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  • richardmitnick 1:44 pm on May 6, 2021 Permalink | Reply
    Tags: "LS2 Report: FASER is born", , , , FASER is designed to study the interactions of high-energy neutrinos and search for new as-yet-undiscovered light and weakly interacting particles., HEP, , ,   

    From European Organization for Nuclear Research (Organisation européenne pour la recherche nucléaire)(EU) [CERN]: “LS2 Report: FASER is born” 

    Cern New Bloc

    Cern New Particle Event

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

    24 March, 2021 [Just now in social media.]
    Anaïs Schaeffer

    1
    The final elements of FASER were put into place this month. (Image: CERN)

    FASER* (Forward Search Experiment), CERN’s newest experiment, is now in place in the LHC tunnel, only two years after its approval by CERN’s Research Board in March 2019. 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.

    FASER is located along the beam collision axis, 480 m from the ATLAS interaction point, in an unused service tunnel that formerly connected the SPS to the LEP collider – an optimal position for detecting the particles into which light and weakly interacting particles will decay.

    The first civil engineering works started in May 2020. “Because of the sloped geometry of the tunnel, the beam collision axis was actually passing under the ground,” says Jamie Boyd, FASER co-spokesperson. “Measurements from the CERN survey team showed that, by excavating a 50-cm-deep trench, sufficient space would be created to house the 5-m-long FASER detector.” In the summer, the first services and power systems were installed, and in November, FASER’s three magnets were put in place in the trench.

    2
    The installation of FASER’s three magnets took place in November, in the narrow trench excavated by CERN’s SCE team. (Image: CERN)

    A pretty simple experiment
    At the entrance to the detector, two scintillator stations are used to veto charged particles coming through the cavern wall from the ATLAS interaction point; these are primarily high-energy muons. The veto stations are followed by a 1.5-m-long dipole magnet. This is the decay volume for long-lived particles decaying into a pair of oppositely charged particles. After the decay volume is a spectrometer consisting of two 1-m-long dipole magnets with three tracking stations, which are located at either end and in between the magnets. Each tracking station is composed of layers of precision silicon strip detectors. Scintillator stations for triggering and precision time measurements are located at the entrance and exit of the spectrometer.

    The final component is the electromagnetic calorimeter. This will identify high-energy electrons and photons and measure the total electromagnetic energy. The whole detector is cooled down to 15 °C by an independent cooling station.

    “FASER uses spare pieces from the ATLAS (for the tracker) and LHCb (for the calorimeter) experiments, which made possible its installation during Long Shutdown 2, so quickly after its approval,” highlights Jamie Boyd.

    FASER will also have a subdetector called FASERν, which is specifically designed to detect neutrinos. No neutrino produced at a particle collider has ever been detected, despite colliders producing them in huge numbers and at high energies. FASERν is made up of emulsion films and tungsten plates to act as both the target and the detector to see the neutrino interactions. FASERν should be ready for installation by the end of the year. The whole experiment will start taking data during Run 3 of the LHC, starting in 2022.

    “We are extremely excited to see this project come to life so quickly and smoothly,” says Jamie Boyd. “Of course, this would not have been possible without the expert help of the many CERN teams involved!”

    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.

    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.

     
  • richardmitnick 9:06 am on May 6, 2021 Permalink | Reply
    Tags: "The superconducting coils for the 11T dipoles have been delivered", , , CERN (CH) Accelerating News, HEP, , ,   

    From CERN (CH) Accelerating News : “The superconducting coils for the 11T dipoles have been delivered” 

    From CERN (CH) Accelerating News

    28 April, 2021
    Anaïs Schaeffer (European Organization for Nuclear Research (Organisation européenne pour la recherche nucléaire)(CH) [CERN])

    35 niobium–tin superconducting coils have been manufactured as part of a fruitful collaboration with the company General Electric. They will be used in the 11 T dipoles for the HL-LHC.

    1
    Control samples fitted to the ends of the niobium–tin coils’ heat-treatment mould to check the conformity of the electrical performance. (Image: CERN).

    Starting in 2018, a team of experts from the company General Electric (GE) worked with the Magnets, Superconductors and Cryogenics (TE-MSC) group at CERN to manufacture superconducting coils for the new 11 T dipoles being developed for the HL-LHC project. In January, following three years of fruitful collaboration, the 15-strong team left the Laboratory.

    The 11 T dipoles are based on superconducting niobium–tin (Nb3Sn). They are just six metres long but, thanks to their higher field, they might be able to replace some of the main 15-metre-long LHC dipoles in strategic parts of the accelerator, notably at Point 7, freeing up space for new collimators. The plan is to install a total of four 11 T dipoles for the HL-LHC.

    “From the very beginning, we established a relationship of trust between the CERN and GE teams to ensure knowledge transfer and cross-fertilisation,” explains Arnaud Devred, leader of the Magnets, Superconductors and Cryogenics group. “We have learned from their industrial approach and their organisational structure, using production units, which has helped us to improve our quality assurance. As for GE, they have developed specific skills in the manufacture of superconducting magnets thanks to their work on the 11 T dipoles, a new technology that is still evolving.”

    A total of 35 coils have been manufactured and assembled in the Large Magnet Facility on the Meyrin site, using tools provided by CERN. They will form part of the 11 T dipoles, which may be installed in the LHC during a future technical stop.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    CERN (CH) Accelerating News is a quarterly online publication for the accelerator community.
    ISSN: 2296-6536

    The publication showcases news and results from the biggest accelerator research and development projects such as ARIES, HL-LHC, TIARA, FCC study, EuroCirCol, EUPRAXIA, EASITrain as well as interesting stories on other accelerator applications. The newsletter also collects upcoming accelerator research conferences and events.

    Accelerating News is published 4 times a year, in mid March, mid June, mid September and mid December.

    You can read Accelerating News via the homepage http://www.acceleratingnews.eu or by email.

    To subscribe to Accelerating News, enter your email in the “Subscribe to our newsletter” box in the footer.

    History

    Accelerating News evolved from the EuCARD quarterly project newsletter (see past issues), which was first published in June 2009 to a subscription list of approximately 200. Initiated by EuCARD and in collaboration with additional FP7 co-funded projects, the first edition of Accelerating News was published in April 2012 to an initial distribution list of about 800 subscribers. Currently more than 1750 members receive the quarterly issues.

     
  • richardmitnick 8:52 am on May 6, 2021 Permalink | Reply
    Tags: "Accelerators probing Gravitational Waves", , , CERN Future Circular Collider (FCC), Chinese Circular Electron Positron Collider (CEPC), European Organization for Nuclear Research (Organisation européenne pour la recherche nucléaire)(CH) [CERN] Accelerating News, HEP, , ,   

    From European Organization for Nuclear Research (Organisation européenne pour la recherche nucléaire)(CH) [CERN] Accelerating News : “Accelerators probing Gravitational Waves” 

    From European Organization for Nuclear Research (Organisation européenne pour la recherche nucléaire)(CH) [CERN] Accelerating News

    8 April, 2021 [Just now in social media.]
    Giuliano Franchetti (GSI Helmholtz Centre for Heavy Ion Research [GSI Helmholtzzentrum für Schwerionenforschung] (DE))
    Marco Zanetti (National Institute for Nuclear Physics [Istituto Nazionale di Fisica Nucleare] – Padova Unit (IT))
    Frank Zimmermann

    1

    After the discovery of gravitational waves (GWs) by the LIGO detector in 2015, and with the advent of proposals for new large storage rings such as the 100 km CERN Future Circular Collider (FCC) or Circular Electron Positron Collider (CEPC), the question whether accelerators can be used for the detection or generation of GWs has gained new importance and urgency.

    In February and March 2021, a topical virtual workshop “Storage Rings and Gravitational Waves” (SRGW2021) [1], organized in the frame of the H2020 project ARIES, shed new light on this tantalizing possibility. More than 100 accelerator experts, particle physicists and members of the gravitational physics community jointly explored possible novel directions of accelerator research.

    After Jorge Cervantes (National Institute for Nuclear Research [Instituto Nacional de Investigaciones Nucleares] (MX)) presented a vivid account of the history of gravitational waves, Bangalore S. Sathyaprakash (Pennsylvania State University (US) and Cardiff University (UK)) reviewed the main sources of gravitational waves expected. The GW frequency range of interest extends from 0.1 nHz to 1 MHz. Raffaele Flaminio (LAPP-Annecy Laboratory of Particle Physics [Laboratoire d’Annecy de Physique des Particules] (FR)) described the extreme precision of the VIRGO and LIGO light-interferometers, while Jörg Wenninger (European Organization for Nuclear Research (Organisation européenne pour la recherche nucléaire)(EU)) reported the impressive sensitivity of large lepton or hadron storage rings – LEP and LHC – to small effects, such as the tides or earthquakes elsewhere.

    A gravitational wave can resonantly interact with either the transverse betatron motion of a stored particle beam at a frequency of several kHz, or with the longitudinal synchrotron motion at a frequency of 10s of Hz. Katsunobu Oide (KEK [高エネルギー加速器研究機構](JP) and CERN) discussed the betatron resonances excited by GWs, and proposed special beam-optical insertions, serving as “gravitational-wave antennas”, to enhance the resonance strength. Suvrat Rao (University of Hamburg [Universität Hamburg] (DE)) discussed the longitudinal beam response [2]. This response is enhanced for perturbations close to the synchrotron frequency. Raffaele D’Agnolo (Institute of Theoretical Physics [Institut de Physique Théorique] (FR)) estimated the sensitivity to the gravitational strain h, without any backgrounds, as h~10-13, and suggested three possible paths to further improve the sensitivity.

    Figure 2 superimposes ideal sensitivity curves from revolution time at the LHC and from the transverse resonant response for a storage ring with GW antenna optics, along with expected sources, in the strain-frequency plane.

    2
    Ideal noise-free GW sensitivity at the LHC for 1 ps resolution in revolution time (red curve, Suvrat Rao, from [2]) and ideal transverse resonant betatron response sensitivity of a 37 km ring with GW-antenna optics under two different assumptions for the beam-position measurement resolution (green and blue curves, Katsunobu Oide and Frank Zimmermann), in the strain-frequency plane, superimposed on a picture of expected sources taken from http://gwplotter.com/. Also shown is the predicted strength of the LHC as a gravitational source for the coherent emission of gravitational synchrotron radiation, assuming all protons in a beam are contributing coherently (red star, Pisin Chen). All three storage-ring lines and the marker require confirmation. (Image: CERN).

