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  • richardmitnick 12:53 pm on March 27, 2015 Permalink | Reply
    Tags: Accelerator Science, , , , ,   

    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 

    FNAL Home

    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.

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    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
    Tags: Accelerator Science, , , , , ,   

    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.

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles

    CERN ALICE New II
    ALICE

    CERN ATLAS New
    ATLAS

    CERN CMS New
    CMS

    CERN LHCb New II
    LHCb

    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 10:25 am on March 12, 2015 Permalink | Reply
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    From FNAL- “Frontier Science Result: CDF and DZero Joining forces to test the Higgs boson’s spin and parity” 

    FNAL Home


    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.

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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 12:46 pm on March 8, 2015 Permalink | Reply
    Tags: Accelerator Science, , ,   

    From BBC: “LHC restart: ‘We want to break physics'” 

    BBC
    BBC

    4 March 2015
    Jonathan Webb

    1
    Inside the CMS experiment, the beam pipe is dwarfed by huge cylindrical detectors that will try to capture everything that emerges from the collisions.

    As the Large Hadron Collider (LHC) gears up for its revamped second run, hurling particles together with more energy than ever before, physicists there are impatient. They want this next round of collisions to shake their discipline to its core.

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

    “I can’t wait for the switch-on. We’ve been waiting since January 2013 to have our proton beams back,” says Tara Shears, a particle physics professor from the University of Liverpool.

    Prof Shears is raising her voice over the occasional noise of fork-lift trucks and tools, as well as the constant hum of the huge experimental apparatus behind her: LHCb, one of four collision points spaced around the LHC’s 27km circumference.

    CERN LHCb New II
    LHCb

    All this noise reverberates because we are perched at the side of an imposing cavern, 30 storeys beneath the French-Swiss border.

    The other three experiments – Atlas, CMS and Alice – occupy similar halls, buried elsewhere on this famous circular pipeline.

    CERN ATLAS New
    ATLAS

    CERN ALICE New II
    ALICE

    ‘Everything unravels’

    In mid-March two beams of protons, driven and steered by super-cooled electromagnets, will do full circuits of the LHC in both directions – for the first time in two years. When that happens, there will be nobody between here and ground level. Then in May, if the protons’ practice laps proceed without a hitch, each of the four separate experiments will recommence its work: funnelling those tightly focussed, parallel beams into a head-on collision and measuring the results. For us, now, the other stations on the ring are a 10-20 minute drive away; for the protons, a lap will take less than one ten-thousandth of a second. They have the advantage of travelling a whisker under the speed of light.

    They are moving with so much energy that when they collide, things get hot. Historically hot. “We’re recreating temperatures that were last seen billionths of a second after the Big Bang,” Prof Shears explains. “When you get to this hot temperature, matter dissociates into atoms, and atoms into nuclei and electrons. “Everything unravels to its constituents. And those constituents are what we study in particle physics.”

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    The two beams of protons are focussed into a tiny, intense blast before being put on a collision course

    Alongside more pedestrian items, like electrons, or the quarks that combine to make protons and neutrons, these constituents include the world-famous Higgs boson.

    Higgs Boson Event
    Higgs Event

    This longed-for and lauded particle – the last major ingredient in the Standard Model of particle physics – was detected by the teams at Atlas and CMS in 2012.

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    Then in early 2013, after countless further collisions with valuable but less sensational results, the LHC was wound down for a planned hiatus.

    __________________________________________________________________________________

    What is an electronvolt?

    3

    Particle accelerators use strong electric fields to speed up tiny pieces of matter
    An electronvolt (eV) is the energy gained by one electron as it accelerates through a potential of one volt
    The LHC reaches particle energies measured in trillions of eV: teraelectronvolts (TeV)
    This is only the energy in the motion of a flying mosquito – per particle
    The LHC beams contain hundreds of trillions of particles, each travelling at 99.99999999% of the speed of light
    In total, an LHC beam has the energy of a TGV high-speed train travelling at 150 km/h

    __________________________________________________________________________________

    Renewed vigour

    The two intervening years have been spent servicing and improving the collider.

    “All the magnets have been surveyed, the connections between them have been X-rayed and strengthened, and all the electrical and cryogenic systems have been checked out and optimised,” Prof Shears says. This effort – between one and two million hours of work, all told – means that the LHC is now ready to operate at its “design energy”. Its initial run, after a dramatic false start in 2008, only reached a maximum collision energy of eight trillion electronvolts. That came after a boost in 2012 and the extra power delivered the critical Higgs observations within a few months.

    When they kick off in May, the proton collisions will be at 13 trillion electronvolts: a leap equivalent to that made by the LHC when it first went into operation and dwarfed the previous peak, claimed by the 6km Tevatron accelerator in the US. “It’s a really significant step in terms of what we might be able to see in the Universe,” says Prof Shears.

