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A gluon is an elementary particle that acts as the exchange particle for the strong force between quarks. It is analogous to the exchange of photons in the electromagnetic force between two charged particles. Gluons bind quarks together, forming hadrons such as protons and neutrons.
A quark is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly observable matter is composed of up quarks, down quarks and electrons. Owing to a phenomenon known as color confinement, quarks are never found in isolation; they can be found only within hadrons, which include baryons and mesons, or in quark–gluon plasmas. For this reason, much of what is known about quarks has been drawn from observations of hadrons.
The up quark or u quark is the lightest of all quarks, a type of elementary particle, and a significant constituent of matter. It, along with the down quark, forms the neutrons and protons of atomic nuclei. It is part of the first generation of matter, has an electric charge of +2/3 e and a bare mass of 2.2+0.5
−0.4 MeV/c2. Like all quarks, the up quark is an elementary fermion with spin 1/2, and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. The antiparticle of the up quark is the up antiquark, which differs from it only in that some of its properties, such as charge have equal magnitude but opposite sign.
The down quark or d quark is the second-lightest of all quarks, a type of elementary particle, and a major constituent of matter. Together with the up quark, it forms the neutrons and protons of atomic nuclei. It is part of the first generation of matter, has an electric charge of −1/3 e and a bare mass of 4.7+0.5
−0.3 MeV/c2. Like all quarks, the down quark is an elementary fermion with spin 1/2, and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. The antiparticle of the down quark is the down antiquark, which differs from it only in that some of its properties have equal magnitude but opposite sign.
Hadronization is the process of the formation of hadrons out of quarks and gluons. There are two main branches of hadronization: quark-gluon plasma (QGP) transformation and colour string decay into hadrons. The transformation of quark-gluon plasma into hadrons is studied in lattice QCD numerical simulations, which are explored in relativistic heavy-ion experiments. Quark-gluon plasma hadronization occurred shortly after the Big Bang when the quark–gluon plasma cooled down to the Hagedorn temperature when free quarks and gluons cannot exist. In string breaking new hadrons are forming out of quarks, antiquarks and sometimes gluons, spontaneously created from the vacuum.
The Positron-Electron Tandem Ring Accelerator (PETRA) is one of the particle accelerators at the German national laboratory DESY in Hamburg, Germany. At the time of its construction, it was the biggest storage ring of its kind and still is DESY's second largest synchrotron after HERA. PETRA’s original purpose was research in elementary particle physics. From 1978 to 1986 it was used to study electron–positron collisions with the four experiments JADE, MARK-J, PLUTO and TASSO. The discovery of the gluon, the carrier particle of the strong nuclear force, by the TASSO collaboration in 1979 is counted as one of the biggest successes. PETRA was able to accelerate electrons and positrons to 19 GeV. Research at PETRA led to an intensified international use of the facilities at DESY. Scientists from China, France, Israel, the Netherlands, Norway, the United Kingdom and the USA participated in the first experiments at PETRA alongside many German colleagues.
In particle physics, a three-jet event is an event with many particles in final state that appear to be clustered in three jets. A single jet consists of particles that fly off in roughly the same direction. One can draw three cones from the interaction point, corresponding to the jets, and most particles created in the reaction will appear to belong to one of these cones. These events are currently the most direct available evidence for the existence of gluons, and were first observed by the TASSO experiment at the PETRA accelerator at the DESY laboratory.
In particle physics, the parton model is a model of hadrons, such as protons and neutrons, proposed by Richard Feynman. It is useful for interpreting the cascades of radiation produced from quantum chromodynamics (QCD) processes and interactions in high-energy particle collisions.
JADE was a particle detector at the PETRA particle accelerator at the German national laboratory DESY in Hamburg. It was operated from 1979 to 1986. JADE's most important scientific achievement was the discovery of the gluon in three-jet events. It also helped greatly in establishing quantum chromodynamics. JADE is an acronym for Japan, Deutschland (Germany) and England, the three countries from which the participating universities originated. The JADE jet chamber is now exhibited in the physics lecture hall at the University of Heidelberg. Although the last data with JADE were taken in 1986, analysis continued, with the most recent paper published in 2012. In 1995, the European Physical Society (EPS) awarded a "Special High Energy and Particle Physics Prize" to the JADE, PLUTO, TASSO and MARK-J collaborations at PETRA for "establishing the existence of the gluon in independent and simultaneous ways".
The timeline of particle physics lists the sequence of particle physics theories and discoveries in chronological order. The most modern developments follow the scientific development of the discipline of particle physics.
Herwig Franz Schopper is a Czech-born experimental physicist and was the director general of CERN from 1981 to 1988.
