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  • richardmitnick 11:46 am on August 18, 2017 Permalink | Reply
    Tags: Accelerator Science, , CBETA, Cornell University, The overall mission for CBETA is to develop a prototype for eRHIC a 2.4 mile-long electron-ion collider proposed to be built at BNL on Long Island New York   

    From Cornell: “Energy-efficient accelerator was 50 years in the making” 

    Cornell Bloc

    Cornell University

    July 5, 2017 [I never saw this in social media. I got it from a BNL article.]
    Rick Ryan

    1
    Main linac cryomodule being placed into its final position by Cornell engineers at Wilson Lab.

    With the introduction of CBETA, the Cornell-Brookhaven ERL Test Accelerator, Cornell University and Brookhaven National Laboratory scientists are following up on the concept of energy-recovering particle accelerators first introduced by physicist Maury Tigner at Cornell more than 50 years ago.

    CBETA tests two energy-saving technologies for accelerators: energy recovery and permanent magnets. An energy recovery linac (ERL) like CBETA reclaims the energy of a used electron beam instead of dumping it after the experiment. The recovered energy is used to accelerate the next beam of particles, creating a beam of electrons that can be used for many areas of research. The beams are accelerated by Superconducting Radio Frequency (SRF) units, another energy-efficient technology pioneered at Cornell.

    By using permanent magnets, the power that is usually needed to steer the beam with electromagnets is saved. While energy recovery linacs and fixed magnets are being used elsewhere, never before has a group been able to steer four particle beams of different energies simultaneously by using fixed magnets through an ERL.

    Imagine four cars traveling at different speeds around a turn. The physics involved is different for each car: One must turn exceptionally hard at a higher speed as opposed to another traveling at a much lower speed. This also holds true for particles with different energy in the beam pipe. Permanent magnets with alternating gradients make it possible to steer each particle of different energy within the same 120 mm-wide chamber.

    While this method recycles energy, it also creates beams that are much more powerful: They are more tightly bound, can produce brighter and more coherent radiation, can have higher currents, and can produce higher luminosity in colliding-beam experiments.

    “The ERL process was invented at Cornell University 50 years ago, and having its first demonstration in a multi-turn SRF ERL shows Cornell’s strong and continuing tradition in this research field,” said Georg Hoffstaetter, Cornell professor of physics and CBETA principal investigator.

    Combining world-record-holding accelerator components constructed by Cornell with the permanent magnet technology developed by the U.S Department of Energy’s Brookhaven National Laboratory (BNL), the CBETA collaboration aims to revolutionize the way in which accelerators are built.

    2
    Artist’s rendering of the main accelerator components in Wilson Lab.

    The overall mission for CBETA is to develop a prototype for eRHIC, a 2.4 mile-long electron-ion collider proposed to be built at BNL on Long Island, New York.

    Roughly two dozen scientists from BNL and Cornell’s Laboratory for Accelerator-based Sciences and Education (CLASSE) are collaborating on the project. They are running initial tests and expect to complete installation of CBETA by summer 2019. They will test and commission the prototype for eRHIC by spring 2020.

    More than 30,000 accelerators are in operation around the world. This prototype ERL has far-reaching implications for biology, chemistry and a host of other disciplines. ERLs are not only envisioned for nuclear and elementary particle physics colliders, as in eRHIC and the LHeC at CERN in Switzerland, but also as coherent X-ray sources for basic research, industrial and medical purposes.

    “Existing linear accelerators have superior beam quality when compared to large circular accelerators,” Hoffstaeter said. “However, they are exceedingly wasteful due to the beam being discarded after use and can therefore only have an extremely low current compared to ring accelerators. This limits the amount of data collected during an experiment. An ERL like CBETA solves the problem of low beam quality in rings and of low beam-current in linear accelerators, all while conserving energy compared to their predecessors.”

    The most complex components of CBETA already exist at Wilson Lab: the DC electron source, the superconducting radio-frequency (SRF) injector linac, the main ERL cryomodule and the high-power beam stop. They were designed, constructed and commissioned in 10 years of National Science Foundation funding.

    Said Karl Smolenski, lead engineer for Cornell ERL development: “If we are successful it will be a great thing for science and industry. So many different departments and scientists will be able to use this technology. It will also put us way ahead in the competitive world.”

    Principal funding for CBETA comes from the New York State Energy Research and Development Authority.

    See the full article here .

