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  • richardmitnick 8:42 pm on September 28, 2021 Permalink | Reply
    Tags: "LS2 report: The new LHC collimators", , , , HEP, , , , Sixteen new collimators have been installed in the accelerator over the last three years in preparation not only for the accelerator’s next period of operation (Run 3) but above all for the HL-LHC.   

    From CERN (CH) ATLAS : “LS2 report: The new LHC collimators” 

    Iconic view of the European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire](CH)CERN ATLAS detector

    CERN ATLAS another view Image Claudia Marcelloni ATLAS CERN

    From CERN (CH) ATLAS

    28 September, 2021

    During LS2, 16 new collimators have been installed in the LHC ready for the next run and above all for the future HL-LHC.

    1
    Installation of the passive collimator absorber TCAPM in IR7, which protects the magnets from the losses produced by the interaction between the LHC beam and the IR7 collimators. In the picture: Cristina Bahamonde Image: CERN.

    Upgrades of the LHC collimation system, which began during LS1, have continued during LS2. Sixteen new collimators have been installed in the accelerator over the last three years in preparation not only for the accelerator’s next period of operation (Run 3) but above all for the future High-Luminosity LHC (HL-LHC).

    The HL-LHC, which is due to be commissioned at the end of 2027, will improve on the current LHC’s performance thanks to a tenfold increase in its integrated luminosity, i.e. the number of collisions per surface unit, thereby increasing the number of collisions inside the experiments. To achieve this, the HL-LHC’s beams of particles will be more intense, which is not without its problems.

    Increasing the number of particles in circulation, and therefore the number of collisions, requires the LHC’s equipment protection systems to be reinforced. Particles that stray from their trajectory could hit sensitive components such as superconducting magnets and interfere with their operation. Protection is particularly crucial in the vicinity of the experiments and the areas of the LHC that are dedicated to beam collimation.

    That’s why the HL-LHC needs a more efficient collimation system. The collimators, which are installed in two areas of the LHC (at Points 3 and 7 of the ring) and around the four big experiments (ALICE, ATLAS, CMS and LHCb), are special devices equipped with jaws – movable blocks made of heavy-duty materials – that close around the beam to clean up the stray particles. The materials used for these jaws are capable of withstanding extreme pressure and temperatures as well as high levels of radiation. Some of the collimators have fixed apertures and are there to protect the magnets from radiation.

    During LS2, 16 new collimators of various types have been installed in the machine. Two TCLD (target collimator long dispersion suppressor) collimators were installed around the ALICE experiment in 2020. The majority of the new collimators was installed in Point 7, where most of the beam “cleaning” takes place. “We’ve installed no fewer than 14 colllimators around Point 7 during LS2. Some have replaced existing collimators to improve them, while others are new additions,” explains Stefano Redaelli, who heads up the collimation upgrade work package for the HL-LHC project. “I’d like to thank all the teams involved from the Accelerator and Technology sector (ATS) for their unfailing commitment – they’ve accomplished a remarkable feat!”

    Three types of collimators have been installed: four primary collimators (TCPPM – target collimator primary pick-up, metallic), eight secondary collimators (TCSPM – target collimator secondary pick-up, metallic) and two fixed-aperture passive absorbers. “The primary and secondary collimators, which were manufactured with contributions by international industrial partners, have a new design,” says Stefano Redaelli. “They are based on a molybdenum–graphite compound that, thanks to its low electrical resistivity, helps to improve the stability of the planned higher-intensity beams. The secondary collimators are also coated in 6 microns of pure molybdenum, which further reduces their electrical resistivity by a factor of 20.” What’s more, these new collimators are equipped with sensors that monitor the beam position to allow the position of the jaws to be adjusted.

    Two new crystal collimators, which were developed for operation with heavy ions, are also due to be installed at Point 7 at the end of this year. We’ll report back next year with more details and the results of the first tests with beam.

    See the full article here .


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    CERN LHC underground tunnel and tube.

     
  • richardmitnick 12:40 pm on September 9, 2021 Permalink | Reply
    Tags: , "Triangle singularity", , , COMPASS experiment at CERN, Helmholtz Institute for Radiation and Nuclear Physics [Helmholtz Institut für Strahlen und Kernphysik](DE), HEP, , Particles can change their identities by exchanging quarks thereby mimicking a new particle., The new short-lived intermediate state however appeared to consist of four quarks., , This triangle singularity mechanism was postulated as early as the 1950s by the Russian physicist Lev Davidovich Landau.   

    From Helmholtz Institute for Radiation and Nuclear Physics [Helmholtz Institut für Strahlen und Kernphysik](DE) at The University of Bonn [Rheinische Friedrich-Wilhelms-Universität Bonn] (DE): “Transformation in the particle zoo” 

    From Helmholtz Institute for Radiation and Nuclear Physics [Helmholtz Institut für Strahlen und Kernphysik](DE)

    at

    The University of Bonn [Rheinische Friedrich-Wilhelms-Universität Bonn] (DE)

    18. August 2021

    Prof. Dr. Bernhard Ketzer
    Helmholtz-Institut für Strahlen- und Kernphysik
    der Universität Bonn
    Tel.: +49 228/73-2539 (Büro)
    oder +49 228/73-2203 (Sekretariat)
    E-Mail: Bernhard.Ketzer@uni-bonn.de

    Study led by the University of Bonn finds evidence of a long-sought effect in CERN data.

    An international study led by the University of Bonn has found evidence of a long-sought effect in accelerator data. The so-called “triangle singularity” describes how particles can change their identities by exchanging quarks thereby mimicking a new particle. The mechanism also provides new insights into a mystery that has long puzzled particle physicists: Protons, neutrons and many other particles are much heavier than one would expect. This is due to peculiarities of the strong interaction that holds the quarks together. The triangle singularity could help to better understand these properties. The publication is now available in Physical Review Letters.

    1
    Representation of the triangle singularity: – The particle a1 produced in the collision decays into two particles K* and K-quer. These interact with each other to produce the two particles pi and f0. © Bernhard Ketzer/Uni Bonn.

    In their study, the researchers analyzed data from the COMPASS experiment at the European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN].

    There, certain particles called pions are brought to extremely high velocities and shot at hydrogen atoms.

    Pions consist of two building blocks, a quark and an anti-quark. These are held together by the strong interaction, much like two magnets whose poles attract each other. When magnets are moved away from each other, the attraction between them decreases successively. With the strong interaction it is different: It increases in line with the distance, similar to the tensile force of a stretching rubber band.

    However, the impact of the pion on the hydrogen nucleus is so strong that this rubber band breaks. The “stretching energy” stored in it is released all at once. “This is converted into matter, which creates new particles,” explains Prof. Dr. Bernhard Ketzer of the Helmholtz Institute for Radiation and Nuclear Physics at the University of Bonn. “Experiments like these therefore provide us with important information about the strong interaction.”

    Unusual signal

    In 2015, COMPASS detectors registered an unusual signal after such a crash test. It seemed to indicate that the collision had created an exotic new particle for a few fractions of a second. “Particles normally consist either of three quarks – this includes the protons and neutrons, for example – or, like the pions, of one quark and one antiquark,” says Ketzer. “This new short-lived intermediate state however appeared to consist of four quarks.”

