Omega meson

Not to be confused with Omega baryon.

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.

Omega meson

Composition	${\textstyle \approx {\frac {u{\bar {u}}+d{\bar {d}}}{\sqrt {2}}}}$
Statistics	Bosonic
Family	Mesons
Interactions	Strong, weak, electromagnetic, gravity
Symbol	ω
Antiparticle	Self
Theorized	Yoichiro Nambu (1957)
Discovered	Lawrence Berkeley National Laboratory (1961)
Types	1
Mass	782.66±0.13 MeV/c2
Mean lifetime	(7.58±0.11)×10−23 s
Decays into	π+ + π0 + π− or π0 + γ
Electric charge	0 e
Spin	1
Isospin	0
Hypercharge	0
Parity	−1
C parity	−1

Properties

The most common decay mode for the ω meson is
π⁺

π⁰

π⁻
at 89.2±0.7%, followed by
π⁰

γ
at 8.34±0.26%.

Particle name	Particle symbol	Antiparticle symbol	Quark content	Rest mass (MeV/c2)	IG	JPC	S	C	B'	Mean lifetime (s)	Commonly decays to (>5% of decays)
Omega meson	ω (782)	Self	${\textstyle {\frac {u{\bar {u}}+d{\bar {d}}}{\sqrt {2}}}}$	782.66 ± 0.13	0−	1−−	0	0	0	(7.58±0.11)×10−23 s	π+ + π0 + π−  or π0 + γ

The quark composition of the
ω
meson can be thought of as a mix between
u

u
,
d

d
and
s

s
states, but it is very nearly a pure symmetric
u

u
-
d

d
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.

$\omega =\psi _{8}\sin \theta +\psi _{1}\cos \theta$,

$\phi =\psi _{8}\cos \theta -\psi _{1}\sin \theta$,

where

$\theta$ is the nonet mixing angle,

$\psi _{1}={\frac {u{\overline {u}}+d{\overline {d}}+s{\overline {s}}}{\sqrt {3}}}$ and

$\psi _{8}={\frac {u{\overline {u}}+d{\overline {d}}-2s{\overline {s}}}{\sqrt {6}}}$.

The mixing angle at which the components decouple completely can be calculated to be ${\textstyle \arctan {\frac {1}{\sqrt {2}}}\approx 35.3^{\circ }}$, which almost corresponds to the actual value calculated from the masses of 35°. Therefore, the
ω
meson is nearly a pure symmetric
u

u
-
d

d
state.

See also

• List of mesons
• Quark model
• Vector meson