Pion

*Pion*
The quark structure of the pion.
Composition	π⁺: ud π⁰: dd / uu π⁻: du
Family	Bosons
Group	Mesons
Interaction	Strong
Theorized	Hideki Yukawa
Symbol	π⁺, π⁰, & π⁻
No. In Particle physics, bosons are particles which obey Bose-Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein In Particle physics, a meson is a strongly interacting Boson &mdashthat is a Hadron with integer spin. In Physics, a fundamental interaction or fundamental force is a mechanism by which particles interact with each other and which cannot be explained in terms In particle physics the strong interaction, or strong force, or color force, holds Quarks and Gluons together to form Protons and né, was a Japanese Theoretical physicist and the first Japanese Nobel laureate. of types	3
Mass	π^±: 139. 57018(35) MeV/c² π⁰: 134. 9766(6) MeV/c²
Electric charge	π^±: ±e π⁰: 0
Spin	π^±: 1(±1), 0⁻ π⁰: 1(0), 0⁻
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In particle physics, pion (short for pi meson) is the collective name for three subatomic particles: π⁰, π⁺ and π⁻. The elementary charge, usually denoted e, is the Electric charge carried by a single Proton, or equivalently the negative of the electric charge carried The elementary charge, usually denoted e, is the Electric charge carried by a single Proton, or equivalently the negative of the electric charge carried In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin Particle physics is a branch of Physics that studies the elementary constituents of Matter and Radiation, and the interactions between them A subatomic particle is an elementary or composite Particle smaller than an Atom. Pions are the lightest mesons (excluding the misnamed "Mu Meson" or muon) and play an important role in explaining low-energy properties of the strong nuclear force. In Particle physics, a meson is a strongly interacting Boson &mdashthat is a Hadron with integer spin. The muon (from the letter mu (μ--used to represent it is an Elementary particle with negative Electric charge and a spin of 1/2 In particle physics the strong interaction, or strong force, or color force, holds Quarks and Gluons together to form Protons and

1 Basic properties
2 History
3 Theoretical overview
4 See also
5 References
6 External links

Basic properties

Feynman diagram of a common pion decay. Motivation and history When calculating Scattering cross sections in Particle physics, the interaction between particles can be described

Pions have zero spin and are composed of first-generation quarks. In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin In Particle physics, a generation is a division of the Elementary particles Between generations particles differ only by their Mass. In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. In the quark model, an up and an anti-down quark compose a π⁺, while a down and an anti-up quark compose the π⁻, its antiparticle. In Physics, the quark model is a classification scheme for Hadrons in terms of their valence quarks, i to most kinds of particles, there is an associated antiparticle with the same Mass and opposite Electric charge. The neutral combinations of up with anti-up and down with anti-down have identical quantum numbers, so they are only found in superpositions. Quantum numbers describe values of conserved numbers in the dynamics of the Quantum system. Quantum superposition is the fundamental law of Quantum mechanics. The lowest-energy superposition is the π⁰, which is its own antiparticle. Together, the pions form a triplet of isospin; each pion has isospin-1 (I = 1) and third-component isospin equal to its charge (I_z = +1, 0 or −1). In Physics, and specifically Particle physics, isospin ( isotopic spin, isobaric spin) is a Quantum number related to the

The π ^± mesons have a mass of 139. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object 6 MeV/c² and a mean life of 2. Given an assembly of elements the number of which decreases ultimately to zero the lifetime (also called the mean lifetime) is a certain number that characterizes the rate 6×10⁻⁸ seconds. They decay due to weak processes. The weak interaction (often called the weak force or sometimes the weak nuclear force) is one of the four Fundamental interactions of nature The main decay mode (99. 9877%) is into a muon and its neutrino:

π⁺ → μ⁺ + νμ

π⁻ → μ⁻ + νμ

The second largest decay mode (0. The muon (from the letter mu (μ--used to represent it is an Elementary particle with negative Electric charge and a spin of 1/2 Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost 0123%) is into an electron and the corresponding neutrino:

