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:

$f_{\pi^{\pm}} = 130.7 \pm 0.1 \pm 0.36~\mbox{MeV}$

$f_{\pi^{0}} = 130 \pm 5~\mbox{MeV}$

Beware: There are several conventions which differ by powers 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

1. Particle Data Group: W.-M. Yao et al., J. Phys. G 33, 1 (2006).
2. Griffiths, David J. (1987). Introduction to Elementary Particles. Wiley, John & Sons, Inc. ISBN 0-471-60386-4. 

External links

1. Particle Data Group & WWW edition of Review of Particle Physics