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  • richardmitnick 8:46 am on September 4, 2015 Permalink | Reply
    Tags: , , BNL PHENIX, , Particle Accelerators,   

    From BNL: “Tiny Drops of Early Universe ‘Perfect’ Fluid” 

    Brookhaven Lab

    August 31, 2015
    Karen McNulty Walsh, (631) 344-8350 or Peter Genzer, (631) 344-3174

    1
    The upper panel of this image represents initial hot spots created by collisions of one, two, and three-particle ions with heavy nuclei. The lower panel shows the geometrical patterns of particle flow that would be expected if the small-particle collisions are creating tiny hot spots of quark-gluon plasma.

    The Relativistic Heavy Ion Collider (RHIC), a particle collider for nuclear physics research at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, smashes large nuclei together at close to the speed of light to recreate the primordial soup of fundamental particles that existed in the very early universe.

    BNL RHIC Campus
    BNL RHIC

    RHIC

    Experiments at RHIC—a DOE Office of Science User Facility that attracts more than 1,000 collaborators from around the world—have shown that this primordial soup, known as quark-gluon plasma (QGP), flows like a nearly friction free “perfect” liquid. New RHIC data just accepted for publication in the journal Physical Review Letters now confirm earlier suspicions that collisions of much smaller particles can also create droplets of this free-flowing primordial soup, albeit on a much smaller scale, when they collide with the large nuclei.

    “These tiny droplets of quark-gluon plasma were at first an intriguing surprise,” said Berndt Mueller, Associate Laboratory Director for Nuclear and Particle Physics at Brookhaven. “Physicists initially thought that only the nuclei of large atoms such as gold would have enough matter and energy to set free the quark and gluon building blocks that make up protons and neutrons. But the flow patterns detected by RHIC’s PHENIX collaboration in collisions of helium-3 nuclei with gold ions now confirm that these smaller particles are creating tiny samples of perfect liquid QGP.”

    These results build on earlier findings from collisions of two-particle ions known as deuterons with gold ions at RHIC, as well as proton-lead and proton-proton collisions at Europe’s Large Hadron Collider (LHC).

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

    They also set the stage for the current run colliding protons with gold at RHIC.

    “The idea that collisions of small particles with larger nuclei might create minute droplets of primordial quark-gluon plasma has guided a series of experiments to test this idea and alternative explanations, and stimulated a rich debate about the implications of these findings,” said University of Colorado physicist Jamie Nagle, a co-spokesperson of the PHENIX collaboration at RHIC. “These experiments are revealing the key elements required for creating quark-gluon plasma and could also offer insight into the initial state characteristics of the colliding particles.”

    Geometrical flow patterns

    2
    Relativistic Heavy Ion Collider’s PHENIX detector

    The discovery of the “perfect” liquid at RHIC, announced definitively in 2005, was largely based on observations of particles flowing in an elliptical pattern from the matter created in RHIC’s most energetic gold-gold collisions. This flow was a clear sign that particles emerging from the collisions were behaving in a correlated, or collective, way that contrasted dramatically with the uniformly expanding gas the scientists had expected. Additional experiments confirmed that this liquid is indeed composed of visible matter’s most fundamental building blocks, quarks and gluons, no longer confined within individual protons and neutrons, and that the flow occurs with minimal resistance—making it a nearly “perfect” liquid QGP.

    “Experiments colliding smaller particles with the heavy ions were originally designed as control experiments because they weren’t supposed to create the QGP,” Nagle said. “But observations at the LHC of very energetic proton-proton collisions and later experiments there colliding protons with lead revealed hints that particles streaming from those tiny collisions were also behaving collectively and flowing. It looked a lot like some of the perfect liquid signatures originally discovered in gold-gold collisions at RHIC, and later in lead-lead collisions at the LHC.”

    When RHIC physicists checked data from the RHIC run of 2008, when deuterons (a nucleus made of one proton and one neutron) were smashed into gold ions, they saw a similar pattern.

    “Since the deuteron is two particles, it creates two separate impacts on the nucleus—two hot spots that appear to merge and form an elongated drop of QGP,” Nagle said.

    Definitive tests

    Those observations triggered the idea of testing for flow patterns in a range of more tightly controlled experiments, which is only possible at RHIC, where physicists can collide a wide variety of ions to control the shape of the droplets of matter created. With additional deuteron-gold collisions already in hand, the RHIC scientists set out to collide three-particle helium-3 nuclei (each made of two protons and one neutron) with gold—and later, single protons with gold.

    “The PHENIX detector can pick up particles coming out of collisions very far forward and backward from the collision point. This large angle coverage allows us to measure the flow in these small collision systems,” said Shengli Huang, a PHENIX collaborator from Vanderbilt University who carried out the analysis. “PHENIX also has a trigger detector that picks up and records the most violent collisions—the ones in which the flow pattern is most apparent,” he said.

