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  • richardmitnick 10:17 am on October 9, 2019 Permalink | Reply
    Tags: Accelerator Science, , CERN FCC Future Circular Collider, China Circular Electron Positron Collider (CEPC), , , , , ,   

    From CERN Courier: “European strategy [for HEP] enters next phase” 

    From CERN Courier

    2 October 2019

    Matthew Chalmers, editor

    European strategy enters next phase

    Physicists in Europe have published a 250-page “briefing book” to help map out the next major paths in fundamental exploration. Compiled by an expert physics-preparatory group set up by the CERN Council, the document is the result of an intense effort to capture the status and prospects for experiment, theory, accelerators, computing and other vital machinery of high-energy physics.

    Last year, the European Strategy Group (ESG) — which includes scientific delegates from CERN’s member and associate-member states, directors and representatives of major European laboratories and organisations and invitees from outside Europe — was tasked with formulating the next update of the European strategy for particle physics. Following a call for input in September 2018, which attracted 160 submissions, an open symposium was held in Granada, Spain, on 13-16 May at which more than 600 delegates discussed the potential merits and challenges of the proposed research programmes. The ESG briefing book distills input from the working groups and the Granada symposium to provide an objective scientific summary.

    “This document is the result of months of work by hundreds of people, and every effort has been made to objectively analyse the submitted inputs,” says ESG chair Halina Abramowicz of Tel Aviv University. “It does not take a position on the strategy process itself, or on individual projects, but rather is intended to represent the forward thinking of the community and be the main input to the drafting session in Germany in January.”

    Collider considerations

    An important element of the European strategy update is to consider which major collider should follow the LHC. The Granada symposium revealed there is clear support for an electron–positron collider to study the Higgs boson in greater detail, but four possible options at different stages of maturity exist: an International Linear Collider (ILC) in Japan, a Compact Linear Collider (CLIC) or Future Circular Collider (FCC-ee) at CERN, and a Circular Electron Positron Collider (CEPC) in China. The briefing book states that, in a global context, CLIC and FCC-ee are competing with the ILC and with CEPC. As Higgs factories, however, the report finds all four to have similar reach, albeit with different time schedules and with differing potentials for the study of physics topics at other energies.

    ILC schematic, being planned for the Kitakami highland, in the Iwate prefecture of northern Japan

    CLIC Collider annotated

    CERN FCC Future Circular Collider details of proposed 100km-diameter successor to LHC

    China Circular Electron Positron Collider (CEPC) map

    Also considered in depth are design studies in Europe for colliders that push the energy frontier, including a 3 TeV CLIC and a 100 TeV circular hadron collider (FCC-hh). The briefing book details the estimated timescales to develop some of these technologies, observing that the development of 16 T dipole magnets for FCC-hh will take a comparable time (about 20 years) to that projected for novel acceleration technologies such as plasma-wakefield techniques to reach conceptual designs.

    “The Granada symposium and the briefing book mention the urgent need for intensifying accelerator R&D, including that for muon colliders,” says Lenny Rivkin of Paul Scherrer Institut, who was co-convener of the chapter on accelerator science and technology. “Another important aspect of the strategy update is to recognize the potential impact of the development of accelerator and associated technology on the progress in other branches of science, such as astroparticle physics, cosmology and nuclear physics.”

    The bulk of the briefing book details the current physics landscape and prospects for progress, with chapters devoted to electroweak physics, strong interactions, flavour physics, neutrinos, cosmic messengers, physics beyond the Standard Model, and dark-sector exploration. A preceding chapter about theory emphasises the importance of keeping theoretical research in fundamental physics “free and diverse” and “not only limited to the goals of ongoing experimental projects”. It points to historical success stories such as Peter Higgs’ celebrated 1964 paper, which had the purely theoretical aim to show that Gilbert’s theorem is invalid for gauge theories at a time when applications to electroweak interactions were well beyond the horizon.

    “While an amazing amount of progress has been made in the past seven years since the Higgs boson discovery, our knowledge of the couplings of the Higgs-boson to the W and Z and to third-generation charged fermions is quite imprecise, and the couplings of the Higgs boson to the other charged fermions and to itself are unmeasured,” says Beate Heinemann of DESY, who co-convened the report’s electroweak chapter. “The imperative to study this unique particle further derives from its special properties and the special role it might play in resolving some of the current puzzles of the universe, for example dark matter, the matter-antimatter asymmetry or the hierarchy problem.”

    Readers are reminded that the discovery of neutrino oscillations constitutes a “laboratory” proof of physics beyond the Standard Model. The briefing book also notes the significant role played by Europe, via CERN, in neutrino-experiment R&D since the last strategy update concluded in 2013. Flavour physics too should remain at the forefront of the European strategy, it argues, noting that the search for flavour and CP violation in the quark and lepton sectors at different energy frontiers “has a great potential to lead to new physics at moderate cost”. An independent determination of the proton structure is needed if present and future hadron colliders are to be turned into precision machines, reports the chapter on strong interactions, and a diverse global programme based on fixed-target experiments as well as dedicated electron-proton colliders is in place.

    Europe also has the opportunity to play a leading role in the searches for dark matter “by fully exploiting the opportunities offered by the CERN facilities, such as the SPS, the potential Beam Dump Facility, and the LHC itself, and by supporting the programme of searches for axions to be hosted at other European institutions”. The briefing book notes the strong complementarity between accelerator and astrophysical searches for dark matter, and the demand for deeper technology sharing between particle and astroparticle physics.

    Scientific diversity

    The diversity of the experimental physics programme is a strong feature of the strategy update. The briefing book lists outstanding puzzles that did not change in the post-Run 2 LHC era – such as the origin of electroweak symmetry breaking, the nature of the Higgs boson, the pattern of quark and lepton masses and the neutrino’s nature – that can also be investigated by smaller scale experiments at lower energies, as explored by CERN’s dedicated Physics Beyond Colliders initiative.

    Finally, in addressing the vital roles of detector & accelerator development, computing and instrumentation, the report acknowledges both the growing importance of energy efficiency and the risks posed by “the limited amount of success in attracting, developing and retaining instrumentation and computing experts”, urging that such activities be recognized correctly as fundamental research activities. The strong support in computing and infrastructure is also key to the success of the high-luminosity LHC which, the report states, will see “a very dynamic programme occupying a large fraction of the community” during the next two decades – including a determination of the couplings between the Higgs boson and Standard Model particles “at the percent level”.

    Following a drafting session to take place in Bad Honnef, Germany, on 20-24 January, the ESG is due to submit its recommendations for the approval of the CERN Council in May 2020 in Budapest, Hungary.

    “Now comes the most challenging part of the strategy update process: how to turn the exciting and well-motivated scientific proposals of the community into a viable and coherent strategy which will ensure progress and a bright future for particle physics in Europe,” says Abramowicz. “Its importance cannot be overestimated, coming at a time when the field faces several crossroads and decisions about how best to maintain progress in fundamental exploration, potentially for generations to come.”

    See the full article here .

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    CERN/ATLAS detector


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  • richardmitnick 2:41 pm on October 7, 2019 Permalink | Reply
    Tags: "Watching the top quark mass run", Accelerator Science, , , , , ,   

    From CERN CMS: “Watching the top quark mass run” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN CMS

    CMS Collaboration

    A candidate event for a top quark–antiquark pair recorded by the CMS detector. Such an event is expected to produce an electron (green), a muon (red) of opposite charge, two high-energy “jets” of particles (orange) and a large amount of missing energy (purple) (Image: CMS/CERN)

    For the first time, CMS physicists have investigated an effect called the “running” of the top quark mass, a fundamental quantum effect predicted by the Standard Model.

    Mass is one of the most complex concepts in fundamental physics, which went through a long history of conceptual developments. Mass was first understood in classical mechanics as a measure of inertia and was later interpreted in the theory of special relativity as a form of energy. Mass has a similar meaning in modern quantum field theories that describe the subatomic world. The Standard Model of particle physics is such a quantum field theory, and it can describe the interaction of all known fundamental particles at the energies of the Large Hadron Collider.

    Quantum Chromodynamics is the part of the Standard Model that describes the interactions of fundamental constituents of nuclear matter: quarks and gluons. The strength of the interaction between these particles depends on a fundamental parameter called the strong coupling constant. According to Quantum Chromodynamics, the strong coupling constant rapidly decreases at higher energy scales. This effect is called asymptotic freedom, and the scale evolution is referred to as the “running of the coupling constant.” The same is also true for the masses of the quarks, which can themselves be understood as fundamental couplings, for example, in connection with the interaction with the Higgs field. In Quantum Chromodynamics, the running of the strong coupling constant and of the quark masses can be predicted, and these predictions can be experimentally tested.