π⁺ → e⁺ + νe

π⁻ → e⁻ + νe

The π⁰ meson has a slightly smaller mass of 135. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J 0 MeV/c² and a much shorter mean life of 8. 4×10⁻¹⁷ seconds. It decays due to electromagnetic force. Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of The main decay mode (98. 798%) is into two photons:

π⁰ → 2 γ

Its second largest decay mode (1. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena 198%) is the so-called Dalitz decay into a photon and an electron-positron pair:

π⁰ → γ + e⁺ + e⁻

The rate at which pions decay features prominently in many subfields of particle physics such as chiral perturbation theory. Richard Henry Dalitz ( 28 February 1925 &ndash 13 January 2006) was an Australian Physicist known for his work in Quantum The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J The positrons or antielectron is the Antiparticle or the Antimatter counterpart of the Electron. Chiral perturbation theory (ChPT is an Effective field theory constructed with a Lagrangian consistent with the (approximate Chiral symmetry of Quantum This rate is parametrized by the pion decay constant (f_π), which is about 90 MeV. In Particle physics, the pion decay constant is the Square root of the coefficient in front of the Kinetic term for the Pion in the low-energy

Particle	Symbol	Anti- particle	Quark Makeup	Spin and parity	Rest mass MeV/c²	S	C	B	Mean lifetime s	Decays to	Notes
Charged Pion	π⁺	π⁻	ud / du	Pseudoscalar	139. In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin In Physics, a parity transformation (also called parity inversion) is the flip in the sign of one Spatial Coordinate. In Particle physics, flavour or flavor (see spelling differences) is a Quantum number of Elementary particles related to their In Particle physics, flavour or flavor (see spelling differences) is a Quantum number of Elementary particles related to their Given an assembly of elements the number of which decreases ultimately to zero the lifetime (also called the mean lifetime) is a certain number that characterizes the rate The second ( SI symbol s) sometimes abbreviated sec, is the name of a unit of Time, and is the International System of Units In Physics, a pseudoscalar is a quantity that behaves like a scalar, except that it changes sign under a parity inversion such as Improper rotations 6	0	0	0	2. 60×10^-8	μ⁺ + νμ
Neutral Pion	π⁰	Self	$\mathrm{\frac{u\bar{u} - d \bar{d}}{\sqrt{2}}}$	Pseudoscalar	135. 0	0	0	0	0. 84×10^-16	2γ	Makeup inexact due to non-zero quark masses

History

Theoretical work by Hideki Yukawa in 1935 had predicted the existence of mesons as the carrier particles of the strong nuclear force. né, was a Japanese Theoretical physicist and the first Japanese Nobel laureate. In particle physics the strong interaction, or strong force, or color force, holds Quarks and Gluons together to form Protons and From the range of the nuclear force (inferred from the radius of the nucleus), Yukawa predicted the existence of a particle having a mass of about 100 MeV. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom Initially after its discovery in 1936, the muon was thought to be this particle, since it has a mass of 106 MeV. The muon (from the letter mu (μ--used to represent it is an Elementary particle with negative Electric charge and a spin of 1/2 However, later experiments showed that the muon did not participate in strong interactions. In modern terminology, this makes it a lepton, not a meson. Leptons are a family of fundamental Subatomic particles comprising the Electron, the Muon, and the Tauon (or tau particle as well as their

