fermi coupling constant

rioo

i'm reading through halzen and martin's chapter 12 on the weak interaction which they calculate the fermi coupling constant form oxygen beta decay using
[itex]\Gamma = 1/\tau = G^2E_0^5/30\pi^3[/itex]
with [itex]E_0 = 1.81[/itex]MeV and [itex]\tau log 2 = 71[/itex] sec. they get [itex]G\approx 10^{-5}/m^2_N[/itex]. where m_N is the nucleon mass.
i cant reproduce this number, just plugging in is way off. are there factors of c or h that i need to include?

Einj

Actually, to have the right dimension, is [itex]\Gamma=\hbar/\tau[/itex]. If you plug all the numbers considering that the calculation gives the correct answer.

rioo

yes it does thanks. natural units are annoying

Meir Achuz

You can use the conversion constant 1=192.33 MeV-fm

Bill_K

Close. ħc = 197.326 MeV-fm.

(Much more useful than whatever it is in Joule-m! )