LIGHT UNFLAVORED MESONS
($\mathit S$ = $\mathit C$ = $\mathit B$ = 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   JSON PDGID:
S009

${{\mathit \pi}^{0}}$

$I^G(J^{PC})$ = $1^-(0^{- +})$ 
We have omitted some results that have been superseded by later experiments.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).
Expand/Collapse All
${{\mathit \pi}^{0}}$ MASS [1] $134.9768$ $\pm0.0005$ MeV (S = 1.1)
 
${\mathit m}_{{{\mathit \pi}^{\pm}}}-{\mathit m}_{{{\mathit \pi}^{0}}}$ $4.5936$ $\pm0.0005$ MeV 
 
${{\mathit \pi}^{0}}$ MEAN LIFE ($8.43$ $\pm0.13$) $ \times 10^{-17}$ s (S = 1.2)
 
▸  ${{\mathit \pi}^{0}}$ ELECTROMAGNETIC FORM FACTOR
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.).
Mode  
Fraction ($\Gamma_i$ / $\Gamma$) Scale Factor/
Conf. Level		 P(MeV/c)  
$\Gamma_{1}$ 2 ${{\mathit \gamma}}$ ($98.823$ $\pm0.034$ ) $\%$ S=1.5  67
 
$\Gamma_{2}$ ${{\mathit e}^{+}}{{\mathit e}^{-}}{{\mathit \gamma}}$ ($1.174$ $\pm0.035$ ) $\%$ S=1.5  67
 
$\Gamma_{3}$ ${{\mathit \gamma}}$ positronium ($1.82$ $\pm0.29$) $ \times 10^{-9}$ 67
 
$\Gamma_{4}$ ${{\mathit e}^{+}}{{\mathit e}^{+}}{{\mathit e}^{-}}{{\mathit e}^{-}}$ ($3.34$ $\pm0.16$) $ \times 10^{-5}$ 67
 
$\Gamma_{5}$ ${{\mathit e}^{+}}{{\mathit e}^{-}}$ ($6.46$ $\pm0.33$) $ \times 10^{-8}$ 67
 
$\Gamma_{6}$ 4 ${{\mathit \gamma}}$ $<2$ $\times 10^{-8}$ CL=90% 67
 
$\Gamma_{7}$ invisible $<4.4$ $\times 10^{-9}$ CL=90%  
 
$\Gamma_{8}$ ${{\mathit \nu}_{{{e}}}}{{\overline{\mathit \nu}}_{{{e}}}}$ $<1.7$ $\times 10^{-6}$ 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
 
$\Gamma_{11}$ ${{\mathit \gamma}}{{\mathit \nu}}{{\overline{\mathit \nu}}}$ $<1.9$ $\times 10^{-7}$ CL=90% 67
 
▸  Charge conjugation ($\mathit C$) or Lepton Family number ($\mathit LF$) violating modes
[1] The ${{\mathit \pi}^{\pm}}$ mass has increased by three (old) standard deviations since our 1992 edition, and the ${{\mathit \pi}^{0}}$ mass, which is determined using the mass difference (${\mathit m}_{{{\mathit \pi}^{\pm}}}–{\mathit m}_{{{\mathit \pi}^{0}}}$), has increased accordingly. See the ``Note on the Charged Pion Mass'' in these Particle Listings for a discussion.
Constrained Fit information