    Workshop participants discussed possible coasting beam experiments, and the sensitivity of heavy ions or of cold crystalline beams. Witek Krasny (LPNHE) suggested relying on “atomic clocks” as for the Gamma factory. Andrey Ivanov (TU Vienna) discussed the possible shrinking of storage ring circumferences under the influence of the relic GW microwave background [3].

    High-quality superconducting radiofrequency cavities could offer an alternative venue to detect gravitational waves, as presented by Sebastian Ellis (IPhT). Atomic beam interferometry is another promising approach, pursued by Oliver Buchmüller (Imperial College London (UK)) and John Ellis (King’s College London (UK)).

    Pisin Chen (NTU Taiwan) discussed how relativistic charged particles in a storage ring can emit gravitational waves [4]. If all particles and bunches excited the GW coherently the spacetime metric perturbation could be as large as hGSR~10-18 for the LHC, as indicated by a red start in Figure 2. This estimate requires further confirmation. John Jowett (GSI, retired from CERN) recalled that gravitational synchrotron radiation from the future LEP, LHC and SSC beams had been discussed at CERN in the late 1980. It was then realised that these beams would be among the most powerful terrestrial sources of gravitational radiation [5].

    The concluding workshop discussion was moderated by John Ellis (King’s College London).

    Gravitational waves are a unique tool to understand the today’s universe and to unravel its history. The great excitement and interest prompted by the ARIES SRGW2021 workshop, and the preliminary findings, call for further investigations.

    References

    [1] SRGW2021 workshop web site https://indico.cern.ch/event/982987
    [2] S. Rao et al. 2020 Phys. Rev. D 102, 122006
    [3] A. Ivanov et al. 2002 arxiv gr-qc/021009
    [4] P. Chen 1994 SLAC-PUB-6666 and 1995 Phys. Rev. Lett. 74, 634
    [5] G. Diambrini Palazzi et al., 1987 Phys. Lett. B 197, 302

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    CERN (CH) Accelerating News is a quarterly online publication for the accelerator community.
    ISSN: 2296-6536

    The publication showcases news and results from the biggest accelerator research and development projects such as ARIES, HL-LHC, TIARA, FCC study, EuroCirCol, EUPRAXIA, EASITrain as well as interesting stories on other accelerator applications. The newsletter also collects upcoming accelerator research conferences and events.

    Accelerating News is published 4 times a year, in mid March, mid June, mid September and mid December.

    You can read Accelerating News via the homepage http://www.acceleratingnews.eu or by email.

    To subscribe to Accelerating News, enter your email in the “Subscribe to our newsletter” box in the footer.

    History

    Accelerating News evolved from the EuCARD quarterly project newsletter (see past issues), which was first published in June 2009 to a subscription list of approximately 200. Initiated by EuCARD and in collaboration with additional FP7 co-funded projects, the first edition of Accelerating News was published in April 2012 to an initial distribution list of about 800 subscribers. Currently more than 1750 members receive the quarterly issues.

     
  • richardmitnick 11:13 pm on May 2, 2021 Permalink | Reply
    Tags: "NA64 sets bounds on how much new X bosons could change the electron’s magnetism", , , , HEP, NA64 describes a search for new unknown particles – lightweight “X bosons” that could carry a new force., , , Physicists continue to search for new particles and forces that could help complete the model and also explain some tensions with the model., , The Standard Model of particle physics is alive and well. But it is not complete.   

    From European Organization for Nuclear Research (Organisation européenne pour la recherche nucléaire)(EU) [CERN]: “NA64 sets bounds on how much new X bosons could change the electron’s magnetism” 

    Cern New Bloc

    Cern New Particle Event

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

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

    29 April, 2021

    Ana Lopes

    CERN NA64.

    NA64

    The Standard Model of particle physics is alive and well.

    Standard Model of Particle Physics, Quantum Diaries

    But it is not complete, so physicists continue to search for new particles and forces that could help complete the model and also explain some tensions with the model – or “anomalies” – in the behaviour of known particles. In a paper accepted for publication in Physical Review Letters, NA64 describes how a search for new unknown particles – lightweight “X bosons” that could carry a new force – has allowed it to set bounds on how much these particles could contribute to a fundamental property of the electron, in which an apparent anomaly has recently emerged.

    The property in question is the anomalous magnetic moment. The magnetic moment of a particle is a measure of how the particle interacts with a magnetic field. The anomalous magnetic moment is the part of the magnetic moment caused by the interaction of the particle with “virtual” particles that continually pop into and out of existence. These virtual particles comprise all the known particles, predicted by the Standard Model, but they could also include particles never before observed. Therefore, a difference between the Standard Model prediction of the anomalous magnetic moment of a particle and a high-precision measurement of this property could be a sign of new physics in the form of new particles or forces.

    The most striking example of such an anomaly is the muon’s anomalous magnetic moment, for which DOE’s Fermi National Accelerator Laboratory (US) in the US recently announced [4.7.21] [Physical Review Letters] a difference with theory at a significance level of 4.2 standard deviations – just a little below the 5 standard deviations required to claim a discovery of new physics. But there is another example, although at a lower significance level: the Standard Model’s prediction of the electron’s anomalous magnetic moment, based on the measurement of the fundamental constant of nature that sets the strength of the electromagnetic force, differs from the direct experimental measurement at a level of 1.6 or 2.4 standard deviations, depending on which of two measurements of the fundamental constant is used.

    Like other anomalies, this anomaly may fade away as more measurements are made or as theoretical predictions improve, but it could also be an early indication of new physics, so it is worth investigating. In its new study, the NA64 collaboration set out to investigate whether new lightweight X bosons could contribute to the electron’s anomalous magnetic moment and explain this apparent anomaly.

    NA64 is a fixed-target experiment that directs an electron beam of 100-150 GeV energy, generated using a secondary beamline from the Super Proton Synchrotron, onto a target to look for new particles produced by collisions between the beam’s electrons and the target’s atomic nuclei.

    In the new study, the NA64 team searched for lightweight X bosons by looking for the “missing” collision energy they would carry away. This energy can be identified by analysing the energy budget of the collisions.

    Analysing data collected in 2016, 2017 and 2018, which in total corresponded to about three hundred billion electrons hitting the target, the NA64 researchers were able to set bounds on the strength of the interaction of X bosons with an electron and, as a result, on the contributions of these particles to the electron’s anomalous magnetic moment. They found that X bosons with a mass below 1 GeV could contribute at most between one part in a quadrillion and one part in ten trillions, depending on the X boson’s mass.

    “These contributions are too small to explain the current anomaly in the electron’s anomalous magnetic moment,” says NA64 spokesperson Sergei Gninenko. “But the fact that NA64 reached an experimental sensitivity that is better than the current accuracy of the direct measurements of the electron’s anomalous magnetic moment, and of recent high-precision measurements of the fine-structure constant, is amazing. It shows that NA64 is well placed to search for new physics, and not only in the electron’s anomalous magnetic moment.”

    See the full article here.


    five-ways-keep-your-child-safe-school-shootings
    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.

     
  • richardmitnick 7:16 pm on May 2, 2021 Permalink | Reply
    Tags: , , , HEP, Large Hadron Collider’s LHCb detector, Many people would say supersymmetry is almost dead., , , , , , Some solutions nevertheless exist that could miraculously fit both. One is the leptoquark—a hypothetical particle that could have the ability to transform a quark into either a muon or an electron ., , , The data that the LHC has produced so far suggest that typical superpartners-if they exist-cannot weigh less than 1000 protons., The LHCb muon anomalies suffer from the same problem as the new muon-magnetism finding: various possible explanations exist but they are all “ad hoc”, There is one other major contender that might reconcile both the LHCb and Muon g – 2 discrepancies. It is a particle called the Z′ boson because of its similarity with the Z boson.   

    From Scientific American: “Muon Results Throw Physicists’ Best Theories into Confusion” 

    From Scientific American

    April 29, 2021
    Davide Castelvecchi

    The Large Hadron Collider’s LHCb detector reported anomalies in the behavior of muons, two weeks before the FNAL Muon g – 2 experiment announced a puzzling finding about muon magnetism.

    Physicists should be ecstatic right now. Taken at face value, the surprisingly strong magnetism of the elementary particles called muons, revealed by an experiment this month [Nature], suggests that the established theory of fundamental particles is incomplete. If the discrepancy pans out, it would be the first time that the theory has failed to account for observations since its inception five decades ago—and there is nothing physicists love more than proving a theory wrong.

    The Muon g − 2 collaboration at the Fermi National Accelerator Laboratory (Fermilab) outside Chicago, Illinois, reported the latest measurements in a webcast on 7 April, and published them in Physical Review Letters. The results are “extremely encouraging” for those hoping to discover other particles, says Susan Gardner, a physicist at the University of Kentucky (US) in Lexington.

    But rather than pointing to a new and revolutionary theory, the result—announced on 7 April by the FNAL Muon g – 2 experiment near Chicago, Illinois—poses a riddle. It seems maddeningly hard to explain it in a way that is compatible with everything else physicists know about elementary particles. And additional anomalies in the muon’s behaviour, reported in March by a collider experiment [LHCb above], only make that task harder. The result is that researchers have to perform the theoretical-physics equivalent of a triple somersault to make an explanation work.

    Zombie models

    Take supersymmetry, or SUSY, a theory that many physicists once thought was the most promising for extending the current paradigm, the standard model of particle physics.

    Supersymmetry comes in many variants, but in general, it posits that every particle in the standard model has a yet-to-be-discovered heavier counterpart, called a superpartner. Superpartners could be among the ‘virtual particles’ that constantly pop in and out of the empty space surrounding the muon, a quantum effect that would help to explain why this particle’s magnetic field is stronger than expected.

    If so, these particles could solve two mysteries at once: muon magnetism and dark matter, the unseen stuff that, through its gravitational pull, seems to keep galaxies from flying apart.

