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  • richardmitnick 11:56 am on March 5, 2021 Permalink | Reply
    Tags: "Physicists Just Found 4 New Subatomic Particles That May Test The Laws of Nature", , , , , CERN(CH), , Hadrons, , Mesons, , , , Protons and neutrons, , Quarks and antiquarks, , , Strong interaction, Tetraquarks and pentaquarks, The four new particles we've discovered recently are all tetraquarks with a charm quark pair and two other quarks., The standard model is certainly not the last word in the understanding of particles., These models are crucial to achieve the ultimate goal of the LHC: find physics beyond the standard model.   

    From CERN(CH) via Science Alert(AU): “Physicists Just Found 4 New Subatomic Particles That May Test The Laws of Nature” 

    Cern New Bloc

    Cern New Particle Event


    From CERN(CH)

    via

    ScienceAlert

    Science Alert(AU)

    5 MARCH 2021
    PATRICK KOPPENBURG
    Research Fellow in Particle Physics
    Dutch National Institute for Subatomic Physics, Dutch Research Council (NWO – Nederlandse Organisatie voor Wetenschappelijk Onderzoek)(NL)

    Harry Cliff
    Particle physicist
    University of Cambridge(UK).

    1
    The Large Hadron Collider. Credit: CERN.

    This month is a time to celebrate. CERN has just announced the discovery of four brand new particles [3 March 2021: Observation of two ccus tetraquarks and two ccss tetraquarks.] at the Large Hadron Collider (LHC) in Geneva.

    This means that the LHC has now found a total of 59 new particles, in addition to the Nobel prize-winning Higgs boson, since it started colliding protons – particles that make up the atomic nucleus along with neutrons – in 2009.

    Excitingly, while some of these new particles were expected based on our established theories, some were altogether more surprising.

    The LHC’s goal is to explore the structure of matter at the shortest distances and highest energies ever probed in the lab – testing our current best theory of nature: the Standard Model of Particle Physics.

    Standard Model of Particle Physics (LATHAM BOYLE AND MARDUS OF WIKIMEDIA COMMONS).

    And the LHC has delivered the goods – it enabled scientists to discover the Higgs boson [below], the last missing piece of the model. That said, the theory is still far from being fully understood.

    One of its most troublesome features is its description of the strong interaction which holds the atomic nucleus together. The nucleus is made up of protons and neutrons, which are in turn each composed of three tiny particles called quarks (there are six different kinds of quarks: up, down, charm, strange, top and bottom).

    If we switched the strong force off for a second, all matter would immediately disintegrate into a soup of loose quarks – a state that existed for a fleeting instant at the beginning of the universe.

    Don’t get us wrong: the theory of the strong interaction, pretentiously called Quantum Chromodynamics, is on very solid footing. It describes how quarks interact through the strong interaction by exchanging particles called gluons. You can think of gluons as analogues of the more familiar photon, the particle of light and carrier of the electromagnetic interaction.

    However, the way gluons interact with quarks makes the strong interaction behave very differently from electromagnetism. While the electromagnetic interaction gets weaker as you pull two charged particles apart, the strong interaction actually gets stronger as you pull two quarks apart.

    As a result, quarks are forever locked up inside particles called hadrons – particles made of two or more quarks – which includes protons and neutrons. Unless, of course, you smash them open at incredible speeds, as we are doing at Cern.

    To complicate matters further, all the particles in the standard model have antiparticles which are nearly identical to themselves but with the opposite charge (or other quantum property). If you pull a quark out of a proton, the force will eventually be strong enough to create a quark-antiquark pair, with the newly created quark going into the proton.

    You end up with a proton and a brand new “meson”, a particle made of a quark and an antiquark. This may sound weird but according to quantum mechanics, which rules the universe on the smallest of scales, particles can pop out of empty space.

    This has been shown repeatedly by experiments – we have never seen a lone quark. An unpleasant feature of the theory of the strong interaction is that calculations of what would be a simple process in electromagnetism can end up being impossibly complicated. We therefore cannot (yet) prove theoretically that quarks can’t exist on their own.

    Worse still, we can’t even calculate which combinations of quarks would be viable in nature and which would not.

    2
    Illustration of a tetraquark. Credit: CERN.

    When quarks were first discovered, scientists realized that several combinations should be possible in theory. This included pairs of quarks and antiquarks (mesons); three quarks (baryons); three antiquarks (antibaryons); two quarks and two antiquarks (tetraquarks); and four quarks and one antiquark (pentaquarks) – as long as the number of quarks minus antiquarks in each combination was a multiple of three.

    For a long time, only baryons and mesons were seen in experiments. But in 2003, the Belle experiment in Japan discovered a particle that didn’t fit in anywhere.

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

    Belle II KEK High Energy Accelerator Research Organization Tsukuba, Japan.

