View source for Omega meson

{{Short description|Meson that is a superposition of an up quark–antiquark and a down quark–antiquark pair}}
{{confused|Omega baryon}}
{{Infobox particle
| name = Omega meson
| image = 
| caption = 
| num_types = 1
| composition = <math display="inline">\approx \frac{u\bar{u}+d\bar{d}}{\sqrt{2}}</math>
| statistics = [[Bosonic]]
| group = [[Meson]]s
| interaction = [[Strong interaction|Strong]], [[Weak interaction|weak]], [[electromagnetic]], [[gravity]]
| antiparticle = Self
| status = 
| theorized = [[Yoichiro Nambu]]<ref>{{cite journal|title=Possible Existence of a Heavy Neutral Meson|first=Yoichiro|last=Nambu|journal=Physical Review|volume=106|issue=6|pages=1366–1367|date=April 25, 1957|doi=10.1103/PhysRev.106.1366|bibcode=1957PhRv..106.1366N}}</ref> (1957)
| discovered = [[Lawrence Berkeley National Laboratory]] (1961)<ref>{{cite journal|doi=10.1103/physrevlett.7.178|title=Evidence for a T=0 three-pion resonance|first1=B. C.|last1=Maglić|first2=L. W.|last2=Alvarez|first3=A. H.|last3=Rosenfeld|first4=M. L.|last4=Stevenson|journal=Physical Review Letters|volume=7|issue=5|pages=178–182|date=August 14, 1961|bibcode = 1961PhRvL...7..178M| s2cid=121570977 }}</ref><ref>{{cite journal|url=https://inspirehep.net/files/bed57fc443ad4a089648fd0574f4d256|title=Discovery of omega meson-first neutral vector meson: one researcher's personal account - Discovery story|date=1976|first=B.|last=Maglich|journal=Advanced Experimental Physics|volume=5|pages=79–105}}</ref>
| symbol = {{Subatomic particle|Omega meson}}
| mass = {{val|782.66|0.13|ul=MeV/c2}}
| mean_lifetime = {{val|7.58|0.11|e=-23|u=s}}
| decay_particle = {{Subatomic particle|Pion+|link=yes}}+{{Subatomic particle|Pion0|link=yes}}+{{Subatomic particle|Pion-|link=yes}} or {{Subatomic particle|Pion0|link=yes}}+{{Subatomic particle|Gamma|link=yes}}
| electric_charge = 0 [[Elementary charge|''e'']]
| spin = 1
| strangeness = 
| charm = 
| bottomness = 
| topness = 
| isospin = 0
| hypercharge = 0
| parity = −1
| c_parity = −1
}}

The '''omega meson''' ({{Subatomic particle|Omega meson}}) is a [[flavour (particle physics)|flavourless]] [[meson]] formed from a [[Quantum superposition|superposition]] of an [[up quark]]–[[antiquark]] and a [[down quark]]–antiquark pair. It is part of the [[vector meson]] nonet<ref name=Eightfold1>{{cite tech report |last=Gell-Mann |first=M. |author-link=Murray Gell-Mann |date=March 15, 1961 |title=The Eightfold Way: A Theory of Strong Interaction Symmetry |publisher=California Inst. of Tech., Synchrotron Laboratory |location=[[Pasadena, CA]] |doi=10.2172/4008239 |number=TID-12608 |url=https://www.osti.gov/scitech/servlets/purl/4008239 |pages=24}}</ref><ref name=Eightfold2>{{cite journal |last=Ne'eman |first=Y. |author-link=Yuval Ne'eman |date=August 1961 |title=Derivation of Strong Interactions from a Gauge Invariance |journal=[[Nuclear Physics (journal)|Nuclear Physics]] |publisher=North-Ho lland Publishing Co. |location=Amsterdam |doi=10.1016/0029-5582(61)90134-1 |volume=26 |issue=2 |pages=222–229 |bibcode=1961NucPh..26..222N}}</ref> and mediates the [[nuclear force]] along with [[pions]] and [[rho meson]]s.

