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| {{Infobox Particle
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| | bgcolour =
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| | name = Mesons
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| | image = [[File:Meson nonet - spin 0.svg|200px]]
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| | caption = Mesons of spin 0 form a [[nonet]]
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| | num_types = ~140 ([[List of mesons|List]])
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| | composition = [[Composite particle|Composite]]—[[Quark]]s and [[Antiparticle|antiquark]]s
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| | statistics = [[Bosonic]]
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| | group = [[Hadron]]s
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| | generation =
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| | interaction = [[Strong interaction|Strong]]
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| | particle =
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| | antiparticle =
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| | status =
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| | theorized = [[Hideki Yukawa]] (1935)
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| | discovered = 1947
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| | symbol =
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| | mass = From 139 MeV/c<sup>2</sup> ({{SubatomicParticle|pion+|link=yes}})<br>to 9.460 GeV/c<sup>2</sup> ({{SubatomicParticle|Upsilon|link=yes}})
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| | decay_time =
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| | decay_particle =
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| | electric_charge = −1 [[elementary charge|e]], 0 e, +1 e
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| | color_charge =
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| | spin = 0, 1
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| | num_spin_states =
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| }}
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| In [[particle physics]], '''mesons''' ({{IPAc-en|ˈ|m|iː|z|ɒ|n|z}} or {{IPAc-en|ˈ|m|ɛ|z|ɒ|n|z}}) are [[hadron|hadronic]] [[subatomic particle]]s 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 {{frac|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 [[electron]]s and [[neutrino]]s. Uncharged mesons may decay to [[photons]].
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| 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 [[cosmic ray]] interactions, for example, such particles are ordinary protons and neutrons. Mesons are also frequently produced artificially in high-energy particle accelerators that collide protons, anti-protons, or other particles.
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| 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. The higher energy (more massive) mesons were created momentarily in the [[Big Bang]] but are not thought to play a role in nature today. However, such particles are regularly created in experiments, in order to understand the nature of the heavier types of quark which compose the heavier mesons.
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| Mesons are part of the [[hadron]] particle family, defined simply as particles composed of quarks. The other members of the hadron family are the [[baryon]]s: subatomic particles composed of three quarks rather than two. Some experiments show evidence of ''[[tetraquark]]s''—"exotic" mesons made of two quarks and two antiquarks; the particle physics community regards their existence as unlikely, although possible.<ref name=PDGTetraquarks2008>C. Amsler ''et al.'' (2008): [http://pdg.lbl.gov/2008/reviews/charmonium_states_m801.pdf Charmonium States]</ref> Because quarks have a spin of {{frac|2}}, the difference in quark-number between mesons and baryons results in mesons being [[boson]]s, whereas baryons are [[fermion]]s.
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| Each type of meson has a corresponding [[antiparticle]] (antimeson) in which quarks are replaced by their corresponding antiquarks and vice-versa. For example, a positive [[pion]] ({{SubatomicParticle|Pion+}}) is made of one up quark and one down antiquark; and its corresponding antiparticle, the negative pion ({{SubatomicParticle|Pion-}}), is made of one up antiquark and one down quark.
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| Because mesons are composed of quarks, they participate in both the [[weak interaction|weak]] and [[strong interaction]]s. Mesons with net [[electric charge]] also participate in the [[electromagnetic interaction]]. They are classified according to their quark content, [[total angular momentum]], [[parity (physics)|parity]], and various other properties such as [[C-parity]] and [[G-parity]]. Although no meson is stable, those of lower [[mass]] are nonetheless more stable than the most massive mesons, and are easier to observe and study in [[particle accelerator]]s or in [[cosmic ray]] experiments. They are also typically less massive than baryons, meaning that they are more easily produced in experiments, and thus exhibit certain higher energy phenomena more readily than baryons composed of the same quarks would. For example, the [[charm quark]] was first seen in the [[J/ψ meson|J/Psi meson]] ({{SubatomicParticle|J/Psi}}) in 1974,<ref>J.J. Aubert ''et al.'' (1974)</ref><ref>J.E. Augustin ''et al.'' (1974)</ref> and the [[bottom quark]] in the [[upsilon meson]] ({{SubatomicParticle|Upsilon}}) in 1977.<ref>S.W. Herb ''et al.'' (1977)</ref>
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| ==History==
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| From theoretical considerations, [[Hideki Yukawa]] in 1934<ref>The Noble Foundation (1949) [http://www.nobelprize.org/nobel_prizes/physics/laureates/1949/press.html Nobel Prize in Physics 1949 – Presentation Speech]</ref><ref name="yukawa">H. Yukawa (1935)</ref> predicted the existence and the approximate mass of the "meson" as the carrier of the [[nuclear force]] that holds [[atomic nucleus|atomic nuclei]] together. If there was no nuclear force, all nuclei with two or more [[proton]]s would fly apart because of the [[Electromagnetism|electromagnetic]] repulsion. Yukawa called his carrier particle the meson, from ''mesos'', the Greek word for ''intermediate'', because its predicted mass was between that of the electron and that of the proton, which has about 1,836 times the mass of the electron. Yukawa had originally named his particle the "mesotron", but he was corrected by the physicist [[Werner Heisenberg]] (whose father was a professor of Greek at the [[University of Munich]]). Heisenberg pointed out that there is no "tr" in the Greek word "mesos".<ref name="mesotron">G. Gamow (1961)</ref>
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| The first candidate for Yukawa's meson, now known in modern terminology as the [[muon]], was discovered in 1936 by [[Carl David Anderson]] and others in the [[decay product]]s of cosmic ray interactions. The mu meson had about the right mass to be Yukawa's carrier of the strong nuclear force, but over the course of the next decade, it became evident that it was not the right particle. It was eventually found that the "mu meson" did not participate in the strong nuclear interaction at all, but rather behaved like a heavy version of the [[electron]], and was eventually classed as a [[lepton]] like the electron, rather than a meson. Physicists in making this choice decided that properties other than particle mass should control their classification.