Rolf-Dieter Heuer is a German particle physicist. From 2009 to 2015 he was Director General of CERN and from 5 April 2016 to 9 April 2018 President of the German Physical Society. Since 2015 he has been Chair of the European Commission's Group of Chief Scientific Advisors, and since May 2017 he has been President of the SESAME Council.
Bjørn Håvard Wiik was a Norwegian elementary particle physicist, noted for his role on the experiment that produced the first experimental evidence for gluons and for his influential role on later accelerator projects. Wiik was director of DESY, in Hamburg, Germany, from 1993 until his death.
Quark–gluon plasma is an interacting localized assembly of quarks and gluons at thermal and chemical (abundance) equilibrium. The word plasma signals that free color charges are allowed. In a 1987 summary, Léon van Hove pointed out the equivalence of the three terms: quark gluon plasma, quark matter and a new state of matter. Since the temperature is above the Hagedorn temperature—and thus above the scale of light u,d-quark mass—the pressure exhibits the relativistic Stefan-Boltzmann format governed by temperature to the fourth power and many practically massless quark and gluon constituents. It can be said that QGP emerges to be the new phase of strongly interacting matter which manifests its physical properties in terms of nearly free dynamics of practically massless gluons and quarks. Both quarks and gluons must be present in conditions near chemical (yield) equilibrium with their colour charge open for a new state of matter to be referred to as QGP.
In high-energy nuclear physics, strangeness production in relativistic heavy-ion collisions is a signature and diagnostic tool of quark–gluon plasma (QGP) formation and properties. Unlike up and down quarks, from which everyday matter is made, heavier quark flavors such as strange and charm typically approach chemical equilibrium in a dynamic evolution process. QGP is an interacting localized assembly of quarks and gluons at thermal (kinetic) and not necessarily chemical (abundance) equilibrium. The word plasma signals that color charged particles are able to move in the volume occupied by the plasma. The abundance of strange quarks is formed in pair-production processes in collisions between constituents of the plasma, creating the chemical abundance equilibrium. The dominant mechanism of production involves gluons only present when matter has become a quark–gluon plasma. When quark–gluon plasma disassembles into hadrons in a breakup process, the high availability of strange antiquarks helps to produce antimatter containing multiple strange quarks, which is otherwise rarely made. Similar considerations are at present made for the heavier charm flavor, which is made at the beginning of the collision process in the first interactions and is only abundant in the high-energy environments of CERN's Large Hadron Collider.
Mary Katharine Gaillard is an American theoretical physicist. Her focus is on particle physics. She is a professor of the Graduate School at the University of California, Berkeley, a member of the Berkeley Center for Theoretical Physics, and visiting scientist at the Lawrence Berkeley National Laboratory. She was Berkeley's first tenured female physicist.
PLUTO was a detector for experimental high-energy particle physics at the German national laboratory DESY in Hamburg. It was operated from 1974 to 1978 at the DORIS synchrotron and was substantially upgraded between 1977 and 1978 for operation at the PETRA accelerator, where it took data until 1979. The name is not an acronym, unlike the other detectors at DORIS.
Paul Heinrich Söding is a German physicist. He is best known for his work in particle physics and as former director of research of the German particle physics lab DESY.
Sau Lan Wu is a Chinese American particle physicist and the Enrico Fermi Distinguished Professor of Physics at the University of Wisconsin-Madison. She made important contributions towards the discovery of the J/psi particle, which provided experimental evidence for the existence of the charm quark, and the gluon, the vector boson of the strong force in the Standard Model of physics. Recently, her team located at the European Organization for Nuclear Research (CERN), using data collected at the Large Hadron Collider (LHC), was part of the international effort in the discovery of a boson consistent with the Higgs boson.
The High Energy and Particle Physics Prize, established in 1989, is awarded every two years by the European Physical Society (EPS) for an outstanding contribution to high energy and particle physics. :) Enjoy
References
- ↑ Burkhardt, H.; Koehler, P.; Riethmüller, R.; Wiik, B.H.; Fohrmann, R.; Franzkea, J.; Krasemann, H.; Maschuw, R.; Poelz, G.; Reichardt, J.; Ringel, J.; Römer, O.; Rüsch, R.; Schmüser, P.; van Staa, R.; Freeman, J.; Lecomte, P.; Meyer, T.; Wu, Sau Lan; Zobernig, G. (June 1981). "The TASSO gas and aerogel Cherenkov counters". Nuclear Instruments and Methods. 184 (2–3): 319–331. Bibcode:1981NucIM.184..319B. doi:10.1016/0029-554X(81)90732-1.
- 1 2 Flegel, I; Söding, P (2004). "Twenty-Five Years of Gluons". DESY: CERN Courier.