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Encyclopedia > Meson
Meson

Mesons of spin 0 form a nonet
Composition: Composite - Quarks and antiquarks
Family: Hadron
Interaction: Strong
Theorized: Hideki Yukawa (1935)
Discovered: 1947
No. of types: ~140 (List)
Spin: Integer
Enlarge
Mesons of spin 1 form a nonet

In particle physics, a meson is a strongly interacting boson, that is, it is a hadron with integral spin. In the Standard Model, mesons are composite (non-elementary) particles composed of an even number of quarks and antiquarks. All known mesons are believed to consist of a quark-antiquark pair — the so-called valence quarks — plus a "sea" of virtual quark-antiquark pairs and virtual gluons. Searches for exotic mesons that have different constituents are ongoing. The valence quarks may exist in a superposition of flavor states; for example, the neutral pion is neither an up-antiup pair nor a down-antidown pair, but an equal superposition of both. Pseudoscalar mesons (spin 0) have the lowest rest energy, where the quark and antiquark have opposite spin, and then the vector mesons (spin 1), where the quark and antiquark have parallel spin. Both come in higher-energy versions where the spin is augmented by orbital angular momentum. All mesons are unstable. Image File history File links Download high resolution version (909x655, 69 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): List of particles List of mesons ... In music, an nonet is a composition which requires nine musicians for a performance or a musical group that consists of nine people. ... Elementary particles An elementary particle is a particle with no measurable internal structure, that is, it is not a composite of other particles. ... These are the 6 quarks and their most likely decay modes. ... Corresponding to each kind of particle, there is an associated antiparticle with the same mass and opposite charges. ... In particle physics, a hadron is a subatomic particle which experiences the strong nuclear force. ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ... The strong interaction or strong force is today understood to represent the interactions between quarks and gluons as detailed by the theory of quantum chromodynamics (QCD). ... Hideki Yukawa Hideki Yukawa FRSE (湯川 秀樹, January 23, 1907 - September 8, 1981) was a Japanese theoretical physicist and the first Japanese to win the Nobel prize. ... A list of mesons. ... In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ... Image File history File links Download high-resolution version (1000x721, 79 KB) Noneto mesônico de spin 1. ... Image File history File links Download high-resolution version (1000x721, 79 KB) Noneto mesônico de spin 1. ... Particles explode from the collision point of two relativistic (100 GeV per nucleon) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... The strong interaction or strong force is today understood to represent the interactions between quarks and gluons as detailed by the theory of quantum chromodynamics (QCD). ... In particle physics, bosons, named after Satyendra Nath Bose, are particles having integer spin. ... In particle physics, a hadron is a subatomic particle which experiences the strong nuclear force. ... In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ... The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ... These are the 6 quarks and their most likely decay modes. ... Corresponding to each kind of particle, there is an associated antiparticle with the same mass and opposite charges. ... The quark model is a classification scheme for hadrons in terms of their valence quarks, ie, the quarks (and antiquarks) which give rise to the quantum numbers of the hadrons. ... In particle physics, gluons are vector gauge bosons that mediate strong color charge interactions of quarks in quantum chromodynamics (QCD). ... Identities and classification of possible tetraquark mesons. ... The quark model is a classification scheme for hadrons in terms of their valence quarks, ie, the quarks (and antiquarks) which give rise to the quantum numbers of the hadrons. ... In particle physics, flavor is a property of a fermion that identifies it, a label that specifies the name of the particle. ... In particle physics, pion (short for pi meson) is the collective name for three subatomic particles: Ï€0, Ï€+ and π−. Pions are the lightest mesons and play an important role in explaining low-energy properties of the strong nuclear force. ... Quantum superposition is the application of the superposition principle to quantum mechanics. ... In high energy physics, a pseudoscalar meson is a meson with total spin 0 and odd parity (usually noted as JP=0−). Compare to scalar meson. ... In high energy physics, a vector meson is a meson with total spin 1 and odd parity (usually noted as JP=1−). Compare to pseudovector meson. ... Gyroscope. ...