In 1947 the first true mesons, the charged pions, were found by the collaboration of Cecil Powell, César Lattes and Giuseppe Occhialini at the University of Bristol. Cecil Frank Powell ( December 5, 1903 &ndash August 9, 1969) was a British Physicist, and Nobel Prize in Physics laureate Cesare Mansueto Giulio Lattes (b July 11, 1924, Curitiba, Paraná, Brazil, d Giuseppe "Beppo" Occhialini ( December 5, 1907 in Fossombrone, Pesaro, Italy – December 30, 1993) the University (or derivatives but lower-case when referring to many universitiesor universities Since the age of particle accelerators had yet to arrive, high energies were only accessible from atmospheric cosmic rays. For the 1962 Bruce Conner film see Cosmic Ray (film Cosmic rays are energetic particles originating from space that impinge on Photographic emulsions using the gelatin-silver process were placed for a long time in sites located at high altitude mountains (first at Pic du Midi de Bigorre in the Pyrenees and later at Chacaltaya in the Andes), where they were exposed to cosmic rays. Photographic emulsion is a layer of light-sensitive material coated onto a substrate The gelatin-silver process is the photographic process used with currently available black-and-white films and printing papers Another Pic du Midi is the Pic du Midi d'Ossau. The Pic du Midi de Bigorre or simply Pic du Midi (altitude) is a mountain in the The Pyrenees (Pirineos French: Pyrénées; Catalan: Pirineus; Occitan: Pirenèus; Aragonese: Perinés Chacaltaya is a Glacierial Mountain range in Bolivia with an elevation of 5421 m (17785 feet and a view of Lake Titicaca in the distance The Andes form the world's longest exposed Mountain range. They lie as a continuous chain of highland along the western coast of South America. After recovery of the plates, microscopic inspection of the emulsions revealed the tracks of charged particles. Pions were first identified by their unusual "double meson" tracks, left by their decay into another "meson" (the "muon"; note that the muon is not classified as a meson in modern particle physics). In 1948, Lattes and Eugene Gardner first achieved artificial production of pion particles at the University of California, Berkeley cyclotron by bombarding carbon atoms with alpha particles. The University of California Berkeley (also referred to as Cal, Berkeley and UC Berkeley) is a major research university located in Berkeley A cyclotron is a type of Particle accelerator. Cyclotrons accelerate Charged particles using a high- Frequency, alternating Voltage (potential Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Alpha particles (named after and denoted by the first letter in the Greek alphabet, α consist of two Protons and two Neutrons bound together into a

The Nobel Prize in Physics was awarded to Yukawa in 1949 (for predicting the existence of mesons) and to Powell in 1950 (for developing the technique of particle detection using photo-emulsions). The Nobel Prize in Physics (Nobelpriset i fysik is awarded once a year by the Royal Swedish Academy of Sciences.

Since it is not electrically charged, the neutral pion is more difficult to observe than the charged pions; it doesn't leave a track in an emulsion. Its existence was inferred from its decay products in cosmic rays, a so-called "soft component" of electrons and photons. The π⁰ was identified at the Berkeley cyclotron in 1950 by its decay into two photons and the same year in cosmic ray balloon experiments at Bristol University, England.

In the modern understanding of the strong interaction (quantum chromodynamics), pions are considered to be the pseudo Nambu-Goldstone bosons of spontaneously broken chiral symmetry. Quantum chromodynamics (abbreviated as QCD is a theory of the Strong interaction ( color force a Fundamental force describing the interactions of the In particle and Condensed matter physics, Goldstone bosons (also known as Nambu -Goldstone bosons) are Bosons that appear in models In Physics, spontaneous symmetry breaking occurs when a system that is symmetric with respect to some Symmetry group goes into a Vacuum state In Quantum field theory, chiral symmetry is a possible symmetry of the Lagrangian under which the left-handed and right-handed parts This explains why the pion masses are considerably lighter than the masses of other mesons like the η′ meson (958 MeV). If their constituent quarks were massless (making chiral symmetry exact), the Goldstone theorem would predict that the pions should have zero mass. In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. Since the quarks actually have small masses, the pions do as well.