    It turned out to be the first of a long series of tetraquarks.

    In 2015, the LHCb experiment [below] at the LHC discovered two pentaquarks.

    3
    Is a pentaquark tightly (above) or weakly bound (see image below)? Credit: CERN.

    The four new particles we’ve discovered recently are all tetraquarks with a charm quark pair and two other quarks. All these objects are particles in the same way as the proton and the neutron are particles. But they are not fundamental particles: quarks and electrons are the true building blocks of matter.

    Charming new particles

    The LHC has now discovered 59 new hadrons. These include the tetraquarks most recently discovered, but also new mesons and baryons. All these new particles contain heavy quarks such as “charm” and “bottom”.

    These hadrons are interesting to study. They tell us what nature considers acceptable as a bound combination of quarks, even if only for very short times.

    They also tell us what nature does not like. For example, why do all tetra- and pentaquarks contain a charm-quark pair (with just one exception)? And why are there no corresponding particles with strange-quark pairs? There is currently no explanation.

    4
    Is a pentaquark a molecule? A meson (left) interacting with a proton (right). Credit: CERN.

    Another mystery is how these particles are bound together by the strong interaction. One school of theorists considers them to be compact objects, like the proton or the neutron.

    Others claim they are akin to “molecules” formed by two loosely bound hadrons. Each newly found hadron allows experiments to measure its mass and other properties, which tell us something about how the strong interaction behaves. This helps bridge the gap between experiment and theory. The more hadrons we can find, the better we can tune the models to the experimental facts.

    These models are crucial to achieve the ultimate goal of the LHC: find physics beyond the standard model. Despite its successes, the standard model is certainly not the last word in the understanding of particles. It is for instance inconsistent with cosmological models describing the formation of the universe.

    The LHC is searching for new fundamental particles that could explain these discrepancies. These particles could be visible at the LHC, but hidden in the background of particle interactions. Or they could show up as small quantum mechanical effects in known processes.

    In either case, a better understanding of the strong interaction is needed to find them. With each new hadron, we improve our knowledge of nature’s laws, leading us to a better description of the most fundamental properties of matter.

    See the full article here.


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    Meet CERN(CH) in a variety of places:

    Quantum Diaries
    QuantumDiaries

    Cern Courier(CH)

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    CERN ATLAS Image Claudia Marcelloni CERN/ATLAS


    ALICE

    CERN/ALICE Detector


    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN map

    CERN LHC Maximilien Brice and Julien Marius Ordan.


    SixTRack CERN LHC particles

    The European Organization for Nuclear Research (Organisation européenne pour la recherche nucléaire)(EU), known as CERN, is a European research organization that operates the largest particle physics laboratory in the world. Established in 1954, the organization is based in a northwest suburb of Geneva on the Franco–Swiss border and has 23 member states. Israel is the only non-European country granted full membership. CERN is an official United Nations Observer.

    The acronym CERN is also used to refer to the laboratory, which in 2019 had 2,660 scientific, technical, and administrative staff members, and hosted about 12,400 users from institutions in more than 70 countries. In 2016 CERN generated 49 petabytes of data.

    CERN’s main function is to provide the particle accelerators and other infrastructure needed for high-energy physics research – as a result, numerous experiments have been constructed at CERN through international collaborations. The main site at Meyrin hosts a large computing facility, which is primarily used to store and analyse data from experiments, as well as simulate events. Researchers need remote access to these facilities, so the lab has historically been a major wide area network hub. CERN is also the birthplace of the World Wide Web.

    The convention establishing CERN was ratified on 29 September 1954 by 12 countries in Western Europe. The acronym CERN originally represented the French words for Conseil Européen pour la Recherche Nucléaire (European Council for Nuclear Research), which was a provisional council for building the laboratory, established by 12 European governments in 1952. The acronym was retained for the new laboratory after the provisional council was dissolved, even though the name changed to the current Organisation Européenne pour la Recherche Nucléaire (European Organization for Nuclear Research)(EU) in 1954. According to Lew Kowarski, a former director of CERN, when the name was changed, the abbreviation could have become the awkward OERN, and Werner Heisenberg said that this could “still be CERN even if the name is [not]”.

    CERN’s first president was Sir Benjamin Lockspeiser. Edoardo Amaldi was the general secretary of CERN at its early stages when operations were still provisional, while the first Director-General (1954) was Felix Bloch.

    The laboratory was originally devoted to the study of atomic nuclei, but was soon applied to higher-energy physics, concerned mainly with the study of interactions between subatomic particles. Therefore, the laboratory operated by CERN is commonly referred to as the European laboratory for particle physics (Laboratoire européen pour la physique des particules), which better describes the research being performed there.