    The experimental verification of the running mass is an essential test of the validity of Quantum Chromodynamics. At the energies probed by the Large Hadron Collider, the effects of physics beyond the Standard Model could lead to modifications of the running of mass. Therefore, a measurement of this effect is also a search for unknown physics. Over the past decades, the running of the strong coupling constant has been experimentally verified for a wide range of scales. Also, evidence was found for the running of the masses of the charm and beauty quarks.

    Figure 1: Display of an LHC collision detected by the CMS detector that contains a reconstructed top quark-antiquark pair. The display shows an electron (green) and a muon (red) of opposite charge, two highly energetic jets (orange) and a large amount of missing energy (purple).

    With a new measurement, the CMS Collaboration investigates for the first time the running of the mass of the heaviest of the quarks: the top quark. The production rate of top quark pairs (a quantity that depends on the top quark mass) was measured at different energy scales. From this measurement, the top quark mass is extracted at those energy scales using theory predictions that predict the rate at which top quark-antiquark pairs are produced.

    Figure 2: The running of the top quark mass determined from the data (black points) compared to the theoretical prediction (red line). As the absolute scale of the top quark mass is not relevant for this measurement, the values have been normalised to the second data point.

    Experimentally, interesting top quark pair collisions are selected by searching for the specific decay products of a top quark-antiquark pair. In the overwhelming majority of cases, top quarks decay into an energetic jet and a W boson, which in turn can decay into a lepton and a neutrino. Jets and leptons can be identified and measured with high precision by the CMS detector, while neutrinos escape undetected and reveal themselves as missing energy. A collision that is likely the production of a top quark-antiquark pair as it is seen in the CMS detector is shown in Figure 1. Such a collision is expected to contain an electron, a muon, two energetic jets, and a large amount of missing energy.

    The measured running of the top quark mass is shown in Figure 2. The markers correspond to the measured points, while the red line represents the theoretical prediction according to Quantum Chromodynamics. The result provides the first indication of the validity of the fundamental quantum effect of the running of the top quark mass and opens a new window to test our understanding of the strong interaction. While a lot more data will be collected in the future LHC runs starting with Run 3 in 2021, this particular CMS result is mostly sensitive to uncertainties coming from the theoretical knowledge of the top quark in Quantum Chromodynamics. To witness the top quark mass running with even higher precision and maybe unveil signs of new physics, theory developments and experimental efforts will both be necessary. In the meantime, watch the top quark run!

    See the full article here.

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  • richardmitnick 10:39 am on September 30, 2019 Permalink | Reply
    Tags: "Stanford physicists funded to pursue ‘tabletop’ physics experiments", Accelerator Science, , , , , ,   

    From Stanford University: “Stanford physicists funded to pursue ‘tabletop’ physics experiments” 

    Stanford University Name
    From Stanford University

    September 25, 2019
    Ker Than
    (650) 723-9820

    Peter Graham and Savas Dimopoulos are among Stanford physicists working on smaller-scale devices to answer large questions. (Image credit: L.A. Cicero)

    With the future of large particle accelerators uncertain, Stanford theorists are exploring the use of smaller, more precise “tabletop” experiments to investigate fundamental questions in physics.

    The history of particle accelerators is one of seemingly constant one-upmanship. Ever since the 1920s, the machines – which spur charged particles to near light speeds before crashing them together – have grown ever larger, more complex and more powerful.

    Consider: When the 2-mile-long linear accelerator at SLAC National Accelerator Laboratory opened for business in 1966, it could boost electrons to energies of about 19 gigaelectronvolts. The Large Hadron Collider (LHC) at CERN, which finished construction in 2008, can boost protons to more than 700 times higher energy levels and resides in a massive elliptical tunnel wide enough to encircle a small town. Future supercolliders being planned by CERN, China and Japan promise to be even more immense and energetic (and also more expensive).

    CERN FCC Future Circular Collider map

    China Circular Electron Positron Collider (CEPC) map

    J-PARC Facility Japan Proton Accelerator Research Complex , located in Tokai village, Ibaraki prefecture, on the east coast of Japan

    The strategy has paid off handsomely with discoveries that have helped confirm the soundness of the Standard Model, our current best understanding of how nature’s fundamental forces and subatomic matter interact.

    As successful as particle accelerators have been, however, Stanford theorists Savas Dimopoulos and Peter Graham are betting that scientific treasures await discovery in the other direction as well. For years, the pair have argued that smaller and less expensive, but more sensitive, instruments could help answer stubborn mysteries in physics that have resisted the efforts of even the largest atom smashers – questions like “What is dark matter?” and “Do extra spatial dimensions exist?”

    “Peter and I and our group have been thinking about this for 15 years,” said Dimopoulos, who is the Hamamoto Family Professor at Stanford’s School of Humanities and Sciences. “We were sort of lonely but very happy because we were exploring new territory all the time and it was a lot of fun. We felt like eternal graduate students.”

    Scalpel vs. hammer

    But their ideas have been slowly gaining traction among physicists, and last fall the Gordon and Betty Moore Foundation awarded Stanford and SLAC researchers three grants totaling roughly $15 million to use quantum technologies to explore new fundamental physics. Key to these efforts are the kinds of small-scale, “tabletop” experiments (so-called because most of them would fit on a lab bench or in a modest-sized room) that Dimopoulos and Graham have long advocated for. “Everything is smaller, except for the ideas,” Dimopoulos quipped. “These types of experiments could help solve some very important problems in physics.”

    The instruments Dimopoulos and Graham have in mind exploit the weird properties of quantum mechanics – such as wave-particle duality and the seemingly telepathic link between entangled particles – to detect and measure minute signals and effects that particle accelerators are simply not attuned to.

    Tabletop experiments are considered high-risk, high-reward projects because they are generally cheaper to build and operate than colliders, said Asimina Arvanitaki, a theoretical physicist at the Perimeter Institute. “If you’re pitching a project that costs several billion dollars, you better have a very good reason for its existence and be reasonably sure you’re going to succeed,” added Arvanitaki, a former Stanford postdoc in Dimopoulos’ lab. “But the cost of tabletop experiments is so low, and the timescales for producing results is so short, that it takes some of that pressure off.”

    Building on existing technologies

    The Moore Foundation grants will fund three projects: Two are experimental and will focus on developing new technologies for detecting dark matter and measuring gravitational waves. But the third, worth about $2.5 million and awarded to Dimopoulos and Graham, will be used to further develop the theoretical underpinnings that will enable future experiments.

    “There’s been a history of particle accelerators discovering new physics and finding new particles, but it’s not clear that that can go on forever, so it’s important to think of other complementary ways to get at these underlying questions about nature,” said Ernie Glover, the Moore Foundation’s science program officer.

    Crucially, the experiments Dimopoulos and Graham are proposing rely on relatively mature, high-precision technologies that, for the most part, were developed with other uses in mind and for other fields, such as medicine and applied physics. “That’s what got us really excited,” Dimopoulos said. “We realized there were all these possibilities out there that particle theorists weren’t really thinking about.”

    A good example is nuclear magnetic resonance, or NMR, imaging, which forms the basis of magnetic resonance imaging, or MRI, a common medical scanning technique.

    A few years ago, Graham and others theorized that a proposed ultralightweight dark matter candidate called an axion could influence the nuclear spin of normal matter. Dark matter is thought to make up the bulk of the matter in the universe, but it has evaded every attempt so far at characterization. Excited, Graham contacted an atomic physicist at the University of California, Berkeley, named Dmitry Budker to discuss designing a dark matter detector based on this effect – only to discover that the technology already exists.

    “He said it’s going to work because what we were describing was basically NMR,” said Graham, a theoretical physicist at the Stanford Institute for Theoretical Physics.

    Graham and Budker teamed up with other physicists to design the Cosmic Axion Spin Precession Experiment, or “CASPEr,” which uses NMR (nuclear magnetic resonance) to detect axion and axion-like particles. These particles are predicted to have such weak interactions and low masses that they would never show up in a collider, which are better equipped to search for massive dark matter candidates such as WIMPs (weakly interacting massive particles).

