 35 years after the seminal paper.

    1

    CERN CMS Higgs Event


    CERN/CMS Detector


    CERN ATLAS Higgs Event


    CERN/ATLAS detector

    Where it all started:

    FNAL Tevatron

    FNAL/Tevatron map


    FNAL/Tevatron DZero detector


    FNAL/Tevatron CDF detector

    Where we failed and handed it to Europe:

    3
    Sight of the planned Superconducting Super Collider, in the vicinity of Waxahachie, Texas. Cancelled by our idiot Congress under Bill Clinton in 1993. We could have had it all.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    FNAL Icon
    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 3:14 pm on December 13, 2016 Permalink | Reply
    Tags: , ATLAS releases first measurement of W mass using LHC data, , , FNAL Tevatron, , , ,   

    From CERN ATLAS: “ATLAS releases first measurement of W mass using LHC data” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    CERN

    13 Dec 2016
    Harriet Kim Jarlett

    1
    ATLAS is one of the four major experiments at the LHC. It is a general-purpose particle physics experiment run by an international collaboration (Image: Claudia Marcelloni/ CERN)

    The ATLAS collaboration today reports the first measurement of the W boson mass using Large Hadron Collider (LHC) proton–proton collision data at a centre-of-mass energy of 7 TeV.

    2
    The ATLAS measurement of the W boson mass (in red) is compared to the Standard Model prediction (in purple), and to the combined values measured at the LEP and Tevatron collider (in blue) (Image: ATLAS Collaboration/CERN)

    The W boson was discovered in 1983 at the CERN SPS collider and led to a Nobel prize in physics in 1984.

    3
    Super Proton Synchrotron (SPS)

    Although the properties of the W boson have been studied for more than 30 years, measuring its mass remains a major challenge. A precise measurement of the W boson mass is vital, as a deviation from the Standard Model’s predictions could hint at new physics.

    The latest results from ATLAS show a measured value of 80370±19 MeV, which is consistent with the Standard Model prediction. It is also consistent with the combined values measured at the LEP and Tevatron colliders, and with the world average (see graph above).

    4
    Large Electron Positron collider

    FNAL/Tevatron machine
    FNAL/Tevatron

    Measuring the W mass is particularly challenging at the LHC, compared to previous colliders, due to the large number of interactions per beam crossing. Despite this, the ATLAS result matches the best single-experiment measurement of the W mass (performed by the CDF collaboration).

    FNAL/Tevatron CDF detector
    FNAL/Tevatron CDF detector

    Read more on the ATLAS experiment’s website: http://cern.ch/go/p6sN

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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 II

    LHC

    CERN LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles

    Quantum Diaries

     
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