Mesons were originally predicted as carriers of the force that binds protons and neutrons together. When first discovered, the muon was identified with this family from its similar mass and was named "mu meson", however it did not show a strong attraction to nuclear matter and is actually a lepton. The pion was the first true meson to be discovered. (The current picture of intranuclear forces is quite complicated; see quantum hadrodynamics for a discussion of modern theories in which nucleon-nucleon interactions are mediated by meson exchange.) Properties [1][2] In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... This article or section does not cite its references or sources. ... The moons shadow, as seen in muons 700m below ground at the Soudan 2 detector. ... In physics, a particle is a lepton if it has a spin of 1/2 and does not experience the strong nuclear force. ... The nuclear force (or nucleon-nucleon interaction or residual strong force) is the force between two or more nucleons. ...


In 1949 Hideki Yukawa was awarded the Nobel Prize in Physics for predicting the existence of the meson. He originally named it 'mesotron', but was corrected by Werner Heisenberg (whose father was a professor in Greek at University of Munich) that there is no 'tr' in the Greek word 'mesos'. Hideki Yukawa Hideki Yukawa FRSE (湯川 秀樹, January 23, 1907 - September 8, 1981) was a Japanese theoretical physicist and the first Japanese to win the Nobel prize. ... Nobel Prize medal. ... Physics (from the Greek, (phúsis), nature and (phusiké), knowledge of nature) is the science concerned with the discovery and understanding of the fundamental laws which govern matter, energy, space and time. ... Werner Karl Heisenberg (December 5, 1901 – February 1, 1976) was a celebrated German physicist and Nobel laureate, one of the founders of quantum mechanics, and acknowledged to be one of the most important physicists of the twentieth century. ...

Contents

Naming of the mesons

The name of a meson is devised so that its main properties can be inferred. Conversely, given a meson's properties, its name is clearly determined. The naming conventions fall in two categories based on flavor, flavorless mesons and flavored mesons. Flavour (or flavor) is a quantum number of elementary particles related to their weak interactions. ...


Flavorless mesons

Flavorless mesons are mesons whose flavor quantum numbers are all equal to zero. This means that these quarks are quarkonium states (quark-antiquark pairs of the same flavor) or a linear superposition of such states. In high energy physics, a quarkonium (pl. ...


The name of a flavorless meson is determined by its total spin S and total orbital angular momentum L. As a meson is composed of two quarks with s = 1/2, the total spin can only be S = 1 (parallel spins) or S = 0 (anti-parallel spins). The orbital quantum number L is due to the revolution of one quark around the other. Usually higher orbital angular momenta translate into a higher mass for the meson. These two quantum numbers determine the parity P and the charge-conjugation parity C of the meson: In atomic physics, the spin quantum number is a quantum number that parametrizes the intrinsic angular momentum (or spin angular momentum, or simply spin) of a given particle. ... It has been suggested that this article or section be merged into Angular momentum quantum number. ... Look up Parity in Wiktionary, the free dictionary Parity is a concept of equality of status or functional equivalence. ... C parity or charge parity is a multiplicative quantum number of some particles that describes its behavior under a symmetry operation of charge conjugation (see C-symmetry). ...

P = (−1)L+1
C = (−1)L+S

Also, L and S add together to form a total angular momentum quantum number J, whose values range from |LS| to L+S in one-unit steps. The different possibilities are summarized with the use of the term symbol 2S+1LJ (a letter code is used instead of the actual value of L, see the spectroscopic notation) and the symbol JPC (here only the sign is used for P and C). The total angular quantum momentum numbers parameterize the total angular momentum of a given electron, by combining its orbital angular momentum and its intrinsic angular momentum (i. ... In quantum mechanics, the term symbol is an abbreviated description of the angular momentum quantum numbers in a multi-electron atom. ... Before the atom electron states were known, spectroscopists saw distintive series in atom spectra, and so they asigned letters to characteristic spectra. ...


The different possibilities and the corresponding meson symbol are given in the following table:

  JPC

(0, 2…)− +

(1, 3…)+ −

(1,2…)− −

(0, 1…)+ +

Quark composition

2S+1LJ*

1(S, D…)J

1(P, F…)J

3(S, D…)J

3(P, F…)J

u bar dmbox{, }u bar u - dbar dmbox{, }dbar u

I = 1 Isospin (isotopic spin, isobaric spin) is a physical quantity which is mathematically analogous to spin. ...