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| There were years of delays in the subatomic particle research during [[World War II]] in 1939–45, with most physicists working in applied projects for wartime necessities. When the war ended in August 1945, many physicists gradually returned to peacetime research. The first true meson to be discovered was what would later be called the "[[pion|pi meson]]" (or pion). This discovery was made in 1947, by [[Cecil Powell]], [[César Lattes]], and [[Giuseppe Occhialini]], who were
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| investigating cosmic ray products at the [[University of Bristol]] in [[England]], based on photographic films placed in the Andes mountains. Some mesons in these films had about the same mass as the already-known meson, yet seemed to decay into it, leading physicist [[Robert Marshak]] to hypothesize in 1947 that it was actually a new and different meson. Over the next few years, more experiments showed that the pion was indeed involved in strong interactions. The pion (as a [[virtual particle]]) is the primary force carrier for the [[nuclear force]] in [[atomic nucleus|atomic nuclei]]. Other mesons, such as the [[rho meson]]s are involved in mediating this force as well, but to lesser extents. Following the discovery of the pion, Yukawa was awarded the 1949 [[Nobel Prize in Physics]] for his predictions.
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| The word ''meson'' has at times been used to mean ''any'' force carrier, such as "[[W and Z bosons|Z<sup>0</sup> meson]]" which is involved in mediating the [[weak interaction]].<ref>J. Steinberger (1998)</ref> However, this spurious usage has fallen out of favor. Mesons are now defined as particles composed of pairs of quarks and antiquarks.
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| ==Overview==
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| ===Spin, orbital angular momentum, and total angular momentum===
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| {{Main|Spin (physics)|angular momentum operator|Total angular momentum|Quantum numbers}}
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| [[Spin (physics)|Spin]] (quantum number S) is a [[Euclidean vector|vector]] quantity that represents the "intrinsic" [[angular momentum]] of a particle. It comes in increments of {{frac|1|2}} [[Planck's constant|ħ]]. The ħ is often dropped because it is the "fundamental" unit of spin, and it is implied that "spin 1" means "spin 1 ħ". (In some systems of [[natural units]], ħ is chosen to be 1, and therefore does not appear in equations).
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| [[Quark]]s are [[fermion]]s—specifically in this case, particles having spin {{frac|1|2}} (''S'' = {{frac|1|2}}). Because spin projections vary in increments of 1 (that is 1 ħ), a single quark has a spin vector of length {{frac|1|2}}, and has two spin projections (''S''<sub>z</sub> = +{{frac|1|2}} and ''S''<sub>z</sub> = −{{frac|1|2}}). Two quarks can have their spins aligned, in which case the two spin vectors add to make a vector of length ''S'' = 1 and three spin projections (''S''<sub>z</sub> = +1, ''S''<sub>z</sub> = 0, and ''S''<sub>z</sub> = −1), called the [[spin-1]] triplet. If two quarks have unaligned spins, the spin vectors add up to make a vector of length S = 0 and only one spin projection (''S''<sub>z</sub> = 0), called the [[spin-0]] singlet. Because mesons are made of one quark and one antiquark, they can be found in triplet and singlet spin states.
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| There is another quantity of quantized angular momentum, called the [[angular momentum operator|orbital angular momentum]] (quantum number ''L''), that comes in increments of 1 ħ, which represent the angular moment due to quarks orbiting around each other. The total angular momentum (quantum number ''J'') of a particle is therefore the combination of intrinsic angular momentum (spin) and orbital angular momentum. It can take any value from {{nowrap|''J'' {{=}} {{!}}''L'' − ''S''{{!}}}} to {{nowrap|''J'' {{=}} {{!}}''L'' + ''S''{{!}}}}, in increments of 1.