    Together with his research group and colleagues at the Technical University of Munich [Technische Universität München] (DE), the physicist has now put the data through a new analysis. “We were able to show that the signal can also be explained in a different way, that is, by the aforementioned triangle singularity,” he stresses. This mechanism was postulated as early as the 1950s by the Russian physicist Lev Davidovich Landau, but has not yet been proven directly.

    According to this, the particle collision did not produce a tetraquark at all, but a completely normal quark-antiquark intermediate. This, however, disintegrated again straight away, but in an unusual manner: “The particles involved exchanged quarks and changed their identities in the process,” says Ketzer, who is also a member of the Transdisciplinary Research Area “Building Blocks of Matter and Fundamental Interactions” (TRA Matter). “The resulting signal then looks exactly like that from a tetraquark with a different mass.” This is the first time such a triangle singularity has been detected directly mimicking a new particle in this mass range. The result is also interesting because it allows new insights into the nature of the strong interaction.

    Only a small fraction of the proton mass can be explained by Higgs mechanism.

    Protons, neutrons, pions and other particles (called hadrons) have mass. They get this from the so-called Higgs mechanism, but obviously not exclusively: A proton has about 20 times more mass than can be explained by the Higgs mechanism alone. “The much bigger part of the mass of hadrons is due to the strong interaction,” Ketzer explains. “Exactly how the masses of hadrons come about, however, is not yet clear. Our data help us to better understand the properties of the strong interaction, and perhaps the ways in which it contributes to the mass of particles.”

    See the full article here.

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    The University of Bonn [Rheinische Friedrich-Wilhelms-Universität Bonn] (DE) is a public research university located in Bonn, North Rhine-Westphalia, Germany. It was founded in its present form as the Rhein-Universität (English: Rhine University) on 18 October 1818 by Frederick William III, as the linear successor of the Kurkölnische Akademie Bonn (English: Academy of the Prince-elector of Cologne) which was founded in 1777. The University of Bonn offers many undergraduate and graduate programs in a range of subjects and has 544 professors. Its library holds more than five million volumes.

    As of October 2020, among its notable alumni, faculty and researchers are 11 Nobel Laureates, 4 Fields Medalists, 12 Gottfried Wilhelm Leibniz Prize winners as well as some of the most gifted minds in Natural science, e.g. August Kekulé, Heinrich Hertz and Justus von Liebig; Major philosophers, such as Friedrich Nietzsche, Karl Marx and Jürgen Habermas; Famous German poets and writers, for example Heinrich Heine, Paul Heyse and Thomas Mann; Painters, like Max Ernst; Political theorists, for instance Carl Schmitt and Otto Kirchheimer; Statesmen, viz. Konrad Adenauer and Robert Schuman; famous economists, like Walter Eucken, Ferdinand Tönnies and Joseph Schumpeter; and furthermore Prince Albert, Pope Benedict XVI and Wilhelm II.

    The University of Bonn has been conferred the title of “University of Excellence” under the German Universities Excellence Initiative.

    Research institutes

    The Franz Joseph Dölger-Institute studies the late antiquity and in particular the confrontation and interaction of Christians, Jews and Pagans in the late antiquity. The institute edits the Reallexikon für Antike und Christentum, a German language encyclopedia treating the history of early Christians in the late antiquity. The institute is named after the church historian Franz Joseph Dölger who was a professor of theology at the university from 1929 to 1940.

    The Research Institute for Discrete Mathematics focuses on discrete mathematics and its applications, in particular combinatorial optimization and the design of computer chips. The institute cooperates with IBM and Deutsche Post. Researchers of the institute optimized the chess computer IBM Deep Blue.

    The Bethe Center for Theoretical Physics “is a joint enterprise of theoretical physicists and mathematicians at various institutes of or connected with the University of Bonn. In the spirit of Hans Bethe it fosters research activities over a wide range of theoretical and mathematical physics.” Activities of the Bethe Center include short and long term visitors program, workshops on dedicated research topics, regular Bethe Seminar Series, lectures and seminars for graduate students.

    The German Reference Center for Ethics in the Life Sciences (German: Deutsches Referenzzentrum für Ethik in den Biowissenschaften) was founded in 1999 and is modeled after the National Reference Center for Bioethics Literature at Georgetown University. The center provides access to scientific information to academics and professionals in the fields of life science and is the only of its kind in Germany.

    After the German Government’s decision in 1991 to move the capital of Germany from Bonn to Berlin, the city of Bonn received generous compensation from the Federal Government. This led to the foundation of three research institutes in 1995, of which two are affiliated with the university:

    The Center for European Integration Studies (German: Zentrum für Europäische Integrationsforschung) studies the legal, economic and social implications of the European integration process. The institute offers several graduate programs and organizes summer schools for students.

    The Center for Development Research (German: Zentrum für Entwicklungsforschung) studies global development from an interdisciplinary perspective and offers a doctoral program in international development.

    The Center of Advanced European Studies and Research (CAESAR) is an interdisciplinary applied research institute. Research is conducted in the fields of nanotechnology, biotechnology and medical technology. The institute is a private foundation, but collaborates closely with the university.

    The Institute for the Study of Labor (German: Forschungsinstitut zur Zukunft der Arbeit) is a private research institute that is funded by Deutsche Post. The institute concentrates on research on labor economics, but is also offering policy advise on labor market issues. The institute also awards the annual IZA Prize in Labor Economics. The department of economics of the University of Bonn and the institute closely cooperate.

    The MPG Institute for Mathematics [MPG Institut für Mathematik](DE) is part of the MPG Society for the Advancement of Science [MPG Gesellschaft zur Förderung der Wissenschaften e. V.] (DE), a network of scientific research institutes in Germany. The institute was founded in 1980 by Friedrich Hirzebruch.

    The MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE) was founded in 1966 as an institute of the MPG Society for the Advancement of Science [MPG Gesellschaft zur Förderung der Wissenschaften e. V.] (DE). It operates the radio telescope in Effelsberg.

    The MPG Institute for Research on Collective Goods[MPG Institut zur Erforschung von Gemeinschaftsgütern)(DE) started as a research group in 1997 and was founded as an institute of the Max-Planck-Gesellschaft in 2003. The institute studies collective goods from a legal and economic perspective.

    The Center for Economics and Neuroscience founded in 2009 by Christian Elger, Gottfried Wilhelm Leibniz Prize winner Armin Falk, Martin Reuter and Bernd Weber, provides an international platform for interdisciplinary work in neuroeconomics. It includes the Laboratory for Experimental Economics that can carry out computer-based behavioral experiments with up to 24 participants simultaneously, two magnetic resonance imaging (MRI) scanners for interactive behavioral experiments and functional imaging, as well as a biomolecular laboratory for genotyping different polymorphisms.

    Research

    University of Bonn researchers made fundamental contributions in the sciences and the humanities. In physics researchers developed the quadrupole ion trap and the Geissler tube, discovered radio waves, were instrumental in describing cathode rays and developed the variable star designation. In chemistry researchers made significant contributions to the understanding of alicyclic compounds and Benzene. In material science researchers have been instrumental in describing the lotus effect. In mathematics University of Bonn faculty made fundamental contributions to modern topology and algebraic geometry. The Hirzebruch–Riemann–Roch theorem, Lipschitz continuity, the Petri net, the Schönhage–Strassen algorithm, Faltings’s theorem and the Toeplitz matrix are all named after University of Bonn mathematicians. University of Bonn economists made fundamental contributions to game theory and experimental economics. Famous thinkers that were faculty at the University of Bonn include the poet August Wilhelm Schlegel, the historian Barthold Georg Niebuhr, the theologians Karl Barth and Joseph Ratzinger and the poet Ernst Moritz Arndt.