The use of pions in radiation therapy was explored at a number of institutions, including the Los Alamos National Laboratory Meson Physics Facility, which treated 228 patients between 1974 and 1981 [1], and TRIUMF in British Columbia, Canada [2]. Los Alamos National Laboratory (LANL (previously known at various times as Site Y, Los Alamos Laboratory, and Los Alamos Scientific Laboratory) is a TRIUMF is Canada’s national laboratory for particle and Nuclear physics located on the University of British Columbia campus in Vancouver

Theoretical overview

The pion can be thought of as the particle that mediates the interaction between a pair of nucleons. This interaction is attractive: it pulls the nucleons together. Written in a non-relativistic form, it is called the Yukawa potential. A Yukawa potential (also called a screened Coulomb potential is a Potential of the form V(r= -g^2 \\frac{e^{-mr}}{r} Hideki Yukawa The pion, being a meson, has kinematics described by the Klein-Gordon equation. Kinematics ( Greek κινειν, kinein, to move is a branch of Classical mechanics which describes the motion of objects without The Klein–Gordon equation ( Klein–Fock–Gordon equation or sometimes Klein–Gordon–Fock equation) is a relativistic version of the Schrödinger In the terms of quantum field theory, the effective field theory Lagrangian describing the pion-nucleon interaction is called the Yukawa interaction. In quantum field theory (QFT the forces between particles are mediated by other particles In Physics, an effective field theory is an approximate theory (usually a Quantum field theory) that includes appropriate degrees of freedom to describe The Lagrangian, L of a Dynamical system is a function that summarizes the dynamics of the system In Particle physics, Yukawa's interaction, named after Hideki Yukawa, is an interaction between a scalar field \phi and a Dirac field

The nearly identical masses of π^± and π⁰ imply that there must be a symmetry at play; this symmetry is called the SU(2) flavour symmetry or isospin. Special Unit 2In Mathematics, the special unitary group of degree n, denoted SU( n) is the group of n × n In Particle physics, flavour or flavor (see spelling differences) is a Quantum number of Elementary particles related to their In Physics, and specifically Particle physics, isospin ( isotopic spin, isobaric spin) is a Quantum number related to the The reason that there are three pions, π⁺, π⁻ and π⁰, is that these are understood to belong to the triplet representation or the adjoint representation 3 of SU(2). In Mathematics, the adjoint representation (or adjoint action) of a Lie group G is the natural representation of G on its By contrast, the up and down quarks transform according to the fundamental representation 2 of SU(2), whereas the anti-quarks transform according to the conjugate representation 2*. In Representation theory of Lie groups and Lie algebras a fundamental representation is an irreducible finite-dimensional representation of a semisimple

With the addition of the strange quark, one can say that the pions participate in an SU(3) flavour symmetry, belonging to the adjoint representation 8 of SU(3). The strange quark is a second- generation Quark with a charge of &minus(1/3 e and a strangeness of &minus1 The other members of this octet are the four kaons and the eta meson. In Particle physics, a kaon (/ˈkeɪɒn/ also called K-meson and denoted) is any one of a group of four Mesons distinguished by the fact that they This is a list of known and predicted Mesons. Mesons are made of Quarks and as such are part of the Subatomic particle family called the Hadrons

Pions are pseudoscalars under a parity transformation. In Physics, a pseudoscalar is a quantity that behaves like a scalar, except that it changes sign under a parity inversion such as Improper rotations In Physics, a parity transformation (also called parity inversion) is the flip in the sign of one Spatial Coordinate. Pion currents thus couple to the axial vector current and pions participate in the chiral anomaly. A chiral anomaly is the anomalous Nonconservation of a chiral current

References

Gerald Edward Brown and A. Pionium is an Exotic atom consisting of a and a Meson. It is generally created by interaction of a Proton beam accelerated by a Particle accelerator This is a list of the different types of particles known and hypothesized In Physics, the quark model is a classification scheme for Hadrons in terms of their valence quarks, i D. Jackson, The Nucleon-Nucleon Interaction, (1976) North-Holland Publishing, Amsterdam ISBN 0-7204-0335-9

External links

Mesons at the Particle Data Group
Mesons at Hyperphysics

Dictionary

-noun

(physics) Any of three semistable mesons, having positive, negative or neutral charge, now known to be composed of a quark and an antiquark.

-proper noun

Shortened form of Rebecca.

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