    Founding members

    At the sixth session of the CERN Council, which took place in Paris from 29 June – 1 July 1953, the convention establishing the organization was signed, subject to ratification, by 12 states. The convention was gradually ratified by the 12 founding Member States: Belgium, Denmark, France, the Federal Republic of Germany, Greece, Italy, the Netherlands, Norway, Sweden, Switzerland, the United Kingdom, and “Yugoslavia”.

    Scientific achievements

    Several important achievements in particle physics have been made through experiments at CERN. They include:

    1973: The discovery of neutral currents in the Gargamelle bubble chamber.
    1983: The discovery of W and Z bosons in the UA1 and UA2 experiments.
    1989: The determination of the number of light neutrino families at the Large Electron–Positron Collider (LEP) operating on the Z boson peak.
    1995: The first creation of antihydrogen atoms in the PS210 experiment.
    1999: The discovery of direct CP violation in the NA48 experiment.
    2010: The isolation of 38 atoms of antihydrogen.
    2011: Maintaining antihydrogen for over 15 minutes.
    2012: A boson with mass around 125 GeV/c2 consistent with the long-sought Higgs boson.

    In September 2011, CERN attracted media attention when the OPERA Collaboration reported the detection of possibly faster-than-light neutrinos. Further tests showed that the results were flawed due to an incorrectly connected GPS synchronization cable.

    The 1984 Nobel Prize for Physics was awarded to Carlo Rubbia and Simon van der Meer for the developments that resulted in the discoveries of the W and Z bosons. The 1992 Nobel Prize for Physics was awarded to CERN staff researcher Georges Charpak “for his invention and development of particle detectors, in particular the multiwire proportional chamber”. The 2013 Nobel Prize for Physics was awarded to François Englert and Peter Higgs for the theoretical description of the Higgs mechanism in the year after the Higgs boson was found by CERN experiments.

    Computer science

    The World Wide Web began as a CERN project named ENQUIRE, initiated by Tim Berners-Lee in 1989 and Robert Cailliau in 1990. Berners-Lee and Cailliau were jointly honoured by the Association for Computing Machinery in 1995 for their contributions to the development of the World Wide Web.

    Current complex

    CERN operates a network of six accelerators and a decelerator. Each machine in the chain increases the energy of particle beams before delivering them to experiments or to the next more powerful accelerator. Currently (as of 2019) active machines are:

    The LINAC 3 linear accelerator generating low energy particles. It provides heavy ions at 4.2 MeV/u for injection into the Low Energy Ion Ring (LEIR).
    The Proton Synchrotron Booster increases the energy of particles generated by the proton linear accelerator before they are transferred to the other accelerators.
    The Low Energy Ion Ring (LEIR) accelerates the ions from the ion linear accelerator LINAC 3, before transferring them to the Proton Synchrotron (PS). This accelerator was commissioned in 2005, after having been reconfigured from the previous Low Energy Antiproton Ring (LEAR).
    The 28 GeV Proton Synchrotron (PS), built during 1954—1959 and still operating as a feeder to the more powerful SPS.
    The Super Proton Synchrotron (SPS), a circular accelerator with a diameter of 2 kilometres built in a tunnel, which started operation in 1976. It was designed to deliver an energy of 300 GeV and was gradually upgraded to 450 GeV. As well as having its own beamlines for fixed-target experiments (currently COMPASS and NA62), it has been operated as a proton–antiproton collider (the SppS collider), and for accelerating high energy electrons and positrons which were injected into the Large Electron–Positron Collider (LEP). Since 2008, it has been used to inject protons and heavy ions into the Large Hadron Collider (LHC).
    The On-Line Isotope Mass Separator (ISOLDE), which is used to study unstable nuclei. The radioactive ions are produced by the impact of protons at an energy of 1.0–1.4 GeV from the Proton Synchrotron Booster. It was first commissioned in 1967 and was rebuilt with major upgrades in 1974 and 1992.
    The Antiproton Decelerator (AD), which reduces the velocity of antiprotons to about 10% of the speed of light for research of antimatter.[50] The AD machine was reconfigured from the previous Antiproton Collector (AC) machine.
    The AWAKE experiment, which is a proof-of-principle plasma wakefield accelerator.
    The CERN Linear Electron Accelerator for Research (CLEAR) accelerator research and development facility.

    Large Hadron Collider

    Many activities at CERN currently involve operating the Large Hadron Collider (LHC) and the experiments for it. The LHC represents a large-scale, worldwide scientific cooperation project.

    The LHC tunnel is located 100 metres underground, in the region between the Geneva International Airport and the nearby Jura mountains. The majority of its length is on the French side of the border. It uses the 27 km circumference circular tunnel previously occupied by the Large Electron–Positron Collider (LEP), which was shut down in November 2000. CERN’s existing PS/SPS accelerator complexes are used to pre-accelerate protons and lead ions which are then injected into the LHC.