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| <center> | |
| {|class="wikitable" style="text-align: center;"
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| |+Meson angular momentum quantum numbers for ''L'' = 0, 1, 2, 3
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| ! style="width:100px;"| [[Spin (physics)|''S'']]
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| ! style="width:100px;"| [[Orbital angular momentum (disambiguation)|''L'']]
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| ! style="width:100px;"| [[Total angular momentum|''J'']]
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| ! style="width:100px;"| [[Parity (physics)|''P'']]<br>([[#Parity|See below]])
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| ! style="width:100px;"| ''J''<sup>''P''</sup>
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| |rowspan="4"| 0 || 0 || 0 || − || 0<sup>−</sup>
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| | 1 || 1 || + || 1<sup>+</sup>
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| |-
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| | 2 || 2 || − || 2<sup>−</sup>
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| |-
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| | 3 || 3 || + || 3<sup>+</sup>
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| |-
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| |rowspan="4"| 1 || 0 || 1 || − ||1<sup>−</sup>
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| | 1 || 2, 1, 0 || + || 2<sup>+</sup>, 1<sup>+</sup>, 0<sup>+</sup>
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| |-
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| | 2 || 3, 2, 1 || − || 3<sup>−</sup>, 2<sup>−</sup>, 1<sup>−</sup>
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| |-
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| | 3 || 4, 3, 2 || + || 4<sup>+</sup>, 3<sup>+</sup>, 2<sup>+</sup>
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| |}
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| </center>
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| Particle physicists are most interested in mesons with no orbital angular momentum (''L'' = 0), therefore the two groups of mesons most studied are the ''S'' = 1; ''L'' = 0 and ''S'' = 0; ''L'' = 0, which corresponds to ''J'' = 1 and ''J'' = 0, although they are not the only ones. It is also possible to obtain ''J'' = 1 particles from ''S'' = 0 and ''L'' = 1. How to distinguish between the ''S'' = 1, ''L'' = 0 and ''S'' = 0, ''L'' = 1 mesons is an active area of research in [[meson spectroscopy]].{{Citation needed|date=November 2008}}
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| ===Parity===
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| {{Main|Parity (physics)}}
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| If the universe were reflected in a mirror, most of the laws of physics would be identical—things would behave the same way regardless of what we call "left" and what we call "right". This concept of mirror reflection is called [[parity (physics)|parity]] (''P''). [[Gravity]], the [[electromagnetic force]], and the [[strong interaction]] all behave in the same way regardless of whether or not the universe is reflected in a mirror, and thus are said to [[P-symmetry|conserve parity]] (P-symmetry). However, the [[weak interaction]] does'' ''distinguish "left" from "right", a phenomenon called [[parity violation]] (P-violation).
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| Based on this, one might think that if the [[wavefunction]] for each particle (more precisely, the [[quantum field]] for each particle type) were simultaneously mirror-reversed, then the new set of wavefunctions would perfectly satisfy the laws of physics (apart from the weak interaction). It turns out that this is not quite true: In order for the equations to be satisfied, the wavefunctions of certain types of particles have to be multiplied by −1, in addition to being mirror-reversed. Such particle types are said to have ''negative'' or ''odd'' parity (''P'' = −1, or alternatively ''P'' = –), whereas the other particles are said to have ''positive'' or ''even'' parity (''P'' = +1, or alternatively ''P'' = +).
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| For mesons, the parity is related to the orbital angular momentum by the relation:<ref name=PDGQuarkmodel>C. Amsler ''et al.'' (2008): [http://pdg.lbl.gov/2008/reviews/quarkmodrpp.pdf Quark Model]</ref>
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| :<math>P = \left( -1 \right)^{L+1}</math>
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| where the ''L'' is a result of the parity of the corresponding [[spherical harmonic]] of the [[wavefunction]]. The '+1' in the exponent comes from the fact that, according to the [[Dirac equation]], a quark and an antiquark have opposite intrinsic parities. Therefore the intrinsic parity of a meson is the product of the intrinsic parities of the quark (+1) and antiquark (−1). As these are different, their product is −1, and so it contributes a +1 in the exponent.
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| As a consequence, mesons with no orbital angular momentum (''L'' = 0) all have odd parity (''P'' = −1).
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| ===C-parity===
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| {{Main|C-parity}}
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| C-parity is only defined for mesons that are their own antiparticle (i.e. neutral mesons). It represents whether or not the wavefunction of the meson remains the same under the interchange of their quark with their antiquark.<ref name=SozziC>M.S. Sozzi (2008b)</ref> If
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| :<math>|q\bar{q}\rangle = |\bar{q}q\rangle</math>
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| then, the meson is "C even" (C = +1). On the other hand, if
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| :<math>|q\bar{q}\rangle = -|\bar{q}q\rangle</math>
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| then the meson is "C odd" (C = −1).
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| C-parity rarely is studied on its own, but the combination of C- and P-parity into [[CP-parity]]. CP-parity was thought to be conserved, but was later found to be violated in [[weak interaction]]s.<ref name="Cronin">J.W. Cronin (1980)</ref><ref name="Fitch">V.L. Fitch (1980)</ref><ref name=SozziCP>M.S. Sozzi (2008c)</ref>
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| ===G-parity===
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| {{Main|G-parity}}
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| G parity is a generalization of the C-parity. Instead of simply comparing the wavefunction after exchanging quarks and antiquarks, it compares the wavefunction after exchanging the meson for the corresponding antimeson, regardless of quark content.<ref>K. Gottfried, V.F. Weisskopf (1986)</ref> In the case of neutral meson, G-parity is equivalent to C-parity because neutral mesons are their own antiparticles.
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| If
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| :<math>|q_1\bar{q_2}\rangle = |\bar{q_1}q_2\rangle</math>
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| then, the meson is "G even" (G = +1). On the other hand, if
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| :<math>|q_1\bar{q_2}\rangle = -|\bar{q_1}q_2\rangle</math>
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| then the meson is "G odd" (G = −1).
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| ===Isospin and charge===
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| {{Main|Isospin}}
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| [[Image:Meson nonet - spin 0.svg|thumb|200px|
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| Combinations of one u, d or s quarks and one u, d, or s antiquark in {{nowrap|J<sup>P</sup> {{=}} 0<sup>−</sup>}} configuration form a [[nonet]].]]