    “The design energy is a little higher again, at 14 TeV. We want to make sure that we can run close to it, first of all. If operations there are smooth, then subsequently, after next year, we can put the energy up that last little bit.” Alongside this radical hike in the beams’ energy, the experiments housed at the four collision sites have also had time to upgrade. Some have added extra detectors as well as finishing, mending or improving equipment that was built for the first run.

    Build it up, tear it down

    In a sense, one of the shiniest new items in the LHC’s armoury for Run Two is the Higgs boson. Now that its existence is confirmed and quantified, it can inform the next round of detection and analysis. “It’s a new door – a new tool that we can use to probe what is beyond the Standard Model,” says Dr Andre David, one of the research team working on the CMS experiment. Dr David is driving me from the CMS site, in France, back down the valley between the Jura Mountains and Lake Geneva to the main Cern headquarters. This main site, adjacent to the Atlas experiment, sits on the southern side of the LHC’s great circle and straddles the Swiss border.

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    5
    Data flow: The LHC has immeasurable miles of cables to carry experimental data – as well as better mobile phone signal than you can get at ground level

    He emphasises that the Higgs is much more than the final item on the Standard Model checklist; there is a great deal still to find out about it. “It’s like a new wrench that we still have to work out exactly where to fit.” Prof Shears agrees: “We’ve only had about a thousand or two of these new particles, to try and understand their nature.

    “And although it looks like the Higgs boson that we expect from our theory, there’s still a chance that it might have partners that would then tell us that we’re not looking at our normal theory at all. We’re looking at something deeper and more exotic.”

    That is the central impatience that is itching all the physicists here: they want to find something that falls completely outside what they expect or understand. “The data so far has confirmed that our theory is really really good, which is frustrating because we know it’s not!” Prof Shears says. “We know it can’t explain a lot of the Universe.

    “So instead of trying to test the truth of this theory, what we really want to do now is break it – to show where it stops reflecting reality. That’s the only way we’re going to make progress.”

    In the canteen at Cern headquarters I meet Dr Steven Goldfarb, a physicist and software developer on the Atlas team. His sentiments are similar. “We have a fantastic model – that we hate,” he chuckles. “It has stood up to precision measurements for 50 years. We get more and more precise, and it stands up and stands up. But we hate it, because it doesn’t explain the universe.”

    6

    Dark matter: present but invisible

    In fact, only about 5% of the universe is accounted for by the Standard Model. Physicists think that the rest is made up of dark energy (70%) and dark matter (25%) – but these are still just proposals without any experimental evidence. Based on how fast galaxies move and spin, we know there is much more stuff in the universe than what we can see with telescopes. One idea for a “new physics” that might allow for more particles, including the mysterious constituents of dark matter, is supersymmetry.

    Supersymmetry standard model
    Standard Model of Supersymmetry

    It has also never been glimpsed in data from the LHC or elsewhere, but remains a popular concept with theorists. Supersymmetry suggests that all the particles we know about have heavier, “super” partners – as yet unseen by science.

    That failure doesn’t faze the theory’s fans, Dr Golfarb explains. “If you say to someone who really likes supersymmetry, ‘Hey, why haven’t we found any of the particles yet?’ they’ll say, ‘We’ve found half of the particles! We just need to find the other half…'”

    7
    8
    The Standard Model equation is etched in stone outside Cern’s control room – but physicists inside want to find something it can’t explain

    Some of those missing, hypothetical particles – notably the gluino and the neutralino – have been mooted as the most likely first results from LHC Run Two.

    They also make promising candidate building blocks for dark matter. But the researchers are open to other possibilities. Dr Goldfarb says the search need not focus on specific, ghostly particles: “It doesn’t have to be supersymmetry. You can also just look for dark matter. That’s why we build our detectors perfectly hermetically.”

    CMS and Atlas are the two “general-purpose” experiments at the LHC. Both of them have detectors completely surrounding the collision point, so that nothing can escape.

    Well, almost nothing. “You can’t build a neutrino detector – so neutrinos do get out. But we know under what circumstances and how often there ought to be neutrinos. So we can account for the missing energy.” What the team really wants to see is a chunk of missing energy that they categorically cannot account for. “When you see a lot of missing momentum – more than is predicted in standard model – then you may have found a candidate for dark matter,” Dr Goldfarb explains.

    9

    Antimatter: missing altogether

    Even within the 5% of the universe that we do know about, there is a baffling imbalance. The Big Bang ought to have produced two flavours of particle – matter and antimatter – in equal amounts. When those two types of particle collide, they “annihilate” each other. A lot of that sort of annihilation went on, physicists say, and everything we can see in the universe is just the scraps left behind. But puzzlingly, nearly all of those scraps are of one flavour: matter.