    The analysis of those events, as described in the new paper, reveals that the helium-gold collisions exhibit a triangular pattern of flow that the scientists say is consistent with the creation of three tiny droplets of QGP. They also say the data indicate that these small particle collisions could be producing the extreme temperatures required to free quarks and gluons—albeit at a much smaller, more localized scale than in the relatively big domains of QGP created in collisions of two heavy ions.

    “This is a pretty definitive measurement,” Nagle said. “The paper has a plot of elliptical and triangular flow that pretty much matches the hydrodynamic flow calculations we’d expect for QGP. We are really engineering different shapes of the QGP to manipulate it and see how it behaves.”

    There are other key signatures of QGP formation, such as the stopping of energetic particle jets, which have not been detected in the tiny droplets. And other theoretical explanations suggest the flow patterns resulting from some of the small particle-nucleus collisions could emerge from the interactions of gluons within the colliding particles, rather than from the formation of QGP.

    “At this time, the only theoretical framework that reproduces the patterns we’re observing in deuteron-gold and helium-3-gold collisions is fluid dynamics,” said Bjoern Schenke, a nuclear theorist at Brookhaven Lab. “It remains to be seen if alternative models can describe these patterns as well.”

    If other models also turn out to be compatible with the helium-3-gold data, physicists will want to explore whether these models make predictions that differ from those of the hydrodynamic flow model, and for which types of collisions.

    “The good news is that RHIC, with its unrivaled versatility, will likely be able to study any system that can discriminate between different models,” Mueller said.

    Research at RHIC is funded primarily by the DOE Office of Science and also by these agencies and organizations.

    See the full article here.

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    BNL Campus

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 1:26 pm on September 1, 2015 Permalink | Reply
    Tags: , , , , Particle Accelerators,   

    From CERN: “ATLAS and CMS experiments shed light on Higgs properties” 

    CERN New Masthead

    01 Sep 2015
    No Writer Credit

    1
    Results of the analyses by individual experiments (coloured) and both experiments together (black), showing the improvement in precision resulting from the combination of results.

    Three years after the announcement of the discovery of a new particle, the so-called Higgs boson, the ATLAS and CMS Collaborations present for the first time combined measurements of many of its properties, at the third annual Large Hadron Collider Physics Conference (LHCP 2015). By combining their analyses of the data collected in 2011 and 2012, ATLAS and CMS draw the sharpest picture yet of this novel boson. The new results provide in particular the best precision on its production and decay and on how it interacts with other particles. All of the measured properties are in agreement with the predictions of the Standard Model and will become the reference for new analyses in the coming months, enabling the search for new physics phenomena. This follows the best measurement of the mass of the Higgs boson, published in May 2015 (link is external) after a combined analysis by the two collaborations.

    “The Higgs boson is a fantastic new tool to test the Standard Model of particle physics and study the Brout-Englert-Higgs mechanism that gives mass to elementary particles,” said CERN* Director General Rolf Heuer.

    1
    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.

    “There is much benefit in combining the results of large experiments to reach the high precision needed for the next breakthrough in our field. By doing so, we achieve what for a single experiment would have meant running for at least 2 more years.”

    There are different ways to produce a Higgs boson, and different ways for a Higgs boson to decay to other particles. For example, according to the Standard Model, the theory that describes best forces and particles, when a Higgs boson is produced, it should decay immediately in about 58% of cases into a bottom quark and a bottom antiquark. By combining their results, ATLAS and CMS determined with the best precision to date the rates of the most common decays.

    Such precision measurements of decay rates are crucially important as they are directly linked to the strength of the interaction of the Higgs particle with other elementary particles, as well as to their masses. Therefore, the study of its decays is essential in determining the nature of the discovered boson. Any deviation in the measured rates compared to those predicted by the Standard Model would bring into question the Brout-Englert-Higgs mechanism and possibly open the door to new physics beyond the Standard Model.

    “This is a big step forward, both for the mechanics of the combinations and in our measurement precision, ” said ATLAS Spokesperson Dave Charlton. “As an example, from the combined results the decay of the Higgs boson to tau particles is now observed with more than 5 sigma significance, which was not possible from CMS or ATLAS alone.”

    “Combining results from two large experiments was a real challenge as such analysis involves over 4200 parameters that represent systematic uncertainties,” said CMS Spokesperson Tiziano Camporesi. “With such a result and the flow of new data at the new energy level at the LHC, we are in a good position to look at the Higgs boson from every possible angle”.

    • CERN, the European Organization for Nuclear Research, is the world’s leading laboratory for particle physics. It has its headquarters in Geneva. At present, its member states are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Israel, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Romania is a Candidate for Accession. Serbia is an Associate Member in the pre-stage to Membership. Pakistan and Turkey are Associate Members. India, Japan, the Russian Federation, the United States of America, the European Union, JINR and UNESCO have observer status.

    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 11:53 am on August 27, 2015 Permalink | Reply
    Tags: , , , , Particle Accelerators, ,   

    From U Maryland: “Evidence Suggests Subatomic Particles Could Defy the Standard Model” 

    U Maryland bloc

    University of Maryland

    August 26, 2015
    Matthew Wright
    301-405-9267
    mewright@umd.edu

    Large Hadron Collider team finds hints of leptons acting out against time-tested predictions

    The Standard Model of particle physics, which explains most of the known behaviors and interactions of fundamental subatomic particles, has held up remarkably well over several decades.