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    Once called “the first American university” by educational historian Frederick Rudolph, Cornell University represents a distinctive mix of eminent scholarship and democratic ideals. Adding practical subjects to the classics and admitting qualified students regardless of nationality, race, social circumstance, gender, or religion was quite a departure when Cornell was founded in 1865.

    Today’s Cornell reflects this heritage of egalitarian excellence. It is home to the nation’s first colleges devoted to hotel administration, industrial and labor relations, and veterinary medicine. Both a private university and the land-grant institution of New York State, Cornell University is the most educationally diverse member of the Ivy League.

    On the Ithaca campus alone nearly 20,000 students representing every state and 120 countries choose from among 4,000 courses in 11 undergraduate, graduate, and professional schools. Many undergraduates participate in a wide range of interdisciplinary programs, play meaningful roles in original research, and study in Cornell programs in Washington, New York City, and the world over.

     
  • richardmitnick 11:32 am on August 18, 2017 Permalink | Reply
    Tags: Accelerator Science, , , Successful Test of Small-Scale Accelerator with Big Potential Impacts for Science and Medicine   

    From BNL: “Successful Test of Small-Scale Accelerator with Big Potential Impacts for Science and Medicine” 

    Brookhaven Lab

    August 16, 2017
    Karen McNulty Walsh
    kmcnulty@bnl.gov

    “Fixed-field” accelerator transports multiple particle beams at a wide range of energies through a single beam pipe.

    1
    Members of the team testing a fixed-field, alternating-gradient beam transport line made with permanent magnets at Brookhaven Lab’s Accelerator Test Facility (ATF), left to right: Mark Palmer (Director of ATF), Dejan Trbojevic, Stephen Brooks, George Mahler, Steven Trabocchi, Thomas Roser, and Mikhail Fedurin (ATF operator and experimental liaison).

    An advanced particle accelerator designed at the U.S. Department of Energy’s Brookhaven National Laboratory could reduce the cost and increase the versatility of facilities for physics research and cancer treatment. It uses lightweight, 3D-printed frames to hold blocks of permanent magnets and an innovative method for fine-tuning the magnetic field to steer multiple beams at different energies through a single beam pipe.

    With this design, physicists could accelerate particles through multiple stages to higher and higher energies within a single ring of magnets, instead of requiring more than one ring to achieve these energies. In a medical setting, where the energy of particle beams determines how far they penetrate into the body, doctors could more easily deliver a range of energies to zap a tumor throughout its depth.

    Scientists testing a prototype of the compact, cost-effective design at Brookhaven’s Accelerator Test Facility (ATF)—a DOE Office of Science User Facility—say it came through with flying colors. Color-coded images show how a series of electron beams accelerated to five different energies successfully passed through the five-foot-long curve of magnets, with each beam tracing a different pathway within the same two-inch-diameter beam pipe.

    2
    Brooks’ proof-of-principle experiment showed that electron beams of five different energies could make their way through the arc of permanent magnets, each taking a somewhat different, color-coded path: dark green (18 million electron volts, or MeV), light green (24MeV), yellow (36MeV), red (54MeV), and purple (70MeV).

    “For each of five energy levels, we injected the beam at the ‘ideal’ trajectory for that energy and scanned to see what happens when it is slightly off the ideal orbit,” said Brookhaven Lab physicist Stephen Brooks, lead architect of the design. Christina Swinson, a physicist at the ATF, steered the beam through the ATF line and Brooks’ magnet assembly and played an essential role in running the experiments.

    “We designed these experiments to test our predictions and see how far away you can go from the ideal incoming trajectory and still get the beam through. For the most part, all the beam that went in came out at the other end,” Brooks said.

    The beams reached energies more than 3.5 times what had previously been achieved in a similar accelerator made from significantly larger electromagnets, with a doubling of the ratio between the highest and lowest energy beams.

    “These tests give us confidence that this accelerator technology can be used to carry beams at a wide range of energies,” Brooks said.

    No wires required

    Most particle accelerators use electromagnets to generate the powerful magnetic fields required to steer a beam of charged particles. To transport particles of different energies, scientists change the strength of the magnetic field by ramping up or down the electrical current passing through the magnets.

    Brooks’ design instead uses permanent magnets, the kind that stay magnetic without an electrical current—like the ones that stick to your refrigerator, only stronger. By arranging differently shaped magnet blocks to form a circle, Brooks creates a fixed magnetic field that varies in strength across different positions within the central aperture of each donut-shaped magnet array.