    Until ten years ago, various lines of evidence had suggested that a superpartner weighing as much as a few hundred protons could constitute dark matter. Many expected that the collisions at the Large Hadron Collider (LHC) outside Geneva, Switzerland, would produce a plethora of these new particles, but so far none has materialized.

    “Many people would say supersymmetry is almost dead,” says Dominik Stöckinger, a theoretical physicist at the Dresden University of Technology [Technische Universität Dresden] (DE), who is a member of the Muon g – 2 collaboration. But he still sees it as a plausible way to explain his experiment’s findings. “If you look at it in comparison to any other ideas, it’s not worse than the others,” he says.

    The data that the LHC has produced so far suggest that typical superpartners-if they exist-cannot weigh less than 1,000 protons (the bounds can be higher depending on the type of superparticle and the flavour of supersymmetry theory).

    There is one way in which Muon g – 2 could resurrect supersymmetry and also provide evidence for dark matter, Stöckinger says. There could be not one superpartner, but two appearing in LHC collisions, both of roughly similar masses—say, around 550 and 500 protons. Collisions would create the more massive one, which would then rapidly decay into two particles: the lighter superpartner plus a run-of-the-mill, standard-model particle carrying away the 50 protons’ worth of mass difference.

    The LHC detectors are well-equipped to reveal this kind of decay as long as the ordinary particle—the one that carries away the mass difference between the two superpartners—is large enough. But a very light particle could escape unobserved. “This is well-known to be a blind spot for LHC,” says Michael Peskin, a theoretician at the DOE’s SLAC National Accelerator Laboratory (US) in Menlo Park, California at Stanford University (US).

    The trouble is that models that include two superpartners with similar masses also tend to predict that the Universe should contain a much larger amount of dark matter than astronomers observe. So an additional mechanism would be needed—one that can reduce the amount of predicted dark matter, Peskin explains. This adds complexity to the theory. For it to fit the observations, all its parts would have to work “just so”.

    Meanwhile, physicists have uncovered more hints that muons behave oddly. An experiment at the LHC, called LHCb, has found tentative evidence that muons occur significantly less often than electrons as the breakdown products of certain heavier particles called B mesons. According to the standard model, muons are supposed to be identical to electrons in every way except for their mass, which is 207 times larger. As a consequence, B mesons should produce electrons and muons at rates that are nearly equal.

    The LHCb muon anomalies suffer from the same problem as the new muon-magnetism finding: various possible explanations exist but they are all “ad hoc”, says physicist Adam Falkowski, at the Paris-Saclay University [Université Paris-Saclay] (FR). “I’m quite appalled by this procession of zombie SUSY models dragged out of their graves,” says Falkowski.

    The task of explaining Muon g – 2’s results becomes even harder when researchers try concoct a theory that fits both those findings and the LHCb results, physicists say. “Extremely few models could explain both simultaneously,” says Stöckinger. In particular, the supersymmetry model that explains Muon g – 2 and dark matter would do nothing for LHCb.

    Some solutions nevertheless exist that could miraculously fit both. One is the leptoquark—a hypothetical particle that could have the ability to transform a quark into either a muon or an electron (which are both examples of a lepton). Leptoquarks could resurrect an attempt made by physicists in the 1970s to achieve a ‘grand unification’ of particle physics, showing that its three fundamental forces—strong, weak and electromagnetic—are all aspects of the same force.

    Most of the grand-unification schemes of that era failed experimental tests, and the surviving leptoquark models have become more complicated—but they still have their fans. “Leptoquarks could solve another big mystery: why different families of particles have such different masses,” says Gino Isidori, a theoretician at the University of Zürich [Universität Zürich ] (CH) in Switzerland. One family is made of the lighter quarks—the constituents of protons and neutrons—and the electron. Another has heavier quarks and the muon, and a third family has even heavier counterparts.

    Apart from the leptoquark, there is one other major contender that might reconcile both the LHCb and Muon g – 2 discrepancies. It is a particle called the Z′ boson because of its similarity with the Z boson, which carries the ‘weak force’ responsible for nuclear decay. It, too, could help to solve the mystery of the three families, says Ben Allanach, a theorist at the University of Cambridge (UK). “We’re building models where some features come out very naturally, you can understand these hierarchies,” he says. He adds that both leptoquarks and the Z′ boson have an advantage: they still have not been completely ruled out by the LHC, but the machine should ultimately see them if they exist.

    The LHC is currently undergoing an upgrade, and it will start to smash protons together again in April 2022. The coming deluge of data could strengthen the muon anomalies and perhaps provide hints of the long-sought new particles (although a proposed electron–positron collider, primarily designed to study the Higgs boson, might be needed to address some of the LHC’s blind spots, Peskin says). Meanwhile, beginning next year, Muon g – 2 will release further measurements. Once it’s known more precisely, the size of the discrepancy between muon magnetism and theory could itself rule out some explanations and point to others.

    Unless, that is, the discrepancies disappear and the standard model wins again. A new calculation, reported this month, of the standard model’s prediction for muon magnetism gave a value much closer to the experimental result. So far, those who have bet against the standard model have always lost, which makes physicists cautious. “We are—maybe—at the beginning of a new era,” Stöckinger says.

    See the full article here .


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    Please help promote STEM in your local schools.


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    Scientific American, the oldest continuously published magazine in the U.S., has been bringing its readers unique insights about developments in science and technology for more than 160 years.

     
  • richardmitnick 1:13 pm on April 30, 2021 Permalink | Reply
    Tags: "Studying top quarks at high and not-so-high energies", , , , HEP, , ,   

    From CERN (CH) ATLAS : “Studying top quarks at high and not-so-high energies” 

    CERN ATLAS another view Image Claudia Marcelloni ATLAS CERN

    From CERN (CH) ATLAS

    11th March 2021 [Just now in social media.]
    ATLAS Collaboration

    CERN’s Large Hadron Collider (LHC) is famous for colliding protons at world-record energies – but sometimes it pays to dial down the energy and see what happens under less extreme conditions. The LHC started operation in 2010 with a collision energy of 7 TeV, and ran at 13 TeV from 2015 to 2018. But for one week in 2017, the LHC produced moderate-intensity collisions at only 5 TeV – allowing scientists to analyse the production of various elementary particles at a lower collision energy.

    One particle they were especially keen to study was the top quark. As the heaviest-known elementary particle, the rate (or cross-section) for producing top-quark pairs depends very strongly on the collision energy achieved. By measuring the production rate at different energies, scientists can learn more about the distributions of the quarks and gluons that make up the proton.

    The ATLAS Collaboration has just released a new measurement of the top-quark pair-production rate in the 5 TeV data sample. With just a single week of data, their final measurement has an uncertainty of just 7.5%. This uncertainty is primarily due to the very small size of the 5 TeV data sample, with systematic uncertainties related to the calibration of the LHC luminosity and the experimental response being only a few percent.

    1
    Figure 1: Top-pair production cross-section as a function of collision energy, showing ATLAS measurements (black circles and red triangle) compared to the theoretical prediction (cyan band). The lower plots show the ratio of the measurements to prediction using various parton distribution functions, i.e. parameterisations of the internal structure of the proton using different assumptions and input datasets. (Image: ATLAS Collaboration/CERN).

    Top quarks decay rapidly and leave a distinct signature in the detector. To spot top-pair collision events, ATLAS physicists looked for events with two electrons, two muons, or an electron–muon pair, one or two ‘b-tagged’ jets of particles (coming from b-quark decays), and a significant momentum imbalance indicating the presence of a neutrino. This selection heavily suppresses background events from the production of other types of particles, particularly in the case of electron–muon events. In events with either two electrons or two muons, there is still a large background from events with Z bosons to contend with. Physicists reduced this background using the measured energies and angles of the electrons and muons, requiring their combination to be inconsistent with originating from a Z boson decay.

    The new measurement is shown by the red triangle in Figure 1, together with previous measurements at higher energies from electron–muon events alone. The cross-section at 5 TeV is more than a factor ten smaller than that at the highest energy of 13 TeV. All the measurements are in excellent agreement with theoretical predictions, which combine the theory of quantum chromodynamics with knowledge of the internal structure of the proton.

    Such comparisons serve to validate the understanding of proton–proton collisions, and act as a springboard to the next LHC run starting in 2022, where CERN hopes to further increase the LHC collision energy towards 14 TeV.

    See the full article here .


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    Please help promote STEM in your local schools.

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    CERN Courier (CH)

    Quantum Diaries
    QuantumDiaries

    European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire(CH) map

    CERN LHC underground tunnel and tube.

     
  • richardmitnick 2:48 pm on April 25, 2021 Permalink | Reply
    Tags: "Search for New Physics with one charged lepton and missing energy", , , , HEP, , ,   

    From CERN (CH) CMS: “Search for New Physics with one charged lepton and missing energy” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN (CH) CMS

    4.28.21
    CMS Collaboration

    1
    Figure 1. Collision event recorded by the CMS experiment, with a balanced high energy electron and missing transverse momentum. The display shows the highest transverse mass (MT) event collected in LHC Run 2 in the electron channel. The event has MT = 3.1 TeV, and the electron energy deposit is shown in the long green bar at the top of the display. The purple line denotes the direction of the missing transverse momentum.

    Event display with an electron. This is the highest MT muon+MET event recorded by CMS in Run 2

    Experimental evidence from the last half-century has established the standard model as a foundational theory of particle physics.

    Still, it is clear that the standard model is not the final theory. There are many open questions: Is the mass of Higgs natural or fine-tuned? If natural, what new physics (symmetry) governs this? How does gravity play with the other forces? Are there more space dimensions than the familiar three? Do all forces unify at high energy? Many compelling theoretical ideas of new physics beyond the standard model have been proposed to address the open questions. Interestingly, many of these new theories have in common that they introduce new massive particles or differences in the behavior of known particles. If these new phenomena exist in the real world, LHC is best positioned to observe them.

