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Pion decay constant
In particle physics, the pion decay constant is the square root of the coefficient in front of the kinetic term for the pion in the low-energy effective action. It is dimensionally an energy scale and it determines the strength of the chiral symmetry breaking. The values are:
\( f_{\pi^{\pm}} = 130.41 \pm 0.03 \pm 0.20~\mbox{MeV} \)
\( f_{\pi^{0}} = 130 \pm 5~\mbox{MeV} \)
Beware: There are several conventions which differ by factors of \( \scriptstyle \sqrt{2} \). The textbook by Weinberg uses the value 184 MeV. The textbook by Peskin and Schroeder uses the value 93 MeV.
References
Particle Data Group: W.-M. Yao et al., J. Phys. G 33, 1 (2006).
Griffiths, David J. (1987). Introduction to Elementary Particles. Wiley, John & Sons, Inc. ISBN 0-471-60386-4.
Particle Data Group: Decay constants of charged pseudoscalar mesons
External links
Particle Data Group & WWW edition of Review of Particle Physics
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