== Properties ==
The most common decay mode for the ω meson is {{Subatomic particle|Pion+|link=yes}}{{Subatomic particle|Pion0|link=yes}}{{Subatomic particle|Pion-|link=yes}} at 89.2±0.7%, followed by {{Subatomic particle|Pion0|link=yes}}{{Subatomic particle|Gamma|link=yes}} at 8.34±0.26%.<ref name=PDG/>

{| class="wikitable"
! class=unsortable|Particle name
! Particle <br>symbol
! Antiparticle <br>symbol
! class=unsortable|Quark<br>content
! [[Rest mass]] ([[electron volt|MeV]]/''[[speed of light|c]]''<sup>2</sup>)
! width="50"|''[[Isospin|I]]<sup>[[G parity|G]]</sup>''
! width="50"|''[[Total angular momentum|J]]<sup>[[Parity (physics)|P]][[C-parity|C]]</sup>''
! width="50"|''[[strangeness|S]]''
! width="50"|''[[charm (quantum number)|C]]''
! width="50"|''[[bottomness|B']]''
! [[Mean lifetime]] ([[second|s]])
! class=unsortable|Commonly decays to<br>
(>5% of decays)
|-
| Omega meson<ref name=PDG>{{cite web|url=https://pdg.lbl.gov/2021/listings/rpp2021-list-omega-782.pdf|title=Particle listing - ω(782)|first=P. A.|last=Zyla|orig-year=2020|year=2021|publisher=[[Particle Data Group]]|access-date=June 9, 2021}}</ref>
|align="center"| {{Subatomic particle|Omega meson}}(782)
|align="center"| Self
|align="center"| <math display="inline">\frac{u\bar{u}+d\bar{d}}{\sqrt{2}}</math>
|align="center"| 782.66&nbsp;±&nbsp;0.13
|align="center"| 0<sup>&minus;</sup>
|align="center"| 1<sup>&minus;&minus;</sup>
|align="center"| 0
|align="center"| 0
|align="center"| 0
|align="center"| {{val|7.58|0.11|e=-23|u=s}}
|align="center"| {{Subatomic particle|Pion+|link=yes}}+{{Subatomic particle|Pion0|link=yes}}+{{Subatomic particle|Pion-|link=yes}}&nbsp;or<br>{{Subatomic particle|Pion0|link=yes}}+{{Subatomic particle|Gamma|link=yes}}
|-
|}

The quark composition of the {{Subatomic particle|Omega meson}} meson can be thought of as a mix between {{Subatomic particle|link=yes|up quark}}{{Subatomic particle|link=yes|up antiquark}}, {{Subatomic particle|link=yes|down quark}}{{Subatomic particle|link=yes|down antiquark}} and {{Subatomic particle|strange quark|link=yes}}{{Subatomic particle|strange antiquark|link=yes}} states, but it is very nearly a pure symmetric {{Subatomic particle|up quark}}{{Subatomic particle|up antiquark}}-{{Subatomic particle|down quark}}{{Subatomic particle|down antiquark}} state. This can be shown by deconstructing the [[wave function]] of the {{Subatomic particle|Omega meson}} into its component parts. We see that the {{Subatomic particle|Omega meson}} and {{Subatomic particle|Phi meson}} mesons are mixtures of the [[SU(3)]] wave functions as follows.<ref>{{cite web|last1=Amsler|first1=C.|last2=DeGrand|first2=T.|last3=Krusche|first3=B.|title=15. Quark Model|url=https://pdg.lbl.gov/2021/reviews/rpp2020-rev-quark-model.pdf|date=August 2019|access-date=9 June 2021|publisher=[[Particle Data Group]]}}</ref>
: <math>\omega = \psi_8 \sin\theta + \psi_1 \cos\theta</math>,
: <math>\phi = \psi_8 \cos\theta - \psi_1 \sin\theta</math>,

where
: <math>\theta</math> is the nonet mixing angle,
: <math>\psi_1 = \frac{u\overline{u} + d\overline{d} + s\overline{s}}{\sqrt{3}}</math> and
: <math>\psi_8 = \frac{u\overline{u} + d\overline{d} - 2s\overline{s}}{\sqrt{6}}</math>.

The mixing angle at which the components decouple completely can be calculated to be <math display="inline">\arctan\frac{1}{\sqrt{2}}\approx35.3^\circ</math>, which almost corresponds to the actual value calculated from the masses of 35°. Therefore, the {{Subatomic particle|Omega meson}} meson is nearly a pure symmetric {{Subatomic particle|up quark}}{{Subatomic particle|up antiquark}}-{{Subatomic particle|down quark}}{{Subatomic particle|down antiquark}} state.

==See also==
* [[List of mesons]]
* [[Quark model]]
* [[Vector meson]]

==References==
{{reflist}}
{{Particles}}
[[Category:Mesons]]
[[Category:Onia]]
[[Category:Subatomic particles with spin 1]]


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