    The university has nine collaborative research centres and five research units funded by the German Science Foundation and attracts more than 75 million Euros in external research funding annually.

    The Excellence Initiative of the German government in 2006 resulted in the foundation of the Hausdorff Center for Mathematics as one of the seventeen national Clusters of Excellence that were part of the initiative and the expansion of the already existing Bonn Graduate School of Economics (BGSE). The Excellence Initiative also resulted in the founding of the Bonn-Cologne Graduate School of Physics and Astronomy (an honors Masters and PhD program, jointly with the University of Cologne). Bethe Center for Theoretical Physics was founded in the November 2008, to foster closer interaction between mathematicians and theoretical physicists at Bonn. The center also arranges for regular visitors and seminars (on topics including String theory, Nuclear physics, Condensed matter etc.).

     
  • richardmitnick 9:59 am on September 2, 2021 Permalink | Reply
    Tags: "The Installation of the BRIL Luminometers: Preparing for a bright Run 3", , , BRIL: "Beam Radiation Instrumentation and Luminosity", , HEP, It is crucial to measure the real-time rate of collisions at CMS in order to optimize both the trigger rates and the quality of the beams delivered by the Large Hadron Collider (LHC)., Once in their final position the BRIL detectors lay at the heart of the CMS detector ~1.8 m from the interaction point just outside the forward pixel tracking detector., One of the most significant design changes has been the implementation of a new active cooling circuit for BCM1F which is essential for a silicon-based detector., , , , The silicon sensors used for BCM1F were sourced from a batch currently being developed for the CMS Phase II upgrade for the High-Luminosity LHC., Three instruments: the Beam Condition Monitor “Fast” (BCM1F); Beam Condition Monitor for Losses (BCM1L); Pixel Luminosity Telescope (PLT)   

    From CERN (CH) CMS: “The Installation of the BRIL Luminometers-Preparing for a bright Run 3” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN (CH) CMS

    9.1.21

    By Andrés G. Delannoy and Joanna Wanczyk, for the BRIL group

    1
    After long months of preparations, the Beam Radiation Instrumentation and Luminosity (BRIL) group has completed the installation of three instruments dedicated to the measurement of luminosity and beam conditions: the Beam Condition Monitor “Fast” (BCM1F), the Beam Condition Monitor for Losses (BCM1L), and the Pixel Luminosity Telescope (PLT). All three of the BRIL subsystems represent a new “generation” in their respective design history. Both PLT and BCM1F implement the use of silicon sensors, while BCM1L uses poly-crystalline diamond sensors.

    2
    Finalized BRIL subsystems, where the PLT is enclosed in the yellow structure with BCM1F directly behind it. Two green BCM1L modules are visible for the top left quadrant. Credits: A.G. Delannoy.

    It is crucial to measure the real-time rate of collisions at CMS in order to optimize both the trigger rates and the quality of the beams delivered by the Large Hadron Collider (LHC). Moreover, continuously assessing the beam conditions is essential to the protection of the LHC machine and sensitive CMS sub-detectors. And, of course, the aggregated luminosity measurements need to be meticulously understood to determine the expected frequency of each type of interaction in nearly every analysis performed on the data collected by the CMS experiment.

    All in all, the design and production of new components, sensor characterization, assembly, stress-testing under thermal cycles troubleshooting and repairs, etc. spanned a few years of challenging work, which ramped up as the Long Shutdown 2 came to a close and the installation date lurked around the corner. Finally, after finalizing all preparations, the transport activities began before sunrise of July 5th, 2021.

    Each half of the detector was carefully loaded onto a special transport vehicle and dry air was circulated inside their transport boxes. Only days before, each quarter of the detector had been delicately readied for its journey, which included labeling them with their affectionately selected aliases: Calabrese, Capricciosa, Diavola, and Margherita. The detector slowly made its way along the base of the Jura mountains until reaching the CMS site. The transport boxes containing the BRIL subsystems are relatively small, which allowed them to ride down in the elevator to the ground floor, 97m underground, to the CMS experimental cavern where they were subsequently craned up to the bulkhead platform.

    3
    +Z side of the BRIL subsystems being craned onto the bulkhead platform. Credits: A.G. Delannoy.

    Once in their final position the BRIL detectors lay at the heart of the CMS detector ~1.8 m from the interaction point just outside the forward pixel tracking detector. The carbon-fiber structure that supports each detector quadrant has small wheels that guide it along purposely designed rails into its final location. After physically installing each of the detector quadrants, the cooling circuit, which provides active coolant to the PLT and BCM1F detectors, had to be tightly sealed using specialized metal o-rings.

    4
    Joanna Wanczyk (left) and Rob Loos (right) install the +Z Far (Margherita) quadrant. Credits: A.G. Delannoy.

    One of the most significant design changes has been the implementation of a new active cooling circuit for BCM1F which is essential for a silicon-based detector. The PLT cooling loop has been modified to include an extension for BCM1F. The design of the BCM1F cooling circuit follows the approach implemented for the PLT during Run 2: the cooling structure is fabricated by 3D printing a titanium alloy using the selective laser melting technique.

    Furthermore, the silicon sensors used for BCM1F were sourced from a batch currently being developed for the CMS Phase II upgrade for the High-Luminosity LHC. The same is the case for three of the sensors used in one of the PLT channels. “This is the first time that these prototype Phase II silicon pixel sensors will be installed in CMS, so the whole community is eager to see how this material behaves,” says Anne Dabrowski, CMS BRIL project manager.

    5
    Joanna Wanczyk (left) and Georg Auzinger (right) work on the -Z side bulkhead platform. Credits: A.G. Delannoy.


    BRIL Upgrade

    See the full article here.


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    Meet CERN (CH) in a variety of places:

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  • richardmitnick 11:29 am on August 31, 2021 Permalink | Reply
    Tags: "Photographing the HL-LHC" Photo Essay, , , , , HEP, , , ,   

    From Symmetry: “Photographing the HL-LHC” Photo Essay 

    Symmetry Mag

    From Symmetry

    08/31/21
    Samuel Hertzog

    A CERN photographer and videographer writes about his experiences documenting the ongoing upgrade that will turn the Large Hadron Collider into the High-Luminosity LHC.

    “It’s August 2019, and I’m a photographer employed by CERN to create audiovisual content for CERN’s internal and external communication. Today a colleague and I are photographing the ongoing civil engineering for new passages, caverns and shafts that will enlarge CERN’s subterranean accelerator complex. When completed, they will house the powering, protection and cryogenic systems for the High-Luminosity LHC. These upgrades will increase the collision rate by a factor of five beyond the LHC’s design value and enable the experiments to search for new physics and phenomena that were previously out of reach.

    A security officer guides us, making sure we stay out of the way of the heavy machinery while he shows us his favorite spots. The lighting is dim, which makes navigating the rocky and uneven pathway even more treacherous.