    2
    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.

    This far-reaching theory does have a few shortcomings, however—most notably that it doesn’t account for gravity. In hopes of revealing new, non-standard particles and forces, physicists have been on the hunt for conditions and behaviors that directly violate the Standard Model.

    Now, a team of physicists working at CERN’s Large Hadron Collider (LHC) has found new hints of particles—leptons, to be more precise—being treated in strange ways not predicted by the Standard Model. The discovery, scheduled for publication in the September 4, 2015 issue of the journal Physical Review Letters, could prove to be a significant lead in the search for non-standard phenomena.

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

    1
    In this event display from the LHCb experiment at CERN’s Large Hadron Collider, proton-proton collisions at the interaction point (far left) result in a shower of leptons and other charged particles. The yellow and green lines are computer-generated reconstructions of the particles’ trajectories through the layers of the LHCb detector. Image credit: CERN/LHCb Collaboration

    3
    LHCb Detector

    The team, which includes physicists from the University of Maryland who made key contributions to the study, analyzed data collected by the LHCb detector during the first run of the LHC in 2011-12. The researchers looked at B meson decays, processes that produce lighter particles, including two types of leptons: the tau lepton and the muon. Unlike their stable lepton cousin, the electron, tau leptons and muons are highly unstable and quickly decay within a fraction of a second.

    According to a Standard Model concept called “lepton universality,” which assumes that leptons are treated equally by all fundamental forces, the decay to the tau lepton and the muon should both happen at the same rate, once corrected for their mass difference. However, the team found a small, but notable, difference in the predicted rates of decay, suggesting that as-yet undiscovered forces or particles could be interfering in the process.

    “The Standard Model says the world interacts with all leptons in the same way. There is a democracy there. But there is no guarantee that this will hold true if we discover new particles or new forces,” said study co-author and UMD team lead Hassan Jawahery, Distinguished University Professor of Physics and Gus T. Zorn Professor at UMD. “Lepton universality is truly enshrined in the Standard Model. If this universality is broken, we can say that we’ve found evidence for non-standard physics.”

    The LHCb result adds to a previous lepton decay finding, from the BaBar experiment at the Stanford Linear Accelerator Center, which suggested a similar deviation from Standard Model predictions.

    SLAC Babar
    SLAC/BaBaR

    (The UMD team has participated in the BaBar experiment since its inception in 1990’s.) While both experiments involved the decay of B mesons, electron collisions drove the BaBar experiment and higher-energy proton collisions drove the LHC experiment.

    “The experiments were done in totally different environments, but they reflect the same physical model. This replication provides an important independent check on the observations,” explained study co-author Brian Hamilton, a physics research associate at UMD. “The added weight of two experiments is the key here. This suggests that it’s not just an instrumental effect—it’s pointing to real physics.”

    “While these two results taken together are very promising, the observed phenomena won’t be considered a true violation of the Standard Model without further experiments to verify our observations,” said co-author Gregory Ciezarek, a physicist at the Dutch National Institute for Subatomic Physics (NIKHEF).

    “We are planning a range of other measurements. The LHCb experiment is taking more data during the second run right now. We are working on upgrades to the LHCb detector within the next few years,” Jawahery said. “If this phenomenon is corroborated, we will have decades of work ahead. It could point theoretical physicists toward new ways to look at standard and non-standard physics.”

    With the discovery of the Higgs boson—the last major missing piece of the Standard Model—during the first LHC run, physicists are now looking for phenomena that do not conform to Standard Model predictions.

    Higgs Boson Event
    Higgs Boson event at CMS

    CERN CMS Detector
    CMS Detector in the LHC at CERN

    Jawahery and his colleagues are excited for the future, as the field moves into unknown territory.

    “Any knowledge from here on helps us learn more about how the universe evolved to this point. For example, we know that dark matter and dark energy exist, but we don’t yet know what they are or how to explain them. Our result could be a part of that puzzle,” Jawahery said. “If we can demonstrate that there are missing particles and interactions beyond the Standard Model, it could help complete the picture.”

    ###

    In addition to Jawahery and Hamilton, UMD Graduate Assistants Jason Andrews and Jack Wimberley are co-authors on the paper. The UMD LHCb team also includes Research Associate William Parker and Engineer Thomas O’Bannon, who are not coauthors on the paper.

    The research paper, “Measurement of the ratio of branching fractions…,” The LHCb Collaboration, is scheduled to appear online August 31, 2015 and to be published September 4, 2015 in the journal Physical Review Letters.

    See the full article here.

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    U Maryland Campus

    Driven by the pursuit of excellence, the University of Maryland has enjoyed a remarkable rise in accomplishment and reputation over the past two decades. By any measure, Maryland is now one of the nation’s preeminent public research universities and on a path to become one of the world’s best. To fulfill this promise, we must capitalize on our momentum, fully exploit our competitive advantages, and pursue ambitious goals with great discipline and entrepreneurial spirit. This promise is within reach. This strategic plan is our working agenda.

