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Pions
In particle physics, a pion (or a pi meson, denoted with the Greek letter pi: ) is any of three subatomic particles: , , and . Each pion consists of a quark and an antiquark and is therefore a meson. Pions are the lightest mesons and, more generally, the lightest hadrons. They are unstable, with the charged pions and decaying after a mean lifetime of 26.033 nanoseconds ( seconds), and the neutral pion decaying after a much shorter lifetime of 85 attoseconds ( seconds). Charged pions most often decay into muons and muon neutrinos, while neutral pions generally decay into gamma rays. The exchange of virtual pions, along with vector, rho and omega mesons, provides an explanation for the residual strong force between nucleons. Pions are not produced in radioactive decay, but commonly are in high-energy collisions between hadrons. Pions also result from some matter–antimatter annihilation events. All types of pions are also produced in natural processes whe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meson
In particle physics, a meson ( or ) is a type of hadronic subatomic particle composed of an equal number of quarks and antiquarks, usually one of each, bound together by the strong interaction. Because mesons are composed of quark subparticles, they have a meaningful physical size, a diameter of roughly one femtometre (10 m), which is about 0.6 times the size of a proton or neutron. All mesons are unstable, with the longest-lived lasting for only a few hundredths of a microsecond. Heavier mesons decay to lighter mesons and ultimately to stable electrons, neutrinos and photons. Outside the nucleus, mesons appear in nature only as short-lived products of very high-energy collisions between particles made of quarks, such as cosmic rays (high-energy protons and neutrons) and baryonic matter. Mesons are routinely produced artificially in cyclotrons or other particle accelerators in the collisions of protons, antiprotons, or other particles. Higher-energy (more massive) me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meson
In particle physics, a meson ( or ) is a type of hadronic subatomic particle composed of an equal number of quarks and antiquarks, usually one of each, bound together by the strong interaction. Because mesons are composed of quark subparticles, they have a meaningful physical size, a diameter of roughly one femtometre (10 m), which is about 0.6 times the size of a proton or neutron. All mesons are unstable, with the longest-lived lasting for only a few hundredths of a microsecond. Heavier mesons decay to lighter mesons and ultimately to stable electrons, neutrinos and photons. Outside the nucleus, mesons appear in nature only as short-lived products of very high-energy collisions between particles made of quarks, such as cosmic rays (high-energy protons and neutrons) and baryonic matter. Mesons are routinely produced artificially in cyclotrons or other particle accelerators in the collisions of protons, antiprotons, or other particles. Higher-energy (more massive) me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Force
The nuclear force (or nucleon–nucleon interaction, residual strong force, or, historically, strong nuclear force) is a force that acts between the protons and neutrons of atoms. Neutrons and protons, both nucleons, are affected by the nuclear force almost identically. Since protons have charge +1 ''e'', they experience an electric force that tends to push them apart, but at short range the attractive nuclear force is strong enough to overcome the electromagnetic force. The nuclear force binds nucleons into atomic nuclei. The nuclear force is powerfully attractive between nucleons at distances of about 0.8 femtometre (fm, or 0.8×10−15 metre), but it rapidly decreases to insignificance at distances beyond about 2.5 fm. At distances less than 0.7 fm, the nuclear force becomes repulsive. This repulsion is responsible for the size of nuclei, since nucleons can come no closer than the force allows. (The size of an atom, measured in angstroms (Å, or 10� ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cecil Powell
Cecil Frank Powell, FRS (5 December 1903 – 9 August 1969) was a British physicist, and Nobel Prize in Physics laureate for heading the team that developed the photographic method of studying nuclear processes and for the resulting discovery of the pion (pi-meson), a subatomic particle. Personal life Powell was born in Tonbridge, Kent, England, the son Frank and Elizabeth Caroline (née Bisacre) Powell. His father was a gunsmith. He was educated at a local primary school before gaining a scholarship to the Judd School, Tonbridge. Following this he attended Sidney Sussex College, Cambridge, graduating in 1925 in Natural Sciences. After completing his bachelor's degree he worked at the Cavendish Laboratory, Cambridge, under C.T.R. Wilson and Lord Rutherford, conducting research into condensation phenomena, and gaining his PhD in Physics in 1929. In 1932 Powell married Isobel Artner (1907-1995), and the couple had two daughters, Jane and Annie. Professional life In 1928 he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Omega Meson
The omega meson () is a flavourless meson formed from a superposition of an up quark–antiquark and a down quark–antiquark pair. It is part of the vector meson nonet and mediates the nuclear force along with pions and rho mesons. Properties The most common decay mode for the ω meson is at 89.2±0.7%, followed by at 8.34±0.26%. The quark composition of the meson can be thought of as a mix between , and states, but it is very nearly a pure symmetric - state. This can be shown by deconstructing the wave function of the into its component parts. We see that the and mesons are mixtures of the SU(3) wave functions as follows. : \omega = \psi_8 \sin\theta + \psi_1 \cos\theta, : \phi = \psi_8 \cos\theta - \psi_1 \sin\theta, where : \theta is the nonet mixing angle, : \psi_1 = \frac and : \psi_8 = \frac. The mixing angle at which the components decouple completely can be calculated to be \arctan\frac\approx35.3^\circ, which almost corresponds to the actual value cal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Muon
