Physics:Omega meson

Short description: Meson that is a superposition of an up quark–antiquark and a down quark–antiquark pair

Omega meson

Composition	[math]\displaystyle{ \approx \frac{u\bar{u}+d\bar{d}}{\sqrt{2}} }[/math]
Statistics	Bosonic
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	Pion++Pion0+Pion- or Pion0+Gamma
electric charge	0 e
Spin	1
Isospin	0
Hypercharge	0
Parity	−1
C parity	−1

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 Pion+Pion0Pion- at 89.2±0.7%, followed by Pion0Gamma 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	[math]\displaystyle{ \frac{u\bar{u}+d\bar{d}}{\sqrt{2}} }[/math]	782.66 ± 0.13	0−	1−−	0	0	0	(7.58±0.11)×10−23 s	Pion++Pion0+Pion- or Pion0+Gamma

The quark composition of the ω meson can be thought of as a mix between up quarkup antiquark, down quarkdown antiquark and strange quarkstrange antiquark 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.

[math]\displaystyle{ \omega = \psi_8 \sin\theta + \psi_1 \cos\theta }[/math],

[math]\displaystyle{ \phi = \psi_8 \cos\theta - \psi_1 \sin\theta }[/math],

where

[math]\displaystyle{ \theta }[/math] is the nonet mixing angle,

[math]\displaystyle{ \psi_1 = \frac{u\overline{u} + d\overline{d} + s\overline{s}}{\sqrt{3}} }[/math] and

[math]\displaystyle{ \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]\displaystyle{ \arctan\frac{1}{\sqrt{2}}\approx35.3^\circ }[/math], 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