    The plan is comprehensive, bold, and action oriented. It sets forth a vision of the University as an institution unmatched in its capacity to attract talent, address the most important issues of our time, and produce the leaders of tomorrow. The plan will guide the investment of our human and material resources as we strengthen our undergraduate and graduate programs and expand research, outreach and partnerships, become a truly international center, and enhance our surrounding community.

    Our success will benefit Maryland in the near and long term, strengthen the State’s competitive capacity in a challenging and changing environment and enrich the economic, social and cultural life of the region. We will be a catalyst for progress, the State’s most valuable asset, and an indispensable contributor to the nation’s well-being. Achieving the goals of Transforming Maryland requires broad-based and sustained support from our extended community. We ask our stakeholders to join with us to make the University an institution of world-class quality with world-wide reach and unparalleled impact as it serves the people and the state of Maryland.

     
  • richardmitnick 9:37 am on August 27, 2015 Permalink | Reply
    Tags: , , , Particle Accelerators,   

    From FNAL- “Frontier Science Result: CDF Never alone” 

    FNAL II photo

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

    Aug. 27, 2015
    Matthew Jones

    2

    1
    The top plot shows the fraction of charged particles produced around a Ds+ meson that are kaons as a function of the particle transverse momentum. The bottom plot shows the fraction produced around a D+ meson. A larger kaon fraction is observed in association with Ds+ production because the kaon contains the strange quark produced in association with the antistrange quark found in the Ds+ meson. The pair of strange quarks is created as the gluon string breaks at the end closest to the heavy quark.

    When produced in high-energy collisions, quarks are never observed in isolation as free particles. Instead, all quarks remain connected to other fundamental particles produced in a collision by a “string” of gluons.

    At low energies, these gluons bind quarks and antiquarks together to form stable mesons. But at higher energies, the string can break and reconnect to new quark-antiquark pairs that are created out of the energy stored in the stretched string.

    We can watch this process in action by studying bottom or charm quarks, which are initially produced in proton-antiproton collisions. The bottom and charm quarks can ultimately be found inside a heavy meson, such as a B+ or D+, respectively. But once the quark is bound inside one of these particles, what happens to the rest of its string?

    Scientists have tuned models to describe the average properties of the mesons created in the fragmentation process, but it would be interesting to watch what happens to the end of the string that remains immediately after the part connected to the heavy quark is broken.

    Recently, the CDF experiment did exactly this by looking at the properties of kaons produced in association with Ds+ mesons.

    FNAL CDF
    CDF

    In this case, when a gluon string breaks, the strange quark in a K- is produced at the same time as the antistrange quark needed to form the Ds+ meson.

    Kaons produced in this way were shown to have distinctly different properties when compared to kaons produced in association with D+ mesons, which instead contain an antidown quark, consistent with fragmentation models.

    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 6:34 pm on August 26, 2015 Permalink | Reply
    Tags: , MAX IV Sweden, Particle Accelerators,   

    From Nature: “Next-generation X-ray source fires up” 

    Nature Mag
    Nature

    26 August 2015
    Davide Castelvecchi

    MAX IV Sweden
    Sweden’s MAX-IV laboratory will host the first two ‘fourth-generation’ light sources. Perry Nordeng/Lund University

    Electrons have begun circulating in a synchrotron in Lund, Sweden, in what researchers hope marks the start of a new era for X-ray science.

    Synchrotrons are particle accelerators that produce X-rays used in research ranging from structural biology to materials science. The next generation of this technology promises to lower the costs of X-ray-light sources around the world, whilst improving their performance and enabling experiments that were not possible before.

    At 10 pm local time on 25 August the first bunches of electrons began circulating inside a new 528-meter-long, 3 gigaelectronvolt (GeV) machine at the MAX IV facility in Lund, project director Christoph Quitmann told Nature. MAX IV is the first ‘fourth-generation’ synchrotron in the world.

    “It means that something fatal has not happened early on,” says Robert Hettel, an accelerator physicist at SLAC National Accelerator Laboratory in Menlo Park, California. “Many rings in the past have had a hard time reaching this early milestone.”

    “Getting the first beam is an absolutely crucial first step” in demonstrating fourth-generation technology, says Chris Jacobsen, an X-ray physicist at Northwestern University in Evanston, Illinois. He adds that MAX IV is “leading the world towards a new path in synchrotron light sources”.

    In synchrotrons, bunches of electrons circulate at nearly the speed of light inside a ring-shaped vacuum tube. Powerful ‘bending’ magnets steer the electrons around the rings and ‘focusing’ magnets push them together against their mutual repulsion. The electrons then pass through special magnets that shake them sideways to produce pulses of X-rays, known as synchrotron radiation.