    Similarly, another Moore Foundation-funded tabletop experiment called MAGIS-100 relies on atom interferometry technology initially developed in the 1990s as a general-purpose tool for making precise measurements. The project, a collaboration between Stanford’s Mark Kasevich and Jason Hogan and researchers at Fermilab and other universities, could potentially detect ripples in spacetime known as gravitational waves around 1 hertz, a frequency range beyond the sensitivity of most existing or even proposed detectors.

    Current gravitational wave detectors like LIGO are sensitive to the very final moments of the black hole collisions that generate the spacetime ripples, but MAGIS-100 could provide scientists with a much longer viewing window.

    “LIGO saw just a fraction of a second of the event, but the black holes were twirling around each other and generating gravitational waves for millions or billions of years before that. Those waves were just in lower frequency bands,” Graham said. “By looking at other frequencies, we could observe the black holes for longer and perhaps discover new gravitational wave sources.”


    Dimopoulos and Graham plan to use the Moore Foundation-funding to continue devising new schemes for co-opting technologies like NMR and atom interferometry in the service of fundamental physics research.

    “It’s that connection that’s hard,” Graham said. “The experimental physicists and engineers who develop the technologies aren’t necessarily thinking about what other deep, fundamental questions could be tested, and the theorists are often unaware that tools for testing their ideas already exist.”

    But Dimopoulos and Graham are now old hands at making such connections. “In principle, you have to know all possible technologies,” Graham said. “In practice, you just have to know the right ones, but it takes a nontrivial intuition to realize something like ‘Oh, wait a minute, it looks like this technique might actually be able to observe extra dimensions or some other new physics.’”

    In one sense, what Dimopoulos and Graham are advocating for is a return to the way physics was done before colliders came to play such an important role in physics and the division of physicists into primarily theoretical and experimental camps.

    “Before World War II, physics was just like what we’re doing right now,” Dimopoulos said. “Felix Bloch was both a theorist and an experimentalist, and so was Enrico Fermi. Even Einstein did experiments. There wasn’t a ready group of experimentalists that you could outsource your ideas to. You had to invent the techniques and look around at emerging technologies.”

    See the full article here .

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    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

  • richardmitnick 12:25 pm on September 29, 2019 Permalink | Reply
    Tags: "Ask Ethan: Why Are There Only Three Generations Of Particles?", Accelerator Science, , , , , ,   

    From Ethan Siegel: “Ask Ethan: Why Are There Only Three Generations Of Particles?” 

    From Ethan Siegel
    Sep 28, 2019

    The particles of the standard model, with masses (in MeV) in the upper right. The Fermions make up the left three columns (three generations); the bosons populate the right two columns. If a speculative idea like mirror-matter is correct, there may be a mirror-matter counterpart for each of these particles. (WIKIMEDIA COMMONS USER MISSMJ, PBS NOVA, FERMILAB, OFFICE OF SCIENCE, UNITED STATES DEPARTMENT OF ENERGY, PARTICLE DATA GROUP)

    With the discovery of the Higgs boson, the Standard Model is now complete. Can we be sure there isn’t another generation of particles out there?

    The Universe, at a fundamental level, is made up of just a few different types of particles and fields that exist amidst the spacetime fabric that composes otherwise empty space. While there may be a few components of the Universe that we don’t understand — like dark matter and dark energy — the normal matter and radiation not only well-understood, it’s perfectly well-described by our best theory of particles and their interactions: the Standard Model. There’s an intricate but ordered structure to the Standard Model, with three “generations” of particles. Why three? That’s what Peter Brouwer wants to know, asking:

    Particle families appear as a set of 3, characterised by the electron, muon and tau families. The last 2 being unstable and decaying. So my question is: Is it possible that higher order particles exist? And if so, what energies might such particles be found? If not, how do we know that they don’t exist.

    This is a big question. Let’s dive in.

    The particles and antiparticles of the Standard Model have now all been directly detected, with the last holdout, the Higgs Boson, falling at the LHC earlier this decade. All of these particles can be created at LHC energies, and the masses of the particles lead to fundamental constants that are absolutely necessary to describe them fully. These particles can be well-described by the physics of the quantum field theories underlying the Standard Model, but they do not describe everything, like dark matter. (E. SIEGEL / BEYOND THE GALAXY)

    There are two classes of particles in the Standard Model: the fermions, which have half-integer spins (±½, ±1½, ±2½, etc.) and where every fermion has an antimatter (anti-fermion) counterpart, and the bosons, which have integer spins (0, ±1, ±2, etc.) and are neither matter nor antimatter. The bosons simply are what they are: 1 Higgs boson, 1 boson (photon) for the electromagnetic force, 3 bosons (W+, W- and Z) for the weak force, and 8 gluons for the strong force.

    The bosons are the force-carrying particles that enable the fermions to interact, but the fermions (and anti-fermions) carry fundamental charges that dictate which forces (and bosons) they’re affected by. While the quarks couple to all three forces, the leptons (and anti-leptons) don’t feel the strong force, and the neutrinos (and anti-neutrinos) don’t feel the electromagnetic force, either.

    This diagram displays the structure of the standard model (in a way that displays the key relationships and patterns more completely, and less misleadingly, than in the more familiar image based on a 4×4 square of particles). In particular, this diagram depicts all of the particles in the Standard Model (including their letter names, masses, spins, handedness, charges, and interactions with the gauge bosons: i.e., with the strong and electroweak forces). It also depicts the role of the Higgs boson, and the structure of electroweak symmetry breaking, indicating how the Higgs vacuum expectation value breaks electroweak symmetry, and how the properties of the remaining particles change as a consequence. Note that the Z boson couples to both quarks and leptons, and can decay through neutrino channels. (LATHAM BOYLE AND MARDUS OF WIKIMEDIA COMMONS)

    But what’s perhaps most puzzling about the Standard Model is that unlike the bosons, there are “copies” of the fermions. In addition to the fermionic particles that make up the stable or quasi-stable matter we’re familiar with:

    protons and neutrons (made of bound states of up-and-down quarks along with the gluons),
    atoms (made of atomic nuclei, which is made of protons and neutrons, as well as electrons),
    and electron neutrinos and electron antineutrinos (created in the nuclear reactions that involve building up to or decaying down from pre-existing nuclear combinations),

    there are two additional generations of heavier particles for each of these. In addition to the up-and-down quarks and antiquarks in 3 colors apiece, there are also the charm-and-strange quarks plus the top-and-bottom quarks. In addition to the electron, the electron neutrino and their antimatter counterparts, there are also the muon and muon neutrino, plus the tau and the tau neutrino.

    A four-muon candidate event in the ATLAS detector at the Large Hadron Collider. (Technically, this decay involves two muons and two anti-muons.) The muon/anti-muon tracks are highlighted in red, as the long-lived muons travel farther than any other unstable particle. The energies achieved by the LHC are sufficient for creating Higgs bosons; previous electron-positron colliders could not achieve the necessary energies. (ATLAS COLLABORATION/CERN)

    For some reason, there are three copies, or generations, of fermionic particles that show up in the Standard Model. The heavier versions of these particles don’t spontaneously arise from conventional particle interactions, but will show up at very high energies.

    In particle physics, you can create any particle-antiparticle pair at all so long as you have enough available energy at your disposal. How much energy do you need? Whatever the mass of your particle is, you need enough energy to create both it and its partner antiparticle (which happens to always have the same mass as its particle counterpart). From Einstein’s E = mc², which details the conversion between mass and energy, so long as you have enough energy to make them, you can. This is exactly how we create particles of all types from high-energy collisions, like the kind occurring in cosmic rays or at the Large Hadron Collider.

    Cosmic rays produced by high-energy astrophysics sources (ASPERA collaboration – AStroParticle ERAnet)


    CERN map

    CERN LHC Maximilien Brice and Julien Marius Ordan

    CERN LHC particles



    CERN ATLAS Image Claudia Marcelloni CERN/ATLAS


    CERN/ALICE Detector

    CERN CMS New

    CERN LHCb New II

    A decaying B-meson, as shown here, may decay more frequently to one type of lepton pair than the other, contradicting Standard Model expectations. If this is the case, we’ll either have to modify the Standard Model or incorporate a new parameter (or set of parameters) into our understanding of how these particles behave, as we needed to do when we discovered that neutrinos had mass. (KEK / BELLE COLLABORATION)

    KEK-Accelerator Laboratory

    KEK Belle detector, at the High Energy Accelerator Research Organisation (KEK) in Tsukuba, Ibaraki Prefecture, Japan

    By the same token, whenever you create one of these unstable quarks or leptons (leaving neutrinos and antineutrinos aside), there’s always the possibility that they’ll decay to a lighter particle through the weak interactions. Because all the Standard Model fermions couple to the weak force, it’s only a matter of a fraction-of-a-second before any of the following particles — strange, charm, bottom, or top quarks, as well as the muon or tau leptons — decay down to that stable first generation of particles.