    1
    Photo by Maximilien Brice.

    2
    Courtesy of Samuel Hertzog and Jules Ordan.

    “Our mission is to collect photos and video footage that both convey the feel of the place and document the action. In just a short time, with limited recording gear and the addition of bulky gloves, boots, masks and protective glasses, we rush to set up our shots.

    Two things stand out: The scale of the place, and how rough an area it is. This, to a photographer, is a sign that it is time to break out the wide-angle lenses and get right up close to the workers. We want to create an immersive feeling for the viewer, a sense that they are right there with us taking in the entire scene.

    3
    Courtesy of Samuel Hertzog and Jules Ordan.

    “Before coming to CERN in winter 2019, I primarily focused on wildlife photography and filmmaking. Working at CERN is unlike anything I’ve done before. I often say shooting the CERN caverns is where a top photographer can really make their mark. You are faced with huge structures but very little room to maneuver. It’s dark, so you need to hold for long exposures. But there are also lots of people and machines moving at all times. To balance all these factors at once is a real test of your skills.

    Toward the end of 2019, the workers break through the wall and connect the new tunnel to the one that holds the LHC. Project leaders and the Director General of CERN hold a ceremony to commemorate the moment. The heads of CERN dress in work suits and descend the shaky metallic steps to pose for a photo and sit for a short interview under bright lights we set up for the occasion. It feels almost like being in a photo studio 100 meters underground.

    4
    Courtesy of Samuel Hertzog and Jules Ordan.

    “In May 2021—18 months after the subterranean photoshoot—we return to the HL-LHC tunnels. The crews have been working 24/7 to get the tunnel construction completed before the LHC restart in Spring 2022. We are told that dust is no longer the issue, but vertigo might be. The temporary elevator is being replaced, so our way down is essentially a large bucket suspended by a rope. No room for unsteady nerves on this site!

    5
    Courtesy of Samuel Hertzog and Jules Ordan

    “When we reach the bottom, the tunnel is radically different. We find ourselves in a clean, white entrance hall, with our path illuminated at regular intervals by elegant blue lights.

    6
    Courtesy of Samuel Hertzog and Jules Ordan.

    “The challenge is now less technically extreme. Creatively, however, this is a whole new game. We still have the heavy machinery and workers in high-vis uniforms. But otherwise, the surroundings are pure science fiction. We respond with a change in style, paying attention to symmetry, proportions and structure to convey the modern, elegant environment.

    7
    Courtesy of Samuel Hertzog and Jules Ordan.

    “It is a photographer’s duty to be adaptable and quick to come up with new ideas when documenting, and CERN’s ever-changing environments certainly test those skills. Conditions and constraints ultimately bring out creativity. It is remarkable to me to look back and see not only the evolution the location but also of my own perspective.”

    See the full article here .


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  • richardmitnick 11:17 am on August 26, 2021 Permalink | Reply
    Tags: "Teaching a particle detector new tricks", , , , , HEP, , , ,   

    From Symmetry: “Teaching a particle detector new tricks” 

    Symmetry Mag

    From Symmetry

    08/26/21
    Sarah Charley

    Scientists hoping to find new, long-lived particles at the Large Hadron Collider recently realized they may already have the detector to do it.

    European Organization for Nuclear Research (Organisation européenne pour la recherche nucléaire)(EU) CMS Detector

    Physicist Cristián Peña grew up in Talca, a small town a few hours south of Santiago, Chile. “The Andes run all the way through the country,” he says. “No matter where you look, you always have the mountains.”

    At the age of 13, he first aspired to climb them.

    Over the years, as his mountaineering skills grew, so did his inventory of tools. Ice axes, crampons and ropes expanded his horizons.

    In Peña’s work as a scientist at the DOE’s Fermi National Accelerator Laboratory (US), he applies this same mindset: He creates the tools his experiment needs to explore new terrain.

    “Detector work is key,” he says.

    Peña’s current focus is the CMS detector, one of two large, general-purpose detectors at the Large Hadron Collider. Peña and colleagues want to use CMS to search for a class of theoretical particles with long lifetimes.

    While working through the problem, they realized that an ideal long-lived particle detector is already installed inside CMS: the CMS muon system. The question was whether they could hack it to do something new.

    1
    Courtesy of CMS Collaboration.

    Long-lived particles

    When scientists designed the CMS detector in the 1990s, they had the most popular and mathematically resilient models of particle physics in mind. As far as they knew, the most interesting particles would live just a fraction of a fraction of a second before transforming into well understood secondary particles, such as photons and electrons. CMS would catch signals from those secondary particles and use them as a trail back to the original.

    The prompt-decay assumption worked in the search for Higgs bosons. But scientists are now realizing that this “live fast, die young” model might not apply to every interesting thing that comes out of a collision at the LHC. Peña says he sees this as a sign that it’s time for the experiment to evolve.

    “If you’re a little kid and you walk a mile in the forest, it’s all completely new,” he says. “Now we have more experience and want to push new frontiers.”

    For CMS scientists, that means finding better ways to look for particles with long lifetimes.

    Long-lived particles are not a radical new concept. Neutrons, for example, live for about 14 minutes outside the confines of an atomic nucleus. And protons are so long-lived that scientists aren’t sure whether they decay at all. If undiscovered particles are moving into the detector before becoming visible, they could be hiding in plain sight.

    “Previously, we hadn’t really thought to look for long-lived particles,” says Christina Wang, a graduate student at The California Institute of Technology (US) working on the CMS experiment. “Now, we have to find new ways to use the CMS detector to see them.”

    A new idea

    Peña was thinking about long-lived particles while attending a conference in Aspen, Colorado, in March 2019.

    “There were a bunch of whiteboards, and we were throwing around ideas,” he says. “In that type of situation, you go with the vibe. There’s a lot of creativity and you start thinking outside the box.”

    Peña and his colleagues visualized what an ideal long-lived particle detector might look like. They would need a detector that was far from the collision point. And they would need shielding to filter out the secondary particles that are the stars of the show in traditional searches.

    “When you look at the CMS muon system,” Peña says, “that’s exactly what it is.”

    Muons, often called the heavier cousins of electrons, are produced during the high-energy collisions inside the LHC. A muon can travel long distances, which is why CMS and its sister experiment, ATLAS, have massive detectors in their outer layers solely dedicated to capturing and recording muon tracks.

    Peña ran a quick simulation to see if the CMS muon system would be sensitive to the firework-like signatures of long-lived particles. “It was quick and dirty,” he says, “but it looked feasible.”

    After the conference, Peña returned to his regular activities. A few months later, Caltech rising sophomore Nathan Suri joined Professor Maria Spiropulu’s lab as a summer student, working with Wang. Peña, who was also collaborating with Spiropulu’s research group, assigned Suri the muon detector idea as his summer project.

    “I was always encouraged to give ideas to young, talented people and let them run with it,” Peña says.

    Suri was excited to take on the challenge. “I was in love with the originality of the project,” he says. “I was eager to sink my teeth into it.”

    Testing the concept

    Suri started by scanning event displays of simulated long-lived particle decays to look for any shared visual patterns. He then explored the original technical design report for the CMS muon detector system to see just how sensitive it could be to these patterns.