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| [[Image:Meson nonet - spin 1.svg|thumb|200px| Combinations of one u, d or s quarks and one u, d, or s antiquark in {{nowrap|J<sup>P</sup> {{=}} 1<sup>−</sup>}} configuration also form a nonet.]]
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| The concept of isospin was first proposed by [[Werner Heisenberg]] in 1932 to explain the similarities between protons and neutrons under the [[strong interaction]].<ref>W. Heisenberg (1932)</ref> Although they had different electric charges, their masses were so similar that physicists believed they were actually the same particle. The different electric charges were explained as being the result of some unknown excitation similar to spin. This unknown excitation was later dubbed ''isospin'' by [[Eugene Wigner]] in 1937.<ref>E. Wigner (1937)</ref> When the first mesons were discovered, they too were seen through the eyes of isospin. The three pions were believed to be the same particle, but in different isospin states.
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| This belief lasted until [[Murray Gell-Mann]] proposed the [[quark model]] in 1964 (containing originally only the u, d, and s quarks).<ref>M. Gell-Mann (1964)</ref> The success of the isospin model is now understood to be the result of the similar masses of the u and d quarks. Because the u and d quarks have similar masses, particles made of the same number of them also have similar masses. The exact specific u and d quark composition determines the charge, because u quarks carry charge +{{frac|2|3}} whereas d quarks carry charge −{{frac|1|3}}. For example the three pions all have different charges ({{SubatomicParticle|Pion+}} ({{SubatomicParticle|up quark}}{{SubatomicParticle|down antiquark}}), {{SubatomicParticle|Pion0}} (a [[quantum superposition]] of {{SubatomicParticle|up quark}}{{SubatomicParticle|up antiquark}} and {{SubatomicParticle|down quark}}{{SubatomicParticle|down antiquark}} states), {{SubatomicParticle|Pion-}} ({{SubatomicParticle|down quark}}{{SubatomicParticle|up antiquark}})), but have similar masses (~{{val|140|u=MeV/c2}}) as they are each made of a same number of total of up and down quarks and antiquarks. Under the isospin model, they were considered to be a single particle in different charged states.
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| The mathematics of isospin was modeled after that of spin. Isospin projections varied in increments of 1 just like those of spin, and to each projection was associated a "[[Quantum state|charged state]]". Because the "pion particle" had three "charged states", it was said to be of isospin ''I'' = 1. Its "charged states" {{SubatomicParticle|Pion+}}, {{SubatomicParticle|Pion0}}, and {{SubatomicParticle|Pion-}}, corresponded to the isospin projections ''I''<sub>3</sub> = +1, ''I''<sub>3</sub> = 0, and ''I''<sub>3</sub> = −1 respectively. Another example is the "[[rho meson|rho particle]]", also with three charged states. Its "charged states" {{SubatomicParticle|rho+}}, {{SubatomicParticle|rho0}}, and {{SubatomicParticle|rho-}}, corresponded to the isospin projections ''I''<sub>3</sub> = +1, ''I''<sub>3</sub> = 0, and ''I''<sub>3</sub> = −1 respectively. It was later noted that the isospin projections were related to the up and down quark content of particles by the relation
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| :<math>I_3=\frac{1}{2}[(n_u-n_\bar{u})-(n_d-n_\bar{d})],</math>
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| where the ''n'''s are the number of up and down quarks and antiquarks.
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| In the "isospin picture", the three pions and three rhos were thought to be the different states of two particles. However in the quark model, the rhos are excited states of pions. Isospin, although conveying an inaccurate picture of things, is still used to classify hadrons, leading to unnatural and often confusing nomenclature. Because mesons are hadrons, the isospin classification is also used, with ''I''<sub>3</sub> = +{{frac|1|2}} for up quarks and down antiquarks, and ''I''<sub>3</sub> = −{{frac|1|2}} for up antiquarks and down quarks.
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| ===Flavour quantum numbers===
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| {{Main|Flavour (particle physics)#Flavour quantum numbers}}
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| The [[strangeness]] [[Flavour quantum numbers|quantum number]] ''S'' (not to be confused with spin) was noticed to go up and down along with particle mass. The higher the mass, the lower the strangeness (the more s quarks). Particles could be described with isospin projections (related to charge) and strangeness (mass) (see the uds nonet figures). As other quarks were discovered, new quantum numbers were made to have similar description of udc and udb nonets. Because only the u and d mass are similar, this description of particle mass and charge in terms of isospin and flavour quantum numbers only works well for the nonets made of one u, one d and one other quark and breaks down for the other nonets (for example ucb nonet). If the quarks all had the same mass, their behaviour would be called ''symmetric'', because they would all behave in exactly the same way with respect to the strong interaction. Because quarks do not have the same mass, they do not interact in the same way (exactly like an electron placed in an electric field will accelerate more than a proton placed in the same field because of its lighter mass), and the symmetry is said to be [[broken symmetry|broken]].