    When the magnets are lined up end-to-end like beads on a necklace to form a curved arc—as they were in the ATF experiment with assistance from Brookhaven’s surveying team to achieve precision alignment—higher energy particles move to the stronger part of the field. Alternating the field directions of sequential magnets keeps particles oscillating along their preferred trajectory as they move through the arc, with no power needed to accommodate particles of different energies.

    No electricity means less supporting infrastructure and easier operation—which all contribute to the significant cost savings potential of this non-scaling, fixed-field, alternating-gradient accelerator technology.

    Simplified design

    4
    Brooks’ successful test lays the foundation for the CBETA accelerator, in which bunches of electrons will be accelerated to four different energies and travel simultaneously within the same beampipe, as shown in this simulation.

    Brooks worked with George Mahler and Steven Trabocchi, engineers in Brookhaven’s Collider-Accelerator Department, to assemble the deceptively simple yet powerful magnets.

    First they used a 3D printer to create plastic frames to hold the shaped magnetic blocks, like pieces in a puzzle, around the central aperture. “Different sizes, or block thicknesses, and directions of magnetism allow a customized field within the aperture,” Brooks said.

    After the blocks were tapped into the frames with a mallet to create a coarse assembly, John Cintorino, a technician in Lab’s magnet division, measured the strength of the field. The team then fine-tuned each assembly by inserting different lengths of iron rods into as many as 64 positions around a second 3D-printed cartridge that fits within the ring of magnets. A computational program Brooks wrote uses the coarse assembly field-strength measurements to determine exactly how much iron goes into each slot. He’s also currently working on a robot to custom cut and insert the rods.

    The end-stage fine-tuning “compensates for any errors in machining and positioning of the magnet blocks,” Brooks said, improving the quality of the field 10-fold over the coarse assembly. The final magnets’ properties match or even surpass those of sophisticated electromagnets, which require much more precise engineering and machining to create each individual piece of metal.

    “The only high-tech equipment in our setup is the rotating coil we use to do the precision measurements,” he said.

    Applications and next steps

    The lightweight, compact components and simplified operation of Brooks’ permanent magnet beam transport line would be “a dramatic improvement from what is currently on the market for delivering particle beams in cancer treatment centers,” said Dejan Trbojevic, Brooks’ supervisor, who holds several patents on designs for particle therapy gantries.

    A gantry is the arced beamline that delivers cancer-killing particles from an accelerator to a patient. In some particle therapy facilities the gantry and supporting infrastructure can weigh 50 tons or more, often occupying a specially constructed wing of a hospital. Trbojevic estimates that a gantry using Brooks’ compact design would weigh just one ton. That would bring down the cost of constructing such facilities.

    “Plus with no need for electricity [to the magnets] to change field strengths, it would be much easier to operate,” Trbojevic said.

    The ability to accelerate particles rapidly to higher and higher energy levels within a single accelerator ring could also bring down the cost of proposed future physics experiments, including a muon collider, a neutrino factory, and an electron-ion collider (EIC). In these cases, additional accelerator components would boost the beams to higher energy.

    For example, Brookhaven physicists have been collaborating with physicists at Cornell University on a similar fixed-field design called CBETA. That project, developed with funding from the New York State Energy Research and Development Authority (NYSERDA), is a slightly larger version of Brooks’ machine and includes all the accelerator components for bringing electron beams up to the energies required for an EIC. CBETA also decelerates electrons once they’ve been used for experiments to recover and reuse most of the energy. It will also test beams of multiple energies at the same time, something Brooks’ proof-of-principle experiment at the ATF did not do. But Brooks’ successful test strengthens confidence that the CBETA design is sound.

    “Everyone in Brookhaven’s Collider-Accelerator Department has been very supportive of this project,” said Trbojevic, Brookhaven’s Principal Investigator on CBETA.

    As Collider-Accelerator Department Chair Thomas Roser noted, “All these efforts are working toward advanced accelerator concepts that will ultimately benefit science and society as a whole. We’re looking forward to the next chapter in the evolution of this technology.”

    The magnets for Brooks’ experiment were built with Brookhaven’s Laboratory Directed Research and Development funds for the CBETA project as part of the R&D effort for an early version of Brookhaven’s proposed design for an EIC, known as eRHIC. Operation of the ATF is supported by the DOE Office of Science.