    Such new particles could be a new charged W’ boson particle decaying into one charged lepton (electron or muon) and a neutrino in the proton-proton collision events recorded in the CMS detector. The W’ boson is usually predicted as a carbon copy of the W boson in the standard model, but it is very heavy, so it can also decay into the two heaviest quarks. In this analysis, the events where the W’ decays to a lepton and neutrino are taken into account because leptons are extremely clean signatures in the detector and give lower contributions from standard model processes that mimic this signature than the hadronic channels. The charged leptons can be accurately detected and measured in the CMS detector, whereas neutrinos are weakly interacting particles that will escape the detector without a signal. Nevertheless, their presence can be inferred by momentum conservation in the transverse plane. We sum the transverse momenta of all the detected particles in the event and assign the missing transverse momentum (generally called MET) to the neutrinos.

    To separate the W’ signal events from the standard model background events, CMS physicists select events with specific properties: the charged lepton and neutrino must be very energetic, the ratio of their energies has to be almost one, and they have to be back-to-back in the plane perpendicular to the beam axis. The event displays of the observed event for electron and muon channels are shown in Figure 1 and 2. One of the main tasks in this analysis is calibrating, identifying, and correctly measuring the most energetic electrons and muons ever detected in a collider experiment. For the invisible neutrino, as stated above, we can only estimate its transverse component so that the mass of the parent particle can be constrained by the transverse mass (MT). This quantity is a key one in this new physics search that distinguishes the standard model W from the new massive W’ one. Assume W’ exists and promptly decayed into two particles. In that case, the signal will be appearing as a peak (called a resonance) at the very high MT tail region, where background events hardly exist making the resonance relatively easy to spot.

    An example of the transverse mass distributions we observed is shown in Figure 3. The experimental data agree well with the standard model expectation, and there is no hint of significant deviation.

    2
    Figure 2: Collision event recorded by the CMS experiment, with a balanced high energy muon and missing transverse momentum. The display shows the highest transverse mass (MT) event collected in LHC Run 2 in the muon channel. The event has MT = 2.9 TeV, and the muon is shown as a red line. The purple line denotes the direction of the missing transverse momentum.

    With these data, it is possible to do two different kinds of search. Figure 3 illustrates the two scenarios: on one side, we assume the new hypothetical W’ particle can be produced at the LHC, and we look for it in our data. This is called a “direct resonance search”, as the resonance from the particle should be directly visible in the data. But the new particle might be very massive and not directly reachable with the current LHC energy. In that case, we might be able to see some hints of it, as explained in Figure 4. This is the “indirect search” and it places restrictions on how far this new physics could lie.

    3
    Figure 3. Transverse mass distribution for events with one energetic lepton (muon) and considerable missing transverse momentum. Shown are the observed data (black dots), the predicted standard model background contributions (colored blocks), and signals with two specific Sequential Standard Model W’ masses of 3.8 TeV (purple line) and 5.6 TeV (green line). The lower panels show the difference between the observed data and the background estimate.

    As the data agrees with what we expect, we can set limits on the new particle’s properties. These results can also be used to constrain a variety of other new physics models predicting a lepton and a neutrino in the final state. This approach (called reinterpretation) tests a host of different physics predictions like the existence of new spatial dimensions, new symmetries in nature, and more. We have also combined all of these interpretations of the data to look for a different effect of new physics: the hypothesis that the Higgs boson we discovered is not an elementary particle but is made of other undiscovered particles. This is known as the Composite Higgs scenario. With this analysis, we can explore this model in a complementary approach to looking at Higgs bosons.

    4
    Figure 4. Sketch showing two kinds of possibilities studied in this analysis. The new particles are at reach at the LHC (direct search), or they are very massive and beyond LHC energy, but they still change the distributions slightly (indirect search).

    It is fascinating to explore an unprecedented region for new particles. As the center-of-mass energy and the amount of accumulated data increases, more signal-like higher MT events can be observed at LHC. This will improve sensitivity for the discovery of the W’ boson if it is slightly too heavy to be seen up to now.

    A new LHC era will soon begin with Run3 (2022-2024) which plans to double the amount of data collected during Run2 (2016-2018). Furthermore, High-Luminosity LHC is scheduled to come into operation at the end of 2027 after upgrading all of the equipment (2025-2027). High-Luminosity LHC will enable us to investigate up to 20 times more data than Run2. With these data, we can test the vast scope of many new theoretical physics models much more effectively. This will lead us towards a deeper understanding of our universe and hopefully unlock many mysteries.

    See the full article here.


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    Meet CERN (CH) in a variety of places:

    Quantum Diaries
    QuantumDiaries

    Cern Courier (CH)

     
  • richardmitnick 10:26 am on April 20, 2021 Permalink | Reply
    Tags: , , HEP, , , ,   

    From ILC : Several articles From International Linear Collider Newsline 

    From International Linear Collider Newsline

    Laboratories and industry in tune for particle physics detector R&D in Europe

    19 April 2021
    Perrine Royole-Degieux

    1

    10 million euros. This will be the amount granted to members of the AIDAinnova project (advancement and innovation for Detectors at Accelerators programme) funded by the European Commission Horizon 2020 programme, under a special ‘Innovation Pilots’ call. As particle physics requires highly-specialised detection equipment, often on an industrial scale, the project will be strongly marked by the collaboration between industry and academic institutions.

    AIDAinnova [no link] builds on the success of its predecessor projects AIDA [no link] and AIDA 2020-Advanced European Infrastructures for Detectors at Accelerators (EU), both of which boosted infrastructure at research labs for the development of new detector technologies. Coordinated by CERN, the successor project receives 10 million Euros for four years and features nine industrial companies, three research and technology organisations and 34 academic institutions in 15 countries. ‘Having companies directly involved in detector development is a novelty that aims at faster turnaround and more innovation both for research and industry,’ said Felix Sefkow (DESY, Germany), AIDAInnova coordinator, and scientific coordinator for the previous project AIDA-2020.

    AIDAinnova will provide state-of-the-art upgrades to research infrastructures, such as test beams, in order to exploit the scientific potential of detector technologies. Among well-defined R&D work packages, scientists have opened the door to ‘greenfield’ projects. A call for tenders will be launched which will allow funding innovative and ‘off-axis’ projects.

    There will be two levels of participation for industry. Companies may simply participate as associates of AIDAInnova member laboratories. Other companies – nine in total – signed to join as full members of the collaboration. They will use the EC funds to design and test detector parts or to employ dedicated staff. A new kind of collaboration with industry, more constraining but also with more benefits.

    ‘The nine industrial companies involved in AIDAInnova will benefit in many ways, first and foremost in terms of visibility,’ said Giovanni Calderini, AIDAInnova coordinator at CNRS/IN2P3, France. Being a full member of the project demonstrates a strong link with the scientific community and is also a heavy responsibility. ‘Collaborating with major institutions or laboratories such as CERN, IN2P3 or DESY to name a few, is a guarantee of quality for their future clients,’ said Calderini. ‘They may become later privileged partners for other scientific experiments, opening up new sectors and new markets.’ And the benefit is mutual. ‘In a collaboration, there is a deeper level of exchange. Sometimes this leads scientists to play an actual role within the company. Getting to know an industrial company in great detail is extremely valuable for us, the exchanges are sincere and transparent,’ concludes Calderini.

    AIDAInnova will cover a wide range of experiments from the second round of upgrades of the LHC detectors, at the mid of the high-luminosity phase (foreseen to be ready around 2030s) to CLIC, FCC and of course ILC detectors. Most work packages may contribute to any of these projects. For the ILC, one challenge will be to design mechanical structures and electronics as thin and light as possible so that incoming particles barely interact with them. Another crucial area of R&D will be the calorimetry, where scientists will try to increase detector granularity and time resolution for a more precise reconstruction of particle showers. Another promising technology for the ILC are monolithic sensors, where sensors and front end electronics are realised on a common silicon structure. ‘We’ve made a lot of progress in this area in the last years, and I’m convinced that these technologies will play a major role in the construction of the ILC detectors,’ says Calderini.

    For all these technological challenges, collaboration with industry will be crucial, as the real difficulty will be to find a compromise between the most advanced technology to date and a reasonable cost for the scientific community. The AIDAInnova kick-off meeting, gathering all partners from academia to industry, will take place from 13 to 16 April 2021.

    See the full article here .

    Call for participation in Physics & Detector WG3

    19 April 2021
    Hitoshi Murayama

    2
    Two detector concepts- SiD(left) and ILD(right)
    Image: Rey.Hori

    The IDT Working Group on Physics & Detector activities (WG3) would like to invite the community to engage in the ILC studies.

    WG3 aims to raise awareness and interest in the ILC development and expand the community, support newcomers to get involved in physics and detector studies, encourage new ideas for experimentations at the ILC.

    The WG3 Steering Group consists of the coordinator (WG3 Chair), two deputy coordinators, subgroup conveners, and additional members of the Steering Group.

    The four subgroups of WG3 are: (1) Machine-Detector Interface Subgroup, (2) Detector and Technology R&D Subgroup, (3) Software and Computing Subgroup, (4) Physics Potential and Opportunities Subgroup.

    The studies provide crucial information about the physics and detectors to the final engineering design of the machine as well as infrastructure and lead up to Expressions of Interest for collider and non-collider experiments. The participation is completely open to anybody interested in the particle physics community.

    You can find the mandate adopted for the WG3 at https://linearcollider.org/idt-wg3-mandate/. The members of the leadership are listed at https://linearcollider.org/team/. You are encouraged to contact convenors of the subgroup of your interest. We look forward to having you involved!

    See the full article here .

    LCWS2021- the community focuses on an ILC Pre-Lab as the next step

    19 April 2021
    Steinar Stapnes

    1
    The table showing the session time slots in 3 time zones; Pacific Daylight Time (PDT) – US West Coast
    Central European Time (CET) – Geneva
    Japan Standard Time (JST) – Tokyo

    The 2021 International Workshop on Future Linear Colliders (LCWS2021), arranged by Europe as an online conference with more than 900 registered participants, took place from 15 to 18 March. As earlier conferences in this series it was primarily devoted to the physics, detector, and accelerator studies for the Compact LInear Collider (CLIC) and the International Linear Collider (ILC).

    Since the last workshop in the series (LCWS2019), many new international developments have taken place. The European Strategy for Particle Physics (ESPP) Update 2020 places an electron-positron Higgs factory as the highest-priority next-generation collider. A linear collider – CLIC or ILC – will operate as a Higgs factory during its initial stage, while maintaining a clear path for future energy upgrades. The CLIC programme and associated high-gradient R&D for 2021-26 have been defined in accordance with the ESPP outcome.

