The omega meson (ω) is a flavourless meson formed from a superposition of an up quark–antiquark and a down quark–antiquark pair. It is part of the vector meson nonet and mediates the nuclear force along with pions and rho mesons.
Properties The most common decay mode for the ω meson is π+π0π− at 89.2%±0.7%, followed by π0γ at 8.34%±0.26%.
The quark composition of the ω meson can be thought of as a mix between uu, dd and ss states, but it is very nearly a pure symmetric uu–dd state. This can be shown by deconstructing the wave function of the ω into its component parts. We see that the ω and ϕ mesons are mixtures of the SU(3) wave functions as follows.
ω = ψ 8 sin θ + ψ 1 cos θ {\displaystyle \omega =\psi _{8}\sin \theta +\psi _{1}\cos \theta } ,
ϕ = ψ 8 cos θ − ψ 1 sin θ {\displaystyle \phi =\psi _{8}\cos \theta -\psi _{1}\sin \theta } , where
θ {\displaystyle \theta } is the nonet mixing angle,
ψ 1 = u u ¯ + d d ¯ + s s ¯ 3 {\displaystyle \psi _{1}={\frac {u{\overline {u}}+d{\overline {d}}+s{\overline {s}}}{\sqrt {3}}}} and
ψ 8 = u u ¯ + d d ¯ − 2 s s ¯ 6 {\displaystyle \psi _{8}={\frac {u{\overline {u}}+d{\overline {d}}-2s{\overline {s}}}{\sqrt {6}}}} . The mixing angle at which the components decouple completely can be calculated to be arctan 1 2 ≈ 35.3 ∘ {\textstyle \arctan {\frac {1}{\sqrt {2}}}\approx 35.3^{\circ }} , which almost corresponds to the actual value calculated from the masses of 35°. Therefore, the ω meson is nearly a pure symmetric uu–dd state.
See also List of mesons Quark model Vector meson
References