    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.
    i1

     
  • richardmitnick 11:32 am on August 14, 2017 Permalink | Reply
    Tags: Accelerator Science, ATLAS sees first direct evidence of light-by-light scattering at high energy, , , , ,   

    From ATLAS at CERN: “ATLAS sees first direct evidence of light-by-light scattering at high energy” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    14th August 2017
    Katarina Anthony

    1
    A light-by-light scattering candidate event measured in the ATLAS detector. (Image: ATLAS Collaboration/CERN).

    Physicists from the ATLAS experiment at CERN have found the first direct evidence of high energy light-by-light scattering, a very rare process in which two photons – particles of light – interact and change direction. The result, published today in Nature Physics , confirms one of the oldest predictions of quantum electrodynamics (QED).

    “This is a milestone result: the first direct evidence of light interacting with itself at high energy,” says Dan Tovey (University of Sheffield), ATLAS Physics Coordinator. “This phenomenon is impossible in classical theories of electromagnetism; hence this result provides a sensitive test of our understanding of QED, the quantum theory of electromagnetism.”

    Direct evidence for light-by-light scattering at high energy had proven elusive for decades – until the Large Hadron Collider’s second run began in 2015. As the accelerator collided lead ions at unprecedented collision rates, obtaining evidence for light-by-light scattering became a real possibility. “This measurement has been of great interest to the heavy-ion and high-energy physics communities for several years, as calculations from several groups showed that we might achieve a significant signal by studying lead-ion collisions in Run 2,” says Peter Steinberg (Brookhaven National Laboratory), ATLAS Heavy Ion Physics Group Convener.

    Heavy-ion collisions provide a uniquely clean environment to study light-by-light scattering. As bunches of lead ions are accelerated, an enormous flux of surrounding photons is generated. When ions meet at the centre of the ATLAS detector, very few collide, yet their surrounding photons can interact and scatter off one another. These interactions are known as ‘ultra-peripheral collisions’.

    Studying more than 4 billion events taken in 2015, the ATLAS collaboration found 13 candidates for light-by-light scattering. This result has a significance of 4.4 standard deviations, allowing the ATLAS collaboration to report the first direct evidence of this phenomenon at high energy.

    “Finding evidence of this rare signature required the development of a sensitive new ‘trigger’ for the ATLAS detector,” says Steinberg. “The resulting signature — two photons in an otherwise empty detector — is almost the diametric opposite of the tremendously complicated events typically expected from lead nuclei collisions. The new trigger’s success in selecting these events demonstrates the power and flexibility of the system, as well as the skill and expertise of the analysis and trigger groups who designed and developed it.”

    ATLAS physicists will continue to study light-by-light scattering during the upcoming LHC heavy-ion run, scheduled for 2018. More data will further improve the precision of the result and may open a new window to studies of new physics. In addition, the study of ultra-peripheral collisions should play a greater role in the LHC heavy-ion programme, as collision rates further increase in Run 3 and beyond.

    See the full article here .

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  • richardmitnick 4:07 pm on August 11, 2017 Permalink | Reply
    Tags: Accelerator Science, , , FAST- Fermilab Accelerator Science and Technology facility,   

    From Symmetry: “Think FAST” 

    Symmetry Mag

    Symmetry

    08/10/17
    Leah Poffenberger

    1
    Photo by Reidar Hahn, Fermilab

    The new Fermilab Accelerator Science and Technology [FAST] facility at Fermilab looks to the future of accelerator science.

    Unlike most particle physics facilities, the new Fermilab Accelerator Science and Technology facility (FAST) wasn’t constructed to find new particles or explain basic physical phenomena. Instead, FAST is a kind of workshop—a space for testing novel ideas that can lead to improved accelerator, beamline and laser technologies.

    Historically, accelerator research has taken place on machines that were already in use for experiments, making it difficult to try out new ideas. Tinkering with a physicist’s tools mid-search for the secrets of the universe usually isn’t a great idea. By contrast, FAST enables researchers to study pieces of future high-intensity and high-energy accelerator technology with ease.

    “FAST is specifically aiming to create flexible machines that are easily reconfigurable and that can be accessed on very short notice,” says Alexander Valishev, head of department that manages FAST. “You can roll in one experiment and roll the other out in a matter of days, maybe months, without expensive construction and operation costs.”

    This flexibility is part of what makes FAST a useful place for training up new accelerator scientists. If a student has an idea, or something they want to study, there’s plenty of room for experimentation.