    Preparations for the ILC in Japan have changed gear with the International Committee for Future Accelerators (ICFA) announcing the establishment of the ILC International Development Team (IDT) hosted by KEK. ILC is currently the focus of a general and broad effort in Japan involving several Ministries as well as the Diet, in close connection with industry, academia and the Tohoku region, the potential construction site. This progress has been summarised in a recent document issued by the ILC Steering Panel established under Japan Association of High Energy Physicists (JAHEP). Besides the progress achieved in Japan, 2020 also saw the emergence and focused effort of the IDT towards defining the ILC Pre-Lab programme – a four-year preparatory phase to bring the ILC project to construction readiness, and the organisational structures and processes needed to start the Pre-Lab. In the US, the Snowmass process is on-going with ILC as the most prominent Higgs-factory possibility on the timescale considered.

    The LCWS2021 started Monday morning with an online version of the 8th Linear Collider Physics school where some 160 students participated. From Monday afternoon to Thursday afternoon plenary and parallel sessions were used to review the progress on accelerator design for linear colliders, detector developments and physics studies and, equally important, looking ahead towards the next steps. ILC topics were overlapping with similar CLIC activities whenever possible.

    The main plenaries were on Monday and Thursday. The Monday plenary session featured reports on technical/scientific aspects on ILC and CLIC, status reports from Japan (KEK, the JAHEP ILC Steering Panel and Tohoku) and North America, and recent progress from IDT. The Thursday plenary included CERN and European perspective talks, an update on the linear-collider-related Snowmass preparation and documentation, and summaries of some of the parallel working group sessions. The Tuesday and Wednesday plenary sessions focused on accelerator and physics & detector studies, respectively.

    With a wide programme of 51 parallel sessions, the workshop provided ample opportunities to present ongoing work as well as getting informed and involved. The Physics and Detector parallel sessions alone attracted 144 submitted abstracts. Altogether 292 talks were given during the four days.

    Besides these sessions, the programme also included a special ‘New Research and Opportunities Tracks’ to discuss ideas of complementary programmes beyond the ILC Higgs factory (e.g. fixed-target and beam-dump experiments – relevant for example for dark sector physics, lower energy beams for accelerator and detector R&D, irradiation possibilities, electron-laser collisions, etc.). In addition, a session on ‘New Technologies & Ideas for Collider Detectors’ was included. These sessions represent a first step towards ILC Expressions of Interest, and these topics will be further pursued in a dedicated ILC workshop, planned to be held in Tsukuba from 26 to 29 October.

    A new feature was a session on advanced and novel accelerator (ANA) technologies prepared by the ICFA-ANA panel. Not only can these technologies be of interest to deploy in the longer term in an LC tunnel to reach multi-TeV energies, but an LC facility can also in the shorter term provide interesting and unique beams and opportunities for developing such novel technologies.

    A very interesting session with around 70 participants was devoted to the industrial aspects of the ILC, offering an opportunity to highlight the expertise and innovation capabilities of national laboratories and their related industrial partners for the ILC Pre-Lab activities and the main ILC technologies.

    Overall the workshop highlighted the large and increasing international community and efforts pursuing a future linear collider, and the community is now very focused on an ILC Pre-Lab as the immediate next step towards an operational Higgs factory by 2035.

    Steinar Stapnes on behalf of – and with sincere thanks to – the Organising Committee
    Europe | European Strategy for Particle Physics | Higgs factory | ILC

    See the full article here .

    New joint French-Japanese laboratory in Tokyo for physics at the largest and smallest scales

    April 01, 2021
    Véronique Etienne

    The French National Centre for Scientific Research [Centre national de la recherche scientifique, CNRS] (FR) and the University of Tokyo[(東京大学; Tōkyō daigaku](JP) have set up a laboratory for physics research at the largest and smallest scales of the Universe.


    ILANCE is the CNRS’s seventh International Research Laboratory in Japan.

    From neutrinos to dark matter, and from particle accelerators to gravitational wave detectors and the first light of the Universe1: the ILANCE laboratory (International Laboratory for Astrophysics, Neutrino and Cosmology Experiments), bringing together the CNRS and the University of Tokyo, will conduct physics research at the very smallest and largest scales of our Universe. Set up on 1 April 2021, the CNRS’s seventh International Research Laboratory in Japan is also the third to be jointly run with the University of Tokyo2. It will be headed by Michel Gonin, Research Professor at the CNRS, who has long been involved in neutrino experiments in Japan3, and co-directed by Takaaki Kajita, Professor at the University of Tokyo and winner of the Nobel Prize in Physics in 2015.

    Based on the Kashiwa campus located in the north-east of the Greater Tokyo Area, the laboratory will permanently host scientists from the University of Tokyo and the CNRS, focusing on five research topics in which both institutions are at the cutting edge: neutrinos (in connection with the Super-Kamiokande and Hyper-Kamiokande projects); the primordial Universe (in connection with the Japanese LiteBIRD satellite, which will follow on from Europe’s Planck spacecraft); gravitational waves (in connection with the Kagra gravitational wave detector4); the dark Universe (dark matter and energy); and particle physics (in connection with the ATLAS experiment at CERN and a particle accelerator project in Japan, the International Linear Collider).

    See the full article here .

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    The International Linear Collider (ILC) is a proposed linear particle accelerator.It is planned to have a collision energy of 500 GeV initially, with the possibility for a later upgrade to 1000 GeV (1 TeV). The host country for the accelerator has not yet been chosen and proposed locations are Japan, Europe (CERN) and the USA (Fermilab). Japan is considered the most likely candidate, as the Japanese government is willing to contribute half of the costs, according to a representative for the European Commission on Future Accelerators.Construction could begin in 2015 or 2016 and will not be completed before 2026.

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

    ILC

     
  • richardmitnick 3:41 pm on April 15, 2021 Permalink | Reply
    Tags: "Investigating heavy quark physics with the LHCb experiment", , , HEP, INFN National Institute for Nuclear Physics (IT), , , , three decades of the LHCb experiment—from its conception to operation at the Large Hadron Collider (LHC)   

    From INFN National Institute for Nuclear Physics (IT) via phys.org : “Investigating heavy quark physics with the LHCb experiment” 

    From INFN National Institute for Nuclear Physics (IT)

    via

    phys.org

    April 15, 2021

    A new review published in The European Physical Journal H by Clara Matteuzzi, Research Director at the National Institute for Nuclear Physics (INFN) and former tenured professor at the University of Milan [Università degli Studi di Milano Statale], and her colleagues, examines almost three decades of the LHCb experiment—from its conception to operation at the Large Hadron Collider (LHC) – documenting its achievements and future potential.

    The LCHb experiment was originally conceived to understand the symmetry between matter and antimatter and where this symmetry is broken—known as charge conjugation parity (CP) violation. Whilst this may seem like quite an obscure area of study, it addresses one of the Universe’s most fundamental questions: how it came to be dominated by matter when it should have equally favoured antimatter?

    “LHCb wants to study by which mechanism our universe, as we see it today, is made of matter, and how antimatter disappeared despite an initial symmetry between the two states,” says Matteuzzi. “The Standard Model contains a tiny amount of violation of this symmetry, whilst the observation of the universe implies a much larger one. This is one of the most fascinating open questions in the Particle Physics field.”

    The LHCb experiment investigates this problem by studying the behaviour of systems and particles made from so-called heavy quarks. These are produced in abundance by highly energetic collisions—explaining why the LHC is the perfect location to study them—and were also abundant in the highly energetic early Universe.

    “The field in which the LHCb is active is so-called ‘heavy quarks physics’ which aims to study and understand the behaviour of the particles containing the c and b heavy quarks—usually named charm and beauty quarks,” says Matteuzzi. “The rich sector—spectroscopy—covered by LHCb is how quarks of different types, or flavours, aggregate together to form particles in a way that is analogous to how ‘Up’ and ‘Down’ quarks in different combinations make protons and neutrons.”

    “It became clear that the potentiality of the LHCb detector was in other fields beyond the study of CP violation that also hinged on aspects of heavy quark interaction. One was the spectacular success of spectroscopy and the measurement of many new states composed by heavy quarks,” concludes Matteuzzi. “This incredibly rich variety of results is demonstrated in our paper—we hope!”

    See the full article here .

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    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy

    INFN Gran Sasso (IT) is the largest underground laboratory in the world devoted to neutrino and astroparticle physics, a worldwide research facility for scientists working in this field of research, where particle physics, cosmology and astrophysics meet. It is unequalled anywhere else, as it offers the most advanced underground infrastructures in terms of dimensions, complexity and completeness.

    LNGS is funded by the National Institute for Nuclear Physics (INFN), the Italian Institution in charge to coordinate and support research in elementary particles physics, nuclear and sub nuclear physics

    Located between L’Aquila and Teramo, at about 120 kilometres from Rome, the underground structures are on one side of the 10-kilometre long highway tunnel which crosses the Gran Sasso massif (towards Rome); the underground complex consists of three huge experimental halls (each 100-metre long, 20-metre large and 18-metre high) and bypass tunnels, for a total volume of about 180.000 m3.

    Access to experimental halls is horizontal and it is made easier by the highway tunnel. Halls are equipped with all technical and safety equipment and plants necessary for the experimental activities and to ensure proper working conditions for people involved.

    The 1400 metre-rock thickness above the Laboratory represents a natural coverage that provides a cosmic ray flux reduction by one million times; moreover, the flux of neutrons in the underground halls is about thousand times less than on the surface due to the very small amount of uranium and thorium of the Dolomite calcareous rock of the mountain.

    The permeability of cosmic radiation provided by the rock coverage together with the huge dimensions and the impressive basic infrastructure, make the Laboratory unmatched in the detection of weak or rare signals, which are relevant for astroparticle, sub nuclear and nuclear physics.

    Outside, immersed in a National Park of exceptional environmental and naturalistic interest on the slopes of the Gran Sasso mountain chain, an area of more than 23 acres hosts laboratories and workshops, the Computing Centre, the Directorate and several other Offices.

