Classical radius of nucleons and quarks

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Discussion Overview

The discussion revolves around the calculation of the classical radius of nucleons and quarks, including considerations of potential energy types involved. Participants explore the significance of the classical radius in comparison to the electron and discuss measurement techniques for nucleon radii.

Discussion Character

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

Main Points Raised

  • One participant inquires about the calculation of the classical radius of nucleons and quarks, questioning whether to include only electrostatic potential energy or also nuclear potential energy.
  • Another participant asserts that the classical radius, defined as e^2//mc^2, lacks physical significance and notes that while it would be smaller for nucleons than electrons, the physical radius of a nucleon is approximately 1 fm, whereas the electron's physical radius is likely 0.
  • A different participant mentions that nucleon radii can be measured indirectly through form factors and structure functions, which relate to the distributions of charge and current.
  • The same participant reiterates the classical radius definition and its implications, asking how it compares with the photon.
  • Another participant states that a photon is regarded as a point particle.

Areas of Agreement / Disagreement

Participants express differing views on the significance of the classical radius and its comparison to the physical radii of nucleons and electrons. There is no consensus on the implications of the classical radius or the inclusion of different types of potential energy in its calculation.

Contextual Notes

Some limitations include the ambiguity surrounding the physical significance of the classical radius and the definitions used in the discussion, as well as the unresolved nature of how potential energies should be treated in calculations.

relativityfan
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hi,

how do you calculate the classical radius of nucleons or quarks? do you include only the electrostatic potential energy or also some nuclear potential energy?. i have read many times that the classical radius of nucleons is lower than the classical radius of the electron, is it right?

thank you for your reply!
 
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The "classical radius", usually defined as e^2//mc^2, has no physical significance.
It would be much smaller for a nucleon than an electron, but the physical radius of a
nucleon is almost 1 fm, while the electron physical radius is probably 0.
 
For nucleons one can measure form factors (and structure functions); form factors are something like the Fourier transform of the corresponding density (charge, current, ...) so one can measure the radius indirectly via the charge, current, ... distributions
 
Meir Achuz said:
The "classical radius", usually defined as e^2//mc^2, has no physical significance.
It would be much smaller for a nucleon than an electron, but the physical radius of a
nucleon is almost 1 fm, while the electron physical radius is probably 0.

thank you, and how does it compare with the photon?
 
A photon is considered a point particle.
 

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