    Fourth-generation light sources promise to squeeze the electrons into tighter bunches, leading to X-ray pulses that concentrate more photons into a tighter, brighter beam. This will enable researchers to do experiments that could take days on a third-generation machine in mere minutes, Jacobsen says.

    My generation

    Eventually, beams from fourth-generation machines could enable materials scientists to observe chemical reactions inside a battery as they happen, or structural biologists to reveal the structure of proteins from smaller protein crystals than those necessary at existing light sources.

    The crucial innovation of the fourth-generation machines is to employ a narrower vacuum pipe to circulate electrons in. In MAX IV’s case, the pipe is 22 millimetres across, about half as wide as a typical current synchrotron. This makes it possible to get stronger magnetic fields using more compact bending and focusing magnets, which are also less expensive and can consume 10 times less electricity than third-generation systems due to their smaller size.

    Keeping such a narrow pipe free of air would not have been possible with traditional high-vacuum pumps though. To do this MAX IV borrowed a technology from the Large Hadron Collider (LHC) near Geneva, Switzerland, which circulates protons rather than electrons. The LHC trick – now adopted by MAX IV – coats the inner surface of pipes with a special alloy that absorbs any molecules of air that happen to bounce around inside them.

    “The Swedes should be very proud of their innovative fabrication techniques, which lower the cost of making these machines,” said physicist Herman Winick, a veteran synchrotron builder at SLAC.

    In the next few weeks, the MAX IV team will have to test that they can circulate the large number of electrons that will be necessary to produce high-quality beams of X-rays, Hettel says. And in subsequent months, they will build eight experimental stations, or beamlines, around the synchrotron, which they plan to open on 20 June 2016, a date chosen for the symbolism of summer solstice.

    The synchrotron that fired up on 25 August is the larger of two that MAX IV is building, with the smaller fourth-generation machine producing electrons of 1.5 GeV for making ‘softer’, or less energetic, X-rays. The combined cost of the machines and of the first eight beamlines will be 4.5 billion Swedish kronor (€450 million), Quitmann says, which is being paid for by the Swedish government.

    Quitmann says his team reached “a major milestone last night”. But, he adds, “We have still a long way to go.”

    See the full article here.

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    Nature is a weekly international journal publishing the finest peer-reviewed research in all fields of science and technology on the basis of its originality, importance, interdisciplinary interest, timeliness, accessibility, elegance and surprising conclusions. Nature also provides rapid, authoritative, insightful and arresting news and interpretation of topical and coming trends affecting science, scientists and the wider public.

     
  • richardmitnick 2:19 pm on August 26, 2015 Permalink | Reply
    Tags: , Particle Accelerators, ,   

    From SLAC: “Antimatter Catches a Wave at SLAC” 


    SLAC Lab

    August 26, 2015

    A study led by researchers from the U.S. Department of Energy’s (DOE) SLAC National Accelerator Laboratory and the University of California, Los Angeles has demonstrated a new, efficient way to accelerate positrons, the antimatter opposites of electrons. The method may help boost the energy and shrink the size of future linear particle colliders – powerful accelerators that could be used to unravel the properties of nature’s fundamental building blocks.

    The scientists had previously shown that boosting the energy of charged particles by having them “surf” a wave of ionized gas, or plasma, works well for electrons. While this method by itself could lead to smaller accelerators, electrons are only half the equation for future colliders. Now the researchers have hit another milestone by applying the technique to positrons at SLAC’s Facility for Advanced Accelerator Experimental Tests (FACET), a DOE Office of Science User Facility.

    SLAC FACET Line
    FACET

    “Together with our previous achievement, the new study is a very important step toward making smaller, less expensive next-generation electron-positron colliders,” said SLAC’s Mark Hogan, co-author of the study published today in Nature. “FACET is the only place in the world where we can accelerate positrons and electrons with this method.”

    SLAC Director Chi-Chang Kao said, “Our researchers have played an instrumental role in advancing the field of plasma-based accelerators since the 1990s. The recent results are a major accomplishment for the lab, which continues to take accelerator science and technology to the next level.”

    2
    Future particle colliders will require highly efficient acceleration methods for both electrons and positrons. Plasma wakefield acceleration of both particle types, as shown in this simulation, could lead to smaller and more powerful colliders than today’s machines. (F. Tsung/W. An/UCLA/SLAC National Accelerator Laboratory)

    3
    Simulation of high-energy positron acceleration in an ionized gas, or plasma – a new method that could help power next-generation particle colliders. The image shows the formation of a high-density plasma (green/orange color) around a positron beam moving from the bottom right to the top left. Plasma electrons pass by the positron beam on wave-like trajectories (lines). (W. An/UCLA)


    This animation explains how researchers accelerate positrons with a plasma – a method that may help boost the energy and shrink the size of future linear particle colliders. (SLAC National Accelerator Laboratory)
    Download the .mp4 here.

    Creating a Plasma Wake for Antimatter

    For positrons – the other required particle ingredient for electron-positron colliders – plasma wakefield acceleration is much more challenging. In fact, many scientists believed that no matter where a trailing positron bunch was placed in a wake, it would lose its compact, focused shape or even slow down.