    As long as it’s energetically allowed and not forbidden by any of the other quantum rules or symmetries that exist in our Universe, the heavier particles will always decay in this fashion. The big question, though, of why there are three generations, is driven not by theoretical motivations, but by experimental results.

    The first muon ever detected, along with other cosmic ray particles, was determined to be the same charge as the electron, but hundreds of times heavier, due to its speed and radius of curvature. The muon was the first of the heavier generations of particles to be discovered, dating all the way back to the 1930s. (PAUL KUNZE, IN Z. PHYS. 83 (1933))

    The muon is the lightest of the fermions to extend beyond the first generation of particles, and caused the famed physicist I. I. Rabi to exclaim, when he was shown the evidence of this particle “who ordered that?” As particle accelerators became more ubiquitous and more energetic over the next decades, particles like mesons and baryons, including ones with strange quarks and later charmed quarks, soon surfaced.

    However, it was only with the advent of the Mark I experiment at SLAC in the 1970s (which co-discovered the charm quark) that evidence for a third generation arose: in the form of the tau (and anti-tau) lepton. That 1976 discovery is now 43 years old. In the time since, we’ve directly detected every particle in the Standard Model, including all of the quarks and neutrinos and anti-neutrinos. Not only have we found them, but we’ve measured their particle properties exquisitely.

    The rest masses of the fundamental particles in the Universe determine when and under what conditions they can be created, and also describe how they will curve spacetime in General Relativity. The properties of particles, fields, and spacetime are all required to describe the Universe we inhabit. (FIG. 15–04A FROM UNIVERSE-REVIEW.CA)

    Based on all we now know, we should be able to predict how these particles interact with themselves and one another, how they decay, and how they contribute to things like cross-sections, scattering amplitudes, branching ratios and event rates for any particle we choose to examine.

    The structure of the Standard Model is what enables us to do these calculations, and the particle content of the Standard Model enables us to predict which light particles the heavier ones will decay into. Perhaps the strongest example is the Z-boson, the neutral particle that mediates the weak force. The Z-boson is the third most massive particle known, with a rest mass of 91.187 GeV/c²: nearly 100 times more massive than a proton. Every time we create a Z-boson, we can experimentally measure the probability that it will decay into any particular particle or combinations of particles.

    At LEP, the large electron-positron collider, thousands upon thousands of Z-bosons were created, and the decays of those Z particles were measured to reconstruct what fraction of Z-bosons became various quark and lepton combinations. The results clearly indicate that there are no fourth-generation particles below 45 GeV/c² in energy. (CERN / ALEPH COLLABORATION)

    CERN LEP Collider

    For detecting the direction and momenta of charged particles with extreme accuracy, the ALEPH detector had at its core a time projection chamber, for years the world’s largest. In the foreground from the left, Jacques Lefrancois, Jack Steinberger, Lorenzo Foa and Pierre Lazeyras. ALEPH was an experiment on the LEP accelerator, which studied high-energy collisions between electrons and positrons from 1989 to 2000.

    By examining what fraction of the Z-bosons we create in accelerators decay to:

    electron/positron pairs,
    muon/anti-muon pairs,
    tau/anti-tau pairs,
    and “invisible” channels (i.e., neutrinos),

    we can determine how many generations of particles there are. As it turns out, 1-out-of-30 Z-bosons decay to each of electron/positron, muon/anti-muon, and tau/anti-tau pairs, while a total out of 1-in-5 Z-boson decays are invisible. According the Standard Model and our theory of particles and their interactions, that translates to 1-in-15 Z-bosons (with ~6.66% odds) will decay to each of the three types of neutrinos that exist.

    These results tell us that if there is a fourth (or more) generation of particles, every single one of them, including leptons and neutrinos, have a mass that’s greater than 45 GeV/c²: a threshold that only the Z, W, Higgs, and top particles are known to exceed.

    The final results from many different particle accelerator experiments have definitively showed that the Z-boson decays to charged leptons about 10% of the time, neutral leptons about 20%, and hadrons (quark-containing particles) about 70% of the time. This is consistent with 3 generations of particles and no other number. (CERN / LEP COLLABORATION)

    Now, there’s nothing forbidding a fourth generation from existing and being much, much heavier than any of the particles we’ve observed so far; theoretically, it’s very much allowed. But experimentally, these collider results aren’t the only thing constraining the number of generational species in the Universe; there’s another constraint: the abundance of the light elements that were created in the early stages of the Big Bang.

    When the Universe was approximately one second old, it contains only protons, neutrons, electrons (and positrons), photons, and neutrinos and anti-neutrinos among the Standard Model particles. Over those first few minutes, protons and neutrons will eventually fuse to form deuterium, helium-3, helium-4, and lithium-7.

    The predicted abundances of helium-4, deuterium, helium-3 and lithium-7 as predicted by Big Bang Nucleosynthesis, with observations shown in the red circles. Note the key point here: a good scientific theory (Big Bang Nucleosynthesis) makes robust, quantitative predictions for what should exist and be measurable, and the measurements (in red) line up extraordinarily well with the theory’s predictions, validating it and constraining the alternatives. The curves and the red line are for 3 neutrino species; more or fewer lead to results that conflict with the data severely, particularly for deuterium and helium-3. (NASA / WMAP SCIENCE TEAM)

    But how much will they form? That’s dependent on just a few parameters, like the baryon-to-photon ratio, which is commonly used to predict these abundances as the only parameter we vary.

    But we can vary any number of parameters we typically assume are fixed, such as the number of neutrino generations. From Big Bang Nucleosynthesis, as well as from the imprint of neutrinos on the leftover radiation glow from the Big Bang (the cosmic microwave background), we can conclude that there are three — not two or fewer and not four or more — generations of particles in the Universe.

    The fit of the number of neutrino species required to match the CMB fluctuation data. Since we know there are three neutrino species, we can use this information to infer the temperature-equivalent of massless neutrinos at these early times, and arrive at a number: 1.96 K, with an uncertainty of just 0.02 K. (BRENT FOLLIN, LLOYD KNOX, MARIUS MILLEA, AND ZHEN PAN (2015) PHYS. REV. LETT. 115, 091301)

    It is eminently possible that there are more particles out there than the Standard Model, as we know it, presently predicts. In fact, given all the components of the Universe that aren’t accounted for in the Standard Model, from dark matter to dark energy to inflation to the origin of the matter-antimatter asymmetry, it’s practically unreasonable to conclude that there aren’t additional particles.

    But if the additional particles fit into the structure of the Standard Model as an additional generation, there are tremendous constraints. They could not have been created in great abundance during the early Universe. None of them can be less massive than 45.6 GeV/c². And they could not imprint an observable signature on the cosmic microwave background or in the abundance of the light elements.

    Experimental results are the way we learn about the Universe, but the way those results fit into our most successful theoretical frameworks is how we conclude what else does and doesn’t exist in our Universe. Unless a future accelerator result surprises us tremendously, three generations is all we get: no more, no less, and nobody knows why.

    See the full article here .


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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

  • richardmitnick 12:21 pm on September 27, 2019 Permalink | Reply
    Tags: Accelerator Science, , , , , , ,   

    From Brookhaven National Lab: “U.S. ATLAS Phase I Upgrade Completed” 

    From Brookhaven National Lab

    September 27, 2019
    Stephanie Kossman
    (631) 344-8671

    Peter Genzer,
    (631) 344-3174

    Major upgrades to the ATLAS experiment at CERN will give unprecedented insight into open physics questions.

    Brookhaven physicist Shaochun Tang is shown with the new ATLAS trigger board he designed and engineered for the U.S. ATLAS Phase I Upgrade project.

    The ATLAS experiment at CERN’s Large Hadron Collider (LHC) is ready to begin another chapter in its search for new physics.

    CERN ATLAS Image Claudia Marcelloni

    A significant upgrade to the experiment, called the U.S. ATLAS Phase I Upgrade, has received Critical Decision-4 approval from the U.S. Department of Energy (DOE), signifying the completion of the project and a transition to operations.

