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GIM Mechanism
In particle physics, the Glashow–Iliopoulos–Maiani (GIM) mechanism is the mechanism through which Flavor-changing neutral current, flavour-changing neutral currents (FCNCs) are suppressed in One-loop_Feynman_diagram, loop diagrams. It also explains why weak interactions that change strangeness by 2 (Δ''S'' = 2 transitions) are suppressed, while those that change strangeness by 1 (Δ''S'' = 1 transitions) are allowed, but only in charged current interactions. It is named after physicists Sheldon Glashow, John Iliopoulos and Luciano Maiani. History The mechanism was put forth in a famous paper by ; at that time, only three quarks (up quark, up, down quark, down, and strange quark, strange) were thought to exist. James Bjorken and Glashow [] had previously predicted a charm quark, fourth quark, but there was little evidence for its existence. The GIM mechanism however, ''required'' the existence of a fourth quark, and the prediction of the charm quark is usually credited to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Particle Physics
Particle physics or high-energy physics is the study of Elementary particle, fundamental particles and fundamental interaction, forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the scale of protons and neutrons, while the study of combinations of protons and neutrons is called nuclear physics. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) and bosons (force-carrying particles). There are three Generation (particle physics), generations of fermions, although ordinary matter is made only from the first fermion generation. The first generation consists of Up quark, up and down quarks which form protons and neutrons, and electrons and electron neutrinos. The three fundamental interactions known to be mediated by bosons are electromagnetism, the weak interaction, and the strong interaction. Quark, Quarks cannot exist on their own but form hadrons. Hadrons that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Down Quark
The down quark (symbol: d) is a type of elementary particle, and a major constituent of matter. The down quark is the second-lightest of all quarks, and combines with other quarks to form composite particles called hadrons. Down quarks are most commonly found in atomic nucleus, atomic nuclei, where it combines with up quarks to form protons and neutrons. The proton is made of one down quark with two up quarks, and the neutron is made up of two down quarks with one up quark. Because they are found in every single known atom, down quarks are present in all everyday matter that we interact with. The down quark is part of the generation (physics), first generation of matter, has an electric charge of − elementary charge, ''e'' and a Quark#Mass, bare mass of . Like all quarks, the down quark is an elementary fermion with Spin (physics), spin spin-1/2, , and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scholarpedia
''Scholarpedia'' is an English-language wiki-based online encyclopedia with features commonly associated with Open access (publishing), open-access online academic journals, which aims to have quality content in science and medicine. ''Scholarpedia'' articles are written by invited or approved expert authors and are subject to peer review. ''Scholarpedia'' lists the real names and affiliations of all authors, curators and editors involved in an article: however, the peer review process (which can suggest changes or additions, and has to be satisfied before an article can appear) is anonymous. ''Scholarpedia'' articles are stored in an online repository, and can be citation, cited as conventional journal articles (''Scholarpedia'' has the ISSN number ). ''Scholarpedia''s citation system includes support for revision numbers. The project was created in February 2006 by Eugene M. Izhikevich, while he was a researcher at the Neurosciences Institute, San Diego, California. Izhikevich ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
World Scientific
World Scientific Publishing is an academic publisher of scientific, technical, and medical books and journals headquartered in Singapore. The company was founded in 1981. It publishes about 600 books annually, with more than 170 journals in various fields. In 1995, World Scientific co-founded the London-based Imperial College Press together with the Imperial College of Science, Technology and Medicine. Company structure The company head office is in Singapore. The Chairman and Editor-in-Chief is Dr Phua Kok Khoo, while the Managing Director is Doreen Liu. The company was co-founded by them in 1981. Imperial College Press In 1995 the company co-founded Imperial College Press, specializing in engineering, medicine and information technology Information technology (IT) is a set of related fields within information and communications technology (ICT), that encompass computer systems, software, programming languages, data processing, data and information processing, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
W And Z Bosons
In particle physics, the W and Z bosons are vector bosons that are together known as the weak bosons or more generally as the intermediate vector bosons. These elementary particles mediate the weak interaction; the respective symbols are , , and . The bosons have either a positive or negative electric charge of 1 elementary charge and are each other's antiparticles. The boson is electrically neutral and is its own antiparticle. The three particles each have a spin of 1. The bosons have a magnetic moment, but the has none. All three of these particles are very short-lived, with a half-life of about . Their experimental discovery was pivotal in establishing what is now called the Standard Model of particle physics. The bosons are named after the ''weak'' force. The physicist Steven Weinberg named the additional particle the " particle", — The electroweak unification paper. and later gave the explanation that it was the last additional particle ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cabibbo–Kobayashi–Maskawa Matrix
