1. Aug 28, 2007

neelakash

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. Aug 28, 2007

LastGuyOnTheLeft

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 $$\hbar/(Mc^{2})$$ before it need to decay into something else.

Last edited: Aug 28, 2007
3. Aug 28, 2007

neelakash

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?

4. Aug 28, 2007

neelakash

OK buddy you are correct.The point where I was stumbling is clear now.Thank you.

5. Aug 29, 2007

Barmecides

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.