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| It was noted that charge (''Q'') was related to the isospin projection (''I''<sub>3</sub>), the [[baryon number]] (''B'') and flavour quantum numbers (''S'', ''C'', ''B''′, ''T'') by the [[Gell-Mann–Nishijima formula]]:<ref name=Wong>S.S.M Wong (1998)</ref>
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| :<math>Q=I_3+\frac{1}{2}(B+S+C+B^\prime+T),</math>
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| where ''S'', ''C'', ''B''′, and ''T'' represent the [[strangeness]], [[charm (quantum number)|charm]], [[bottomness]] and [[topness]] flavour quantum numbers respectively. They are related to the number of strange, charm, bottom, and top quarks and antiquark according to the relations:
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| :<math>S=-(n_s-n_\bar{s})</math>
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| :<math>C=+(n_c-n_\bar{c})</math>
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| :<math>B^\prime=-(n_b-n_\bar{b})</math>
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| :<math>T=+(n_t-n_\bar{t}),</math>
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| meaning that the Gell-Man–Nishijima formula is equivalent to the expression of charge in terms of quark content:
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| :<math>Q=\frac{2}{3}[(n_u-n_\bar{u})+(n_c-n_\bar{c})+(n_t-n_\bar{t})]-\frac{1}{3}[(n_d-n_\bar{d})+(n_s-n_\bar{s})+(n_b-n_\bar{b})].</math>
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| ==Classification==
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| Mesons are classified into groups according to their [[isospin]] (''I''), [[total angular momentum]] (''J''), [[parity (physics)|parity]] (''P''), [[G-parity]] (''G'') or [[C-parity]] (''C'') when applicable, and [[quark]] (q) content. The rules for classification are defined by the [[Particle Data Group]], and are rather convoluted.<ref name=PDGMesonsymbols>C. Amsler ''et al.'' (2008): [http://pdg.lbl.gov/2008/reviews/namingrpp.pdf Naming scheme for hadrons]</ref> The rules are presented below, in table form for simplicity.
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| ===Types of meson===
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| Mesons are classified into types according to their spin configurations. Some specific configurations are given special names based on the mathematical properties of their spin configuration.
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| <center>
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| {| class="wikitable" style="margin:auto; text-align:center;"
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| |+Types of mesons<ref>W.E. Burcham, M. Jobes (1995)</ref>
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| |-
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| ! style="width:150px;"|Type
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| ! style="width:60px;"| [[Spin (physics)|''S'']]
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| ! style="width:60px;"| [[Orbital angular momentum (disambiguation)|''L'']]
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| ! style="width:60px;"| [[Parity (physics)|''P'']]
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| ! style="width:60px;"| [[Total angular momentum|''J'']]
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| ! style="width:60px;"| ''J''<sup>''P''</sup>
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| |-
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| | [[Pseudoscalar meson]] || 0 || 0 || − || 0 || 0<sup>−</sup>
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| |-
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| | [[Pseudovector meson]] || 1 || 1 || + || 1 || 1<sup>+</sup>
| |
| |-
| |
| | [[Vector meson]] || 1 ||0 || − || 1 || 1<sup>−</sup>
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| |-
| |
| |[[Scalar meson]] || 1 || 1 || + || 0 || 0<sup>+</sup>
| |
| |-
| |
| |[[Tensor meson]] || 1 || 1 || + ||2 || 2<sup>+</sup>
| |
| |}
| |
| </center>
| |
| | |
| === Nomenclature ===
| |
| | |
| ==== Flavourless mesons ====
| |
| Flavourless mesons are mesons made of pair of quark and antiquarks of the same flavour (all their [[flavour quantum number]]s are zero: ''[[Strangeness|S]]'' = 0, ''[[Charm (quantum number)|C]]'' = 0, [[Bottomness|''B''′]] = 0, ''[[Topness|T]]'' = 0).<ref name=note>For the purpose of nomenclature, the isospin projection ''I''<sub>3</sub> isn't considered a flavour quantum number. This means that the charged pion-like mesons (π<sup>±</sup>, a<sup>±</sup>, b<sup>±</sup>, and ρ<sup>±</sup> mesons) follow the rules of flavourless mesons, even if they aren't truly "flavourless".</ref> The rules for flavourless mesons are:<ref name=PDGMesonsymbols/>
| |
| <center>
| |
| {|class="wikitable" style="text-align:center"
| |
| |+Nomenclature of flavourless mesons
| |
| |-
| |
| ! {{SubatomicParticle|quark}}{{SubatomicParticle|antiquark}} content !! [[Total angular momentum|''J'']] <sup>[[Parity (physics)|''P'']][[C-parity|''C'']]{{ref|Cparity|†}}</sup>→<br>[[Isospin|''I'']] ↓!! 0<sup>−+</sup>, 2<sup>−+</sup>, 4<sup>−+</sup>, ... !! 1<sup>+−</sup>, 3<sup>+−</sup>, 5<sup>+−</sup>, ... !! 1<sup>−−</sup>, 2<sup>−−</sup>, 3<sup>−−</sup>, ... !! 0<sup>++</sup>, 1<sup>++</sup>, 2<sup>++</sup>, ...
