What is the physical meaning of form factor?

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Discussion Overview

The discussion centers around the concept of form factor, particularly in the context of high energy physics, electronics, and PC-engineering. Participants explore its definitions, implications, and various interpretations within these fields.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants suggest that form factor is defined as the Fourier transforms of charge and current distributions, relating it to the strength of electrical and magnetic interactions.
  • Others propose that there are multiple interpretations of form factor in high energy physics, including a topological explanation where the form factor can be visualized as a surface whose deformation indicates the strength of interactions.
  • A participant mentions a specific definition of form factor in quantum hadrodynamics (QHD) found in a referenced paper.
  • There is a discussion about the relationship between invariant amplitude and invariant mass amplitude, with some participants expressing confusion about their equivalence and their connection to mass.
  • One participant acknowledges gaining a better understanding of form factor through the discussion.

Areas of Agreement / Disagreement

Participants express varying interpretations of form factor, with no consensus on a singular definition or understanding. Confusion remains regarding the relationship between invariant amplitude and mass.

Contextual Notes

Some claims depend on specific definitions and contexts, such as the application of form factor in different areas of physics. The discussion also highlights unresolved questions about the relationship between invariant amplitudes and mass.

Who May Find This Useful

Individuals interested in high energy physics, quantum mechanics, and the mathematical underpinnings of particle interactions may find this discussion relevant.

man@SUT
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I am a new member of the forum. I don't understand the physical meaning of the form factor. Could you help me?
 
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Well there are different area's where the concept of form factor is used. Eg : electronics, PC-engineering and high energy physics. In the latter, the form factor is defined as the Fourier transforms of charge and current distributions. Basically, one could look at the form factor as the strength of an interaction (electrical and magnetic) in the Fourier base. This concept is widely used in effective field theories in which the basic degrees of freedom (like particles for example) are NOT elementary.

marlon
 
Thank you, Malon. I found this in the cross section of e-e+ to vector meson. Is there another meaning of form factor in high energy physics.
 
man@SUT said:
Thank you, Malon. I found this in the cross section of e-e+ to vector meson. Is there another meaning of form factor in high energy physics.
Well, i guess there are other ways to look at it but the basic idea will be the "link to strength of interaction". I know there is also a topological explanation where you can plot the form factor as a surface. The deformation of that surface during an interaction gives an idea about what is going on and how strong that interaction is. In QHD (quantum hadro dynamics), this is used very often.


marlon
 
If you look http://inwpent5.ugent.be/papers/phys_art_0003.pdf you will see a definition of the form factor in QHD, at the end of page 5 and the top of page 6.

This is a paper written by an old fellow student of mine who is doing her PhD at the university of Ghent, Belgium.

regards
marlon
 
Last edited by a moderator:
Thank you for your help, Malon.

regards,
man@SUT
 
For invariant amplitude and invariant mass amplitude, I think they are the same. We calculate them on the way to find the cross section. So, how does it relate to mass if both are the same? I am a bit confused.
 
man@SUT said:
For invariant amplitude and invariant mass amplitude, I think they are the same. We calculate them on the way to find the cross section. So, how does it relate to mass if both are the same? I am a bit confused.
Mass ? Keep in mind that mass is not the coupling constant of electromagnetic or (in general) weak interactions. Again, read the definition in the paper, the key notion is the "squared four momentum Q² dependency" .

marlon
 
Last edited:
I'm sorry that the topic had changed. I didn't ask you about the form factor but I asked you about the invariant mass amplitude or invariant amplitude that we can meet them on the way to find the cross-section,
for example, the cross section of e-e+ annihilation and the cross section of mu-decay.

For the form factor, I think I get more understanding about it.
 

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