π

b

ρ

a

u bar u + d bar d mbox{, }s bar s

I = 0

η, η

h, h’

phi,!, ω

f, f

c bar c

I = 0

ηc

hc

ψ

χc

b bar b

I = 0

ηb

hb

Υ **

χb

Notes:

* Note that some combinations are forbidden: 0− −, 0+ −, 1− +, 2+ −, 3− +...
First row form isospin triplets: π, π0, π+ etc.
Second row contains pairs of elements: φ is supposed to be a sbar s state, and ω a u bar u + d bar d state. on the other cases it is not known the exact composition so a prime is used to distinguish the two forms.
For historical reasons, 13S1 form of ψ is called J
** The bottomonium state symbol is a capital upsilon (may be rendered as a capital Y depending of the font/browser)

The normal spin-parity series is formed by those mesons were P=(−1)J. In the normal series, S = 1 so PC = +1 (i.e., P = C). This corresponds to some of the triplet states (triplet states appear on the last two columns). The title given to this article is incorrect due to technical limitations. ... In high energy physics, a bottomonium is any of the flavorless, heavy mesons that are composed by a bottom quark and an anti-bottom quark. ...

Feynman diagram of one mode in which the eta particle can decay into 3 pions by gluon emission.
Enlarge
Feynman diagram of one mode in which the eta particle can decay into 3 pions by gluon emission.

Since some of these symbols can refer to more than one particle, some extra rules are added: Image File history File links Eta-decay. ... Image File history File links Eta-decay. ... In this Feynman diagram, an electron and positron annihilate and become a quark-antiquark pair. ... In particle physics, pion (short for pi meson) is the collective name for three subatomic particles: π0, π+ and π−. Pions are the lightest mesons and play an important role in explaining low-energy properties of the strong nuclear force. ... In particle physics, gluons are vector gauge bosons that mediate strong color charge interactions of quarks in quantum chromodynamics (QCD). ...

  • In this scheme, particles with JP = 0 are known as pseudoscalars, and mesons with JP = 1 are called vectors. For particles other than those, the number J is added as a subindex: a0, a1, χc1, etc.
  • For most of ψ, Υ and χ states is common to include the spectroscopic information: Υ(1S), Υ(2S). The first number is the principal quantum number, and the letter is the spectroscopic notation for L. Multiplicity is omitted since is implied by the symbol, and J appears as a subindex when needed: χb2(1P). If the spectroscopic information is not available, the mass is used instead: Υ(9460)
  • The naming scheme does not differentiate between "pure" quark states and gluonium states, so gluonium states follow the same naming scheme.
  • However, exotic mesons with "forbidden" quantum numbers JPC = 0− −, 0+ −, 1− +, 2+ −, 3− +... would use the same convention as the meson with identical JP numbers, but adding a J subindex. A meson with isospin 0 and JPC = 1− + would be denoted ω1.

When the quantum numbers of a particle are unknown, it is designated with an X followed by its mass in parentheses. In atomic physics, the principal quantum number symbolized as n is the first quantum number of an atomic orbital. ... Non-quark model mesons consist of Exotic mesons, which have quantum numbers not possible for mesons in the quark model glueballs or gluonium, which have no valence quarks at all tetraquarks, which have two valence quark-antiquark pairs, and hybrid mesons, which contain a valence quark-antiquark pair and one...


Flavored mesons

For flavored mesons, the naming scheme is a little simpler.


1. The meson name is given by the heaviest of the two quarks. From more to less massive, the order is: t > b > c > s > d > u. However, u and d do not carry any flavor, so they do not influence the naming scheme. Quark t never forms hadrons, but a symbol for t-containing mesons is reserved anyway.

quark symbol quark symbol
c D t T
s bar K b bar B
Note the fact that for s and b quarks we get an antiparticle symbol. This is because it is adopted the convention that flavor charge and electric charge must agree in sign. This is also true for the third component of isospin: quark up has positive I3 and charge, quark down has negative charge and I3. The effect of that is: any flavor of a charged meson has the same sign than the meson's electric charge.