    “This milestone will enable us to push the boundaries of our understanding, following the discovery of the Higgs boson at CERN, which resulted in the 2013 Nobel Prize in Physics,” said Project Director Jonathan Kotcher, a senior scientist at DOE’s Brookhaven National Laboratory. “The completion of this project is a major step in the physics campaign being mounted at the energy frontier, which integrates state-of-the-art accelerator and detector technology to probe the fundamental forces and particles of nature. We are very excited to turn to the physics and data analysis that all this hard work has enabled.”

    Led by Brookhaven Lab and Stony Brook University (SBU), the U.S. ATLAS Phase I Upgrade is the initial stage of a larger upgrade planned for the LHC—the High Luminosity Large Hadron Collider (HL-LHC) project.

    The goal is to substantially increase the LHC’s luminosity, enabling scientists to collect 10 times more data from particle collisions, observe very rare processes, and make new discoveries about the building blocks of matter. But first, long-term experiments like ATLAS needed to undergo initial upgrades to prepare for the coming years before the LHC will transition to the HL-LHC mode.

    “The ATLAS experiment has been at the forefront of high-energy particle physics exploration and discoveries for a decade now,” said Deputy Project Manager Marc-André Pleier, a physicist at Brookhaven. “While we have learned a lot so far, our current understanding of the universe cannot explain phenomena such as dark matter, dark energy, or antimatter/matter asymmetry. Providing these detector upgrades for ATLAS will enable us to study even rarer processes than ever before and shed light on poorly understood or unexplored corners of our understanding of how the universe works.”

    “The U.S. ATLAS Phase I Upgrade involved building modern electronics to replace ageing elements with more efficient ones, but it also provided the experiment with new and improved functionalities,” said Project Manager Christopher Bee, a senior scientist at SBU.

    Specifically, the project focused on three components of ATLAS: the trigger/data acquisition system, the liquid argon calorimeter, and the forward muon detector (known as the New Small Wheel). Combined, upgrades to these three components will provide scientists with the ability to collect data more efficiently and at higher data collection rates.

    “Every second, there are several billion proton-proton collision events detected by ATLAS, but only a few hundred are recorded,” said Bee. Those events are selected by the trigger system, which sifts through a wealth of uninteresting events to find ones that may point to new physics or rare Standard Model events. “The data acquisition system moves data from the detector through the trigger system, and then it puts the selected events onto storage for further analysis. Upgrades to this system will improve its ability to select key events.”

    Upgrades to the calorimeter electronics will increase the precision of data coming out of the calorimeter detector. The New Small Wheel will dramatically improve ATLAS’s triggering capability and efficiency for events with muons, subatomic particles known as the “heavy cousins” of electrons.

    “In the experiment’s initial runs, the muon trigger had a substantial ‘fake’ muon rate,” said Pleier. “It was giving the ‘OK’ to accept a large fraction of events that were not interesting. The principle goal of the new small wheel is to reduce the fake trigger rate dramatically.”

    12 U.S. universities and DOE’s Argonne National Laboratory collaborated with Brookhaven Lab and SBU to complete the U.S. ATLAS Phase I Upgrade on time and under budget. This $44 million upgrade project was supported by DOE ($33 million) and the National Science Foundation (NSF) ($11 million).

    “We very much appreciate the support from both DOE and NSF that has allowed us to realize our goals in helping prepare ATLAS for a bright future,” said Bee. “We look forward to capitalizing on the new scientific opportunities enabled by these upgrades.”

    See the full article here .


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    BNL Campus

    BNL Center for Functional Nanomaterials



    BNL RHIC Campus

    BNL/RHIC Star Detector


    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.

  • richardmitnick 11:28 am on September 25, 2019 Permalink | Reply
    Tags: Accelerator Science, , , In 2018 the NA62 team reported finding one candidate event for the K+ → π+ ν ν decay in a dataset recorded in 2016 that comprised about 100 billion K+ decays., , , , , The NA62 experiment produces positively charged kaons (K+) and other particles by hitting a beryllium target with protons from the Super Proton Synchrotron accelerator., The transformation or “decay” of a positively charged variant of a particle known as kaon into a positively charged pion and a neutrino–antineutrino pair.   

    From CERN : “NA62 spots two potential instances of rare particle decay” 

    Cern New Bloc

    Cern New Particle Event

    From CERN

    23 September, 2019
    Ana Lopes

    The NA62 experiment has detected two candidate events for the decay of a positively charged kaon into a pion and a neutrino–antineutrino pair.

    CERN NA62

    CERN NA62

    CERN NA62 innards

    Are there new, unknown particles that can explain dark matter and other mysteries of the universe? To try to answer this question, particle physicists typically sift through the myriad of particles that are produced in particle collisions. But they also have an indirect but powerful way of looking for new particles, which is to measure processes that are both rare and precisely predicted by the Standard Model of particle physics. A slight discrepancy between the Standard Model prediction and a high-precision measurement would be a sign of new particles or phenomena never before observed.

    One such process is the transformation, or “decay”, of a positively charged variant of a particle known as kaon into a positively charged pion and a neutrino–antineutrino pair. In a seminar that took place today at CERN, the NA62 collaboration reported two potential instances of this ultra-rare kaon decay. The result, first presented at the International Conference on Kaon Physics, shows the experiment’s potential to make a precise test of the Standard Model.

    The Standard Model predicts that the odds of a positively charged kaon decaying into a positively charged pion and a neutrino–antineutrino pair (K+ → π+ ν ν) are only about one in ten billion, with an uncertainty of less than ten percent. Finding a deviation, even if small, from this prediction would indicate new physics beyond the Standard Model.

    The NA62 experiment produces positively charged kaons (K+) and other particles by hitting a beryllium target with protons from the Super Proton Synchrotron accelerator. It then uses several types of detector to identify and measure the K+ kaons and the particles into which they decay.

    In 2018, the NA62 team reported finding one candidate event for the K+ → π+ ν ν decay in a dataset recorded in 2016 that comprised about 100 billion K+ decays. In its new study, the collaboration analysed an approximately 10-fold larger dataset recorded in 2017 and spotted two candidate events. By combining this result with the previous result, the team finds that the relative frequency (known as “branching ratio”) of the K+ → π+ ν ν decay would be at most 24.4 in 100 billion K+ decays. This combined result is compatible with the Standard Model prediction and allowed the team to put limits on beyond-Standard-Model theories that predict frequencies larger than this upper bound.

    “This is a great achievement and one we will build upon. Having clearly established our experimental technique, we’ll now explore ways to perfect it using a dataset that we took in 2018,” says spokesperson Cristina Lazzeroni. “The 2018 dataset is twice as large as the 2017 dataset, so it should allow us to find more events and make a more precise test of the Standard Model.”

    For a detailed account of the results, see the recording of the CERN seminar and the EP newsletter article.

    See the full article here.

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    Meet CERN in a variety of places:

    Quantum Diaries

    Cern Courier



    CERN ATLAS Image Claudia Marcelloni CERN/ATLAS


    CERN/ALICE Detector

    CERN CMS New

    CERN LHCb New II


    CERN map

    CERN LHC Tunnel

    CERN LHC particles

  • richardmitnick 2:36 pm on September 24, 2019 Permalink | Reply
    Tags: A new efficient way to cool superconducting accelerator components, Accelerator Science, , , , , , Using cryogenic refrigerators or cryocoolers for removing the heat dissipated by a superconducting accelerator cavity.   

    From Fermi National Accelerator Lab: “Cool and dry: a revolutionary method for cooling a superconducting accelerator cavity” 

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    From Fermi National Accelerator Lab , an enduring source of strength for the US contribution to scientific research world wide.

    September 24, 2019
    Charles Thangaraj

    Fermilab scientists and engineers have achieved a landmark result in an ongoing effort to design and build compact, portable particle accelerators. Our group successfully demonstrated a new, efficient way to cool superconducting accelerator components, cutting down on the bulk of the traditional cooling infrastructure needed for this technology.

    The importance of this advance is apparent if you happen to walk around the Fermilab site. You really can’t miss it: Particle accelerators built for discovery are big machines. They stretch for hundreds of meters, even kilometers. They also require large and complex infrastructure, which restricts their use primarily to science research laboratories.

    And yet, particle accelerators are very useful tools outside science research labs. They have applications in security, medicine, manufacturing, and roadways. And their impact might be even greater if we could make these traditionally giant machines compact. Miniaturize them. Design high-power accelerators that could fit, literally, inside the back of a truck.

