Gluon Gluons /ˈɡluːɒnz/ are elementary particles that act as the exchange particles (or gauge bosons) for the strong force between quarks, analogous to the exchange of photons in the electromagnetic force between two charged particles. In technical terms, gluons are vector gauge bosons that mediate strong interactions of quarks in quantum chromodynamics (QCD). Gluons themselves carry the color charge of the strong interaction. This is unlike the photon, which mediates the electromagnetic interaction but lacks an electric charge. Gluons therefore participate in the strong interaction in addition to mediating it, making QCD significantly harder to analyze than QED (quantum electrodynamics). Properties Diagram 1: e+e− -> Y(9.46) -> 3g Numerology of gluons Unlike the single photon of QED or the three W and Z bosons of the weak interaction, there are eight independent types of gluon in QCD. This may be difficult to understand intuitively. Color charge and superposition A.
Higgs boson The Higgs boson is named after Peter Higgs, one of six physicists who, in 1964, proposed the mechanism that suggested the existence of such a particle. Although Higgs's name has come to be associated with this theory, several researchers between about 1960 and 1972 each independently developed different parts of it. In mainstream media the Higgs boson has often been called the "God particle", from a 1993 book on the topic; the nickname is strongly disliked by many physicists, including Higgs, who regard it as inappropriate sensationalism. In 2013 two of the original researchers, Peter Higgs and François Englert, were awarded the Nobel Prize in Physics for their work and prediction (Englert's co-researcher Robert Brout had died in 2011). A non-technical summary "Higgs" terminology Overview If this field did exist, this would be a monumental discovery for science and human knowledge, and is expected to open doorways to new knowledge in many fields. History
Graviton Theory The three other known forces of nature are mediated by elementary particles: electromagnetism by the photon, the strong interaction by the gluons, and the weak interaction by the W and Z bosons. The hypothesis is that the gravitational interaction is likewise mediated by an – as yet undiscovered – elementary particle, dubbed as the graviton. In the classical limit, the theory would reduce to general relativity and conform to Newton's law of gravitation in the weak-field limit. Gravitons and renormalization When describing graviton interactions, the classical theory (i.e., the tree diagrams) and semiclassical corrections (one-loop diagrams) behave normally, but Feynman diagrams with two (or more) loops lead to ultraviolet divergences; that is, infinite results that cannot be removed because the quantized general relativity is not renormalizable, unlike quantum electrodynamics. Comparison with other forces Gravitons in speculative theories See also
Photon Nomenclature In 1900, Max Planck was working on black-body radiation and suggested that the energy in electromagnetic waves could only be released in "packets" of energy. In his 1901 article  in Annalen der Physik he called these packets "energy elements". The word quanta (singular quantum) was used even before 1900 to mean particles or amounts of different quantities, including electricity. Later, in 1905, Albert Einstein went further by suggesting that electromagnetic waves could only exist in these discrete wave-packets. He called such a wave-packet the light quantum (German: das Lichtquant). The name photon derives from the Greek word for light, φῶς (transliterated phôs). Physical properties The cone shows possible values of wave 4-vector of a photon. A photon is massless,[Note 2] has no electric charge, and is stable. Photons are emitted in many natural processes. Since p points in the direction of the photon's propagation, the magnitude of the momentum is
Meson In particle physics, mesons (/ˈmiːzɒnz/ or /ˈmɛzɒnz/) are hadronic subatomic particles composed of one quark and one antiquark, bound together by the strong interaction. Because mesons are composed of sub-particles, they have a physical size, with a radius roughly one femtometre, which is about 2⁄3 the size of a proton or neutron. All mesons are unstable, with the longest-lived lasting for only a few hundredths of a microsecond. Charged mesons decay (sometimes through intermediate particles) to form electrons and neutrinos. Uncharged mesons may decay to photons. Mesons are not produced by radioactive decay, but appear in nature only as short-lived products of very high-energy interactions in matter, between particles made of quarks. In nature, the importance of lighter mesons is that they are the associated quantum-field particles that transmit the nuclear force, in the same way that photons are the particles that transmit the electromagnetic force. History Overview If
