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# List of mesons

This is a list of mesons. This list is not comprehensive; it is a stub.

Particle Symbol Anti-
particle
Quark
Makeup
Spin and parity Rest mass
MeV/c²
S C B Mean lifetime
s
Principal decays Notes
Charged
Pion
π + π $\mathrm{u \bar{d}}$ Pseudoscalar 139.6 0 0 0 2.60×10-8 μ+ + νμ
Neutral
Pion
π0 Self $\mathrm{\frac{u\bar{u} - d \bar{d}}{\sqrt{2}}}$ Pseudoscalar 135.0 0 0 0 0.84×10-16 Makeup inexact due to non-zero quark masses
Charged
Kaon
K + K $\mathrm{u\bar{s}}$ Pseudoscalar 493.7 +1 0 0 1.24×10-8 μ + νμ
or π+ + π0
Neutral
Kaon
K0 $\mathrm{\bar{K}^0}$ $\mathrm{d\bar{s}}$ Pseudoscalar 497.7 +1 0 0 weak decay Strong eigenstate - no definite lifetime (see kaon notes below)
K-Short $\mathrm{K_S^0}$ $\mathrm{K_S^0}$ $\mathrm{\frac{d\bar{s} - s\bar{d}}{\sqrt{2}}}$ Pseudoscalar 497.7 (*) 0 0 0.89×10-10 π+ + π-
or 2π0
Weak eigenstate - makeup is missing small CP-violating term (see kaon notes below)
K-Long $\mathrm{K_L^0}$ $\mathrm{K_L^0}$ $\mathrm{\frac{d\bar{s} + s\bar{d}}{\sqrt{2}}}$ Pseudoscalar 497.7 (*) 0 0 5.2×10-8 π+ + e- + νe Weak eigenstate - makeup is missing small CP-violating term (see kaon notes below)
Eta η Self $\mathrm{\frac{u\bar{u} + d\bar{d} - 2s\bar{s}}{\sqrt{6}}}$ Pseudoscalar 547.8 0 0 0 5×10-19 Makeup inexact due to non-zero quark masses
Eta
Prime
η' Self $\mathrm{\frac{u\bar{u} + d\bar{d} + s\bar{s}}{\sqrt{3}}}$ Pseudoscalar 957.6 0 0 0 3×10-21 Makeup inexact due to non-zero quark masses
Rho ρ + ρ $\mathrm{u\bar{d}}$ Vector 776 0 0 0 0.4×10-23
Phi φ Self $\mathrm{s\bar{s}}$ Vector 1020 0 0 0 16×10-23
D D + D $\mathrm{c\bar{d}}$ Pseudoscalar 1869 0 +1 0 10.6×10-13
D D0 $\mathrm{\bar{D^0}}$ $\mathrm{c\bar{u}}$ Pseudoscalar 1865 0 +1 0 4.1×10-13
Ds $\mathrm{D_s^+}$ $\mathrm{D_s^-}$ $\mathrm{c\bar{s}}$ Pseudoscalar 1968 +1 +1 0 4.9×10-13
J/Psi J / ψ Self $\mathrm{c\bar{c}}$ Vector 3096.9 0 0 0 7.2×10-21 e+ + e- or
μ+ + μ- ...
See charmonium
B B + B $\mathrm{u\bar{b}}$ Pseudoscalar 5279 0 0 +1 1.7×10-12
B B0 $\mathrm{\bar{B^0}}$ $\mathrm{d\bar{b}}$ Pseudoscalar 5279 0 0 +1 1.5×10-12
Bs $\mathrm{B_s^0}$ $\mathrm{\bar{B}_s^0}$ $\mathrm{s\bar{b}}$ Pseudoscalar 5369 -1 0 +1 1.46×10-12
Bc $\mathrm{B_c^+}$ $\mathrm{B_c^-}$ $\mathrm{c\bar{b}}$ Pseudoscalar 6400 0 +1 +1 5×10-13
Upsilon $\Upsilon\,$ Self $\mathrm{b\bar{b}}$ Vector 9460 0 0 0 1.3×10-20 e+ + e- or
μ+ + μ- ...
See bottomonium

## Notes on neutral kaons

There are two complications with neutral kaons:

1. Due to neutral kaon mixing, the $\mathrm{K_S^0}$ and $\mathrm{K_L^0}$ are not eigenstates of strangeness. However, they are eigenstates of the weak force, which determines how they decay, so these are the particles with definite lifetime.
2. Furthermore, the linear combinations given in the table for the $\mathrm{K_S^0}$ and $\mathrm{K_L^0}$ are not exactly correct, since there is a small correction due to CP violation. See CP violation in kaons.

Note that these issues also exist in principle for other neutral flavored mesons; however, the weak eigenstates are considered separate particles only for kaons because of their dramatically different lifetimes.