    For the first time, a team at Fermilab has cooled and operated a superconducting radio-frequency cavity — a crucial component of superconducting particle accelerators using cryogenic refrigerators, breaking the tradition of cooling cavities by immersing them in a bath of liquid helium. It achieved an accelerating gradient of 6.6 million volts per meter. Photo: Marty Murphy

    At Fermilab, we relish such practical physics challenges. And last month, our team rose to the challenge, achieving a major milestone in our quest to realize powerful, compact accelerators that have an impact on our everyday lives. The core team included Ram Dhuley, Michael Geelhoed, Sam Posen and Charles Thangaraj.

    Combining a verve for practicality with cutting-edge science, our team successfully demonstrated a new, revolutionary method for cooling a superconducting accelerator cavity without using liquid helium — counterintuitive for most in accelerator science.

    This new method — based on a Fermilab idea patented five years ago — uses cryogenic refrigerators, or cryocoolers, for removing the heat dissipated by a superconducting accelerator cavity. By compressing and expanding helium gas across a regenerative heat exchanger in a “closed” cycle, the cryocoolers produce cooling without letting the helium out. This closed-cycle operation of cryocoolers makes our system very compact — more so than the standard liquid helium cooling equipment used by traditional accelerator cavities.

    Superconducting cavities are crucial components in particle accelerators, propelling the particle beam to higher energies by giving it an electromagnetic push. We used a 650-megahertz niobium cavity, and we all watched with pride the first successful results delivered by our new method: an accelerator gradient of 6.6 million volts per meter. That is already sufficient for the applications we have in mind, and still, we know we can do better.

    Superconducting cavities used in large accelerators are usually cooled to around 2 kelvins, colder than the 2.7 kelvins (minus 455 degrees Fahrenheit) of outer space. The typical way to achieve this is by immersing the cavities in liquid helium and pumping on the helium to lower its pressure, and therefore its temperature. All of this requires large and complex cryogenic systems – a factor that severely limits the portability and therefore the potential applications of superconducting accelerators in industrial and other environments.

    Celebrating the success of the first results from the conduction-cooling project are, from left: Michael Geelhoed, Ram Dhuley, Sam Posen and Charles Thangaraj. Photo: Laura Rogas

    Our team broke this barrier by successfully realizing a technique conceptualized by Fermilab physicist Bob Kephart, now retired. The technique proposed to make superconducting accelerators practical by 1) coating a thin layer of a material called niobium-tin to the inside of the niobium cavities, and 2) cooling the coated cavities using cryocoolers via conduction links connecting the two. The cryocooler-cavity setup dispenses with a bath of cryogenic liquid and any need for a cryogenic plant to achieve superconductivity.

    The demonstration also shows how this method could simplify superconducting accelerators and make them accessible for broader needs beyond basic science – better pavements, wastewater treatment, medical device sterilization, and advanced manufacturing.

    Applying the scientific breakthroughs at Fermilab and transforming them to solve challenges outside fundamental science involves systematic entrepreneurial thinking – identifying an opportunity and asking and answering a whole host of questions to validate the opportunity. A great value in all of this is converting DOE’s investment in science and technology into innovation that could allow new industries to emerge.
    At Fermilab, we will continue to apply our frontier technologies for novel applications beyond discovery science. This major breakthrough is an exciting step in that direction, and we will continue to push the envelope.

    This project is supported by the Laboratory Directed Research and Development Program at Fermilab. The work is also supported by the DOE Office of Science.

    Charles Thangaraj is the science and technology manager at Fermilab’s Illinois Accelerator Research Center.

    See the full here.


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    FNAL Icon

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

  • richardmitnick 11:24 am on September 19, 2019 Permalink | Reply
    Tags: "How to Get a Particle Detector on a Plane", Accelerator Science, , , , , ,   

    From Lawrence Berkeley National Lab: “How to Get a Particle Detector on a Plane” 

    Berkeley Logo

    From Lawrence Berkeley National Lab

    September 19, 2019
    Glenn Roberts Jr.
    (510) 486-5582

    Berkeley Lab researchers have been assembling components for an upgrade of the ALICE particle collider experiment’s detector array at CERN laboratory. Learn about their work and how it could help to unravel the inner workings of an exotic state of matter known as the quark-gluon plasma in this short video. (Credit: Marilyn Chung/Berkeley Lab)

    You may have observed airplane passengers accompanied by pets or even musical instruments on flights. But have you ever been seated next to a particle detector?

    For more than a year, a small team at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has been working to assemble, test, and transport detector pieces for an upgrade of the ALICE (A Large Ion Collider Experiment) detector array at CERN laboratory in Europe.

    CERN/ALICE Detector

    Detector panels ride as ‘passengers’

    The Berkeley Lab team’s solution to ensuring that each of these carefully assembled, delicate pieces gets from Point A to Point B intact: treat them as travel companions.

    ALICE, a nuclear physics experiment, is designed to collide high-energy lead ions with one another and with protons to explore an exotic state of superhot matter known as quark-gluon plasma that is thought to have existed in the early universe.

    Berkeley Lab’s Nicole Apadula inspects a detector stave that was built for the ALICE inner tracking system detector upgrade at CERN laboratory. (Credit: Marilyn Chung/Berkeley Lab)

    Berkeley Lab is one of five sites around the globe that is building detector panels (called “staves”) for the upgrade project, which will improve the performance of the ALICE detector’s inner tracking system – including its resolution to take snapshots of particle collisions, its durability, and data-collection speed.

    Nuclear physics researchers at Berkeley Lab take turns in transporting four long detector staves at a time in a custom-built clear container equipped with a shoulder strap. When loaded, the meter-long container weighs about 25 pounds. The staves are stacked with sequences of silicon chips and related circuitry and power components.

    Each stave the Berkeley Lab team is responsible for has eight sensor modules, and each module is equipped with 14 sensors, for a total of 112 sensors per stave.

    This seat is taken

    “We ended up buying seats on commercial flights for them because there is no other reliable way to get them there,” said Leo Greiner, a staff scientist in Berkeley Lab’s Nuclear Science Division who leads the team working on the ALICE detector upgrade components.

    The team had used mechanical models of the detector modules to see how they would hold up in an airplane’s cargo hold, and they didn’t fare well: The units were visibly damaged, with some parts breaking off.

    “It was pretty clear the transportation couldn’t happen in the way we originally envisioned,” Greiner said. So he researched the best way to get the staves inside the cabin – a more protected environment. The rules for purchasing a seat for the staves are similar to those for expensive musical instruments that musicians want to hand-carry onto the plane, he said.

    The clear, Berkeley Lab-built carrying case is designed for ease of airport security inspections, and airport X-ray scans are not a problem as the detector components are designed to withstand far more intense radiation.

    Nicole Apadula holds a custom-built carrying case designed for four detector staves. The case is hand-carried aboard commercial flights to ensure safe transport of the detector components to CERN laboratory in Europe. (Credit: Marilyn Chung/Berkeley Lab)

    Once aboard the plane, researchers request a seatbelt extension to safely buckle the carrying case into the adjoining seat. Their usual route is to fly to Newark or Washington, D.C., from the San Francisco Bay Area, and then to connect to an international flight to Geneva, Switzerland. The round trip usually involves two full days of travel and two days at CERN to check for any damage to the components.

    Members of the Berkeley Lab team have completed about 14 of these trips over the past year, with the last trip scheduled for mid-October.

    Science outreach made easy

    The unusual carry-ons are quite a conversation starter, Greiner said.

    “It’s the most fantastic outreach I’ve ever done,” he said. “Everyone has questions.”

    Nikki Apadula, a project scientist in the Nuclear Science Division and a member of the ALICE team who has participated in the detector excursions, said, “I spent an entire trip to Newark using the back of the seat to explain what particles do in the detector.”

    Apadula said that the tall travel containers can be cumbersome at times. “The fact that these things are a meter long – it’s just awkward. It’s almost as tall as me.”

    Other members of the Berkeley Lab’s ALICE detector upgrade team, including research assistants Erica Zhang and Winston DeGraw, who both began working on the project as undergrads, have been the most frequent flyers on the detector trips.

    Assembling the staves

    The Berkeley Lab team is contributing 60 detector staves for the middle layers of ALICE’s upgraded outer-barrel detector – the largest contribution by a U.S. lab.

    The completed detector will have seven concentric layers that will hold a total of 24,000 silicon sensors for detecting particle interactions. It is scheduled for installation in March 2020, and will be operational in early 2021.