    “Looking at the unique detector design and highly sensitive elements, I was able to realize what a powerful tool it was,” he says.

    By the end of the summer, Suri’s work had shown that not only was it feasible to use the muon system to detect long-lived particles, but that CMS scientists could use pre-existing LHC data to get a jump start on the search.

    “At this point, the floodgates opened,” Suri says.

    In fall 2019, Wang took the lead on the project. Suri had shown that the idea was possible; Wang wanted to know if it was realistic.

    So far, they had been working with processed data from the muon system, which was not adapted to the kind of search they wanted to do. “All the reconstruction techniques used in the muon system are optimized to detect muons,” Wang says.

    Wang, Peña and Caltech Professor Si Xie set-up a Zoom meeting with muon system experts to ask for advice.

    “They were really surprised that we wanted to use the muon system to infer long-lived particles,” Wang says. “They were like, ‘It’s not designed to do that.’ They thought it was a weird idea.”

    The experts suggested the team should try looking at the raw data instead.

    Doing so would require extracting unprocessed information from tapes and then developing new software and simulations that could reinterpret thousands of raw detector hits. The task would be arduous, if not impossible.

    After the muon system experts left the call, Wang remembers, “we were still in the Zoom room and like, ‘Do we want to continue this?’”

    She says it was not a serious question. Of course they did.

    A trigger of their own

    In fall 2020, Martin Kwok started a postdoctoral position at Fermilab. “We’re encouraged to talk to as many groups as we can and think about what we want to work on most,” he says.

    He met with Fermilab researcher Artur Apresyan, who told him about the collaboration with Caltech to convert the CMS muon system into a long-lived particle detector. “It was immediately attractive,” Kwok says. “It’s not very often that we get to explore new uses for our detector.”

    Wang and her colleagues had forged ahead with the idea, extracting, processing, and analyzing raw data recorded by the CMS muon system between 2016 and 2018.

    It had worked, but the dataset they had available to study was not ideal.

    The LHC generates around a billion collisions every second—much more than scientists can record and process. So scientists use filters called triggers to quickly evaluate and sort fresh collision data.

    For every billion collisions, only about 1000 are deemed “interesting” by the triggers and saved for further analysis. Wang and her colleagues had determined the filters closest to what they were looking for were the ones programmed to look for signs of dark matter.

    Apresyan pitched to Kwok that he could design a new trigger, one actually meant to look for signs of long-lived particles. They could install it in the CMS muon system before the LHC restarts operation in spring 2022.

    With a dedicated trigger, they could increase the number of events deemed “interesting” for long-lived particle searches by up to a factor of 30. “It’s not often that we see a 30-times increase in our ability to capture potential signal events,” Kwok says.

    Kwok was up for the challenge. And it was a challenge.

    “The price of doing something different—of doing something innovative—is that you have to invent your own tools,” Kwok says.

    The CMS collaboration consists of thousands of scientists all using collective research tools that they developed and honed over the last two decades. “It’s a bit like building with Legos,” Kwok says. “All the pieces are there, and depending on how you use and combine them, you can make almost anything.”

    But developing this specialized trigger was less like picking the right Legos and more like creating a new Lego piece out of melted plastic.

    Kwok dug into the experiment’s archives in search of his raw materials. He found an old piece of software that had been developed by CMS but rarely used. “This left-over tool that faded out of popularity turned out to be very handy,” he says.

    Kwok and his collaborators also had to investigate if integrating a new trigger into the muon system was even possible. “There’s only so much bandwidth in the electronics to send information upstream,” Kwok says.

    “I’m thankful that our collaboration ancestors designed the CMS muon system with a few unused bits. Otherwise, we would have had to reinvent the whole triggering scheme.”

    What started as a feasibility study has now evolved into an international effort, with many more institutions contributing to data analysis and trigger R&D. The US institutions contributing to this research are funded by the Department of Energy (US) and the National Science Foundation (US).

    “Because we don’t have dedicated long-lived particle triggers yet, we have a low efficiency,” Wang says. “But we showed that it’s possible—and not only possible, but we are overhauling the CMS trigger system to further improve the sensitivity.”

    The LHC is scheduled to continue into the 2030s, with several major accelerator and detector upgrades along the way. Wang says that to keep probing nature at its most fundamental level, scientists must remain at the frontier of detector technology and question every assumption.

    “Then new areas to explore will naturally follow,” she says. “Long-lived particles are just one of these new areas. We’re just getting started.”

    See the full article here .


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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 8:30 pm on August 24, 2021 Permalink | Reply
    Tags: "Can light melt atoms into goo?", , , Brookhaven National Laboratory (US) Relativistic Heavy Ion Collider, , HEP, , , , , ,   

    From Symmetry: “Can light melt atoms into goo?” 

    Symmetry Mag

    From Symmetry

    08/24/21
    Sarah Charley

    1
    Courtesy of Christopher Plumberg

    The ATLAS experiment [CH] at European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN]. sees possible evidence of quark-gluon plasma production during collisions between photons and heavy nuclei inside the Large Hadron Collider.

    Photons—the massless particles also known as the quanta of light—are having a moment in physics research.

    Scientists at the Large Hadron Collider have recently studied how, imbued with enough energy, photons can bounce off of one another like massive particles do. Scientists at the LHC and the DOE’s Brookhaven National Laboratory (US) Relative Heavy Ion Collider (US) have also reported seeing photons colliding and converting that energy into massive particles.

    The photon’s most recent seemingly impossible feat? Smashing so hard into a lead nucleus that the collision seems to produce the same state of matter that existed moments after the Big Bang.


    Simulated quark-gluon plasma formation. Courtesy of Chistopher Plumberg.

    “I did not expect that photons could produce a quark-gluon plasma until I actually saw the results,” says theoretical nuclear physicist Jacquelyn Noronha-Hostler, an assistant professor at the University of Illinois -Urbana-Champaign (US).

    Scientists at the LHC at CERN and at RHIC at DOE’s Brookhaven National Laboratory (US) have known for years they could produce small amounts of quark-gluon plasma in collisions between heavy ions. But this is the first time scientists have reported possible evidence of quark-gluon plasma in the aftermath of a collision between the nucleus of a heavy ion and a massless particle of light.

    The scenario seems unlikely. Unlikely, but not impossible, says ATLAS physicist Dennis Perepelitsa, who is an assistant professor at The University of Colorado-Boulder (US).

    “In quantum mechanics, everything that is not forbidden is compulsory,” Perepelitsa says. “If it can happen, it will happen. The question is just how often.”

    Collisions between photons and lead nuclei are common inside the LHC. Perepelitsa and his colleagues are the first to examine them to find out whether they ever produce a quark-gluon plasma. Their first round of results indicate the answer could be yes, an insight that might provide a new understanding of fluid dynamics.

    Scientists contributing to LHC research from US institutions are funded by the Department of Energy (US) and the National Science Foundation (US).

    The Large Light Collider

    Perepelitsa and his colleagues on the ATLAS experiment went looking for collisions between photons and nuclei, called photonuclear collisions, in data collected during the lead-ion runs at the LHC. These runs have happened in the few weeks just before the LHC’s winter shutdown each year that the LHC has been in operation.

