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Please clarify

  1. Aug 28, 2007 #1
    In a standard model book I find this:
    a particle of mass M can exist as a part of an intermediate state for time `h/(Mc^2) where `h=h/2π


    I cannot understand the underlined part.Which intermediate state are they referring to?
     
  2. jcsd
  3. Aug 28, 2007 #2
    Spontaneously I would say that with "as a part of an intermediate state" the mean a state like, for example, the Z in the following diagram?
    http://www-sldnt.slac.stanford.edu/alr/images/epem_toZ.jpg

    That is, it can not be the final product, but only exist for the time [tex]\hbar/(Mc^{2})[/tex] before it need to decay into something else.
     
    Last edited: Aug 28, 2007
  4. Aug 28, 2007 #3
    Since I do not know very much the Weak interaction...are you sure that it would be a Z boson in a Feynmann diagram?Do not take me otherwise,the formula holds for any type of bosons:like photon.Since photon mass is zero,the lifetime and range of photon is infinite...So,in such cases how will you explain the intermediate state?
     
  5. Aug 28, 2007 #4
    OK buddy you are correct.The point where I was stumbling is clear now.Thank you.
     
  6. Aug 29, 2007 #5
    Experimentally, we often caracterize particles as resonances (when the particle is unstable).
    In the case of the Z quoted above you can find the resonance plot on this web page (first plot) :
    http://aleph.web.cern.ch/aleph/aleph/newpub/physics.html
    Below the resonance, contributions of feynman graphs like e+e- -> photon* -> qq are negligible.
     
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