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Fermi coupling constant

  1. Nov 17, 2012 #1
    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?
  2. jcsd
  3. Nov 18, 2012 #2
    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.
  4. Nov 18, 2012 #3
    yes it does thanks. natural units are annoying
  5. Nov 20, 2012 #4

    Meir Achuz

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    You can use the conversion constant 1=192.33 MeV-fm
  6. Nov 20, 2012 #5


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    Close. ħc = 197.326 MeV-fm.

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