    Eight experiments (CMS, ATLAS, LHCb, MoEDAL, TOTEM, LHCf, FASER and ALICE) are located along the collider; each of them studies particle collisions from a different aspect, and with different technologies. Construction for these experiments required an extraordinary engineering effort. For example, a special crane was rented from Belgium to lower pieces of the CMS detector into its cavern, since each piece weighed nearly 2,000 tons. The first of the approximately 5,000 magnets necessary for construction was lowered down a special shaft at 13:00 GMT on 7 March 2005.

    The LHC has begun to generate vast quantities of data, which CERN streams to laboratories around the world for distributed processing (making use of a specialized grid infrastructure, the LHC Computing Grid). During April 2005, a trial successfully streamed 600 MB/s to seven different sites across the world.

    The initial particle beams were injected into the LHC August 2008. The first beam was circulated through the entire LHC on 10 September 2008, but the system failed 10 days later because of a faulty magnet connection, and it was stopped for repairs on 19 September 2008.

    The LHC resumed operation on 20 November 2009 by successfully circulating two beams, each with an energy of 3.5 teraelectronvolts (TeV). The challenge for the engineers was then to try to line up the two beams so that they smashed into each other. This is like “firing two needles across the Atlantic and getting them to hit each other” according to Steve Myers, director for accelerators and technology.

    On 30 March 2010, the LHC successfully collided two proton beams with 3.5 TeV of energy per proton, resulting in a 7 TeV collision energy. However, this was just the start of what was needed for the expected discovery of the Higgs boson. When the 7 TeV experimental period ended, the LHC revved to 8 TeV (4 TeV per proton) starting March 2012, and soon began particle collisions at that energy. In July 2012, CERN scientists announced the discovery of a new sub-atomic particle that was later confirmed to be the Higgs boson.

    CERN CMS Higgs Event May 27, 2012.


    CERN ATLAS Higgs Event
    June 12, 2012.


    Peter Higgs

    In March 2013, CERN announced that the measurements performed on the newly found particle allowed it to conclude that this is a Higgs boson. In early 2013, the LHC was deactivated for a two-year maintenance period, to strengthen the electrical connections between magnets inside the accelerator and for other upgrades.

    On 5 April 2015, after two years of maintenance and consolidation, the LHC restarted for a second run. The first ramp to the record-breaking energy of 6.5 TeV was performed on 10 April 2015. In 2016, the design collision rate was exceeded for the first time. A second two-year period of shutdown begun at the end of 2018.

    Accelerators under construction

    As of October 2019, the construction is on-going to upgrade the LHC’s luminosity in a project called High Luminosity LHC (HL-LHC).

    This project should see the LHC accelerator upgraded by 2026 to an order of magnitude higher luminosity.

    As part of the HL-LHC upgrade project, also other CERN accelerators and their subsystems are receiving upgrades. Among other work, the LINAC 2 linear accelerator injector was decommissioned, to be replaced by a new injector accelerator, the LINAC4 in 2020.

    Possible future accelerators

    CERN, in collaboration with groups worldwide, is investigating two main concepts for future accelerators: A linear electron-positron collider with a new acceleration concept to increase the energy (CLIC) and a larger version of the LHC, a project currently named Future Circular Collider.

    CLIC collider

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

    Not discussed or described, but worthy of consideration is the ILC, International Linear Collider in the planning stages for construction in Japan.

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

    Participation

    Since its foundation by 12 members in 1954, CERN regularly accepted new members. All new members have remained in the organization continuously since their accession, except Spain and Yugoslavia. Spain first joined CERN in 1961, withdrew in 1969, and rejoined in 1983. Yugoslavia was a founding member of CERN but quit in 1961. Of the 23 members, Israel joined CERN as a full member on 6 January 2014, becoming the first (and currently only) non-European full member.

    Enlargement

    Associate Members, Candidates:

    Turkey signed an association agreement on 12 May 2014 and became an associate member on 6 May 2015.
    Pakistan signed an association agreement on 19 December 2014 and became an associate member on 31 July 2015.
    Cyprus signed an association agreement on 5 October 2012 and became an associate Member in the pre-stage to membership on 1 April 2016.
    Ukraine signed an association agreement on 3 October 2013. The agreement was ratified on 5 October 2016.
    India signed an association agreement on 21 November 2016. The agreement was ratified on 16 January 2017.
    Slovenia was approved for admission as an Associate Member state in the pre-stage to membership on 16 December 2016. The agreement was ratified on 4 July 2017.
    Lithuania was approved for admission as an Associate Member state on 16 June 2017. The association agreement was signed on 27 June 2017 and ratified on 8 January 2018.
    Croatia was approved for admission as an Associate Member state on 28 February 2019. The agreement was ratified on 10 October 2019.
    Estonia was approved for admission as an Associate Member in the pre-stage to membership state on 19 June 2020. The agreement was ratified on 1 February 2021.