Baryon A baryon is a composite subatomic particle made up of three quarks (as distinct from mesons, which comprise one quark and one antiquark). Baryons and mesons belong to the hadron family, which are the quark-based particles. The name "baryon" comes from the Greek word for "heavy" (βαρύς, barys), because, at the time of their naming, most known elementary particles had lower masses than the baryons. As quark-based particles, baryons participate in the strong interaction, whereas leptons, which are not quark-based, do not. The most familiar baryons are the protons and neutrons that make up most of the mass of the visible matter in the universe. Background Baryons are strongly interacting fermions — that is, they experience the strong nuclear force and are described by Fermi−Dirac statistics, which apply to all particles obeying the Pauli exclusion principle. Baryons, along with mesons, are hadrons, meaning they are particles composed of quarks. Baryonic matter Baryogenesis
Strangeness In particle physics, strangeness S is a property of particles, expressed as a quantum number, for describing decay of particles in strong and electromagnetic reactions, which occur in a short period of time. The strangeness of a particle is defined as: where ns represents the number of strange quarks (s) and ns represents the number of strange antiquarks (s). Strangeness conservation In our modern understanding, strangeness is conserved during the strong and the electromagnetic interactions, but not during the weak interactions. See also References D.J. Further reading Lessons in Particle Physics Luis Anchordoqui and Francis Halzen, University of Wisconsin, 18th Dec. 2009
Sigma baryon The Sigma baryons are a family of subatomic hadron particles which have a +2, +1 or −1 elementary charge or are neutral. They are baryons containing three quarks: two up and/or down quarks, and one third quark, which can be either a strange (symbols Σ+, Σ0, Σ−), a charm (symbols Σ++ c, Σ+ c, Σ0 c), a bottom (symbols Σ+ b, Σ0 b, Σ− b) or a top (symbols Σ++ t, Σ+ t, Σ0 t) quark. However, the top Sigmas are not expected to be observed as the Standard Model predicts the mean lifetime of top quarks to be roughly 5×10−25 s. This is about 20 times shorter than the timescale for strong interactions, and therefore it does not form hadrons. List Antiparticles are not listed in the table; however, they simply would have all quarks changed to antiquarks, and Q, B, S, C, B′, T, would be of opposite signs. JP = 1⁄2+ Sigma baryons † ^ Particle currently unobserved, but predicted by the standard model. JP = 3⁄2+ Sigma baryons See also References Bibliography
D meson The D mesons are the lightest particle containing charm quarks. They are often studied to gain knowledge on the weak interaction. The strange D mesons (Ds) were called the "F mesons" prior to 1986. Overview In November 2011, researchers at the LHCb experiment at CERN reported (3.5 sigma significance) that they have observed a direct CP violation in the neutral D meson decay, possibly beyond the Standard Model. List of D mesons [a] ^ PDG reports the resonance width (Γ). See also References
Kaon Basic properties The four kaons are : The negatively charged K− (containing a strange quark and an up antiquark) has mass 493.667±0.013 MeV and mean lifetime (1.2384±0.0024)×10−8 s.Its antiparticle, the positively charged K+ (containing an up quark and a strange antiquark) must (by CPT invariance) have mass and lifetime equal to that of K−. The mass difference is 0.032±0.090 MeV, consistent with zero. The difference in lifetime is (0.11±0.09)×10−8 s.The K0 (containing a down quark and a strange antiquark) has mass 497.648±0.022 MeV. [a] ^ Strong eigenstate. Although the K0 and its antiparticle K0 are usually produced via the strong force, they decay weakly. The long-lived neutral kaon is called the K L ("K-long"), decays primarily into three pions, and has a mean lifetime of 5.18×10−8 s.The short-lived neutral kaon is called the K S ("K-short"), decays primarily into two pions, and has a mean lifetime 8.958×10−11 s. (See discussion of neutral kaon mixing below.) Strangeness
Charm quark The charm quark or c quark (from its symbol, c) is the third most massive of all quarks, a type of elementary particle. Charm quarks are found in hadrons, which are subatomic particles made of quarks. Example of hadrons containing charm quarks include the J/ψ meson (J/ψ), D mesons (D), charmed Sigma baryons (Σ c), and other charmed particles. The existence of a fourth quark had been speculated by a number of authors around 1964 (for instance by James Bjorken and Sheldon Glashow), but its prediction is usually credited to Sheldon Glashow, John Iliopoulos and Luciano Maiani in 1970 (see GIM mechanism). The first charmed particle (a particle containing a charm quark) to be discovered was the J/ψ meson. Hadrons containing charm quarks Some of the hadrons containing charm quarks include: D mesons contain a charm quark (or its antiparticle) and an up or down quark.D s mesons contain a charm quark and a strange quark.There are many charmonium states, for example the J/ψ particle. R.