    “You just don’t get antimatter in the universe,” says Prof Shears. “You get it in sci-fi and you get it when things decay radioactively, but there are no good deposits of it around.” This glaring absence is “one of the biggest mysteries we have”, she adds. And it is the primary target of the LHCb experiment.

    There, a series of slab-shaped detectors is waiting to try and pinpoint the difference between the particles and anti-particles that pop out of the proton collisions. Run One did reveal some of those differences – but nothing that could explain the drastic tipping of the universal scales towards matter.

    9
    10
    The beam pipe runs directly through the middle of the huge, slab-shaped detectors at LHCb

    “We think now that the answer has to lie in some new physics,” says Prof Shears. She hopes the near doubling of the collision energy will offer a peek. “We’ve got a million crazy ideas. All we can do is to keep our options open, to sift through the data – and to look for the unexpected.”

    Gravity gap

    There are other questions, too. Gravity, somewhat alarmingly, is nowhere to be found in the Standard Model. “There’s no gravity on that mug,” says Dr Goldfarb, pointing to an LHC souvenir with the model’s equation emblazoned on its side. “That’s annoying! But there’s no answer in sight.” And there is always the ongoing quest to smash the things we currently think are the smallest in existence, and find smaller ones. Dr Goldfarb calls this “the oldest physics” and imagines a cavewoman – the first physicist – banging rocks together to see what was inside.

    12
    Final touches at CMS: ‘It’s like you’ve put a ship in the harbour and replaced every single plank’ “We’re still doing that today, and we still wonder what’s inside,” he says. “There’s nothing that discounts the idea that electrons, or quarks, are made up of something else. We just call them fundamental because as far as we know, they are.”

    The extra power in Run Two might produce just this kind of fundamental fruit. “The more energy we have for these collisions, the smaller the bits that we can look at,” says Dr David.

    “The ultimate goal here is to understand what matter is made of.” And the world’s largest laboratory is not just repaired, but renewed and ready for that goal. “It’s like you’ve put a ship in the harbour and replaced every single plank,” Dr David says with pride. “It’s not the same ship. It’s a whole new ship and it’s going on a new adventure.”

    See the full article here.

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  • richardmitnick 3:40 pm on March 7, 2015 Permalink | Reply
    Tags: Accelerator Science, , ,   

    From Quanta: “In LHC’s Shadow, America’s Collider Awakens” 

    Quanta Magazine
    Quanta Magazine

    March 6, 2015
    Natalie Wolchover

    1
    The 2.5-mile tunnel of the Relativistic Heavy Ion Collider. (Thomas Lin/Quanta Magazine)

    BNL RHIC
    RHIC

    BNL RHIC Campus
    RHIC map

    America’s last major particle collider lies coiled beneath the pine barrens and sparse outbuildings of Brookhaven National Laboratory on Long Island, N.Y. The Relativistic Heavy Ion Collider (RHIC), as it’s called, recently came out of hibernation equipped with new gear for spilling the secrets of atoms.

    RHIC pales next to Europe’s Large Hadron Collider when it comes to the energy with which its particles collide — energy that determines whether collisions will give rise to new, exotic particles.

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

    But the machine clings to relevance (and Department of Energy funding) by forgoing the new in favor of a closer look at the mysterious familiar: the quarks and gluons that comprise the cores of atoms, and thus 99 percent of all visible matter, about which several things are not known.

    2
    Gene van Buren in front of the STAR detector.(Thomas Lin/Quanta Magazine)

    In a typical run, gold nuclei fly in opposite directions through RHIC’s central artery at 99.995 percent the speed of light before slamming together with the energy of colliding mosquitoes — objects 10 trillion times their weight — inside the two main detectors, STAR and PHENIX. The crash momentarily produces a several-trillion-degree droplet of “quark-gluon plasma” — matter in which quarks and gluons shed their individuality and form a single, flowing entity. It was here at RHIC in the early 2000s that experiments first definitively recreated this strange liquid, which researchers believe filled the universe in its infancy.

    At RHIC, the plasma droplet survives for about a hundred-thousandth of a billionth of a billionth of a second before cooling and condensing into individual particles. Measurements over the years, along with calculations that exploit the plasma’s peculiar mathematical relationship to black holes, have revealed that it is an almost “perfect” liquid, possessing the lowest viscosity (or internal friction) allowed by quantum physics.

    4
    A monitor in the control room for the STAR detector displays debris from a gold-gold collision (other collisions, such as proton-gold and proton-proton, also occur) (Thomas Lin/Quanta Magazine).

    With gold nuclei and their nearly 200 constituent protons and neutrons, scientists take a shotgun approach to the problem of initiating contact between quantum-scale targets. A collision can produce thousands of particles. “It’s like trying to reconstruct a firecracker from the debris,” said Gene Van Buren, co-leader of STAR’s computing group.