     
  • richardmitnick 11:54 am on February 1, 2021 Permalink | Reply
    Tags: "Andreas Ekström will explore the secrets of the strong force in atomic nuclei", , , , , , , , , Strong interaction   

    From Chalmers University of Technology [ tekniska högskola ](SE): “Andreas Ekström will explore the secrets of the strong force in atomic nuclei” 

    From Chalmers University of Technology [ tekniska högskola ](SE)

    25 Aug 2017 [Brought forward 1.31.21. Why now?]

    1
    For the next five years, Andreas Ekström will lead a research project funded with 1,5 M€ from the European Research Council (ERC). The goal is to establish new methods and theories to model atomic nuclei. Credit: Mia Halleröd Palmgren.

    All visible matter in the universe consists of atoms. The constituents of the atomic nucleus are held together by a force called the strong force. Despite its central importance, we do not yet know how it works. Researchers from Chalmers University of Technology will therefore try to reveal new information about atomic nuclei.

    “We need to create a solid theoretical framework to describe the strong force between protons and neutrons in atomic nuclei. Today’s theories form an incomplete patchwork”, says Andreas Ekström, researcher at the Department of Physics at Chalmers University of Technology.

    For the next five years, he will lead a research project funded with 1,5 M€ from the European Research Council (ERC). The goal is to establish new methods and theories to model atomic nuclei. He will focus on heavy, unstable, and exotic nuclei that so far have eluded researchers all over the world.

    ” To generate new knowledge about the strong force, I will investigate heavy atomic nuclei such as oxygen and calcium. A heavy nucleus typically contains more information than a light nucleus such as helium. However, it’s a greater challenge to analyze heavy nuclei”, says Andreas Ekström.

    1

    In his project, he will introduce new ways to exploit data from existing experiments and theoretically disassemble atomic nuclei to better understand the strong force. More or less laying the puzzle backwards. Since a heavy nucleus consists of considerably more neutrons and protons than a light one, it will be a tricky puzzle with many pieces to keep track of.

    But the research project is not only about describing the strong force in nuclei. It is also essential to work out methods for calculating the uncertainties in the models.

    “Many fields of research are based on input from fundamental . It is also very expensive and time consuming to conduct large experiments. Therefore, it is important that we can offer predictions with great precision.”

    The basic research that is conducted by Andreas Ekström is essential for understanding stellar physics and fusion processes in the sun as well as neutrino physics. The aim is to solve one of the great mysteries of our universe.

    “The strong force affects everything – from the smallest atomic nucleus to the biggest star – and a well-functioning society is based on understanding the world we live in. We need fundamental research as a pillar of society. Even though we will not have all the answers in five years, I hope that we can make important progress. My previous research has shown that the proposed method of laying the puzzle backwards is a possible way ahead”, says Andreas Ekström.

    See the full article here .

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    Chalmers University of Technology [tekniska högskola](SE) is a Swedish university located in Gothenburg that focuses on research and education in technology, natural science, architecture, maritime and other management areas

    The University was founded in 1829 following a donation by William Chalmers, a director of the Swedish East India Company. He donated part of his fortune for the establishment of an “industrial school”. Chalmers was run as a private institution until 1937, when the institute became a state-owned university. In 1994, the school was incorporated as an aktiebolag under the control of the Swedish Government, the faculty and the Student Union. Chalmers is one of only three universities in Sweden which are named after a person, the other two being Karolinska Institutet and Linnaeus University.

     
  • richardmitnick 4:04 pm on January 27, 2021 Permalink | Reply
    Tags: "Size of helium nucleus measured more precisely than ever before", , Helium is the second most abundant element in the universe., Helium=two protons and two neutrons., , , , Paul Scherrer Institute [Paul Scherrer Institut](CH), , Proton radius mystery is fading away, , , Resonance frequency, Rydberg constant, Slow muons; complicated laser system, Strong interaction   

    From Paul Scherrer Institute [Paul Scherrer Institut](CH): “Size of helium nucleus measured more precisely than ever before” 

    From Paul Scherrer Institute [Paul Scherrer Institut](CH)

    27 January 2021

    Text: Barbara Vonarburg

    Dr. Aldo Antognini
    Labor für Teilchenphysik
    Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI (CH)
    &
    Institute for Particle Physics and Astrophysics
    ETH Zürich, Otto-Stern-Weg 5, 8093 Zürich (CH)
    +41 56 310 46 14
    aldo.antognini@psi.ch

    Dr. Franz Kottmann
    Labor für Teilchenphysik
    Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI (CH)
    Institute for Particle Physics and Astrophysics
    ETH Zürich, Otto-Stern-Weg 5, 8093 Zürich (CH)
    +41 79273 16 39
    franz.kottmann@psi.ch