| |
| |-
| |
| |{{SubatomicParticle|up quark}}{{SubatomicParticle|down antiquark}}<br><math>\mathrm{\tfrac{u\bar{u} - d\bar{d}}{\sqrt{2}}}</math><br>{{SubatomicParticle|down quark}}{{SubatomicParticle|up antiquark}} || 1 || {{SubatomicParticle|link=yes|pion+}}<br>{{SubatomicParticle|link=yes|pion0}}<br>{{SubatomicParticle|link=yes|pion-}} || b<sup>+</sup><br>b<sup>0</sup><br>b<sup>−</sup> || {{SubatomicParticle|link=yes|rho+}}<br>{{SubatomicParticle|link=yes|rho0}}<br>{{SubatomicParticle|link=yes|rho-}} || a<sup>+</sup><br>a<sup>0</sup><br>a<sup>−</sup>
| |
| |-
| |
| |Mix of {{SubatomicParticle|up quark}}{{SubatomicParticle|up antiquark}}, {{SubatomicParticle|down quark}}{{SubatomicParticle|down antiquark}}, {{SubatomicParticle|strange quark}}{{SubatomicParticle|strange antiquark}} || 0 || {{SubatomicParticle|link=yes|Eta}}<br>{{SubatomicParticle|link=yes|Eta prime}} || h<br>h′ || {{SubatomicParticle|link=yes|omega meson}}<br>{{SubatomicParticle|link=yes|phi meson}} || f<br>f′
| |
| |-
| |
| |{{SubatomicParticle|Charm quark}}{{SubatomicParticle|Charm antiquark}} || 0 || {{SubatomicParticle|link=yes|Charmed Eta}} || h<sub>c</sub> || ψ{{ref|JPsi|††}} || χ<sub>c</sub>
| |
| |-
| |
| |{{SubatomicParticle|Bottom quark}}{{SubatomicParticle|Bottom antiquark}} || 0 || {{SubatomicParticle|link=yes|Bottom Eta}} || h<sub>b</sub> || {{SubatomicParticle|link=yes|Upsilon}} || χ<sub>b</sub>
| |
| |-
| |
| |{{SubatomicParticle|Top quark}}{{SubatomicParticle|Top antiquark}} || 0 || {{SubatomicParticle|link=yes|Top Eta}} || h<sub>t</sub> || {{SubatomicParticle|link=yes|Theta meson}} || χ<sub>t</sub>
| |
| |}
| |
| <sup>†</sup> {{note|Cparity}} The C parity is only relevant to neutral mesons.<br>
| |
| <sup>††</sup> {{note|JPsi}} For ''J''<sup>''PC''</sup>=1<sup>−−</sup>, the ψ is called the {{SubatomicParticle|link=yes|J/Psi}}
| |
| </center>
| |
| | |
| In addition: | |
| *When the [[Meson spectroscopy|spectroscopic state]] of the meson is known, it is added in parentheses.
| |
| *When the spectroscopic state is unknown, mass (in [[electronvolt|MeV]]/''[[speed of light|c]]''<sup>2</sup>) is added in parentheses.
| |
| *When the meson is in its [[ground state]], nothing is added in parentheses.
| |
| | |
| ====Flavoured mesons====
| |
| Flavoured mesons are mesons made of pair of quark and antiquarks of different flavours. The rules are simpler in this case: the main symbol depends on the heavier quark, the superscript depends on the charge, and the subscript (if any) depends on the lighter quark. In table form, they are:<ref name=PDGMesonsymbols/>
| |
| | |
| <center>
| |
| {|class="wikitable" style="text-align:center"
| |
| |+Nomenclature of flavoured mesons
| |
| |-
| |
| !antiquark →<br>quark ↓ !! up !! down !! charm !! strange !! top !! bottom
| |
| |-
| |
| | up || — ||<ref name=note/> || {{SubatomicParticle|link=yes|AntiD0}} || {{SubatomicParticle|link=yes|Kaon+}} || {{SubatomicParticle|link=yes|AntiT0}}|| {{SubatomicParticle|link=yes|B+}}
| |
| |-
| |
| | down ||<ref name=note/> || — || {{SubatomicParticle|link=yes|D-}} || {{SubatomicParticle|link=yes|Kaon0}} || {{SubatomicParticle|link=yes|T-}} || {{SubatomicParticle|link=yes|B0}}
| |
| |-
| |
| | charm || {{SubatomicParticle|link=yes|D0}} || {{SubatomicParticle|link=yes|D+}} || — || {{SubatomicParticle|link=yes|Strange D+}} || {{SubatomicParticle|link=yes|Charmed AntiT0}}|| {{SubatomicParticle|link=yes|Charmed B+}}
| |
| |-
| |
| | strange || {{SubatomicParticle|link=yes|Kaon-}} || {{SubatomicParticle|link=yes|AntiKaon0}} || {{SubatomicParticle|link=yes|Strange D-}} || — || {{SubatomicParticle|link=yes|Strange T-}} || {{SubatomicParticle|link=yes|Strange B0}}
| |
| |-
| |
| | top || {{SubatomicParticle|link=yes|T0}} || {{SubatomicParticle|link=yes|T+}} || {{SubatomicParticle|link=yes|Charmed T0}} || {{SubatomicParticle|link=yes|Strange T+}} || — ||{{SubatomicParticle|link=yes|Bottom T+}}
| |
| |-
| |
| | bottom || {{SubatomicParticle|link=yes|B-}} || {{SubatomicParticle|link=yes|antiB0}} || {{SubatomicParticle|link=yes|Charmed B-}} || {{SubatomicParticle|link=yes|Strange AntiB0}} || {{SubatomicParticle|link=yes|Bottom T-}} || —
| |
| |}
| |
| </center>
| |
| | |
| In addition:
| |
| *If [[Total angular momentum|''J'']]<sup>[[Parity (physics)|''P'']]</sup> is in the "normal series" (i.e., [[Total angular momentum|''J'']]<sup>[[Parity (physics)|''P'']]</sup> = 0<sup>+</sup>, 1<sup>−</sup>, 2<sup>+</sup>, 3<sup>−</sup>, ...), a superscript ∗ is added.