    “We want students to come and do their thesis research at FAST, and we already have a number of students working.” Valishev says. “We have already had a PhD awarded on the basis of work done at FAST, but we want more of that.”

    2
    This yellow cyromodule will house the superconducting cavities that take the beam’s energy from 50 to 300 MeV. Courtesy of Fermilab.

    Small ring, bright beam

    FAST will eventually include three parts: an electron injector, a proton injector and a particle storage ring called the Integrable Optics Test Accelerator, or IOTA. Although it will be small compared to other rings—only 40 meters long, while Fermilab’s Main Injector has a circumference of 3 kilometers—IOTA will be the centerpiece of FAST after its completion in 2019. And it will have a unique feature: the ability to switch from being an electron accelerator to a proton accelerator and back again.

    “The sole purpose of this synchrotron is to test accelerator technology and develop that tech to test ideas and theories to improve accelerators everywhere,” says Dan Broemmelsiek, a scientist in the IOTA/FAST department.

    One aspect of accelerator technology FAST focuses on is creating higher-intensity or “brighter” particle beams.

    Brighter beams pack a bigger particle punch. A high-intensity beam could send a detector twice as many particles as is usually possible. Such an experiment could be completed in half the time, shortening the data collection period by several years.

    IOTA will test a new concept for accelerators called integrable optics, which is intended to create a more concentrated, stable beam, possibly producing higher intensity beams than ever before.

    “If this IOTA thing works, I think it could be revolutionary,” says Jamie Santucci, an engineering physicist working on FAST. “It’s going to allow all kinds of existing accelerators to pack in way more beam. More beam, more data.”

    3
    The beam starts here: Once electrons are sent down the beamline, they pass through the a set of solenoid magnets—the dark blue rings—before entering the first two superconducting cavities. Courtesy of Fermilab.

    Maximum energy milestone

    Although the completion of IOTA is still a few years away, the electron injector will reach a milestone this summer: producing an electron beam with the energy of 300 million electronvolts (MeV).

    “The electron injector for IOTA is a research vehicle in its own right,” Valishev says. It provides scientists a chance to test superconducting accelerators, a key piece of technology for future physics machines that can produce intense acceleration at relatively low power.

    “At this point, we can measure things about the beam, chop it up or focus it,” Broemmelsiek says. “We can use cameras to do beam diagnostics, and there’s space here in the beamline to put experiments to test novel instrumentation concepts.”

    The electron beam’s previous maximum energy of 50 MeV was achieved by passing the beam through two superconducting accelerator cavities and has already provided opportunities for research. The arrival of the 300 MeV beam this summer—achieved by sending the beam through another eight superconducting cavities—will open up new possibilities for accelerator research, with some experiments already planned to start as soon as the beam is online.

    4
    Electronics for IOTA. Chip Edstrom.

    FAST forward

    The third phase of FAST, once IOTA is complete, will be the construction of the proton injector.

    “FAST is unique because we will specifically target creating high-intensity proton beams,” Valishev says.

    This high-intensity proton beam research will directly translate to improving research into elusive particles called neutrinos, Fermilab’s current focus.

    “In five to 10 years, you’ll be talking to a neutrino guy and they’ll go, ‘I don’t know what the accelerator guys did, but it’s fabulous. We’re getting more neutrinos per hour than we ever thought we would,’” Broemmelsiek says.

    Creating new accelerator technology is often an overlooked area in particle physics, but the freedom to try out new ideas and discover how to build better machines for research is inherently rewarding for people who work at FAST.

    “Our business is science, and we’re supposed to make science, and we work really hard to do that,” Broemmelsiek says. “But it’s also just plain ol’ fun.”

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 12:05 pm on July 20, 2017 Permalink | Reply
    Tags: Accelerator Science, , , , ,   

    From CERN: “HIE-ISOLDE: Nuclear physics gets further energy boost” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    CERN

    17 July 2017
    Harriet Kim Jarlett

    CERN ISOLDE


    This is the Miniball germanium array, which is using the first HIE-ISOLDE beams for the experiments described below (Image: Julien Ordan /CERN)

    For the first time in 2017, the HIE- ISOLDE linear accelerator began sending beams to an experiment, marking the start of ISOLDE’s high-energy physics programme for this year.