    Dr. Julian J. Krauth
    LaserLaB, Faculty of Sciences
    Quantum Metrology and Laser Applications
    Vrije Universiteit Amsterdam
    De Boelelaan 1081, 1081HV Amsterdam (NL)
    +31 20 5987438
    j.krauth@vu.nl

    Prof. Dr. Randolf Pohl
    Institut für Physik
    Johannes Gutenberg Universität, 55128 Mainz (DE)
    +49 171 41 70 752, e-mail:
    pohl@uni-mainz.de

    In experiments at the Paul Scherrer Institute PSI, an international research collaboration has measured the radius of the atomic nucleus of helium five times more precisely than ever before. With the aid of the new value, fundamental physical theories can be tested and natural constants can be determined even more precisely. For their measurements, the researchers needed muons – these particles are similar to electrons but are around 200 times heavier. PSI is the only research site in the world where enough so-called low-energy muons are produced for such experiments. The researchers are publishing their results today in the journal Nature.

    1
    Both Franz Kottmann (left) and Karsten Schuhmann did essential preparatory work for the crucial experiment. Credit: Paul Scherrer Institute/Markus Fischer)

    After hydrogen, helium is the second most abundant element in the universe. Around one-fourth of the atomic nuclei that formed in the first few minutes after the Big Bang were helium nuclei. These consist of four building blocks: two protons and two neutrons. For fundamental physics, it is crucial to know the properties of the helium nucleus, among other things to understand the processes in other atomic nuclei that are heavier than helium. “The helium nucleus is a very fundamental nucleus, which could be described as magical,” says Aldo Antognini, a physicist at PSI and ETH Zürich (CH). His colleague and co-author Randolf Pohl from Johannes Gutenberg University Mainz (DE) adds: “Our previous knowledge about the helium nucleus comes from experiments with electrons. At PSI, however, we have for the first time developed a new type of measurement method that allows much better accuracy.”

    With this, the international research collaboration succeeded in determining the size of the helium nucleus around five times more precisely than was possible in previous measurements. The group is publishing its results today in the renowned scientific journal Nature [above]. According to their findings, the so-called mean charge radius of the helium nucleus is 1.67824 femtometers (there are 1 quadrillion femtometers in 1 meter).

    “The idea behind our experiments is simple,” explains Antognini. Normally two negatively charged electrons orbit the positively charged helium nucleus. “We don’t work with normal atoms, but with exotic atoms in which both electrons have been replaced by a single muon,” says the physicist. The muon is considered to be the electron’s heavier brother; it resembles it, but it’s around 200 times heavier. A muon is much more strongly bound to the atomic nucleus than an electron and encircles it in much narrower orbits. Compared to electrons, a muon is much more likely to stay in the nucleus itself. “So with muonic helium, we can draw conclusions about the structure of the atomic nucleus and measure its properties,” Antognini explains.

    Slow muons, complicated laser system

    The muons are produced at PSI using a particle accelerator. The specialty of the facility: generating muons with low energy. These particles are slow and can be stopped in the apparatus for experiments. This is the only way researchers can form the exotic atoms in which a muon throws an electron out of its orbit and replaces it. Fast muons, in contrast, would fly right through the apparatus. The PSI system delivers more low-energy muons than all other comparable systems worldwide. “That is why the experiment with muonic helium can only be carried out here,” says Franz Kottmann, who for 40 years has been pressing ahead with the necessary preliminary studies and technical developments for this experiment.

    The muons hit a small chamber filled with helium gas. If the conditions are right, muonic helium is created, where the muon is in an energy state in which it often stays in the atomic nucleus. “Now the second important component for the experiment comes into play: the laser system,” Pohl explains. The complicated system shoots a laser pulse at the helium gas. If the laser light has the right frequency, it excites the muon and advances it to a higher energy state, in which its path is practically always outside the nucleus. When it falls from this to the ground state, it emits X-rays. Detectors register these X-ray signals.

    In the experiment, the laser frequency is varied until a large number of X-ray signals arrive. Physicists then speak of the so-called resonance frequency. With its help, then, the difference between the two energetic states of the muon in the atom can be determined. According to theory, the measured energy difference depends on how large the atomic nucleus is. Hence, using the theoretical equation, the radius can be determined from the measured resonance. This data analysis was carried out in Randolf Pohl’s group in Mainz (DE).

    Proton radius mystery is fading away

    The researchers at PSI had already measured the radius of the proton in the same way in 2010. At that time, their value did not match that obtained by other measurement methods. There was talk of a proton radius puzzle, and some speculated that a new physics might lie behind it in the form of a previously unknown interaction between the muon and the proton. This time there is no contradiction between the new, more precise value and the measurements with other methods. “This makes the explanation of the results with physics beyond the standard model more improbable,” says Kottmann. In addition, in recent years the value of the proton radius determined by means of other methods has been approaching the precise number from PSI. “The proton radius puzzle still exists, but it is slowly fading away,” says Kottmann.