    “Our key breakthrough was to find a new regime that lets us accelerate positrons in plasmas efficiently,” said study co-author Chandrashekhar Joshi from UCLA.

    Instead of using two separate particle bunches – one to create a wake and the other to surf it – the team discovered that a single positron bunch can interact with the plasma in such a way that the front of it generates a wake that both accelerates and focuses its trailing end. This occurs after the positrons have traveled about four inches through the plasma.

    “In this stable state, about 1 billion positrons gained 5 billion electronvolts of energy over a short distance of only 1.3 meters,” said former SLAC researcher Sébastien Corde, the study’s first author, who is now at the Ecole Polytechnique in France. “They also did so very efficiently and uniformly, resulting in an accelerated bunch with a well-defined energy.”

    4
    Computer simulations of the interaction of electrons (left, red areas) and positrons (right, red areas) with a plasma. The approximate locations of tightly packed bundles of particles, or bunches, are within the dashed lines. Left: For electrons, a drive bunch (on the right) generates a plasma wake (white area) on which a trailing electron bunch (on the left) gains energy. Right: For positrons, a single bunch can interact with the plasma in such a way that the front of the bunch generates a wake that accelerates the bunch tail. (W. An/UCLA)

    Looking into the Future

    All of these properties are important qualities for particle beams in accelerators. In the next step, the team will look to further improve their experiment.

    “We performed simulations to understand how the stable state was created,” said co-author Warren Mori of UCLA. “Based on this understanding, we can now use simulations to look for ways of exciting suitable wakes in an improved, more controlled way. This will lead to ideas for future experiments.”

    Although plasma-based particle colliders will not be built in the near future, the method could be used to upgrade existing accelerators much sooner.

    “It’s conceivable to boost the performance of linear accelerators by adding a very short plasma accelerator at the end,” Corde said. “This would multiply the accelerator’s energy without making the entire structure significantly longer.”

    Additional contributors included researchers from the University of Oslo in Norway and Tsinghua University in China. The research was supported by DOE, the National Science Foundation, the Research Council of Norway and the Thousand Young Talents Program of China.

    Citation: S. Corde et al., Nature, 27 August 2015 (10.1038/nature14890)

    Press Office Contact: Andrew Gordon, agordon@slac.stanford.edu, (650) 926-2282

    See the full article here.

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    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 10:35 am on August 21, 2015 Permalink | Reply
    Tags: , , , , , Particle Accelerators,   

    From FNAL: LHC Run II: first analysis 

    FNAL II photo

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

    Aug. 21, 2015
    FNAL Don Lincoln
    Don Lincoln

    CERN CMS Detector
    CMS Detector

    It was Lao-Tzu who said, “A journey of a thousand miles begins with a single step.” While this proverb from the Tao Te Ching is universally true, it has an especially apropos meaning for scientists working at the LHC.

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN
    LHC at CERN

    Our journey isn’t always a physical one, but rather travels into intellectual realms never before investigated. We look to understand the behavior of matter at the highest energies ever achieved and to explore the conditions of the universe a tenth of a trillionth of a second after it began.

    Our one-step-at-a-time approach served us well using the data recorded from 2010–12 (what scientists called LHC Run I), in which the Higgs boson was discovered, vast swaths of ideas for new theories were ruled out and the most energetic collisions ever achieved were characterized.

    2
    Proposed Higgs event at CMS

    This was an enormous success, leading to about 1,000 separate publications from the four big LHC experiments. During this period, scientists thoroughly explored the behavior of matter at collision energies of 7 and then 8 trillion electronvolts.

    After two years downtime, the LHC resumed operations in 2015 (which we are calling Run II) and is now delivering beams of protons that collide at even higher energies, specifically 13 trillion electronvolts. There is no way to know what we will discover, as this is truly intellectual terra incognito.

    As it happens, not all collisions occur with equal probability. Glancing collisions can occur a billion times more often than, for example, ones in which Higgs bosons are made. This allows scientists to quickly study certain data while waiting for enough data to accumulate for the rarer collisions. In addition, in the rarer collisions, two of the protons’ constituents collide energetically, but the remainder experience only glancing interactions. Thus understanding the physics of glancing collisions is important even for events in which the discovery potential is much higher.

    On July 21, CMS submitted for publication the first physics paper using the Run II data. The analysis studied the most common collisions to characterize both the number and direction of charged particles created in the collisions. Even in these gentlest of collisions, more than 20 charged particles are created on average. Further, it is always possible when exploring a new energy regime that surprises might arise, so the researchers compared their measurement to those taken at lower collision energies and observed no real surprises.

    The real message is the LHC publication juggernaut has pounced on Run II data with a vengeance. This paper is the first, but it won’t be the last.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 10:42 am on July 31, 2015 Permalink | Reply
    Tags: , , , , , , Particle Accelerators,   

    From FNAL- “Frontier Science Result: CMS Shedding light on the invisible Higgs” 

    FNAL II photo

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

    July 31, 2015
    Jim Pivarski

    1
    Event recorded with the CMS detector in 2012 at a proton-proton center of mass energy of 8 TeV. The event shows characteristics expected from the decay of the Standard Model Higgs boson to a pair of photons (dashed yellow lines and green towers). The event could also be due to known standard model background processes..