    Currently 1100 scientists from 29 different Countries are taking part in the experimental activities of LNGS.
    LNGS research activities range from neutrino physics to dark matter search, to nuclear astrophysics, and also to earth physics, biology and fundamental physics.

     
  • richardmitnick 10:09 am on April 11, 2021 Permalink | Reply
    Tags: "Peering inside the atom", , , , HEP, , , , , Undated compilation of the History of Particle Physics   

    From European Organization for Nuclear Research (Organisation européenne pour la recherche nucléaire)(EU) [CERN] via Science News : “Peering inside the atom” 

    Cern New Bloc

    Cern New Particle Event

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

    via

    Science News

    Undated compilation of the History of Particle Physics

    13
    About Century of Science | Science News
    © De Agostini Picture Library/SCIENCE SOURCE.

    13
    How physicists revealed subatomic particles and cracked matter’s secrets | Science News
    Copyright: Connie Zhou / OTTO.

    Matter is a lush tapestry, woven from a complex assortment of threads. Diverse varieties of subatomic particles intertwine to fabricate the universe we inhabit. But a century ago, people believed that matter was so simple that it could be constructed with just two types of subatomic fibers — electrons and protons. That vision of matter was a no-nonsense plaid instead of an ornate brocade.

    Physicists of the 1920s thought they had a solid grasp on what made up matter. They knew that atoms contained electrons surrounding a positively charged nucleus. And they knew that each nucleus contained a number of protons, positively charged particles identified in 1919. Combinations of those two particles made up all of the matter in the universe, it was thought. That went for everything that ever was or might be, across the vast, unexplored cosmos and at home on Earth.

    The scheme was appealingly tidy, but it swept under the carpet a variety of hints that all was not well in physics. Two discoveries in one revolutionary year, 1932, would force physicists to peek underneath the rug. First, the discovery of the neutron unlocked new ways to peer into the hearts of atoms and even split them in two. Then came news of the positron — identical to the electron but with the opposite charge. Its discovery would foreshadow many more surprises to come. Additional particle discoveries ushered in a new framework for the fundamental bits of matter, now known as the Standard Model.

    Standard Model of Particle Physics via Particle Fever movie.

    1
    A particle track in a cloud chamber in the early 1930s was the first evidence of a positron, a positively charged particle with the mass of an electron. The track curves due to a magnetic field, and the curvature increases as the positron loses energy after crossing the center lead plate from below. Credit: C. D. Anderson/Emilio Segrè Visual Archives.

    And that annus mirabilis — miraculous year — would set physicists on two parallel tracks of exploration. One would blossom into the modern discipline of particle physics. After the positron’s appearance, the discovery of dozens more particles would lead to a new insight: Protons and neutrons aren’t elementary. They have even smaller components called quarks. Particle physics scrutinizes those most fundamental bits of matter — quarks, electrons, positrons and the like.

    The other track would lead to modern nuclear physics, concerned with the workings of atoms’ hearts, how they decay, transform and react. Discoveries there would put scientists on a trajectory toward a most devastating technology: nuclear weapons. The bomb would cement the importance of science — and science journalism — in the public eye, says nuclear historian Alex Wellerstein of Stevens Institute of Technology in Hoboken, N.J. “The atomic bomb becomes the ultimate proof that … indeed this is world-changing stuff.”

    In the decades that followed, these fields would fundamentally alter how humankind understood and manipulated matter. Soon, physicists were busier than ever. — Emily Conover

    ________________________________________________________________________________________________________________________________

    Goodbye, two particles

    Physicists of the 1920s embraced a particular type of conservatism. Embedded deep in their psyches was a reluctance to declare the existence of new particles. Researchers stuck to the status quo of matter composed solely of electrons and protons. It’s an idea that has been dubbed the “two-particle paradigm,” and it held until about 1930. In that time period, says historian of science Helge Kragh of the University of Copenhagen [Københavns Universitet](DK), “I’m quite sure that not a single mainstream physicist came up with the idea that there might exist more than two particles.” The utter simplicity of two particles explaining everything nature’s bounty could produce was so appealing to physicists’ sensibilities that they found the idea difficult to let go of.
    ________________________________________________________________________________________________________________________________

    The paradigm held back theoretical descriptions of the neutron and the positron, two particles found one after the other in 1932. And another would-be new particle, the neutrino, proposed in 1930, was likewise considered unappealing. “To propose the existence of other particles was widely regarded as reckless and contrary to the spirit of Occam’s razor,” science biographer Graham Farmelo wrote in Contemporary Physics in 2010.

    Still, during the early 20th century, physicists were diligently investigating a few puzzles of matter that would, after some hesitation, inevitably lead to new particles. These included unanswered questions about the details of radioactive decay, the identities and origins of energetic particles called cosmic rays, and why chemical elements occur in different varieties called isotopes, which have similar chemical properties but varying masses.

    2
    Physicists including Ernest Rutherford investigated the atom at the Cavendish Laboratory at University of Cambridge(UK) (Rutherford’s lab shown) in the 1920s.Science History Images/Alamy Stock Photo.

    New Zealand–born British physicist Ernest Rutherford stopped just short of positing a fundamentally new particle in 1920. He realized that neutral particles in the nucleus could explain the existence of isotopes. Such particles came to be known as “neutrons.” But rather than proposing that neutrons were fundamentally new, he thought they were composed of protons combined in close proximity with electrons to make neutral particles. He was correct about the role of the neutron, but wrong about its identity.

    Rutherford’s idea was convincing, British physicist James Chadwick recounted in a 1969 interview, “The only question was how the devil could one get evidence for it.” The neutron’s lack of electric charge made it a particularly wily target. In between work on other projects, Chadwick began hunting for the particles at Cavendish Laboratory at the University of Cambridge, then led by Rutherford. Chadwick found his evidence in 1932 — reporting that mysterious radiation emitted when beryllium was bombarded with the nuclei of helium atoms could be explained by a particle with no charge and with a mass similar to the proton’s. In other words, a neutron. Chadwick didn’t expect the important role his discovery would play. “I am afraid neutrons will not be of any use to anyone,” he told The New York Times shortly after his discovery.

    Physicists would grapple with the neutron’s identity over the following years before accepting it as an entirely new particle, not the amalgamation that Rutherford had suggested. For one, a proton-electron mash-up conflicted with the young theory of quantum mechanics, which characterizes physics on small scales. The Heisenberg uncertainty principle — which states that if the location of an object is well known, its momentum cannot be — suggests an electron confined within a nucleus would have an unreasonably large energy. And certain nuclei’s spins, a quantum mechanical measure of angular momentum, likewise suggested that the neutron was a full-fledged particle, as did improved measurements of the particle’s mass.

    Physicists also resisted the positron, until it became difficult to ignore.

    The positron’s 1932 detection had been foreshadowed by the work of British theoretical physicist Paul Dirac. But it took some floundering about before physicists realized the meaning of his work. In 1928 Dirac formulated an equation that combined quantum mechanics and the special theory of relativity, formulated by Albert Einstein back in 1905, which describes physics close to the speed of light. Now known simply as the Dirac equation, the expression explained the behavior of electrons in a way that satisfied both theories.

    The Dirac equation in the form originally proposed by Dirac is:

    4

    But the equation suggested something odd: the existence of another type of particle, one with the opposite electric charge. At first, Dirac and other physicists clung to the idea that this charged particle might be the proton. But the two particles should have the same mass, and protons are almost 2,000 times as heavy as electrons. In 1931 Dirac proposed a new particle, with the same mass as the electron but with opposite charge.

    Meanwhile, American physicist Carl Anderson of California Institute of Technology(US), independent of Dirac’s work, was using a device called a cloud chamber to study energetic particles originating in space, called cosmic rays. Cosmic rays, discovered in 1912, fascinated scientists because they didn’t fully understand what the particles were or how they were produced. Within Anderson’s chamber, liquid droplets condensed along the paths of energetic charged particles, a result of the particles ionizing gas molecules as they zipped along. The experiments revealed positively charged particles with masses equal to an electron’s. Soon, the connection to Dirac’s theory became clear.

    Science News Letter, the predecessor of Science News, had a hand in naming the newfound particle. Editor Watson Davis proposed “positron” in a telegram to Anderson, who had independently considered the moniker, according to a 1933 Science News Letter article. In a 1966 interview, Anderson recounted mulling over Davis’ suggestion during a game of bridge, and finally going along with it. But he later regretted the choice, saying in the interview, “I think that’s a very poor name.”

    6
    The Feb. 25, 1933 issue of Science News Letter reported the discovery of the “positron,” a particle that the publication’s editor helped to name.Science News

    The discovery of the positron, the antimatter partner of the electron, marked the advent of antimatter research. And today, antimatter’s existence still seems baffling. Every object we can see and touch is made of matter, making antimatter seem downright extraneous. Antimatter’s lack of relevance to daily life — and the liberal use of the term in Star Trek — means that many nonscientists still envision it as the stuff of science fiction. But even a banana sitting on a counter emits antimatter multiple times a day, periodically spitting out positrons in radioactive decays of the potassium it contains.

    Physicists would go on to discover many other antiparticles — all of which are identical to their matter partners except for an opposite electric charge — including the antiproton in 1955. The subject still keeps physicists up at night. Scientists think the Big Bang should have produced equal amounts matter and antimatter, so researchers today are studying how antimatter became rare.

    In the 1930s, antimatter was such a leap that Dirac’s hesitation to propose the positron was understandable. Not only would the positron break the two-particle paradigm, but it would also suggest that electrons had mirror images with no apparent role in making up atoms. When asked, decades later, why he had not predicted the positron after he first formulated his equation, Dirac replied, “pure cowardice.”

    The discoveries came on the heels of yet another particle prediction, the neutrino. Reluctantly postulated by Austrian physicist Wolfgang Pauli in 1930, the particle has no electric charge and interacts very rarely, suggesting it would never be detected: “I have done something very bad today by proposing a particle that cannot be detected; it is something no theorist should ever do,” Pauli reportedly said.

