Quarks Without Color: Investigating the Consequences of a Colorless Universe

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Discussion Overview

The discussion revolves around the concept of color charge in quarks, specifically investigating how electron-positron annihilation might support the existence of three color states for quarks. Participants also explore the implications of a hypothetical colorless universe on the states of baryons in the 1/2 octet and 3/2 decuplet, particularly regarding the identity of quarks of the same flavor.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant asks how electron-positron annihilation supports the conjecture of three color states for quarks, linking it to the behavior of baryons in a colorless scenario.
  • Another participant expresses uncertainty about how leptons can prove the existence of three color states.
  • A different participant argues that the introduction of color quantum numbers is necessary to satisfy the antisymmetry requirement of certain wavefunctions, such as that of the Δ++ particle, which consists of three identical quarks.
  • Another participant proposes a Feynman diagram approach to illustrate how electron-positron annihilation could lead to quark-antiquark pairs, suggesting that the presence of color increases the likelihood of producing baryons or mesons compared to a scenario without color.
  • This participant also notes the need for antisymmetric wavefunctions with respect to flavor and spin in the absence of color, while mentioning a reference to Griffiths' book on elementary particles for further reading.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the role of electron-positron annihilation in supporting the existence of three color states for quarks. There are multiple competing views regarding the necessity and implications of color in quantum mechanics, and the discussion remains unresolved.

Contextual Notes

There are limitations regarding the assumptions made about the nature of quark wavefunctions and the implications of color charge, as well as the dependence on specific definitions of symmetry and antisymmetry in quantum states.

babtridge
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Hi there,
Could anybody please explain how electron-positron annihilation supports the conjecture that 3 colour states exist for quarks?
Plus in the Baryon 1/2 octet and 3/2 decuplet, what would be the corresponding set of states if colour did not exist, such that quarks of the same flavour were identical?

Thanks a lot in advance guys and gals...
 
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uhhhh i don't know how leptons can prove that 3 colour states exists.
 
babtridge said:
Hi there,
Could anybody please explain how electron-positron annihilation supports the conjecture that 3 colour states exist for quarks?
Plus in the Baryon 1/2 octet and 3/2 decuplet, what would be the corresponding set of states if colour did not exist, such that quarks of the same flavour were identical?

Thanks a lot in advance guys and gals...

This has nothing to do with the existence of the colour-quantum-number. This number was introduced because certain wavefunctions (like that of the [tex]\Delta^{++}[/tex])-particle) could exhibit "all equal" quantumnumbers. In the case of the above mentioned particle the wavefunction consists out of three up quarks + three spin up-numbers + three 1s-energy levels. This kind of wave function does not obey the Pauli-exclusion rule and because of this, the wavefunction must be antisymmetric. In order to obey this anti-symmetry, colours were introduced.

regards
marlon
 
Last edited:
babtridge said:
Hi there,
Could anybody please explain how electron-positron annihilation supports the conjecture that 3 colour states exist for quarks?
Do a Feynman diagram as follows. Going in you have an electron and a positron, that annihilate into a virtual photon; the photon then turns into a quark-antiquark pair that go out.

The idea is that for high enough energies, this diagram contributes to the total electron-positron cross section. Let's assume only the light quarks contribute, then you can sum up the amplitudes for annihilation into u and b quark/antiquark pairs and calculate the fraction of the time quarks are produced as opposed to a photon pair or a muon-antimuon. If color exists, then there are 3 diagrams as far as the EM interaction is concerned for each quark flavor; one for each color. This increases the fraction of producing baryons or mesons compared to the no-color case.
Plus in the Baryon 1/2 octet and 3/2 decuplet, what would be the corresponding set of states if colour did not exist, such that quarks of the same flavour were identical?
I do not have the time to work this out now; the idea is that you are now looking for quark wavefunctions that are antisymmetric wrt flavor and spin instead of symmetric. The spatial wavefunction is always symmetric in the ground state, and the color singlet wavefunction is always antisymmetric if it is included.

Edit: if you have Griffiths' book on elementary particles, he touches on this somewhere in the chapter on building baryon wavefunctions.
 
Thanks for taking the time to help me out on this one...you've all made stuff a lot clearer.
Tekiteasy peeps!
 

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