Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Fermi's Golden Rule (Decay Amplitude)

  1. May 9, 2010 #1
    This question relates to Griffiths: Introduction to Elementary Particles, p. 196

    The process in question is a neutral pion decay into two photons. It is stated that because the secondary particles are massless, the amplitude for this process is:


    where [tex]p_2[/tex] and [tex]p_3[/tex] are the momentum three-vectors of the secondary photons. Conservation of momentum further implies that [tex]p_2=-p_3[/tex]. So far, so good.

    However, Griffiths then states that
    is a function of |p_2| only, meaning that |M|^2 has no angular dependency. Why is this?
    Last edited: May 9, 2010
  2. jcsd
  3. May 10, 2010 #2


    User Avatar
    Science Advisor

    The pi zero has spin zero, so its decay cannot have any angular dependence.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook