pion


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pion

(pī`ŏn) or

pi meson,

lightest of the mesonmeson
[Gr.,=middle (i.e., middleweight)], class of elementary particles whose masses are generally between those of the lepton class of lighter particles and those of the baryon class of heavier particles. From a technical point of view mesons are strongly interacting bosons; i.
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 family of elementary particleselementary particles,
the most basic physical constituents of the universe. Basic Constituents of Matter

Molecules are built up from the atom, which is the basic unit of any chemical element. The atom in turn is made from the proton, neutron, and electron.
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. The existence of the pion was predicted in 1935 by Hideki Yukawa, who theorized that it was responsible for the forceforce,
commonly, a "push" or "pull," more properly defined in physics as a quantity that changes the motion, size, or shape of a body. Force is a vector quantity, having both magnitude and direction.
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 of the strong interactionsstrong interactions,
actions between elementary particles mediated, or carried, by gluons. They are responsible for the binding of protons and neutrons in the nucleus and interactions between quarks.
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 holding the atomic nucleusnucleus,
in physics, the extremely dense central core of an atom. The Nature of the Nucleus
Composition

Atomic nuclei are composed of two types of particles, protons and neutrons, which are collectively known as nucleons.
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 together. It was first detected in cosmic rayscosmic rays,
charged particles moving at nearly the speed of light reaching the earth from outer space. Primary cosmic rays consist mostly of protons (nuclei of hydrogen atoms), some alpha particles (helium nuclei), and lesser amounts of nuclei of carbon, nitrogen, oxygen, and
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 by C. F. Powell in 1947. The pion is actually a multiplet of three particles. The neutral pion, π0, has a mass about 264 times that of the electron. The charged pions, π+ and π, each have a mass about 273 times that of the electron. The neutral pion is its own antiparticleantiparticle,
elementary particle corresponding to an ordinary particle such as the proton, neutron, or electron, but having the opposite electrical charge and magnetic moment.
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, while the negative pion is the antiparticle of the positive pion. It is now known that each pion (and, more generally, each meson) consists of a quark bound to an antiquark. Free pions are unstable. The charged pions decay with an average lifetime of 2.55 × 10−8 sec into a muonmuon
, elementary particle heavier than an electron but lighter than other particles having nonzero rest mass. The name muon is derived from mu meson, the former name of the particle. The muon was first observed in cosmic rays by Carl D.
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 of like charge and a neutrinoneutrino
[Ital.,=little neutral (particle)], elementary particle with no electric charge and a very small mass emitted during the decay of certain other particles. The neutrino was first postulated in 1930 by Wolfgang Pauli in order to maintain the law of conservation of energy
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 or antineutrino; the neutral pion decays in about 10−15 sec, usually into a pair of photons but occasionally into a positron-electron pair and a photon.

pion

[′pī‚än]
(particle physics)

pion

, pi meson
Physics a meson having a positive or negative charge and a rest mass 273.13 times that of the electron, or no charge and a rest mass 264.14 times that of the electron
References in periodicals archive ?
Hence, in order to avoid contradictions with the existence of charged pions and [W.
18) This is supported by the occurrence of PION after radical neck dissection (21,23-25) as compared with other surgical procedures causing PION, such as oral tumor resections, open heart surgery, (14) hip arthroplasty, or even partial gastrectomy.
If a contractor "front-loads" the general requirements with a detailed itemization of costs, "then you can demand that he be extremely accurate on his square-foot estimate," said Pion.
Another old-fashioned notion that Pion is proud of: "The paper has been annoying the self-anointed 'power people' in this town for some six years.
Atomic Labs is the creator of Pion, the powerful open source solution for handling your toughest data acquisition, processing, loading and streaming challenges.
Pion starts work at Destination Worcester on July 8.
Pion is currently being held on $15,000 bail awaiting trial for "seven counts of felony unlawful mischief, one count of misdemeanor unlawful mischief, one count aggravated assault on a law enforcement officer, one count of gross negligent operation, and one count of leaving the scene of an accident.
Both found that these particles, called pions, could not possibly have had enough energy to give rise to the faster-than-light, or superluminal, speeds indicated by OPERA.
We've shown in this paper that if the neutrino that comes out of a pion decay were going faster than the speed of light, the pion lifetime would get longer, and the neutrino would carry a smaller fraction of the energy shared by the neutrino and the muon," Cowsik says.
The Nottingham welterweight, 27, will be the first Brit to challenge for an U l t i m a t e F i g h t i n g Cham pion ship title when he faces reigning champ Georges St-Pierre at UFC 111 next Saturday in New Jersey.
Pion, executive vice president of the Beverly Hills office, wrote in an assessment of the quarter.
Pion exchange mediates the only long range component of the interaction, and ought to be the dominant contribution to observed parity-violating effects in a wide range of nuclear systems.