LIGHT UNFLAVORED MESONS
($\boldsymbol S$ = $\boldsymbol C$ = $\boldsymbol B$ = 0)
For $\mathit I = 1$ (${{\mathit \pi}}$, ${{\mathit b}}$, ${{\mathit \rho}}$, ${{\mathit a}}$): ${\mathit {\mathit u}}$ ${\mathit {\overline{\mathit d}}}$, ( ${\mathit {\mathit u}}$ ${\mathit {\overline{\mathit u}}}−$ ${\mathit {\mathit d}}$ ${\mathit {\overline{\mathit d}}})/\sqrt {2 }$, ${\mathit {\mathit d}}$ ${\mathit {\overline{\mathit u}}}$;
for $\mathit I = 0$ (${{\mathit \eta}}$, ${{\mathit \eta}^{\,'}}$, ${{\mathit h}}$, ${{\mathit h}^{\,'}}$, ${{\mathit \omega}}$, ${{\mathit \phi}}$, ${{\mathit f}}$, ${{\mathit f}^{\,'}}$): ${\mathit {\mathit c}}_{{\mathrm {1}}}$( ${{\mathit u}}{{\overline{\mathit u}}}$ $+$ ${{\mathit d}}{{\overline{\mathit d}}}$ ) $+$ ${\mathit {\mathit c}}_{{\mathrm {2}}}$( ${{\mathit s}}{{\overline{\mathit s}}}$ )
INSPIRE search

${{\boldsymbol \pi}^{0}}$ $I^G(J^{PC})$ = $1^-(0^{- +})$ 

We have omitted some results that have been superseded by later experiments. The omitted results may be found in our 1988 edition Physics Letters B204 1 (1988).
${{\mathit \pi}^{0}}$ MASS   $134.9770 \pm0.0005$ MeV (S = 1.1)
${\mathit m}_{{{\mathit \pi}^{\pm}}}–{\mathit m}_{{{\mathit \pi}^{0}}}$   $4.5936 \pm0.0005$ MeV 
${{\mathit \pi}^{0}}$ MEAN LIFE   $(8.52 \pm0.18) \times 10^{-17}$ s (S = 1.2)
${{\boldsymbol \pi}^{0}}$ ELECTROMAGNETIC FORM FACTOR
LINEAR COEFFICIENT OF ${{\mathit \pi}^{0}}$ ELECTROMAGNETIC FORM FACTOR   $0.0335 \pm0.0031$  
For decay limits to particles which are not established, see the appropriate Search sections (${{\mathit A}^{0}}$ (axion) and Other Light Boson (${{\mathit X}^{0}}$) Searches, etc.).
$\Gamma_{1}$ 2 ${{\mathit \gamma}}$ $(98.823\pm{0.034})\%$S=1.5 67
$\Gamma_{2}$ ${{\mathit e}^{+}}{{\mathit e}^{-}}{{\mathit \gamma}}$ $(1.174\pm{0.035})\%$S=1.5 67
$\Gamma_{3}$ ${{\mathit \gamma}}$ positronium $(1.82\pm{0.29})\times 10^{-9}$67
$\Gamma_{4}$ ${{\mathit e}^{+}}{{\mathit e}^{+}}{{\mathit e}^{-}}{{\mathit e}^{-}}$ $(3.34\pm{0.16})\times 10^{-5}$S=1.0 67
$\Gamma_{5}$ ${{\mathit e}^{+}}{{\mathit e}^{-}}$ $(6.46\pm{0.33})\times 10^{-8}$67
$\Gamma_{6}$ 4 ${{\mathit \gamma}}$ $<2\times 10^{-8}$CL=90%67
$\Gamma_{7}$ ${{\mathit \nu}}{{\overline{\mathit \nu}}}$ [1]$<2.7\times 10^{-7}$CL=90%67
$\Gamma_{8}$ ${{\mathit \nu}_{{e}}}{{\overline{\mathit \nu}}_{{e}}}$ $<1.7\times 10^{-6}$CL=90%67
$\Gamma_{9}$ ${{\mathit \nu}_{{\mu}}}{{\overline{\mathit \nu}}_{{\mu}}}$ $<1.6\times 10^{-6}$CL=90%67
$\Gamma_{10}$ ${{\mathit \nu}_{{\tau}}}{{\overline{\mathit \nu}}_{{\tau}}}$ $<2.1\times 10^{-6}$CL=90%67
$\Gamma_{11}$ ${{\mathit \gamma}}{{\mathit \nu}}{{\overline{\mathit \nu}}}$ $<6\times 10^{-4}$CL=90%67
    constrained fit information