    “Our measurement can be used in different ways,” says Julian Krauth, first author of the study: “The radius of the helium nucleus is an important touchstone for nuclear physics.” Atomic nuclei are held together by the so-called strong interaction, one of the four fundamental forces in physics. With the theory of strong interaction, known as quantum chromodynamics, physicists would like to be able to predict the radius of the helium nucleus and other light atomic nuclei with a few protons and neutrons. The extremely precisely measured value for the radius of the helium nucleus puts these predictions to the test. This also makes it possible to test new theoretical models of the nuclear structure and to understand atomic nuclei even better.

    The measurements on muonic helium can also be compared with experiments using normal helium atoms and ions. In experiments on these, too, energy transitions can be triggered and measured with laser systems – here, though, with electrons instead of muons. Measurements on electronic helium are under way right now. By comparing the results of the two measurements, one can draw conclusions about fundamental natural constants such as the Rydberg constant, which plays an important role in quantum mechanics.

    See the full article here.

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Paul Scherrer Institute [Paul Scherrer Institut](CH) is the largest research institute for natural and engineering sciences within Switzerland. We perform world-class research in three main subject areas: Matter and Material; Energy and the Environment; and Human Health. By conducting fundamental and applied research, we work on long-term solutions for major challenges facing society, industry and science.

    The Paul Scherrer Institute (PSI) is a multi-disciplinary research institute for natural and engineering sciences in Switzerland. It is located in the Canton of Aargau in the municipalities Villigen and Würenlingen on either side of the River Aare, and covers an area over 35 hectares in size. Like ETH Zurich and EPFL, PSI belongs to the Swiss Federal Institutes of Technology Domain of the Swiss Confederation. The PSI employs around 2100 people. It conducts basic and applied research in the fields of matter and materials, human health, and energy and the environment. About 37% of PSI’s research activities focus on material sciences, 24% on life sciences, 19% on general energy, 11% on nuclear energy and safety, and 9% on particle physics.

    PSI develops, builds and operates large and complex research facilities and makes them available to the national and international scientific communities. In 2017, for example, more than 2500 researchers from 60 different countries came to PSI to take advantage of the concentration of large-scale research facilities in the same location, which is unique worldwide. About 1900 experiments are conducted each year at the approximately 40 measuring stations in these facilities.

    In recent years, the institute has been one of the largest recipients of money from the Swiss lottery fund.

     
  • richardmitnick 12:24 pm on April 30, 2020 Permalink | Reply
    Tags: "The large boson-boson collider", , , , , , , , Strong interaction, Weak Interaction   

    From Symmetry: “The large boson-boson collider” 

    Symmetry Mag
    From Symmetry<

    04/30/20
    Sarah Charley

    1
    Courtesy of CERN

    Scientists study rare, one-in-a-trillion heavy boson collisions happening inside the LHC.

    The Large Hadron Collider is the world’s most powerful particle accelerator. It accelerates and smashes protons and other atomic nuclei to study the fundamental properties of matter.

    LHC

    CERN map


    CERN LHC Maximilien Brice and Julien Marius Ordan


    CERN LHC particles

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    CERN ATLAS Image Claudia Marcelloni CERN/ATLAS

    ALICE

    CERN/ALICE Detector


    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    Normally scientists look at the particles produced during these collisions to learn about the laws of nature. But scientists can also learn about subatomic matter by peering into the collisions themselves and asking: What exactly is doing the colliding?

    When the answer to that question involves rarely seen, massive particles, it gives scientists a unique way to study the Higgs boson.

    Protons are not solid spheres, but composite particles containing even tinier components called quarks and gluons.

    The quark structure of the proton 16 March 2006 Arpad Horvath

    “As far as we know the quarks and gluons are point-like particles with no internal structure,” says Aram Apyan, a research associate at the US Department of Energy’s Fermi National Accelerator Laboratory.

    According to Apyan, two quarks cannot actually hit each other; they don’t have volume or surfaces. So what really happens when these point-like particles collide?

    “When we talk about two quarks colliding, what we really mean is that they are very close to each other spatially and exchanging particles,” says Richard Ruiz, a theorist at Université Catholique de Louvain in Belgium. “Namely, they exchange force-carrying bosons.”

    All elementary matter particles (like quarks and electrons) communicate with each other through bosons. For instance, quarks know to bind together by throwing bosons called gluons back and forth, which carry the message, “Stick together!”

    Almost every collision inside the LHC starts with an exchange of bosons (the only exceptions are when matter particles meet antimatter particles).

    The lion’s share of LHC collisions happen when two passing energetic gluons meet, fuse and then transform into all sorts of particles through the wonders of quantum mechanics.

    Gluons carry the strong interaction, which pulls quarks together into particles like protons and neutrons. Gluon-gluon collisions are so powerful that the protons they are a part of are ripped apart and the original quarks in those protons are consumed.