    The HIE-ISOLDE (High-Intensity and Energy upgrade of ISOLDE) project incorporates a new linear accelerator (Linac) into CERN’s ISOLDE facility (which stands for the Isotope mass Separator On-Line). ISOLDE is a unique nuclear research facility, which produces radioactive nuclei (ones with too many, or too few, neutrons) that physicists use to research a range of topics, from studying the properties of atomic nuclei to biomedical research and to astrophysics.

    Although ISOLDE has been running since April, when the accelerator chain at CERN woke up from its technical stop over winter, HIE-ISOLDE had to wait until now as new components, specifically a new cryomodule, needed to be installed, calibrated, aligned and tested.

    Each cryomodule contains five superconducting cavities used to accelerate the beam to higher energies. With a third module installed, HIE-ISOLDE is able to accelerate the nuclei up to an average energy of 7.5 MeV per nucleon, compared with the 5.5 MeV per nucleon reached in 2016.

    This higher energy also allows physicists to study the properties of heavier isotopes – ones with a mass up to 200, with a study of 206 planned later this year, compared to last year when the heaviest beam was 142. From 2018, the HIE-ISOLDE Linac will contain four of these cryomodules and be able to reach up to 10 MeV per nucleon.

    “Each isotope we study is unique, so each experiment either studies a different isotope or a different property of that isotope. The HIE-ISOLDE linac gives us the ability to tailor make a beam for each experiment’s energy and mass needs,” explains Liam Gaffney, who runs the Miniball station where many of HIE-ISOLDE’s experiments are connected.

    The HIE-ISOLDE beams will be available until the end of November, with thirteen experiments hoping to use the facility during that time – more than double the number that took data last year. The first experiment, which begins today, will study the electromagnetic interactions between colliding nuclei of the radioactive isotope Selenium 72 and a platinum target. With this reaction they can measure whether or not the nuclei is more like a squashed disc or stretched out, like a rugby ball; or some quantum mechanical mixture of both shapes.

    See the full article here.

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    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New

    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

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  • richardmitnick 12:01 pm on July 9, 2017 Permalink | Reply
    Tags: Accelerator Science, , , , , , Probing physics beyond the Standard Model with heavy vector bosons   

    From ATLAS: “Probing physics beyond the Standard Model with heavy vector bosons” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    8th July 2017
    ATLAS Collaboration

    1
    Figure 1: The reconstructed mass of the selected candidate events decaying to WW or ZZ bosons, with the qqqq final state. The black markers represent the data. The blue and green curves represent the hypothesized signal for two different masses. The red curve represents the Standard Model processes. (Image: ATLAS Collaboration/CERN)

    Although the discovery of the Higgs boson by the ATLAS and CMS Collaborations in 2012 completed the Standard Model, many mysteries remain unexplained. For instance, why is the mass of the Higgs boson so much lighter than one would expect and why is gravity so weak?

    CERN CMS Higgs Event


    CERN ATLAS Higgs Event

    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.

    Numerous models beyond the Standard Model attempt to explain these mysteries. Some explain the apparent weakness of gravity by introducing additional dimensions of space in which gravity propagates. One model goes beyond that, and considers the real world as a higher-dimensional universe described by warped geometry, which leads to strongly interacting massive graviton states. Other models propose, for example, additional types of Higgs bosons.

    All these models predict the existence of new heavy particles that can decay into pairs of massive weak bosons (WW, WZ or ZZ). The search for such particles has benefited greatly from the increase in the proton–proton collision energy during Run 2 of the Large Hadron Collider (LHC).

    _______________________________________________________________________
    The search for new heavy particles has benefited greatly from the LHC’s increase in proton–proton collision energy.
    _______________________________________________________________________

    2
    Figure 2: The limit on the cross-section times branching ratio of hypothetical particle described by one of the models for the different final states. (Image: ATLAS Collaboration/CERN)

    The W and Z bosons are carrier particles that mediate the weak force. They decay into other Standard Model particles, like charged leptons (l), neutrinos (ν) and quarks (q). These particles are reconstructed differently in the detector. Quarks, for instance, are reconstructed as localized sprays of hadrons, denoted jets. The two bosons could yield several combinations of these particles in the final states. The ATLAS Collaboration has released results on searches involving all relevant decays of the boson pair: ννqq, llqq, lνqq and qqqq (where the lepton is an electron or muon).

