`G_F/h^3 = 1.166 364 e-5 0.000 005 e-5 GeV^-2`

Failed to evaluate at line 1

In nuclear physics The strength of Fermi's interaction is given by the Fermi coupling constant G_F. The most precise experimental determination of the Fermi constant comes from measurements of the muon lifetime, which is inversely proportional to the square of G_F (when neglecting the muon mass against the mass of the W boson). 

G_F/`h_bar`³ =(`sqrt`2/8)*(g²/m²_w) = 

Here g is the coupling constant of the weak interaction, and m_W is the mass of the W boson which mediates the decay in question.

Notes

http://en.wikipedia.org/wiki/Fermi's_interaction

http://physics.nist.gov/cgi-bin/cuu/Value?gf