| |
| *If the meson is not pseudoscalar ([[Total angular momentum|''J'']]<sup>[[Parity (physics)|''P'']]</sup> = 0<sup>−</sup>) or vector ([[Total angular momentum|''J'']]<sup>[[Parity (physics)|''P'']]</sup> = 1<sup>−</sup>), ''J'' is added as a subscript.
| |
| *When the [[Meson spectroscopy|spectroscopic state]] of the meson is known, it is added in parentheses.
| |
| *When the spectroscopic state is unknown, mass (in [[electronvolt|MeV]]/[[speed of light|''c'']]<sup>2</sup>) is added in parentheses.
| |
| *When the meson is in its [[ground state]], nothing is added in parentheses.
| |
| | |
| ==List==
| |
| {{Main|List of mesons}}
| |
| | |
| ==See also==
| |
| {{Wikipedia books
| |
| |1=Hadronic Matter
| |
| |3=Particles of the Standard Model
| |
| }}
| |
| * [[Standard Model]]
| |
| {{-}}
| |
| | |
| == Notes ==
| |
| {{Reflist|2}}
| |
| | |
| == References ==
| |
| <div class="references-small">
| |
| * <!--no inline citation, should have some-->{{cite book |title=Discrete Symmetries and CP Violation: From Experiment to Theory |author=M.S. Sozzi |year=2008a |chapter=Parity |pages=15–87 |isbn=0-19-929666-9 |publisher=[[Oxford University Press]]}}
| |
| * {{cite book |title=Discrete Symmetries and CP Violation: From Experiment to Theory |author=M.S. Sozzi |year=2008b |chapter=Charge Conjugation |pages=88–120 |isbn=0-19-929666-9 |publisher=[[Oxford University Press]]}}
| |
| * {{cite book |title=Discrete Symmetries and CP Violation: From Experiment to Theory |author=M.S. Sozzi |year=2008c |chapter=CP-Symmetry |pages=231–275 |isbn=0-19-929666-9 |publisher=[[Oxford University Press]]}}
| |
| * {{cite journal |author=C. Amsler ''et al.'' ([[Particle Data Group]]) |title=Review of Particle Physics |journal=[[Physics Letters B]] |volume=667 |issue=1 |pages=1–1340 |year=2008 |doi=10.1016/j.physletb.2008.07.018|bibcode = 2008PhLB..667....1P }}
| |
| * {{cite book |title=Introductory Nuclear Physics |edition=2nd |author=S.S.M. Wong |year=1998 |publisher=[[John Wiley & Sons]] |location=New York (NY) |isbn=0-471-23973-9|chapter=Nucleon Structure |pages=21–56}}
| |
| * {{cite book |title=Nuclear and Particle Physics |edition=2nd |author=W.E. Burcham, M. Jobes |year=1995 |publisher=[[Longman Publishing]] |isbn=0-582-45088-8}}
| |
| *<!--unused-->{{cite book |title=Principles of Quantum Mechanics |edition=2nd |author=R. Shankar |year=1994 |publisher=[[Plenum Press]] |location=New York (NY) |isbn=0-306-44790-8}}
| |
| * {{cite journal |author=J. Steinberger |title=Experiments with high-energy neutrino beams |year=1989 |journal=[[Reviews of Modern Physics]] |volume=61 |issue=3 |pages=533–545 |doi=10.1103/RevModPhys.61.533|bibcode = 1989RvMP...61..533S }}
| |
| * {{cite book |title=Concepts of Particle Physics |volume=2 |author=K. Gottfried, V.F. Weisskopf |chapter=Hadronic Spectroscopy: G-parity |year=1986 |pages=303–311 |isbn=0-19-503393-0 |publisher=[[Oxford University Press]]}}
| |
| * {{cite web |title=CP Symmetry Violation—The Search for its origin |url=http://nobelprize.org/nobel_prizes/physics/laureates/1980/cronin-lecture.pdf |year=1980 |author=J.W. Cronin |publisher=[[The Nobel Foundation]]}}
| |
| * {{cite web |title=The Discovery of Charge—Conjugation Parity Asymmetry |url=http://nobelprize.org/nobel_prizes/physics/laureates/1980/fitch-lecture.pdf |year=1980 |author=V.L. Fitch |publisher=[[The Nobel Foundation]]}}
| |
| * {{cite journal |title=Observation of a Dimuon Resonance at 9.5 Gev in 400-GeV Proton-Nucleus Collisions |doi=10.1103/PhysRevLett.39.252|year=1977|author=S.W. Herb ''et al.''|journal=[[Physical Review Letters]] |volume=39|issue=5|pages=252–255|bibcode = 1977PhRvL..39..252H |last2=Hom |first2=D. |last3=Lederman |first3=L. |last4=Sens |first4=J. |last5=Snyder |first5=H. |last6=Yoh |first6=J. |last7=Appel |first7=J. |last8=Brown |first8=B. |last9=Brown |first9=C. }}
| |