A muon ( ; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 '' e'' and a spin of , but with a much greater mass. It is classified as a lepton. As with other leptons, the muon is not thought to be composed of any simpler particles; that is, it is a fundamental particle. The muon is an unstable subatomic particle with a mean lifetime of , much longer than many other subatomic particles. As with the decay of the non-elementary neutron (with a lifetime around 15 minutes), muon decay is slow (by subatomic standards) because the decay is mediated only by the weak interaction (rather than the more powerful strong interaction or electromagnetic interaction), and because the mass difference between the muon and the set of its decay products is small, providing few kinetic degrees of freedom for decay. Muon decay almost always produces at least three particles, which must include an electr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antiquark
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 (such as protons and neutrons) and mesons, or in quark–gluon plasmas. There is also the theoretical possibility of more exotic phases of quark matter. For this reason, much of what is known about quarks has been drawn from observations of hadrons. Quarks have various intrinsic properties, including electric charge, mass, color charge, and spin. They are the only elementary particles in the Standard Model of particle physics to experience all four fundamental interactions, also known as ''fundamental forces'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quark
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 (such as protons and neutrons) and mesons, or in quark–gluon plasmas. There is also the theoretical possibility of more exotic phases of quark matter. For this reason, much of what is known about quarks has been drawn from observations of hadrons. Quarks have various intrinsic properties, including electric charge, mass, color charge, and spin. They are the only elementary particles in the Standard Model of particle physics to experience all four fundamental interactions, also known as ''fundamental forces'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
César Lattes
Cesare Mansueto Giulio Lattes (11 July 1924 – 8 March 2005), also known as César Lattes, was a Brazilian experimental physicist, one of the discoverers of the pion, a composite subatomic particle made of a quark and an antiquark. Life Lattes was born to a family of Italian immigrants in Curitiba, Paraná Brazil. He did his first studies there and also in São Paulo. He then went to the University of São Paulo, graduating in 1943, in mathematics and physics. He was part of an initial group of young Brazilian physicists who worked under European teachers such as Gleb Wataghin and Giuseppe Occhialini. Lattes was considered the most brilliant of those and was noted at a very young age as a bold researcher. His colleagues, who also became important Brazilian scientists, were Oscar Sala, Mário Schenberg, Roberto Salmeron, Marcelo Damy de Souza Santos and Jayme Tiomno. At the age of 25, he was one of the founders of the Brazilian Center for Physical Research (''Centro Brasile ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Giuseppe Occhialini
Giuseppe Paolo Stanislao "Beppo" Occhialini ForMemRS (; 5 December 1907 – 30 December 1993) was an Italian physicist who contributed to the discovery of the pion or pi-meson decay in 1947 with César Lattes and Cecil Frank Powell, the latter winning the Nobel Prize in Physics for this work. At the time of this discovery, they were all working at the H. H. Wills Laboratory of the University of Bristol. The X-ray satellite SAX was named BeppoSAX in his honour after its launch in 1996. Biography His father was the physicist Raffaele Augusto Occhialini (1878–1951), a pioneer in the fields of spectroscopy and electronics theory. Giuseppe Paolo Stanislao Occhialini graduated at Florence in 1929. In 1932, he collaborated in the discovery of the positron in cosmic rays at the Cavendish Laboratory of Cambridge, under the leadership of Patrick Blackett, using cloud chambers. He returned in Italy in 1934, where he suffered from the political climate generated by fascism. Thus, fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strong Interaction
The strong interaction or strong force is a fundamental interaction that confines quarks into proton, neutron, and other hadron particles. The strong interaction also binds neutrons and protons to create atomic nuclei, where it is called the nuclear force. Most of the mass of a common proton or neutron is the result of the strong interaction energy; the individual quarks provide only about 1% of the mass of a proton. At the range of 10−15 m (slightly more than the radius of a nucleon), the strong force is approximately 100 times as strong as electromagnetism, 106 times as strong as the weak interaction, and 1038 times as strong as gravitation. The strong interaction is observable at two ranges and mediated by two force carriers. On a larger scale (of about 1 to 3 fm), it is the force (carried by mesons) that binds protons and neutrons (nucleons) together to form the nucleus of an atom. On the smaller scale (less than about 0.8 fm, the radius of a nuc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rho Meson
Rho (uppercase Ρ, lowercase ρ or ; el, ρο or el, ρω, label=none) is the 17th letter of the Greek alphabet. In the system of Greek numerals it has a value of 100. It is derived from Phoenician letter res . Its uppercase form uses the same glyph, Ρ, as the distinct Latin letter P; the two letters have different Unicode encodings. Uses Greek Rho is classed as a liquid consonant (together with Lambda and sometimes the nasals Mu and Nu), which has important implications for morphology. In both Ancient and Modern Greek, it represents a alveolar trill , alveolar tap , or alveolar approximant . In polytonic orthography, a rho at the beginning of a word is written with a rough breathing, equivalent to ''h'' ( ''rh''), and a double rho within a word is written with a smooth breathing over the first rho and a rough breathing over the second ( ''rrh''). That apparently reflected an aspirated or voiceless pronunciation in Ancient Greek, which led to the various Greek- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
_P.S._Occhialini_(1907–1993)_and_Patrick_M.S._Blackett_(1897–1974)_in_1932_or_1933.png "Click for more on -> Giuseppe Occhialini")