    What do these searches have in common? In each of these, at least one of the bosons decays into a pair of quarks. When the sought-after particle is very massive, the two bosons from its decay are ejected with such large momenta that their respective decay products are collimated and the pair of quarks merge into a single large jet. This phenomenon provides a powerful means to distinguish the new physics signal from strong-interaction Standard Model processes. As some exemplary results of the searches, Figure 1 shows the distributions of the reconstructed mass of the candidate particle. Figure 2 shows the limit on the cross-section times branching ratio of a hypothetical particle described by one of the models.

    So far, no evidence of a new particle has been observed. The search continues with increased sensitivity as ATLAS collects more data.

    Links:
    See the full article for further references with links.

    See the full article here .

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

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

    New York Times

    The New York Times

    JULY 6, 2017
    KENNETH CHANG

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

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

    Physicists have discovered a particle that is doubly charming.

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

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

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

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

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

    LHC

    CERN/LHC Map

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

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

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

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

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

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

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

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

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

    FNAL Tevatron

    FNAL/Tevatron map


    FNAL/Tevatron DZero detector


    FNAL/Tevatron CDF detector

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

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

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

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

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

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

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

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

    See the full article here .

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  • richardmitnick 8:51 am on July 7, 2017 Permalink | Reply
    Tags: Accelerator Science, , CERN Data Centre passes the 200-petabyte milestone, , ,   

    From CERN: “CERN Data Centre passes the 200-petabyte milestone” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    CERN

    6 July 2017
    Mélissa Gaillard

    1
    CERN’s Data Centre (Image: Robert Hradil, Monika Majer/ProStudio22.ch)

    On 29 June 2017, the CERN DC passed the milestone of 200 petabytes of data permanently archived in its tape libraries. Where do these data come from? Particles collide in the Large Hadron Collider (LHC) detectors approximately 1 billion times per second, generating about one petabyte of collision data per second. However, such quantities of data are impossible for current computing systems to record and they are hence filtered by the experiments, keeping only the most “interesting” ones. The filtered LHC data are then aggregated in the CERN Data Centre (DC), where initial data reconstruction is performed, and where a copy is archived to long-term tape storage. Even after the drastic data reduction performed by the experiments, the CERN DC processes on average one petabyte of data per day. This is how the the milestone of 200 petabytes of data permanently archived in its tape libraries was reached on 29 June.

    2
    This map shows the routes for the three 100 Gbit/s fibre links between CERN and the Wigner RCP. The routes have been chosen carefully to ensure we maintain connectivity in the case of any incidents. (Image: Google)

    See the full article here.

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  • richardmitnick 7:00 am on July 7, 2017 Permalink | Reply
    Tags: Accelerator Science, , , , ,   

    From ATLAS: “Why should there be only one? Searching for additional Higgs Bosons beyond the Standard Model” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    6th July 2017
    ATLAS Collaboration

    1
    Figure 1: Feynman diagram for leading order production of a neutral MSSM Higgs boson in association with b-quarks. (Image: ATLAS Collaboration/CERN)

    CERN CMS Higgs Event

    Since the discovery of the elusive Higgs boson in 2012, researchers have been looking beyond the Standard Model to answer many outstanding questions. An attractive extension to the Standard Model is Supersymmetry (SUSY), which introduces a plethora of new particles, some of which may be candidates for Dark Matter.

    Standard model of Supersymmetry DESY

    One of the most popular SUSY models – the Minimal Supersymmetric Standard Model (MSSM) – predicts the existence of five Higgs bosons. In this model, the recently discovered Higgs boson (h) would be considered to be the lightest of the set. Two charged Higgs (H+, H–) and two neutral Higgs (A/H) would complete the set, and could exist within a wide range of masses above that of the discovered Higgs boson. The LHC experiments are poised to search for these additional bosons using techniques similar to those used in the initial Higgs searches.

    In July 2017, the ATLAS collaboration presented a new result on the search for neutral (A/H) Higgs bosons decaying to two tau leptons. Taus are particularly interesting to the search as there is a stronger coupling between A/H and down-type fermions (e, μ, τ, d, s, b) for certain values of the MSSM parameter-space. This will enhance the probability of decays to tau leptons, as well as the production of A/H in association with b-quarks (Figure 1), providing a larger cross-section. Like with the Standard Model Higgs boson, gluon-fusion production of A/H remains an important production process in the MSSM to varying degrees (depending on the chosen model parameters). Thus, by classifying events by their probability of containing b-flavoured jets, the ATLAS search has been optimised for both b-associated and gluon-fusion production of A/H, respectively.

