Intermediate State in Standard Model Book - Clarify!

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Discussion Overview

The discussion revolves around the concept of intermediate states in the context of the Standard Model of particle physics, specifically focusing on the time a particle of mass M can exist in such a state. Participants explore the implications of this concept, particularly in relation to the Z boson and other particles.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the specific intermediate state referred to in the Standard Model book, seeking clarification on its meaning.
  • Another participant suggests that the intermediate state could refer to the Z boson in a Feynman diagram, indicating that such states cannot be final products and must decay within a certain time frame.
  • A different participant expresses uncertainty about the identification of the Z boson in the context of weak interactions, noting that the formula for intermediate states applies to any boson, including massless particles like photons, which complicates the explanation of their intermediate states.
  • One participant acknowledges a misunderstanding and expresses gratitude for the clarification provided by others.
  • A participant reiterates the concept of particles being characterized as resonances when unstable, linking this to the Z boson and providing a reference to a resonance plot for further exploration.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the specific intermediate state being discussed, and multiple viewpoints regarding the nature of intermediate states and their relation to different particles remain present.

Contextual Notes

There are unresolved questions regarding the definitions of intermediate states and the implications for massless particles, as well as the specific examples used in the discussion.

neelakash
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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?
 
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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.
 
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Since I do not know very much the Weak interaction...are you sure that it would be a Z boson in a Feynman 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?
 
OK buddy you are correct.The point where I was stumbling is clear now.Thank you.
 
neelakash said:
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?

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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