    Lead nuclei are made up of protons and neutrons, which are made up of even smaller fundamental particles called quarks. “You can think of the nucleus like a bag of quarks,” Noronha-Hostler says.

    This bag of quarks is held together by gluons, which “glue” small groups of quarks into composite particles called hadrons.

    When two lead nuclei collide at high energy inside the LHC, the gluons can lose their grip, causing the protons and neutrons to melt and merge into a quark-gluon plasma. The now-free quarks and gluons pull on each other, holding together as the plasma expands and cools.

    Eventually, the quarks cool enough to reform into distinct hadrons. Scientists can reconstruct the production, size and shape of the original quark-gluon plasma based on the number, identities and paths of hadrons that escape into their detectors.

    During the lead-ion runs at the LHC, nuclei aren’t the only things colliding. Because they have a positive charge, lead nuclei carry strong electromagnetic fields that grow in intensity as they accelerate. Their electromagnetic fields spit out high-energy photons, which can also collide—a fairly common occurence. “There’s a lot of photons, and the nucleus is big,” Perepelitsa says.

    Despite their frequency, no one had ever closely examined the detailed patterns of these kinds of photonuclear collisions at the LHC. For this reason, ATLAS scientists had to develop a specialized trigger that could pick out the photon-zapped lead ions from everything else.

    According to Blair Seidlitz, a graduate student at CU Boulder, this was tricky. “People have a lot more experience triggering on lead-lead collisions,” he says.

    Luckily, photonuclear collisions have a special asymmetrical shape due to the momentum differences between the tiny photon and the massive lead ion: “It’s like a truck hitting a trash can,” Seidlitz says. “All the debris from the collision will move in the direction of the truck.”

    Seidlitz designed a trigger that looked for collisions that generated a small number of particles, had a skewed shape, and saw remnants of the partially obliterated lead ion embedded in special detectors 140 meters away from the collision point.

    After collecting and analyzing the data, Seidlitz, Perepelitsa and their colleagues saw a particle-flow signature characteristic of a quark-gluon plasma.

    The finding alone is not enough to prove the formation of a quark-gluon plasma, but it’s a first clue. “There are always potential competing explanations, and we need to look for other signatures of quark-gluon plasma that could be there,” Perepelitsa says, “but we haven’t measured them yet.”

    If the photonuclear collisions are indeed creating quark-gluon plasma, it could be a kind of quantum trick, Perepelitsa says.

    Perepelitsa and his colleagues are dubious that a massless photon could pack a powerful enough punch to melt part of a lead nucleus, which contains 82 protons and 126 neutrons. “It would be like throwing a needle into a bowling ball,” he says.

    Instead, he thinks that just before impact, these photons are undergoing a transformation originally predicted by Nobel Laureate Paul Dirac.

    A quantum transformation

    In 1931, Dirac published a paper predicting a new type of particle. The particle would share the mass of the electron but have the opposite charge [positron]. Also, he predicted, “if it collides with an electron, the two will have a chance of annihilating one another.”

    It was the positron, the first predicted particle of antimatter. In 1932, The California Institute of Technology (US) physicist Carl Anderson discovered the particle, and later physicists spotted the annihilation process Dirac had predicted as well.

    When matter and antimatter meet, the two particles are destroyed, releasing their energy in the form of a pair of photons.

    Scientists also see this process happening in reverse, Noronha-Hostler says. “Two photons can interact and create a quark-antiquark pair.”

    Before annihilating, that quark-antiquark pair can bind together to make a hadron.

    Perepelitsa and his colleagues suspect that the collisions they’ve observed, in which photons appear to be colliding with lead nuclei and creating a small amount of quark-gluon plasma, are not actually collisions between nuclei and photons. Instead, they’re collisions between nuclei and those tiny, ephemeral hadrons.

    This makes more sense, Perepelitsa says, as hadrons are bigger in size than photons and are capable of more substantial interactions. “It’s no longer a needle going into a bowling ball, but more like a bullet.”

    The smallest drop

    For now, the exact mechanism that may be causing this quark-gluon plasma signature within photonuclear collisions remains a mystery. Whatever is going on, Noronha-Hostler says figuring out these collisions could be an important step in quark-gluon plasma research.

    LHC scientists’ usual method of studying the quark-gluon plasma has been to examine crashes between lead nuclei, which create a complex soup of quarks and gluons. “We thought originally that the only way we could produce a quark gluon plasma was two massive nuclei hitting each other,” she says. “And then experimentalists started playing around and running smaller things, like protons. With photonuclear collisions, that’s even smaller.”

    If photonuclear collisions are creating quark-gluon plasma, it’s in the form of a tiny droplet composed of a few vaporized protons and neutrons.

    Scientists are hoping to study these droplets to learn more about how liquids behave on subatomic scales.

    “We’re pushing to the most extremes in fluid dynamics,” Noronha-Hostler says. “Not only do we have something that is moving at the speed of light and at the highest temperatures known to humanity, but it looks like we are going to be able to answer ‘What is the smallest droplet of a liquid?’ No other field can do that.”

    See the full article here .


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    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 10:47 am on August 19, 2021 Permalink | Reply
    Tags: , , , CERN COMPASS experiment, , HEP, , , , Representation of the triangle singularity,   

    From The University of Bonn [Rheinische Friedrich-Wilhelms-Universität Bonn] (DE): “Transformation in the particle zoo” 

    From The University of Bonn [Rheinische Friedrich-Wilhelms-Universität Bonn] (DE)

    18. August 2021

    Prof. Dr. Bernhard Ketzer
    Helmholtz Institute for Radiation and Nuclear Physics [Helmholtz Institut für Strahlen und Kernphysik](DE) Bonn
    Tel.: +49 228/73-2539 (Büro)
    oder +49 228/73-2203 (Sekretariat)
    Bernhard.Ketzer@uni-bonn.de

    Study led by the University of Bonn finds evidence of a long-sought effect in CERN data.

    An international study led by the University of Bonn has found evidence of a long-sought effect in accelerator data. The so-called “triangle singularity” describes how particles can change their identities by exchanging quarks, thereby mimicking a new particle. The mechanism also provides new insights into a mystery that has long puzzled particle physicists: Protons, neutrons and many other particles are much heavier than one would expect. This is due to peculiarities of the strong interaction that holds the quarks together. The triangle singularity could help to better understand these properties. The publication is now available in Physical Review Letters.

    1
    Representation of the triangle singularity: – The particle a1 produced in the collision decays into two particles K* and K-quer. These interact with each other to produce the two particles pi and f0. © Bernhard Ketzer/Uni Bonn.

    In their study, the researchers analyzed data from the COMPASS experiment at the European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN]. in Geneva. There, certain particles called pions are brought to extremely high velocities and shot at hydrogen atoms.

    Pions consist of two building blocks, a quark and an anti-quark. These are held together by the strong interaction, much like two magnets whose poles attract each other. When magnets are moved away from each other, the attraction between them decreases successively. With the strong interaction it is different: It increases in line with the distance, similar to the tensile force of a stretching rubber band.

    However, the impact of the pion on the hydrogen nucleus is so strong that this rubber band breaks. The “stretching energy” stored in it is released all at once. “This is converted into matter, which creates new particles,” explains Prof. Dr. Bernhard Ketzer of the Helmholtz Institute for Radiation and Nuclear Physics at the University of Bonn. “Experiments like these therefore provide us with important information about the strong interaction.”