    Berkeley Lab’s Erica Zhang conducts measurements of a detector stave during assembly. (Credit: Marilyn Chung/Berkeley Lab)

    Detector assembly at Berkeley Lab was conducted in a specially constructed plastic-walled clean room environment. Researchers carefully measured and glued eight detector modules to each stave, with accuracy typically measured in tens of microns, or tens of millionths of a meter.

    The staves feature tubes that allow cool water to circulate along their length and prevent overheating, and all of the materials – down to the glue that affixes the detector modules – must be tested to ensure they can withstand the detector environment.

    Each stave features a wedge-shaped carbon-fiber support along its length, and aluminum electrical components rather than copper to provide better tracking resolution to capture the particle interactions while withstanding the barrage of radiation produced in particle collisions. In the early stages of the project the Berkeley Lab team used powerful charged-particle beams at Berkeley Lab’s 88-Inch Cyclotron to test the durability of the detector materials, Greiner noted.

    LBNL 88 inch cyclotron

    Next-gen detector design

    The detectors in the upgrade are based on a monolithic pixel detector technology – an earlier generation of this type of detector was used for the STAR (Solenoidal Tracker at RHIC) detector at Brookhaven National Laboratory’s Relativistic Heavy Ion Collider (RHIC).

    BNL/RHIC Star Detector

    Berkeley Lab has particular expertise in this type of detector, Greiner noted, and contributed to early R&D.

    The ALICE upgrade detectors are designed for a longer lifespan, can process signals about 10 times faster than earlier detectors, and have an individual pixel size of about 30 microns. The improved resolution will allow researchers to better differentiate particles produced in the initial lead nuclei collisions from those that branch out from the particle decays that follow these initial interactions.

    “The technology has really matured,” Greiner said. “They can take data more quickly, don’t die as quickly, and dissipate less power.”

    Other assembly sites for the new detectors are in China, England, France, Italy, the Netherlands, and Korea. The ALICE collaboration numbers about 1,500 scientists from over 100 physics institutes in 30 nations. Berkeley Lab participation in ALICE is supported by the U.S. DOE Office of Science’s Office of Nuclear Physics.

    These silicon chip components are prepared for placement on a detector stave. (Credit: Marilyn Chung/Berkeley Lab)

    See the full article here .


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    Bringing Science Solutions to the World
    In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

    Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

    Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

    A U.S. Department of Energy National Laboratory Operated by the University of California.

    University of California Seal

  • richardmitnick 3:30 pm on September 17, 2019 Permalink | Reply
    Tags: "LS2 Report: CMS set to glitter with installation of new GEMs", Accelerator Science, , GEMs-Gas Electron Multipliers, , , ,   

    From CERN CMS: “LS2 Report: CMS set to glitter with installation of new GEMs” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN CMS

    17 September, 2019
    Achintya Rao

    The GEMs being installed in CMS (Image: Maximilien Brice/CERN)

    Muons – heavy, weakly interacting particles – zip past the inner layers of the Compact Muon Solenoid (CMS), after being produced in collisions by the Large Hadron Collider (LHC). They are observed using special detectors placed on the periphery of the cylindrical device, where they are the particles most likely to register a signal. Although CMS, as the name suggests, was designed with the ability to observe with high precision nearly every muon produced within it, it will become more challenging to do so in a few years’ time. The High-Luminosity LHC (HL-LHC) will begin operations in 2026, providing on average over five times more simultaneous proton–proton collisions than before. Various components of CMS, including the muon system, are being upgraded during the ongoing second long shutdown (LS2) of CERN’s accelerator complex, in order to cope with the HL-LHC’s higher data rates.

    Muon detectors contain different mixtures of gases that get ionised when high-energy muons fly through them, providing information about where the muon was at a given instant. The CMS muon system has so far used three different types of detectors: Drift Tubes (DT), Cathode Strip Chambers (CSC) and Resistive Plate Chambers (RPC). Around a decade ago, at about the time that CMS began collecting LHC collision data, it was decided to build a completely new type of detector called Gas Electron Multipliers, or GEM, to improve the muon-detection abilities of CMS in the HL-LHC era. After extensive R&D, the first GEMs were assembled and tested at CERN’s Prévessin site in a dedicated fabrication facility. In July, two of 72 so-called “superchambers” of GEMs were transported carefully to Point 5 and installed within CMS. Each superchamber had a bottle of gas strapped on top of it on the trolley so the detector could keep “breathing” the inert air. The remaining 70 superchambers will be installed later in LS2.

    “The GEMs are new technology for CMS and Run 3 of the LHC will give us the opportunity to evaluate their performance,” says Archana Sharma, who has led the CMS-GEM team since 2009. “Of course,” she continues, “it’s not only there to be tested. The first GEMs will work with the existing CSCs to provide valuable triggering information to select the most interesting collision events.” Two more GEM stations with 288 and 216 modules respectively will be definitively installed in the coming years, in time for the HL-LHC.

    The muon-system team have been busy upgrading the electronics of the 180 CSCs located closest to the beam line to prepare for the HL-LHC. “We have already removed, refurbished and reinstalled 54 CSCs this year,” notes Anna Colaleo, CMS muon-system manager. “Work on replacing the electronics for another batch of CSCs is in progress and we plan on completing this endeavour by the summer of 2020.”

    A timelapse showing the extraction of CSCs from the CMS endcap and their transport to the refurbishment area on the surface (Video: CMS/CERN)

    CMS is also performing critical maintenance on the rest of the muon detectors during LS2. As expected, over the course of several years of operation, some components of these detectors have deteriorated slightly. The RPCs have been made more airtight to reduce gas leaks, while both DTs and RPCs have had some broken components replaced. In addition, neutron shielding is being added to the top of the DTs located in the central barrel to protect CMS from the neutron background caused by the particle beam interacting with the beam pipe.

    With nearly a year and a half of LS2 left, the CMS experiment site at LHC Point 5 continues to be a hub of activity as the collaboration prepares for the LHC’s Run 3 and beyond.

    See the full article here.

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  • richardmitnick 12:28 pm on September 13, 2019 Permalink | Reply
    Tags: Accelerator Science, , CBETA-Cornell-Brookhaven “Energy-Recovery Linac” Test Accelerator or, , , Innovative particle accelerator, , ,   

    From Brookhaven National Lab & Cornell University: “Innovative Accelerator Achieves Full Energy Recovery” 

    From Brookhaven National Lab

    September 10, 2019
    Karen McNulty Walsh

    Collaborative Cornell University/Brookhaven Lab project known as CBETA offers promise for future accelerator applications.

    Brookhaven Lab members of the CBETA team with Laboratory Director Doon Gibbs, front row, right.

    An innovative particle accelerator designed and built by scientists from the U.S. Department of Energy’s Brookhaven National Laboratory and Cornell University has achieved a significant milestone that could greatly enhance the efficiency of future particle accelerators. After sending a particle beam for one pass through the accelerator, machine components recovered nearly all of the energy required for accelerating the particles. This recovered energy can then be used for the next stage of acceleration—to accelerate another batch of particles—thus greatly reducing the potential cost of accelerating particles to high energies.

    “No new power is required to maintain the radiofrequency (RF) fields in the RF cavities used for acceleration, because the accelerated beam deposits its energy in the RF cavities when it is decelerated,” said Brookhaven Lab accelerator physicist Dejan Trbojevic, who led the design and construction of key components for the project and serves as the Principal Investigator for Brookhaven’s contributions.

    The prototype accelerator—known as the Cornell-Brookhaven ERL Test Accelerator (CBETA), where ERL stands for “energy-recovery linac”—was built at Cornell with funding from Brookhaven Science Associates (the managing entity of Brookhaven Lab) and the New York State Energy Research and Development Authority (NYSERDA) as a research and development project in support of a possible future nuclear physics facility, the Electron-Ion Collider (EIC). The energy-recovery approach could play an essential role in generating reusable electron beams for enhancing operations at a future EIC. The electrons would reduce the spread of ion beams in the EIC, thus increasing the number of particle collisions scientists can record to make physics discoveries.

    Schematic of the CBETA energy recovery linac installed at Cornell University. Electrons produced by a direct-current (DC) photo-emitter electron source are transported by a high-power superconducting radiofrequency (SRF) injector linac into the high-current main linac cryomodule, where SRF cavities accelerate them to high energy before sending them around the racetrack-shaped accelerator. Each curved arc is made of a series of fixed field, alternating gradient (FFA) permanent magnets. After passing through the second FFA arc, the electrons re-enter the main linac cryomodule, which decelerates them and returns their energy to the RF cavities so it can be used again.