2. If the second quark has also flavor (it is not u or d) then the identity of that second quark is given by a subindex (s, c or b, and in theory t). Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interactions. ... Isospin (isotopic spin, isobaric spin) is a physical quantity which is mathematically analogous to spin. ...


3. Add a "*" superindex if the meson is in the normal spin-parity series, i.e. JP = 0+, 1, 2+...


4. For mesons other than pseudoscalars (0) and vectors (1) the total angular momentum quantum number J is added as a subindex. The total angular quantum momentum numbers parameterize the total angular momentum of a given electron, by combining its orbital angular momentum and its intrinsic angular momentum (i. ...


To sum it up, we have:

quark composition Isospin JP = 0, 1+, 2... JP = 0+, 1, 2+...
bar su, bar sd 1/2 KJ K^*_J
c bar u, cbar d 1/2 DJ D^*_J
c bar s 0 DsJ D^*_{sJ}
bar bu, bar bd 1/2 BJ B^*_J
bar bs 0 BsJ B^*_{sJ}
bar bc 0 BcJ B^*_{cJ}
J is omitted for 0 and 1

In some cases, particles can mix between them. For example, the neutral kaon, K^0,(bar sd) and its antiparticle bar K^0,(sbar d) can combine in a symmetric or antisymmetric manner, originating two new particles, the short-lived and the long-lived neutral kaons K^0_S = begin{matrix}{1 over sqrt 2}end{matrix}(K^0-bar K^0),;K^0_L = begin{matrix}{1 over sqrt 2}end{matrix}(K^0 + bar K^0) (neglecting a small CP-violating term). In physics, and specifically particle physics, CP violation is a violation of the postulated CP symmetry of the laws of physics. ...


See also


A list of mesons. ... This is a list of particles in particle physics, including currently known and hypothetical elementary particles, as well as the composite particles that can be built up from them. ... In physics, the quark model is a classification scheme for hadrons in terms of their valence quarks, ie, the quarks (and antiquarks) which give rise to the quantum numbers of the hadrons. ...

Hadrons: Baryons (list) | Mesons (list)

Baryons: Nucleons | Hyperons | Exotic baryons | Pentaquarks
Mesons: Pions | Kaons | Quarkonium | Exotic mesons
Atomic nuclei | Atoms | Molecules Particles explode from the collision point of two relativistic (100 GeV per nucleon) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... Elementary particles An elementary particle is a particle with no measurable internal structure, that is, it is not a composite of other particles. ... In particle physics, a hadron is a subatomic particle which experiences the strong nuclear force. ... In particle physics, the baryons are a family of subatomic particles including the proton and the neutron (collectively called nucleons), as well as a number of unstable, heavier particles (called hyperons). ... Baryon decuplet: Spin=3/2 Baryon octet: Spin=1/2 This is a list of baryons. ... A list of mesons. ... In physics a nucleon is a collective name for two baryons: the neutron and the proton. ... In particle physics, a hyperon is any subatomic particle which is a baryon (and hence a hadron and a fermion) with non-zero strangeness, but with zero charm and zero bottomness. ... Ordinary baryons are bound states of 3 quarks. ... A pentaquark is a subatomic particle consisting of a group of five quarks (compared to three quarks in normal baryons and two in mesons), or more specifically four quarks and one anti-quark. ... In particle physics, pion (short for pi meson) is the collective name for three subatomic particles: π0, π+ and π−. Pions are the lightest mesons and play an important role in explaining low-energy properties of the strong nuclear force. ... In particle physics, Kaons (also called K-mesons and denoted K) are a group of four mesons distinguished by the fact that they carry a quantum number called strangeness. ... In high energy physics, a quarkonium (pl. ... Identities and classification of possible tetraquark mesons. ... A semi-accurate depiction of the helium atom. ... Properties In chemistry and physics, an atom (Greek ἄτομος or átomos meaning indivisible) is the smallest particle of a chemical element that retains its chemical properties. ... In chemistry, a molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical bonds [1] [2] [3] [4] [5]. Chemical substances are not infinitely divisible into smaller fractions of the same substance: a molecule is generally considered the smallest particle of a pure...

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