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

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

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

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

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

    CERN CMS Detector
    CMS in the LHC at CERN

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

    Supersymmetry standard model
    Standard Model of Supersymmetry

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

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

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 8:38 am on July 31, 2015 Permalink | Reply
    Tags: , , , , Particle Accelerators,   

    From LC Newsline: “Learn from the experience of others – Tohoku University campus planning group visits DESY” 

    Linear Collider Collaboration header
    Linear Collider Collaboration

    23 July 2015
    Ricarda Laasch

    Temp 1
    Tohoku University campus planning group at DESY (from left: Tokiko Onuki, Nick Walker, Eisaku Nashiyama, and Akihiko Nagasaka)

    German national laboratory Deutsches Elektronen Synchrotron (DESY) welcomed three Japanese visitors on 30 June, 2015, who asked to be introduced to DESY – its campus and organizational structure as an example of a research institute. The group is studying the size and needs of a possible International Linear Collider (ILC) campus in Tohoku.

    ILC schematic
    Possible ILC

    Tokiko Onuki, Campus Designer of Tohoku University, together with Eisaku Nashiyama, General Manager of the Industry and Economy Group from Tohoku Economic Federation and also the Executive Director of the Tohoku ILC Promotion Council, and Akihiko Nagasaka, ILC Promotion Division of the Mayor’s Office at Ichinoseki City, were welcomed at DESY by Manfred Fleischer, Deputy Director of the High Energy Physics Department of DESY, and Nick Walker, Global Coordinator for ILC Accelerator Design & Integration.

    A program alternating between tours around the campus and presentations by different departments of DESY was the day filling schedule which Fleischer and his colleagues presented to the Japanese visitors. The program started with a historical overview of DESY and the present status of the institute as a national laboratory with many international projects. The broad variety of topics encompassed: civil architecture and planning of the campus, needed infrastructure for a laboratory, transportation along the DESY sites (mainly during HERA times), introduction of foreign researcher’s families to life in Germany and the DESY’s social support systems, possible schools and education for researcher’s children, and regional impact of DESY in many facets of life.

    Onuki was interested in different models for office space and their functionality within the research community. The ILC will need offices for resident staff, long-term guest-scientists and also short-term visitors. At DESY different models for the different groups are used which were presented to the visitors. Further needs concerning seminar rooms and other equipment was addressed and also well received by the visitors.
    Of course an institute for the ILC needs more than office buildings. A tour through workshops and a look inside the cavity testing facility AMTF was part of the visit at DESY. “Such a facility like AMTF or even bigger will be needed for the building phase of the ILC.” was a statement from Nick Walker during the tour through AMTF. The ILC will use the same accelerating technology but it has 20 times as many accelerating structures than the European XFEL (which already needed a mass production). Here additional space and planning for the necessary mass production of accelerating structures is needed for the ILC campus. Walker could give many important insights about the ongoing European XFEL production as stepping stones for the ILC.

    Campus transportation of equipment and personnel will also be an issue for the possible site of the 30km long ILC with all buildings and needed infrastructure. “A good number of bicycles are in use at DESY but they also need maintenance and parking space.” was one of the first answers which were given by Fleischer. DESY solved some of the issues of transportation on campus site by using bicycles, installing a car pool (including transport vans) and during the time of the use of the HERA accelerator a bus shuttle was provided towards the experimental halls. Onuki and their colleagues were interested in all those solutions and of course how these things are used and received within DESY staff.

    Steffi Killough, Leader of the International Office at DESY, was giving helpful insights about social support which would be needed for foreign researchers and their families. DESY supports the guest-scientists starting with the visa application until the end of their stay in the country. Especially the tax system, insurances and other legal matters need explanations and advising. Also the education system for children is an important topic to visiting scientists and support for the integration into those systems needs to be provided. This issue is also very important for the ILC and its possible host nation Japan. “What would you like to provide if you had more resources?” was one of the questions from Onuki and her colleagues. Here the answer was very clear to Killough: more time which can be dedicated to provide support for each individual, also to provide more language support to address a greater variety of visitors in their native language, and to organize more social events.

    At the end of the day many other topics had been addressed like: scientific outreach, visitor numbers to DESY on open house days and the cooperation with the University of Hamburg and other Universities. “A key factor in the 50 year history of DESY was a close collaboration between Hamburg University and DESY, which has grown over the years.” is one of the statements of Frank Lehner towards the visitors from Tohoku University.
    Also the regional impact of DESY towards Hamburg was detailed and discussed in all areas like economy and education. The possibility for spin-off companies, regional investment for the needed infrastructure, training of skilled personnel in a variety of professions which are needed to provide the support system of a laboratory and growth for the regional economy were also further topics of the discussions.