    In designing and executing this project, the Brookhaven team drew on its vast experience of improving the performance of the Relativistic Heavy Ion Collider (RHIC), a DOE Office of Science user facility for nuclear physics research.


    The accelerator technologies being developed for the EIC would push beyond the capabilities at RHIC and open up a new frontier in nuclear physics.

    The injector and main linac cryomodule.

    Tech specs

    CBETA consists of a direct-current (DC) photo-emitter electron source that creates the electron beams to be accelerated. These electrons pass through a high-power superconducting radiofrequency (SRF) injector linac that transports them into a high-current main linac cryomodule (MLC). There, six SRF cavities accelerate the electrons to high energy, sending them around the racetrack-shaped accelerator. Each curved section of the racetrack is a single arc of permanent magnets designed with fixed-field alternating-gradient (FFA) optics that allow a single vacuum tube to accommodate beams at four different energies at the same time. After passing through the second FFA arc, the electrons re-enter the MLC, which has been uniquely optimized to decelerate the particles after a single pass and return their energy to the RF cavities so it can be used again.

    When completed, CBETA will accelerate particles through four complete turns, adding energy with each pass—all of which will be recovered during deceleration after the beams have been used. This will make it the world’s first four-turn superconducting radiofrequency ERL.

    Many scientists and engineers at Brookhaven Lab contributed to the design and construction of the magnets and other components of the accelerator, as well as the electronic devices that monitor the positions of the accelerated and decelerated beams: Francois Meot, Scott Berg, Stephen Brooks, and Nicholaos Tsoupas drove the design of the ERL’s optics; Brookhaven physicists led by Brooks and George Mahler designed, built, measured, and applied corrections to the permanent magnets; and Rob Michnoff led the design and construction of the beam position monitor system.

    “After building and successfully testing prototypes of the magnets, we established a very successful collaboration with Cornell, led by Principal Investigator Georg Hoffstaetter, to build the ERL using the refined fixed-field magnet designs,” Trbojevic said.

    Cornell provided the DC electron injector—the world’s record holder for producing high intensity, low emittance electron beams—which they recommissioned for the CBETA project. A team of young scientists and graduate students, including Adam Bartnik, Colwyn Gulliford, Kirsten Deitrick, and Nilanjan Banerjee, made other essential contributions: successfully commissioning the main linac cryomodule, and preparing the “command scripts”—computer-driven instructions—for running and commissioning the ERL in collaboration with Berg and other Brookhaven physicists.

    Part of one of the fixed field, alternating gradient (FFA) permanent magnet arcs.

    “We hold weekly internet-based collaboration meetings and we had several visits and meetings at Cornell to ensure that the project was reaching the key milestones and that installation was proceeding according to the schedule,” said Michnoff, the Brookhaven Lab project manager.

    In May 2019, the team sent an electron beam with an energy of 42 million electron volts (MeV) through the FFA return loop for the first time. The beam made it through all 200 permanent magnets without the need for a single correction. In early June 2019, an energy scan in the FFA loop showed that the return beamline transported particles of different energies superbly, agreeing very well with the expectations for the design.

    Next, on June 13, the beam was accelerated to 42 MeV, transported through the FFA return loop back to the MLC, where the electrons were decelerated from 42 MeV back to the injection energy of 6 MeV, with the rest of their energy transferred back into the six SRF cavities of the main linac. And on June 24, the CBETA team achieved full energy recovery for the first time—demonstrating that each cavity could accelerate electrons on their second pass through the MLC without requiring additional external power.

    “Each cavity successfully regained the energy it expended in beam acceleration, eliminating or dramatically reducing the power needed to accelerate electrons,” Trbojevic said.

    “The successful demonstration of single-turn energy recovery shows that we are on the path toward creating this first-of-its-kind facility,” Trbojevic said. “The entire team is committed and excited to complete this four-turn energy-recovery linac—one of the most interesting and innovative accelerator physics project in the world today.”

    From Cornell University



    Update on Beam Commissioning

    Cornell physicists, working with Brookhaven National Lab, are constructing a new type of particle accelerator called CBETA at Cornell’s Wilson Lab. This Energy Recovery Linac (ERL) is a test accelerator built with permanent magnets as well as electro magnets.

    How it works: CBETA will recirculate multiple beams of different energies around the accelerator at one time. The electrons will make four accelerating passes around the accelerator, while building up energy as they pass through a cryomodule with superconducting RF (SRF) accelerating structures. In four more passes, they will return to the superconducting cavities that accelerated them and return their energy back to these cavities – hence it is an Energy Recovery Linac (ERL). While this method conserves energy, it also creates beams that are tightly bound and are a factor of 1,000 times brighter than other sources. For more details, please contact the Cornell PI Prof. Georg Hoffstaetter.

    Although linear accelerators (Linac) can have superior beam densities when compared to large circular accelerators, 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 means that the amount of data collected in one hour in a circular accelerator may take several years to collect in a linear accelerator. In an ERL, the energy is recovered, and the beam current can therefore be as large as in a circular accelerator while its beam density remains as large as in a Linac.

    CBETA: the first multi-turn SRF ERL

    The lynchpin of CBETA’s design is to repeat the acceleration in a SRF cavities four times by recirculating multiple beams at four different energies. The beam with highest energy (150MeV) is to be used for experiments and is then decelerated in the same cavities four times to recapture the beam’s energies into the SRF cavities. Reusing the same cavity multiple times significantly reduces the construction and operational costs of the accelerator. It also means that an accelerator which would span roughly a foot ball field can fit into a single experimental Hall at Cornell’s Wilson Laboratory.

    However, beams of different energies require different amounts of bending, in the same way that it is hard for your car to navigate a sharp bend at 100 miles per hour. Traditional magnet designs are simply unable to keep different beams on the same “track”. Instead, the CBETA design relies on cutting edge Fixed-Field Alternating Gradient (FFAG) magnets to contain all of the beams in a single 3 inch beam pipe. CBETA will be the first SRF ERL with more than one turn and it is also the first project in the history of accelerator physics to implement this new magnet technology in an Energy Recovery Linac.

    The task of creating and controlling eight beams of four different energies in a single accelerating structure sounds daunting. But by leveraging the pre-existing infrastructure and experience of Cornell with the power and expertise of Brookhaven National Laboratory, it will soon become a reality.

    Cornell University has prototyped technology essential for CBETA, including a DC gun and an SRF injector Linac with world-record current and normalized brightness in a bunch train, a high-current CW cryomodule for 70 MeV energy gain, a high-power beam stop, and several diagnostics tools for high-current and high-brightness beams, e.g. a beamline for measuring 6-D phase-space densities, a fast wire scanner for beam profiles, and beam loss diagnostics. All these now being used in the contrition of CBETA.

    Within the next several years, CBETA will develop into a powerhouse of accelerator physics and technology, and will be one of the most advanced on the planet (earth). When this prototype ERL is complete and expanded upon, it will be a critical resource to New York State and the nation, propelling high-power accelerator science, enabling applications of many particle accelerators, from biomedical advancement to basic physics and from computer-chip lithography to material science, driving economic development.


    CBETA is composed of 4 main parts:

    -The Photoinjector that creates and prepares high-current electron beams to be injected into the Main Linac Cryomodule (MLC). The photoinjector in turn consists of a laser system that illuminates a photo-emitter cathode to produce electrons within a high-current DC electron source. These electrons traverses an emittance-matching section to produce a high-brightness beam which is then sent thorough the high-power injector cryomodule (ICM) for acceleration to the ERL’s injection energy.

    -The Main Linac Cryomodule (MLC) that accelerates the beam through several passages and then decelerates the beam the same number of times to recapture its energy.

    -The high-power Beam Stop where the electron beam is discarded after most of its energy has been recaptured.
    4 Spreaders and 4 combiners with electro magnets that separate beams at 4 different energies after the MLC to match them into the FFAG return loop and then combine them again before re-entering the MLC.

    -FFAG Magnets residing in the return loop. These cause very strong focusing so that beams with energies that differ by up to a factor 4 can be transported simultaneously.

    Dominant funding for CBETA comes from NYSERDA (2016 to 2020). Important for this agency is that CBETA emphasizes energy savings by its use of energy recovery technology, its application of permanent magnets, and its particle acceleration by superconducting structures. Previous funding came from the NSF (2005 – 2015) for the development of the complete accelerator chain from the source to the main ERL accelerating module, from DOE supporting developments for the LCLS (2014-2015), and from the industrial company ASML (2015-2016) for applications in computer chip lithography.

    See the full article here .


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    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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