    Unusual signal

    In 2015, COMPASS detectors registered an unusual signal after such a crash test. It seemed to indicate that the collision had created an exotic new particle for a few fractions of a second. “Particles normally consist either of three quarks – this includes the protons and neutrons, for example – or, like the pions, of one quark and one antiquark,” says Ketzer. “This new short-lived intermediate state, however, appeared to consist of four quarks.”

    Together with his research group and colleagues at the Technical University of Munich, the physicist has now put the data through a new analysis. “We were able to show that the signal can also be explained in a different way, that is, by the aforementioned triangle singularity,” he stresses. This mechanism was postulated as early as the 1950s by the Russian physicist Lev Davidovich Landau, but has not yet been proven directly.

    According to this, the particle collision did not produce a tetraquark at all, but a completely normal quark-antiquark intermediate. This, however, disintegrated again straight away, but in an unusual manner: “The particles involved exchanged quarks and changed their identities in the process,” says Ketzer, who is also a member of the Transdisciplinary Research Area “Building Blocks of Matter and Fundamental Interactions” (TRA Matter). “The resulting signal then looks exactly like that from a tetraquark with a different mass.” This is the first time such a triangle singularity has been detected directly mimicking a new particle in this mass range. The result is also interesting because it allows new insights into the nature of the strong interaction.

    Only a small fraction of the proton mass can be explained by Higgs mechanism

    Protons, neutrons, pions and other particles (called hadrons) have mass. They get this from the so-called Higgs mechanism, but obviously not exclusively: A proton has about 20 times more mass than can be explained by the Higgs mechanism alone. “The much bigger part of the mass of hadrons is due to the strong interaction,” Ketzer explains. “Exactly how the masses of hadrons come about, however, is not yet clear. Our data help us to better understand the properties of the strong interaction, and perhaps the ways in which it contributes to the mass of particles.”

    See the full article here.

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    Stem Education Coalition

    The University of Bonn [Rheinische Friedrich-Wilhelms-Universität Bonn] (DE) is a public research university located in Bonn, North Rhine-Westphalia, Germany. It was founded in its present form as the Rhein-Universität (English: Rhine University) on 18 October 1818 by Frederick William III, as the linear successor of the Kurkölnische Akademie Bonn (English: Academy of the Prince-elector of Cologne) which was founded in 1777. The University of Bonn offers many undergraduate and graduate programs in a range of subjects and has 544 professors. Its library holds more than five million volumes.

    As of October 2020, among its notable alumni, faculty and researchers are 11 Nobel Laureates, 4 Fields Medalists, 12 Gottfried Wilhelm Leibniz Prize winners as well as some of the most gifted minds in Natural science, e.g. August Kekulé, Heinrich Hertz and Justus von Liebig; Major philosophers, such as Friedrich Nietzsche, Karl Marx and Jürgen Habermas; Famous German poets and writers, for example Heinrich Heine, Paul Heyse and Thomas Mann; Painters, like Max Ernst; Political theorists, for instance Carl Schmitt and Otto Kirchheimer; Statesmen, viz. Konrad Adenauer and Robert Schuman; famous economists, like Walter Eucken, Ferdinand Tönnies and Joseph Schumpeter; and furthermore Prince Albert, Pope Benedict XVI and Wilhelm II.

    The University of Bonn has been conferred the title of “University of Excellence” under the German Universities Excellence Initiative.

     
  • richardmitnick 3:20 pm on August 16, 2021 Permalink | Reply
    Tags: "Table-top electron camera catches ultrafast dynamics of matter", , , , Electron diffraction is one way to investigate the inner structure of matter., HEP, , , , , Terahertz radiation, The accelerator components-here a bunch compressor-can be a hundred times smaller., The scientists fired bunches with roughly 10000 electrons each at a silicon crystal that was heated by a short laser pulse., The system is perfectly synchronised since it is using just one laser for all steps: generating; manipulating; measuring; and compressing the electron bunches., Typically ultrafast electron diffraction (UED) uses bunch lengths-or exposure times-of some 100 femtoseconds which is 0.1 trillionths of a second.   

    From DESY German Electron Synchrotron [Deütsches Elektronen-Synchrotron] (DE) : “Table-top electron camera catches ultrafast dynamics of matter” 

    From DESY German Electron Synchrotron [Deütsches Elektronen-Synchrotron] (DE)

    2021/08/13

    DESY team demonstrates first Terahertz enhanced electron diffractometer.
    Scientists at DESY have built a compact electron camera that can capture the inner, ultrafast dynamics of matter. The system shoots short bunches of electrons at a sample to take snapshots of its current inner structure and is the first such electron diffractometer that uses Terahertz radiation for pulse compression. The developer team around DESY scientists Dongfang Zhang and Franz Kärtner from the CFEL Center for Free-Electron Laser Science [Zentrum für Freie-Elektronen-Laserwissenschaft] (DE) validated their Terahertz-enhanced ultrafast electron diffractometer with the investigation of a silicon sample and present their work in the first issue of the journal Ultrafast Science, a new title in the Science group of scientific journals.

    1
    The system fits on a lab table. It is adjusted with the help of an optical laser (green). Credit: DESY, Timm Rohwer.

    Electron diffraction is one way to investigate the inner structure of matter. However, it does not image the structure directly. Instead, when the electrons hit or traverse a solid sample, they are deflected in a systematic way by the electrons in the solid’s inner lattice. From the pattern of this diffraction, recorded on a detector, the internal lattice structure of the solid can be calculated. To detect dynamic changes in this inner structure, short bunches of sufficiently bright electrons have to be used. “The shorter the bunch, the faster the exposure time,” says Zhang, who is now a professor at Shanghai Jiao Tong University [海交通大学](CN). “Typically ultrafast electron diffraction (UED) uses bunch lengths-or exposure times-of some 100 femtoseconds which is 0.1 trillionths of a second.”

    Such short electron bunches can be routinely produced with high quality by state-of-the-art particle accelerators. However, these machines are often large and bulky, partly due to the radio frequency radiation used to power them, which operates in the Gigahertz band. The wavelength of the radiation sets the size for the whole device. The DESY team is now using Terahertz radiation instead with roughly a hundred times shorter wavelengths. “This basically means, the accelerator components-here a bunch compressor-can be a hundred times smaller, too,” explains Kärtner, who is also a professor and a member of the cluster of excellence “CUI: Advanced Imaging of Matter“ at the University of Hamburg [Universität Hamburg](DE).

    2
    Schematic set-up of the Terahertz Ultrafast Electron Diffractometer. Credit: DESY, Dongfang Zhang.

    For their proof-of-principle study, the scientists fired bunches with roughly 10,000 electrons each at a silicon crystal that was heated by a short laser pulse. The bunches were about 180 femtoseconds long and show clearly how the crystal lattice of the silicon sample quickly expands within a picosecond (trillionths of a second) after the laser hits the crystal. “The behaviour of silicon under these circumstances is very well known, and our measurements fit the expectation perfectly, validating our Terahertz device,” says Zhang. He estimates that in an optimised set-up, the electron bunches can be compressed to significantly less than 100 femtoseconds, allowing even faster snapshots.