| * {{cite journal |title=Experimental Observation of a Heavy Particle ''J'' |doi=10.1103/PhysRevLett.33.1404|year=1974|author=J.J. Aubert ''et al.''|journal=[[Physical Review Letters]] |volume=33|issue=23|pages=1404–1406|bibcode = 1974PhRvL..33.1404A |last2=Becker |first2=U. |last3=Biggs |first3=P. |last4=Burger |first4=J. |last5=Chen |first5=M. |last6=Everhart |first6=G. |last7=Goldhagen |first7=P. |last8=Leong |first8=J. |last9=McCorriston |first9=T. }}
| |
| * {{cite journal |title=Discovery of a Narrow Resonance in e<sup>+</sup>e<sup>−</sup> Annihilation |doi=10.1103/PhysRevLett.33.1406|year=1974|author=J.E. Augustin ''et al.''|journal=[[Physical Review Letters]] |volume=33|issue=23|pages=1406–1408|bibcode = 1974PhRvL..33.1406A |last2=Boyarski |first2=A. |last3=Breidenbach |first3=M. |last4=Bulos |first4=F. |last5=Dakin |first5=J. |last6=Feldman |first6=G. |last7=Fischer |first7=G. |last8=Fryberger |first8=D. |last9=Hanson |first9=G. }}
| |
| * {{cite journal |author=M. Gell-Mann |title=A Schematic of Baryons and Mesons |journal=[[Physics Letters]] |volume=8|issue=3|pages=214–215|year=1964|doi=10.1016/S0031-9163(64)92001-3|bibcode = 1964PhL.....8..214G }}
| |
| *{{cite journal |author=[[Ishfaq Ahmad]] |title=the Interactions of 200 MeV π± -Mesons with Complex Nuclei Proposal to Study the Interactions of 200 MeV π± -Mesons with Complex Nuclei |journal=CERN documents |volume=3|issue=5|pages=|year=1965| url = http://cdsweb.cern.ch/record/1117270/files/CM-P00073662.pdf}}
| |
| * {{cite book | author= G. Gamow |title=The Great Physicists from Galileo to Einstein |url=http://books.google.com/books?id=mHvE-OyY3OsC&pg=PA315&lpg=PA315#v=onepage&q=&f=false |page=315 |edition=Reprint |origyear=1961 |year=1988 |publisher=[[Dover Publications]] |isbn=978-0-486-25767-9 }}
| |
| * {{cite journal |author=E. Wigner |title=On the Consequences of the Symmetry of the Nuclear Hamiltonian on the Spectroscopy of Nuclei |journal=[[Physical Review]] |volume=51 |issue=2 |year=1937|pages=106–119 |doi=10.1103/PhysRev.51.106|bibcode = 1937PhRv...51..106W }}
| |
| * {{cite journal |author=H. Yukawa |title=On the Interaction of Elementary Particles |journal=Proc. Phys. Math. Soc. Jap. |volume=17 |issue=48 |pages= |year=1935 |url=http://web.ihep.su/dbserv/compas/src/yukawa35/eng.pdf}}
| |
| * {{cite journal |author=W. Heisenberg |year=1932 |title=Über den Bau der Atomkerne I |journal=[[Zeitschrift für Physik]] |volume=77 |pages=1–11 |doi=10.1007/BF01342433|bibcode = 1932ZPhy...77....1H }} {{de icon}}
| |
| * {{cite journal |author=W. Heisenberg |year=1932 |title=Über den Bau der Atomkerne II |journal=[[Zeitschrift für Physik]] |volume=78 |pages=156–164 |doi=10.1007/BF01337585|bibcode = 1932ZPhy...78..156H |issue=3–4 }} {{de icon}}
| |
| * {{cite journal |author=W. Heisenberg |year=1932 |title=Über den Bau der Atomkerne III |journal=[[Zeitschrift für Physik]] |volume=80 |pages=587–596 |doi=10.1007/BF01335696|bibcode = 1933ZPhy...80..587H |issue=9–10 }} {{de icon}}
| |
| </div>
| |
| | |
| ==External links==
| |
| * [http://hyperphysics.phy-astr.gsu.edu/hbase/particles/meson.html#c1 A table of some mesons and their properties]
| |
| * [http://pdg.lbl.gov ''Particle Data Group'']—Compiles authoritative information on particle properties
| |
| * [http://arxiv.org/abs/hep-ph/0211411 hep-ph/0211411: The light scalar mesons within quark models]
| |
| * [http://pdg.lbl.gov/2004/reviews/namingrpp.pdf Naming scheme for hadrons] (a PDF file)
| |
| * [http://www.thingsmadethinkable.com/item/mesons.php Mesons made thinkable], an interactive visualisation allowing physical properties to be compared
| |
| | |
| ===Recent findings===
| |
| * [http://www.fnal.gov/pub/presspass/press_releases/DZeroB_s.html What Happened to the Antimatter? Fermilab's DZero Experiment Finds Clues in Quick-Change Meson]
| |
| * [http://www.fnal.gov/pub/presspass/press_releases/CDF_meson.html CDF experiment's definitive observation of matter-antimatter oscillations in the Bs meson]
| |
| | |
| {{particles}}
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| | |
| [[Category:Mesons| ]]
| |