    The Campus Planning Group from Tohoku University was given as many answers as possible from DESY in all possible areas to assist with the future ILC campus plans.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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 3:00 pm on July 30, 2015 Permalink | Reply
    Tags: , , , , Particle Accelerators, , ,   

    From Symmetry: “One Higgs is the loneliest number” 

    Symmetry

    July 30, 2015.
    Katie Elyce Jones

    Physicists discovered one type of Higgs boson in 2012. Now they’re looking for more.

    1

    When physicists discovered the Higgs boson in 2012, they declared the Standard Model of particle physics complete; they had finally found the missing piece of the particle puzzle.

    2
    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.

    And yet, many questions remain about the basic components of the universe, including: Did we find the one and only type of Higgs boson? Or are there more?

    A problem of mass

    The Higgs mechanism gives mass to some fundamental particles, but not others. It interacts strongly with W and Z bosons, making them massive. But it does not interact with particles of light, leaving them massless.

    These interactions don’t just affect the mass of other particles, they also affect the mass of the Higgs. The Higgs can briefly fluctuate into virtual pairs of the particles with which it interacts.

    Scientists calculate the mass of the Higgs by multiplying a huge number—related to the maximum energy for which the Standard Model applies—with a number related to those fluctuations. The second number is determined by starting with the effects of fluctuations to force-carrying particles like the W and Z bosons, and subtracting the effects of fluctuations to matter particles like quarks.

    While the second number cannot be zero because the Higgs must have some mass, almost anything it adds up to, even at very small numbers, makes the mass of the Higgs gigantic.

    But it isn’t. It weighs about 125 billion electronvolts; it’s not even the heaviest fundamental particle.

    “Having the Higgs boson at 125 GeV is like putting an ice cube into a hot oven and it not melting,” says Flip Tanedo, a theoretical physicist and postdoctoral researcher at the University of California, Irvine.

    A lightweight Higgs, though it makes the Standard Model work, doesn’t necessarily make sense for the big picture. If there are multiple Higgses—much heavier ones—the math determining their masses becomes more flexible.

    “There’s no reason to rule out multiple Higgs particles,” says Tim Tait, a theoretical physicist and professor at UCI. “There’s nothing in the theory that says there shouldn’t be more than one.”

    The two primary theories that predict multiple Higgs particles are Supersymmetry and compositeness.

    Supersymmetry standard model
    Standard Model of Supersymmetry

    Supersymmetry

    Popular in particle physics circles for tying together all the messy bits of the Standard Model, Supersymmetry predicts a heavier (and whimsically named) partner particle, or “sparticle,” for each of the known fundamental particles. Quarks have squarks and Higgs have Higgsinos.

    “When the math is re-done, the effects of the particles and their partner particles on the mass of the Higgs cancel each other out and the improbability we see in the Standard Model shrinks and maybe even vanishes,” says Don Lincoln, a physicist at Fermi National Accelerator Laboratory.

    The Minimal Supersymmetric Standard Model—the supersymmetric model that most closely aligns with the current Standard Model—predicts four new Higgs particles in addition to the Higgs sparticle, the Higgsino.

    While Supersymmetry is maybe the most popular theory for exploring physics beyond the Standard Model, physicists at the LHC haven’t seen any evidence of it yet. If Supersymmetry exists, scientists will need to produce more massive particles to observe it.

    “Scientists started looking for Supersymmetry five years ago in the LHC,” says Tanedo. “But we don’t really know where they will find it: 10 TeV? 100 TeV?”

    Compositeness

    The other popular theory that predicts multiple Higgs bosons is compositeness. The composite Higgs theory proposes that the Higgs boson is not a fundamental particle but is instead made of smaller particles that have not yet been discovered.

    “You can think of this like the study of the atom,” says Bogdan Dobrescu, a theoretical physicist at Fermi National Accelerator Laboratory. “As people looked closer and closer, they found the proton and neutron. They looked closer again and found the ‘up’ and ‘down’ quarks that make up the proton and neutron.”

    Composite Higgs theories predict that if there are more fundamental parts to the Higgs, it may assume a combination of masses based on the properties of these smaller particles.

    The search for composite Higgs bosons has been limited by the scale at which scientists can study given the current energy levels at the LHC.

    On the lookout

    Physicists will continue their Higgs search with the current run of the LHC.

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

    At 60 percent higher energy, the LHC will produce Higgs bosons more frequently this time around. It will also produce more top quarks, the heaviest particles of the Standard Model. Top quarks interact energetically with the Higgs, making them a favored place to start picking at new physics.

    Whether scientists find evidence for Supersymmetry or a composite Higgs (if they find either), that discovery would mean much more than just an additional Higgs.

    “For example, finding new Higgs bosons could affect our understanding of how the fundamental forces unify at higher energy,” Tait says.

    “Supersymmetry would open up a whole ‘super’ world out there to discover. And a composite Higgs might point to new rules on the fundamental level beyond what we understand today. We would have new pieces of the puzzle to look at it.”

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
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