    Pauli’s prediction was what he called a “desperate remedy.” Researchers studying a type of radioactive decay known as beta decay had hit on a quandary that threatened to undermine the basics of physics. In beta decay, an atom spits out an electron and converts into a different element. A central physics principle, conservation of energy, suggests that the particles emitted in radioactive decays from identical atoms should always carry the same amount of energy. But the wayward electrons had a range of energies. That apparent noncompliance led some physicists to propose the radical idea that energy was not always conserved.

    In a letter to a group of nuclear physicists, which Pauli famously addressed, “Dear radioactive ladies and gentlemen,” he proposed that the electron in beta decay was accompanied by a second, undetected particle that would carry away some energy.

    Soon, Italian physicist Enrico Fermi would popularize the name “neutrino” for the particle, Italian for “little neutral one.” In 1934 he would come up with a mathematical theory based on the particle’s existence that successfully described beta decay. In Fermi’s scheme, the electron and neutrino were released when a neutron converted into a proton in the atom’s nucleus. That general interpretation still stands, though today’s physicists now refer to the particle as an electron antineutrino, because three types of neutrinos and their antiparticles are now known. Fermi’s explanation bolstered belief in neutrinos, conclusively detected in 1956.

    So by the mid-1930s, the two-particle paradigm was out. Physicists’ understanding had advanced, but their austere vision of matter had to be jettisoned. That shift in mindset would soon be reinforced with even more particle discoveries, and the simple picture of nature was further demolished. — Emily Conover

    _______________________________________________________________________________________________________________________________________________________
    Many, many particles

    Physicists have long revered elegance, expecting that nature at its most basic should be simple. That sensibility was evident in the 1920s insistence that the electron and proton made up all of matter. But after the conceptual logjam against new particles broke down, and technological advances opened up new ways to explore the subatomic realm, physicists found themselves drowning in a flood of new particles. Fleshing out an explanation would consume physicists for decades.
    _______________________________________________________________________________________________________________________________________________________

    In the 1950s and ’60s, new particles were detected by the dozens, forming an alphabet soup of Greek letters: phi baryons, xi baryons, eta mesons and many, many more. “If I could remember the names of all these particles I’d be a botanist,” physicist Enrico Fermi famously said. Many of these newfound particles were exotic varieties, formed when particles collide at high energies and not present within atoms.

    Physicists quickly tired of the deluge. In 1955, physicist Willis Lamb, Jr. recounted a saying of the time, “the finder of a new elementary particle used to be rewarded by a Nobel Prize, but such a discovery now ought to be punished by a $10,000 fine.”

    At first, the particles were found gradually, by studying natural collisions, produced from energetic particles from space called cosmic rays. But in the mid-1950s, particle accelerators kicked things up a notch. With this new technology, physicists could boost beams of particles to high speeds, smashing them into targets or other beams of particles, to see what might emerge from the smashups.

    7
    Today, scientists use large detectors such as Super-Kamiokande (JP) (shown) in Hida, Japan to detect and study the mysterious particles called neutrinos.The Asahi Shimbun via Getty Images.

    At the time, scientists couldn’t explain why so many apparently fundamental particles existed, especially given that everyday matter required only protons, neutrons and electrons. “By 1960 or so it was a widespread feeling that there were too many particles, and that there had to be some family resemblance between them,” says historian of science Helge Kragh of the University of Copenhagen. Soon the concept of quarks would bring some order to the menagerie.

    As Science News Letter reported in 1964, “A quark is not an animal out of Alice in Wonderland or the sound a duck might make.” Instead, quarks, proposed in 1964 and confirmed in experiments over the next decade, are smaller particles that, mashed together in different combinations, make up many of the particles previously considered fundamental, including protons and neutrons.

    Additional work led physicists to a coherent picture of the fundamental particles and forces of nature, called the standard model. The work of many physicists operating independently and in groups, the framework consists of 17 particles, plus antiparticle partners. Included on the list are six types of quarks and six leptons. Electrons and their heavier relatives, muons and taus, are leptons, as are a trio of lightweight particles called neutrinos. Rounding out the crew are bosons, which, among others, include the particles of light called photons and the Higgs boson, which explains the origin of particles’ mass.

    All the standard particles

    The standard model is the theory of the fundamental particles and forces of nature. It includes 12 particles that make up the material world: matter, shown on the left of this diagram, and their antimatter partners. Another four particles (right) transmit the forces of nature and one, the Higgs boson, results from the process by which fundamental particles gain mass.

    The standard model also accounts for three of the four known fundamental forces: electromagnetism, the weak nuclear force and the strong nuclear force. The weak force governs certain radioactive decays, and the strong force holds quarks together inside particles. (One of nature’s most familiar forces, gravity, is not yet incorporated into the framework.)

    Four decades passed between the establishment of the standard model in the 1970s and the detection of all its particles. The effort to find each and every particle required a succession of increasingly larger and more energetic particle accelerators, to unleash more exotic particles and those with higher masses. Accelerators advanced from a few billions of electron volts in the mid-1950s to the trillions of electron volts needed to discover the final predicted standard model particle, the Higgs boson, found with the Large Hadron Collider at CERN (CH) near Geneva in 2012.

    Physicists frequently describe the standard model as one of the most successful theories ever created, as it has correctly predicted a wide variety of experimental results. But despite the successes, physicists can’t explain why its various fundamental particles and forces exist.

    “The standard model is a great thing … but it leaves unanswered an enormous number of questions, and … in so far as the theory can talk it says, ‘I can’t answer those questions. Find something better,’ ” physicist Sheldon Glashow said in a 1998 interview.

    Physicists have been searching for that “something better” by studying potential additions or modifications to the standard model. For example, an idea called supersymmetry gained traction in the 1970s, proposing that every known particle has a heavier partner. Among other appealing characteristics, supersymmetry, if it exists, could reveal that the standard model’s three fundamental forces are actually different aspects of one unified force.

    But so far, there’s no evidence for supersymmetry or any other modifications to the standard model. Adding to the frustration is the clear evidence that the standard model can’t explain everything. For example, cosmic observations suggest the universe contains an unidentified type of matter, known as dark matter. Though evidence of its existence came in 1933, just a year after the neutron’s discovery, dark matter remains an enduring puzzle, showing that scientists still have more to learn about the foundations of matter. After decades of searches with increasingly more sensitive detectors, a favored class of hypothetical dark matter particles called WIMPs have failed to turn up. Yet there’s still hope: A new generation of experiments is beginning, and searches for another proposed type of dark matter particles, called axions, are just getting going.

    Particle physicists are now struggling to move forward. Some are pushing for even bigger colliders, but such projects may be prohibitively expensive. Dark matter hunters and others are focused on performing highly precise experiments looking for rare, subtle effects that might hint at a new theory. And some are studying the strange behavior of neutrinos, which could reveal new secrets about the differences between matter, common in the universe, and the rarer antimatter.

    One of these tactics, physicists hope, will lead to a new, simpler, more satisfying theory of matter. — Emily Conover

    _______________________________________________________________________________________________________________________________________________________
    Unleashing the atom

    8
    n August 1945, the United States dropped two atomic bombs on Japan, one on Hiroshima and one on Nagasaki (shown), the only time nuclear weapons have been used in combat.Prisma Bildagentur/Universal Images Group via Getty Images.
    _______________________________________________________________________________________________________________________________________________________

    Radioactive decay hints that atoms hold stores of energy locked within, ripe for the taking. Although radioactivity was discovered in 1896, that energy long remained an untapped resource. The neutron’s discovery in the 1930s would be key to unlocking that energy — for better and for worse.

    Opening up a better understanding of the nucleus, the neutron’s discovery gave scientists new abilities to split atoms into two or transform them into other elements. Developing that nuclear know-how led to useful technologies, like nuclear power, but also devastating nuclear weapons.

    Just a year after the neutron was found, Hungarian-born physicist Leo Szilard envisioned using neutrons to split atoms and create a bomb. “[I]t suddenly occurred to me that if we could find an element which is split by neutrons and which would emit two neutrons when it absorbed one neutron, such an element, if assembled in sufficiently large mass, could sustain a nuclear chain reaction, liberate energy on an industrial scale, and construct atomic bombs,” he later recalled. It was a fledgling idea, but prescient.

    Because neutrons lack electric charge, they can penetrate atoms’ hearts. In 1934, physicist Enrico Fermi and colleagues started bombarding dozens of different elements with neutrons, producing a variety of new, radioactive isotopes. Each isotope of a particular element contains a different number of neutrons in its nucleus, with the result that some isotopes may be radioactive while others are stable. Fermi had been inspired by another striking discovery of the time. In 1934 French chemists Frédéric and Irène Joliot-Curie reported the first artificially created radioactive isotopes, produced by bombarding elements with helium nuclei, called alpha particles. Now, Fermi was doing something similar, but with a more penetrating probe.

    There were a few scientific missteps on the way to understanding the results of such experiments. A major goal was to produce brand-new elements, those beyond the last known element in the periodic table at that time, uranium. After blasting uranium with neutrons, Fermi and colleagues reported evidence of success. But that conclusion would turn out to be incorrect.

    German chemist Ida Noddack had an inkling that all was not right with Fermi’s interpretation. She came close to the correct explanation for his experiments in a 1934 paper, writing, “When heavy nuclei are bombarded by neutrons, it is conceivable that the nucleus breaks up into several large fragments.” But Noddack didn’t follow up on the idea. “She didn’t provide any kind of supporting calculation and nobody took it with much seriousness,” says physicist Bruce Cameron Reed of Alma College (US) in Michigan.

    In Germany, physicist Lise Meitner and chemist Otto Hahn had also begun bombarding uranium with neutrons. But Meitner, an Austrian of Jewish heritage in increasingly hostile Nazi Germany, was forced to flee in July 1938. She had only an hour and a half to pack her suitcases. Hahn and a third member of the team, chemist Fritz Strassmann, continued the work, corresponding from afar with Meitner, who had landed in Sweden. The results of the experiments were puzzling at first, but when Hahn and Strassmann reported to Meitner that barium — a much lighter element than uranium — was a product of the reaction, it became clear what was happening. The nucleus was splitting.