    In extremely rare instances, colliding quarks can also interact through a different force: the weak interaction, which is carried by the massive W and Z bosons. The weak interaction arbitrates all nuclear decay and fusion, such as when the protons in the center of the sun are squished and squeezed into helium nuclei.

    The weak interaction passes the message, “Time to change!’’and inspires quarks to take on a new identity–for instance, change from a down quark to an up quark or vice versa.

    Although it may seem counterintuitive, the W and Z bosons that carry the weak interaction are extremely heavy–roughly 80 times more massive than the protons the LHC smashes together. For two minuscule quarks to produce two enormous W or Z bosons simultaneously, they need access to a big pot of excess energy.

    That’s where the LHC comes in; by accelerating protons to nearly the speed of light, it produces the most energetic collisions ever seen in a particle accelerator. “The LHC is special,” Ruiz says. “The LHC is the first collider in which we have evidence of W and Z boson scattering; the weak interaction bosons themselves are colliding.”

    Even inside the LHC, weak interaction boson-boson collisions are extremely rare. This is because the range of the weak interaction extends to only about 0.1% of the diameter of a proton. (Compare this to the range of the strong interaction, which is equivalent to the proton’s diameter.)

    “This range is quite small,” Apyan says. “Two quarks have to be extremely close and radiate a W or Z boson simultaneously for there to be a chance of the bosons colliding.”

    Apyan studies collisions in which two colliding quarks simultaneously release a W or Z boson, which then scatter off one another before transforming into more stable particles. Unlike other processes, the W and Z boson collisions maintain their quarks, which then fly off into the detector as the proton falls apart. “This process has a nice signature,” Apyan says. “The remnants of the original quarks end up in our detector, and we see them as jets of particles very close to the beampipe.”

    The probability of this happening during an LHC collision is about one in a trillion. Luckily, the LHC generates about 600 million proton-proton collisions every second. At this rate, scientists are able to see this extremely rare event about once every other minute when the LHC is running.

    These heavy boson-boson collisions inside the LHC provide physicists with a unique view of the subatomic world, Ruiz says.

    Creating and scattering bosons allows physicists to see how their mathematical models hold up under stringent experimental tests. This can allow them to search for physics beyond the Standard Model.

    The scattering of W and Z bosons is a particularly pertinent test for the strength of the Higgs field. “The coupling strength between the Higgs boson and W and Z bosons is proportional to the masses of the W and Z bosons, and this raises many interesting questions,” Apyan says.

    Even small tweaks to the Higgs field could have major implications for the properties of Z and W bosons and how they ricochet off each other. By studying how these particles collide inside the LHC, scientists are able to open yet another window into the properties of the Higgs.

    See the full article here .


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

    Please help promote STEM in your local schools.


    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 4:13 pm on September 13, 2016 Permalink | Reply
    Tags: , , D+ mesons, , , Strong interaction   

    From FNAL: “CDF can’t stop being charming” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

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

    September 8, 2016
    Jeffrey Appel

    FNAL/Tevatron map
    FNAL/Tevatron map

    FNAL/Tevatron CDF detector
    FNAL/Tevatron CDF detector

    Good news: there is a theory to describe the strong interaction, the interactions that bind the constituents of protons and neutrons together and create the strong force. Bad news: Calculations using the theory can be made in only a limited selection of natural phenomena.

    Quantitative predictions for interactions beyond that subset depend on measurements. This can be either for direct use or to help guide the theory about the inputs used in calculations, such as the distributions of the quark and gluon constituents inside protons and neutrons. Using the production of particles containing heavy charm and bottom quarks helps especially with gluon distributions.

    CDF is now reporting new measurements of the rate of production at the Tevatron of D+ mesons, which contain charm quarks. Furthermore, the new measurements are made in the region where the D+ mesons have the smallest momentum transverse to the incident beams. This is the region that is the hardest to calculate using the theory of strong interactions and has never been explored in proton-antiproton collisions.

    1
    This plot shows the measures, in bins of momentum transverse to incident protons, of the average probability of producing a D+ meson at the Tevatron. Shown as bands are the averages predicted in the same bins by the latest theoretical calculations.

    To probe such small transverse momenta, CDF physicists examined all types of interactions of the incoming protons and antiprotons, not just those selected to study rare occurrences.

    The results of this new analysis appear in the figure. The measurements lie within the band of uncertainty of the theoretical predictions. Using the results here, theorists can reduce the size of the band of uncertainty. They might also be able to improve the general trend of the predictions to agree better with the trends in the measurements.

    This measurement is an example of CDF’s continuing effort to produce unique and useful results that complement and supplement those of the LHC. These help improve our understanding of the fundamental forces of nature.

    Learn more.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    FNAL Icon
    Fermilab Campus

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

     
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