    7
    The PHENIX detector. (Thomas Lin/Quanta Magazine)

    The strong force, which binds quarks together into protons and neutrons and those objects into atomic nuclei, is conveyed through the exchange of gluons. But the equations that describe the strong force are so difficult to solve that physicists do not have a complete understanding of quark-gluon dynamics. For example, quark-gluon plasma droplets form much faster than expected during collisions. For RHIC’s 15th run, which began Feb. 10, scientists have upgraded the PHENIX detector with a new tungsten-silicon hybrid tracking device to help detect radiation from gluons deep inside the colliding particles. “One idea is that we have the wrong picture of gluon distribution,” explained PHENIX scientist Barbara Jacak, who is a professor of physics at the University of California, Berkeley. A super-dense gluon “field,” rather than discrete gluons, might permeate the protons, she said.

    As the world’s only polarized proton collider, RHIC also aims to address what’s known as the “spin crisis,” an unresolved question concerning a property of particles called “spin.” A proton’s three quarks only account for one-fifth of its spin, suggesting the lion’s share comes from the spins of gluons and from quarks and gluons orbiting one another. By colliding protons as they spin in a range of directions, scientists hope to identify the spins and orbits of their component parts.

    8
    A section of the beam pipe mounted for display. Particles travel through the central tube. (Thomas Lin/Quanta Magazine)

    The future of RHIC, which employs 850 people and costs the Department of Energy about $160 million annually, is uncertain. In a 2012 white paper making the case for continued operations, scientists argued that “RHIC is in its prime” with new upgrades poised to answer key questions in nuclear physics. Yet a panel of scientists recommended shuttering the collider in the stead of two other nuclear physics facilities vying for the same funding. So far, all three laboratories have made the cut, yet every run of RHIC could be its last.

    See the full article here.

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

     
  • richardmitnick 4:07 am on March 6, 2015 Permalink | Reply
    Tags: Accelerator Science, ,   

    From CERN: “LHC injector tests to begin” 

    CERN New Masthead

    6 Mar 2015
    Cian O’Luanaigh

    1
    A “splash event” in the LHCb detector, recorded during an injection test in 2009 (Image: LHCb)

    With the Large Hadron Collider (LHC) due to start up again at the end of this month, the team in the LHC Control Centre are busy testing the systems that deliver the beams.

    At CERN, a series of accelerators boosts protons or ions to successively higher energies until they are injected into the LHC. The LHC then further accelerates the particles before delivering collisions to the four detectors ALICE, ATLAS, CMS and LHCb. The penultimate accelerator in the chain is the Super Proton Synchrotron (SPS), a machine nearly 7 kilometres in circumference, which receives particles from the Proton Synchrotron at 26 GeV, and boosts them to the 450 GeV needed for injection to the LHC.

    Now, the LHC control team is testing the injection systems to ensure that the upcoming startup of the accelerator runs as smoothly as possible. Though particles will be injected into parts of the LHC this weekend, there will be no fully circulating beams until the planned startup at the end of this month.

    “We will do two tests,” says Ronaldus Suykerbuyk of the LHC operation team. “Beam 1 will pass through the ALICE detector up to point 3, where we will dump the beam on a collimator, and for Beam 2 we will go through the LHCb detector up to the beam dump at point 6.” A screen placed in the beam pipe will register a successful pass as a bright dot. The team will also record other parameters, including the timings of the injection kickers – fast pulsing dipole magnets that “kick” the beam into the accelerator – and the beam trajectory in the injection lines and LHC beam pipe.

    2
    Beams will not circulate all the way around the LHC, but rather reach point 3 and point 6 during the tests (Image: Leonard Rimensberger/CERN)

    “This test really is a massive debugging exercise,” says Mike Lamont, head of the operations team. “We’ve already pre-tested all the control systems without beam. If the beam goes around we’ll be happy!”

    The ALICE and LHCb experiments are preparing their detectors to receive the pulses of particles. “ALICE will receive muons originating from the SPS beam dump,” says ALICE physicist Despina Hatzifotiadou, “They will be used for trigger timing studies and to align the muon spectrometer”.

    LHCb will also be taking data. “These tests create an excellent opportunity for us to commission the LHCb detector and data-acquisition system. The collected data are also invaluable for detector studies and alignment purposes, that is, determining the relative geometrical locations of the different sub-detectors with respect to each other,” says Patrick Robbe of LHCb. “It’s exciting because the tests show that we are getting closer and closer to the restart!”

    But there is still much work to do before first circulating beams, says Suykerbuyk. “We have to finish all the powering tests and magnet training as well as test all the other hardware and beam-diagnostic systems.” It’s going to be a busy few weeks for all concerned.

    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

     
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