    Meitner and her nephew, physicist Otto Frisch, worked together to explain the phenomenon, a process the pair would call “fission.” Hahn received the 1944 Nobel Prize in chemistry for the discovery of fission, but Meitner never won a Nobel, in a decision now widely considered unjust. Meitner was nominated for the prize in either physics or chemistry a whopping 48 times, most after the discovery of fission. “Her peers in the physics community recognized that she was part of the discovery,” says chemist Ruth Lewin Sime of Sacramento City College (US), who has written extensively about Meitner. “That included just about anyone who was anyone.”

    9
    Lise Meitner (left) and Otto Hahn are shown in their lab in Germany in 1913. Together, they established that atoms could split, or fission, when bombarded with neutrons. The two worked together before Nazi policies forced Meitner to flee to Sweden.Credit: Science Source.

    Word of the discovery soon spread, and on January 26, 1939, renowned Danish physicist Niels Bohr publicly announced at a scientific meeting that fission had been achieved. The potential implications were immediately apparent: Fission could unleash the energy stored in atomic nuclei, potentially resulting in a bomb. A Science News Letter story describing the announcement attempted to dispel any concerns the discovery might raise. The article, titled Atomic energy released, reported that scientists “are fearful lest the public become worried about a ‘revolution’ in civilization as a result of their researches,” such as “the suggested possibility that the atomic energy may be used as some super-explosive, or as a military weapon.” But downplaying the catastrophic implications didn’t prevent them from coming to pass.

    The question of whether a bomb could be created rested, once again, on neutrons. For fission to ignite an explosion, it would be necessary to set off a chain reaction. That means each fission would release additional neutrons, which could then go on to induce more fissions, and so on. Experiments quickly revealed that enough neutrons were released to make such a chain reaction feasible.

    In October of 1939, shortly after Germany invaded Poland at the start of World War II, an ominous letter from Albert Einstein reached President Franklin Delano Roosevelt. Composed at the urging of Szilard, the letter reported, “it is conceivable … that extremely powerful bombs of a new type may thus be constructed.” American researchers were not alone in their interest in the topic: German scientists, the letter noted, were also on the case.

    Roosevelt responded by setting up a committee to investigate. That step would be the first toward the U.S. effort to build an atomic bomb, the Manhattan Project.

    On December 2, 1942, Enrico Fermi, who by then had immigrated to the United States, and 48 colleagues achieved the first controlled, self-sustaining nuclear chain reaction in an experiment with a pile of uranium and graphite at the University of Chicago (US). Science News Letter would later call it “an event ranking with man’s first prehistoric lighting of a fire.” While the physicists celebrated their success, the possibility of an atomic bomb was closer than ever. “I thought this day would go down as a black day in the history of mankind,” Szilard recalled telling Fermi.

    9
    The first controlled, self-sustaining nuclear chain reaction took place in a pile of uranium and graphite (illustrated, right) at the University of Chicago (US) in 1942. Credit: Atomic Energy Commission/National Archive.

    The experiment was a key step in the Manhattan Project. And on July 16, 1945, at about 5:30 a.m., the scientists, led by J. Robert Oppenheimer, detonated the first atomic bomb, in the New Mexico desert — the Trinity test.

    It was a striking sight, as physicist Isidor Isaac Rabi recalled in his 1970 book, Science: The Center of Culture. “Suddenly, there was an enormous flash of light, the brightest light I have ever seen or that I think anyone has ever seen. It blasted; it pounced; it bored its way right through you. It was a vision which was seen with more than the eye. It was seen to last forever. You would wish it would stop; although it lasted about two seconds. Finally it was over, diminishing, and we looked toward the place where the bomb had been; there was an enormous ball of fire which grew and grew and it rolled as it grew; it went up into the air, in yellow flashes and into scarlet and green. It looked menacing. It seemed to come toward one. A new thing had just been born; a new control; a new understanding of man, which man had acquired over nature.”

    Physicist Kenneth Bainbridge put it more succinctly: “Now we are all sons of bitches,” he said to Oppenheimer in the moments after the test.

    The bomb’s construction was motivated by the fear that Germany would obtain it first. But it turned out that the Germans weren’t even close to producing a bomb when Germany surrendered in May 1945. Instead, the United States’ bombs would be used on Japan. On August 6, 1945, the United States dropped an atomic bomb on Hiroshima, followed by another August 9 on Nagasaki. In response, Japan surrendered. More than 100,000 people died as a result of the two attacks, and perhaps as many as 210,000.

    “I saw a blinding bluish-white flash from the window. I remember having the sensation of floating in the air,” survivor Setsuko Thurlow recalled in a speech given upon the awarding of the 2017 Nobel Peace Prize to the International Campaign to Abolish Nuclear Weapons. She was 13 years old when the bomb hit Hiroshima. “Thus, with one bomb my beloved city was obliterated. Most of its residents were civilians who were incinerated, vaporized, carbonized.”

    Humankind entered a new era, with new dangers to the survival of civilization.

    “With nuclear physics, you have something that within 10 years … goes from being this arcane academic research area … to something that bursts on the world stage and completely changes the relationship between science and society,” says Reed.

    In 1949, the Soviet Union set off its first nuclear weapon, kicking off the decades-long nuclear rivalry with the United States that would define the Cold War. And then came a bigger, more dangerous weapon: the hydrogen bomb. Whereas atomic bombs are based on nuclear fission, H-bombs harness nuclear fusion, the melding of atomic nuclei, in conjunction with fission, resulting in much larger blasts. The first H-bomb, detonated by the United States in 1952, was 1,000 times more powerful than the bomb dropped on Hiroshima. Within less than a year, the Soviet Union also tested an H-bomb. The H-bomb had been called a “weapon of genocide” by scientists serving on an advisory committee for the U.S. Atomic Energy Commission, which had previously recommended against developing the technology.

    Fears of the devastation that would result from an all-out nuclear war have fed repeated attempts to rein in nuclear weapons stockpiles and tests. Since the signing of the Comprehensive Nuclear Test Ban Treaty in 1996, the United States, Russia and many other countries have a maintained a testing moratorium. However, North Korea tested a nuclear weapon as recently as 2017.

    10
    Shown in 1962, the first full-scale commercial nuclear power plant, known as Calder Hall, switched on in 1956 in Cumbria, England.Credit: Bettmann/Getty Images.

    Still, the dangers of nuclear weapons were accompanied by a promising new technology: nuclear power.

    In 1948, scientists first demonstrated that a nuclear reactor could harness fission to produce electricity. The X-10 Graphite Reactor at DOE’s Oak Ridge National Laboratory (US) in Tennessee generated steam that powered an engine, lighting up a small Christmas lightbulb. In 1951, Experimental Breeder Reactor-I at Idaho National Laboratory (US) near Idaho Falls produced the first usable amount of electricity from a nuclear reactor. The world’s first commercial nuclear power plants began to switch on in the mid- and late 1950s. But nuclear disasters dampened enthusiasm for the technology, including the 1979 Three Mile Island accident in Pennsylvania and the 1986 Chernobyl disaster in Ukraine, then part of the Soviet Union. In 2011, the disaster at the Fukushima Daiichi power plant in Japan rekindled society’s smoldering nuclear anxieties. But today, in an era when the effects of climate change are becoming alarming, nuclear power is appealing because it emits no greenhouse gases directly.

    11
    Concerns about the dangers of nuclear power came to the forefront after an accident at the Three Mile Island nuclear plant (shown in background) near Middletown, Pa. in 1979.Credit: Bettmann/Getty Images.

    11
    A 2011 tsunami caused an accident at the Fukushima Daiichi nuclear power plant. Explosions and meltdowns at the plant led to widespread evacuations of the surrounding areas.Cedit: IAEA ImageBank/Flickr (CC BY-SA 2.0)

    And humankind’s mastery over matter is not yet complete. For decades, scientists have been dreaming of another type of nuclear power, based on fusion, the process that powers the sun. Unlike fission, fusion power wouldn’t produce long-lived nuclear waste. But so far, progress has been slow. The ITER experiment has been in planning since the 1980s.


    ITER Tokamak in Saint-Paul-lès-Durance, which is in southern France.

    Once constructed in southern France, ITER aims to, for the first time, produce more energy from fusion than is put in. Whether it is successful may help determine the energy outlook for future centuries.

    From today’s perspective, the breakneck pace of progress in nuclear and particle physics in less than a century can seem unbelievable. The neutron and positron were both found in laboratories that are small in comparison to today’s, and each discovery was attributed to a single physicist, relatively soon after the particles had been proposed. And the discoveries kicked off frantic developments that seemed to roll in one after another.

    Now, finding a new element, discovering a new elementary particle or creating a new type of nuclear reactor can take decades, international collaborations of thousands of scientists, and huge, costly experiments.

    As physicists uncover the tricks to understanding and controlling nature, it seems, the next level of secrets becomes increasingly difficult to expose. — Emily Conover.

    12
    Today’s nuclear power plants produce energy via fission, the splitting of atomic nuclei. The ITER experiment, illustrated, under construction in France, aims to produce power from nuclear fusion, the melding of nuclei.Credit: ITER.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    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
    CERN AEGIS

    CERN AEgIS 1T antimatter trap stack

    CERN ALPHA

    CERN ALPHA Antimatter Factory.

    CERN ALPHA-g Detector

    CERN ALPHA-g Detector

    CERN AMS

    CERN AMS.

    CERN ACACUSA

    CERN ASACUSA

    CERN ATRAP

    CERN ATRAP


    CERN ANTIPROTON DECELERATOR

    CERN Antiproton Decelerator


    CERN AWAKE

    CERN AWAKE


    CERN BASE

    BASE: Baryon Antibaryon Symmetry Experiment

    CERN BASE experiment

    CERN CAST

    CERN CAST Axion Solar Telescope

    CERN CLOUD

    CERN CLOUD

    CERN COMPASS

    CERN COMPASS

    CERN DIRAC

    CERN DIRAC

    CERN FASER

    CERN FASER experiment schematic

    CERN GBAR

    CERN GBAR

    CERN ISOLDE

    CERN ISOLDE Looking down into the ISOLDE experimental hall.

    CERN LHCf

    CERN LHCf

    CERN NA62

    CERN NA62

    CERN NA64.

    CERN NTOF

    CERN NTOF

    CERN TOTEM

    CERN TOTEM.

    CERN UA9

    CERN UA9

    CERN Proto Dune

    CERN Proto Dune

     
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