    2
    Figure 2 (left): The observed and expected 95% CL upper limits on the production cross section times di-tau branching fraction for a scalar boson produced via b-associated production. Figure 3 (right): The observed and expected 95% CL limits on tanβ as a function of the mass of the A boson in the hMSSM scenario. The area above the black curve has been excluded. The exclusion arising from the Standard Model Higgs boson coupling measurements and the exclusion limit from the ATLAS 2015 H/A→ ττ search are shown. (Images: ATLAS Collaboration/CERN)

    See the full article here .

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  • richardmitnick 1:18 pm on July 6, 2017 Permalink | Reply
    Tags: Accelerator Science, , , Chasing the invisible, , , ,   

    From ATLAS: “Chasing the invisible” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    6th July 2017
    ATLAS Collaboration

    1
    Figure 1: The second highest ETmiss monojet event in the 2016 ATLAS data. A jet with pT of 1707 GeV is indicated by the green and yellow bars corresponding to the energy deposition in the electromagnetic and hadronic calorimeters respectively. The ETmiss of 1735 GeV is shown as the white dashed line in the opposite side of the detector. No additional jets with pT above 30 GeV are found. (Image: ATLAS Collaboration/CERN)

    Cosmological and astrophysical observations based on gravitational interactions indicate that the matter described by the Standard Model of particle physics constitutes only a small fraction of the entire known Universe. These observations infer the existence of Dark Matter, which, if of particle nature, would have to be beyond the Standard Model.

    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.

    Although the existence of Dark Matter is well-established, its nature and properties still remain one of the greatest unsolved puzzles of fundamental physics. Excellent candidates for Dark Matter particles are weakly interacting massive particles (WIMPs). These “invisible” particles cannot be detected directly by collision experiments.

    At the LHC, most collisions of protons produce sprays of energetic particles that bundle together into so-called “jets”. Momentum conservation requires that if particles are reconstructed in one part of the detector there have to be recoiling particles in the opposite direction. However, if WIMPs are produced they will leave no trace in the detector, causing a momentum imbalance called “missing transverse momentum” (ETmiss). However, a pair of WIMPs can be produced together with a quark or gluon that is radiated from an incoming parton (a generic constituent of the proton) producing a jet which allows to tag this kind of events.

    The jets+ETmiss search looks at final states where a highly energetic jet is produced in association with large ETmiss. Many beyond the Standard Model theories can be probed by looking for an excess of events with large missing transverse momentum compared to the Standard Model expectation. Among those theories, Supersymmetry and models which foresee the existence of Large Extra Spatial Dimensions (LED), predict additional particles that are invisible to collider experiments. These theories could give an elegant explanation to several anomalies still unsolved in the Standard Model.

    2
    Figure 2: Missing transverse momentum distribution after the jets+ETmiss selection in data and in the Standard Model predictions. The different background processes are shown in different colors. The expected spectra of LED, Supersymmetric and WIMP scenarios are also illustrated with dashed lines. (Image: ATLAS Collaboration/CERN)

    The combination of data-driven techniques and high-precision theoretical calculations has allowed ATLAS to predict the main Standard Model background processes with great precision. The shape of the ETmiss spectrum is used to increase the discovery potential of the analysis and increase the discrimination power between signals and background.

    The figure shows the missing transverse momentum spectrum compared to the measurement with the Standard Model expectation. Since no significant excess is observed, the level of agreement between data and the prediction is translated into limits on unknown parameters of the Dark Matter, Supersymmetry and LED models.

    In the WIMP scenario, the latest analysis using data collected in 2015 and 2016 in a specific interaction model are able to exclude Dark Matter masses up to 440 GeV and interaction mediators up to 1.55 TeV. Under the considered model, these represent competitive results when compared with other experiments using different detection approaches.

    Over the next two years the LHC aims to increase the data available by a factor of three. This will be a unique opportunity for ATLAS to investigate the energy frontier and the jets+ETmiss channel will continue to hold the potential to profoundly revise our understanding of the universe.

    Links:

    Search for dark matter and other new phenomena in events with an energetic jet and large missing transverse momentum using the ATLAS detector (ATLAS-CONF-2017-060): link coming soon
    EPS 2017 presentation by Shin-Shan Yu: Dark matter searches at colliders
    See also the full lists of ATLAS Conference Notes and ATLAS Physics Papers.

    See the full article here .

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