In the Standard Model of particle physics, the Cabibbo–Kobayashi–Maskawa matrix, CKM matrix, quark mixing matrix, or KM matrix is a unitary matrix that contains information on the strength of the flavour-changing weak interaction. Technically, it specifies the mismatch of quantum states of quarks when they propagate freely and when they take part in the weak interactions. It is important in the understanding of CP violation. This matrix was introduced for three generations of quarks by Makoto Kobayashi and Toshihide Maskawa, adding one generation to the matrix previously introduced by Nicola Cabibbo. This matrix is also an extension of the GIM mechanism, which only includes two of the three current families of quarks. The matrix Predecessor – the Cabibbo matrix In 1963, Nicola Cabibbo introduced the Cabibbo angle () to preserve the universality of the weak interaction. Cabibbo was inspired by previous work by Murray Gell-Mann and Maurice Lévy, on the effectivel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physics Letters
''Physics Letters'' was a scientific journal published from 1962 to 1966, when it split in two series now published by Elsevier Elsevier ( ) is a Dutch academic publishing company specializing in scientific, technical, and medical content. Its products include journals such as ''The Lancet'', ''Cell (journal), Cell'', the ScienceDirect collection of electronic journals, ...: *''Physics Letters A'': condensed matter physics, theoretical physics, nonlinear science, statistical physics, mathematical and computational physics, general and cross-disciplinary physics (including foundations), atomic, molecular and cluster physics, plasma and fluid physics, optical physics, biological physics and nanoscience. *''Physics Letters B'': nuclear physics, theoretical nuclear physics, experimental high-energy physics, theoretical high-energy physics, and astrophysics. ''Physics Letters B'' is part of the SCOAP3 initiative. References See also * List of periodicals published by Elsevier ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charm Quark
The charm quark, charmed quark, or c quark is an elementary particle found in composite subatomic particles called hadrons such as the J/psi meson and the charmed baryons created in particle accelerator collisions. Several bosons, including the W and Z bosons and the Higgs boson, can decay into charm quarks. All charm quarks carry Charm (quantum number), charm, a quantum number. This second-Generation (particle physics), generation particle is the third-most-massive quark, with a mass of as measured in 2022, and a charge of + Elementary charge, ''e''. The existence of the charm quark was first predicted by James Bjorken and Sheldon Glashow in 1964, and in 1970, Glashow, John Iliopoulos, and Luciano Maiani showed how its existence would account for experimental and theoretical discrepancies. In 1974, its existence was confirmed through the independent discoveries of the J/psi meson at Brookhaven National Laboratory and the Stanford Linear Accelerator Center. In the ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
James Bjorken
James Daniel "BJ" Bjorken (June 22, 1934 – August 6, 2024) was an American theoretical physicist. He was a Putnam Fellow in 1954, received a BS in physics from MIT in 1956, and obtained his PhD from Stanford University in 1959. Bjorken was a visiting scholar at the Institute for Advanced Study in the fall of 1962. He was also emeritus professor in the SLAC Theory Group at the Stanford Linear Accelerator Center, and was a member of the Theory Department of the Fermi National Accelerator Laboratory (1979–1989). Bjorken was awarded the Dirac Medal (ICTP), Dirac Medal of the ICTP in 2004; and, in 2015, the Wolf Prize in Physics and the European Physical Society, EPS High Energy and Particle Physics Prize. Early life and education James Bjorken's father, J. Daniel Bjorken, was an immigrant from Sweden near Lake Siljan. He changed his surname from "Björkén" to Bjorken upon arriving in the US; he moved to Chicago to work as an electrical engineer, which was where he met his f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strange Quark
The strange quark or s quark (from its symbol, s) is the third lightest of all quarks, a type of elementary particle. Strange quarks are found in subatomic particles called hadrons. Examples of hadrons containing strange quarks include kaons (), strange D mesons (), Sigma baryons (), and other strange particles. According to the IUPAP, the symbol s is the official name, while "strange" is to be considered only as a mnemonic. The name sideways has also been used because the s quark (but also the other three remaining quarks) has an isospin, I value of 0 while the u ("up") and d ("down") quarks have values of + and − respectively. Along with the charm quark, it is part of the generation (physics), second generation of matter. It has an electric charge of elementary charge, ''e'' and a bare mass of . Like all quarks, the strange quark is an elementary particle, elementary fermion with Spin (physics), spin spin-1/2, , and experiences all four fundamental interactions: gravit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Up Quark
The up quark or u quark (symbol: u) 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 (one up quark, two down quarks) and protons (two up quarks, one down quark) of atomic nucleus, atomic nuclei. It is part of the generation (physics), first generation of matter, has an electric charge of + elementary charge, ''e'' and a Quark#Mass, bare mass of . Like all quarks, the up quark is an elementary particle, elementary fermion with Spin (physics), spin 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 (sometimes called ''antiup quark'' or simply ''antiup''), which differs from it only in that some of its properties, such as electric charge, charge have additive inverse, equal magnitude but opposite sign. Its existence (along with that of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flavor-changing Neutral Current
In particle physics, flavor-changing neutral currents or flavour-changing neutral currents (FCNCs) are hypothetical interactions that change the flavor of a fermion without altering its electric charge. Details If they occur in nature (as reflected by Lagrangian interaction terms), these processes may induce phenomena that have not yet been observed in experiment. Flavor-changing neutral currents may occur in the Standard Model beyond the tree level, but they are highly suppressed by the GIM mechanism. Several collaborations have searched for FCNC. The Tevatron CDF experiment observed evidence of FCNC in the decay of the strange B-meson to phi mesons in 2005. FCNCs are generically predicted by theories that attempt to go beyond the Standard Model, such as the models of supersymmetry or technicolor. Their suppression is necessary for an agreement with observations, making FCNCs important constraints on model-building. Example Consider a toy model in which an undiscovered bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