    On top of its reduced size, the Terahertz electron diffractometer has another advantage that might be even more important to researchers: “Our system is perfectly synchronised since we are using just one laser for all steps: generating; manipulating; measuring; and compressing the electron bunches, producing the Terahertz radiation and even heating the sample,” Kärtner explains. Synchronisation is key in this kind of ultrafast experiments. To monitor the swift structural changes within a sample of matter like silicon, researchers usually repeat the experiment many times while delaying the measuring pulse a little more each time. The more accurate this delay can be adjusted, the better the result. Usually, there needs to be some kind of synchronisation between the exciting laser pulse that starts the experiment and the measuring pulse, in this case the electron bunch. If both, the start of the experiment and the electron bunch and its manipulation are triggered by the same laser, the synchronisation is intrinsically given.

    In a next step, the scientists plan to increase the energy of the electrons. Higher energy means the electrons can penetrate thicker samples. The prototype set-up used rather low-energy electrons and the silicon sample had to be sliced down to a thickness of just 35 nanometres (millionths of a millimetre). Adding another acceleration stage could give the electrons enough energy to penetrate 30 times thicker samples with a thickness of up to 1 micrometre (thousandth of a millimetre), as the researchers explain. For even thicker samples, X-rays are normally used. While X-ray diffraction is a well established and hugely successful technique, electrons usually do not damage the sample as quickly as X-rays do. “The energy deposited is much lower when using electrons,“ explains Zhang. This could prove useful when investigating delicate materials.

    See the full article here .


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    desi

    DESY German Electron Synchrotron [Deütsches Elektronen-Synchrotron] (DE) is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

    [/caption]

     
  • richardmitnick 8:07 pm on August 12, 2021 Permalink | Reply
    Tags: "SPS experiments are back in action", , , , HEP, , ,   

    From European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN]: “SPS experiments are back in action” 


    Cern New Bloc

    Cern New Particle Event

    From European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN]

    12 August, 2021
    Ana Lopes

    The Super Proton Synchrotron (SPS) lives up to its superlative designation. It’s CERN’s second-largest accelerator and is the last link in the accelerator chain that feeds particle beams to the Large Hadron Collider (LHC). What’s more, it supplies beams to a range of non-LHC experiments that address an impressive array of topics, from precision tests of the Standard Model of particle physics to studies of the quark–gluon plasma, a state of matter believed to have existed shortly after the Big Bang.

    Following hot on the heels of the restart of the Proton Synchrotron Booster and the Proton Synchrotron after the second long shutdown of CERN’s accelerator complex, the SPS and its experiments are now also back in action.

    The SPS delivers particle beams to all of CERN’s North Area (NA) experiments, to the associated test beam areas, as well as to the AWAKE experiment [below], which investigates the use of a wakefield created by protons zipping through a plasma to accelerate charged particles, and to the HiRadMat facility, which tests materials and accelerator components in extreme conditions.

    The NA experiments are an essential strand of the Laboratory’s experimental programme. NA58/COMPASS [below] studies how quarks and gluons form composite particles such as protons and pions. NA61/SHINE investigates the quark–gluon plasma and takes particle measurements for neutrino and cosmic-ray experiments. NA62 studies rare kaon decays and searches for new heavy neutral leptons. NA63 [below] investigates radiation processes in strong electromagnetic fields. NA64 searches for new particles that could carry a new force between visible matter and dark matter, or that could make up dark matter themselves. Last but not least, NA65, a new experiment that was approved in 2019, will take measurements of tau neutrinos for neutrino experiments and for tests of the Standard Model.

    NA62 has just restarted taking data for physics studies, and the remaining experiments will start doing so in the coming weeks and months. Highlights include the start of NA65 in September and the first pilot runs in October for experiments proposed in the Physics Beyond Colliders initiative, such as AMBER (the successor of COMPASS) and NA64m (NA64 running with beams of muons).

    “It’s always a thrill to witness the restart of the experiments, as is to see the fresh data that they deliver, not least after the extensive upgrades they have undergone over the past two years,” says Johannes Bernhard, the leader of the Liaison to Experiments section at CERN. “And if the past seasons of data-taking are any indication, there will be plenty of new physics results to digest and to direct future studies.”

    See the full article here.


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Meet CERN in a variety of places:

    Quantum Diaries
    QuantumDiaries

    Cern Courier


    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    ALICE

    CMS

    LHCb

    LHC

    OTHER PROJECTS AT CERN

    European Organization for Nuclear Research (Organisation européenne pour la recherche nucléaire)(EU)[CERN] AEGIS.


    CERN FASER is designed to study the interactions of high-energy neutrinos and search for new as-yet-undiscovered light and weakly interacting particles. Such particles are dominantly produced along the beam collision axis and may be long-lived particles, travelling hundreds of metres before decaying. The existence of such new particles is predicted by many models beyond the Standard Model that attempt to solve some of the biggest puzzles in physics, such as the nature of dark matter and the origin of neutrino masses.

    CERN The SPS’s new RF system. Image: CERN

     
  • richardmitnick 1:38 pm on August 7, 2021 Permalink | Reply
    Tags: "Successful installation of the CMS Pixel Tracker", , , , HEP, , ,   

    From CERN (CH) CMS: “Successful installation of the CMS Pixel Tracker” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN (CH) CMS

    1
    The pixel tracker is the subdetector that is closest to the beamline in the CMS experiment. Image: CERN.

    After more than two years of maintenance and upgrades, the Pixel Tracker has been installed at the centre of the CMS detector and is now ready for commissioning.

    Of all the CMS subdetectors, the Pixel Tracker is the closest to the interaction point (IP) – the point of collision between the proton beams. In the core of the detector, it reconstructs the paths of high-energy electrons, muons and electrically charged hadrons, but also the decay of very short-lived particles such as those containing beauty or “b” quarks. Those decays are used, among other things, to study the differences between matter and antimatter.

    The Pixel Tracker is composed of concentric layers and rings of 1800 small silicon modules. Each of these modules contains about 66 000 individual pixels, for a total of 120 million pixels. The pixels’ tiny size (100×150 μm2) allows the trajectory of a particle passing through the detector to be precisely measured and its origin determined with a precision of about 10 μm.

    Due to its location very close to the IP, the Pixel Tracker suffers a great deal of radiation damage from particle collisions. In the innermost layer, a mere 2.9 cm away from the beam pipe, around 600 million particles pass through one square centimetre of the detector every second. Low temperatures help to protect the Pixel Tracker from this high radiation (it is kept at -20 °C), but some damage still occurs.

    To tackle this issue, the subdetector underwent extensive repairs and upgrades in the clean room where it was stored after its extraction from the cavern at the beginning of Long Shutdown 2. Its design was improved and its innermost layer replaced. The pixel detector was then reinstalled at the centre of the CMS detector and is now ready for commissioning.

    The final installation was the latest of the many achievements of the CMS Tracker group, one of the largest sub-groups of the CMS collaboration with about 600 people from over 70 institutions in 19 countries.

    Relive the event, including footage of the operations and interviews from Lea Caminada, John Conway and Erik Butz, on CERN’s social media channels:

    CERN’s YouTube channel
    CERN’s Instagram account


    CMS Pixel tracker installation 2021

    See the full article here.


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