Why is the mass of the singlet meson higher than the octet mesons in QCD?

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Discussion Overview

The discussion revolves around the mass differences between singlet and octet mesons in Quantum Chromodynamics (QCD), particularly focusing on why the mass of the singlet meson is higher than that of the octet mesons. Participants explore theoretical aspects related to group theory and quark states.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that the mass difference between the singlet and octet mesons is not addressed in their source, raising a question about the underlying reasons for this discrepancy.
  • Another participant inquires about the mass differences between the eta prime and eta mesons, suggesting a potential connection to the broader topic of meson classification.
  • A later post prompts discussion on identifying the singlet particle and requests participants to provide wavefunctions for both the singlet and the particle they believe to be the singlet.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the reasons behind the mass differences, and multiple viewpoints regarding the classification and properties of mesons remain evident.

Contextual Notes

The discussion includes assumptions about quark states and interactions, but these are not fully explored or resolved within the thread.

Malamala
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Hello! I am reading some group theory applied to QCD and they show how by using the lightest 3 quarks in the ##l=0## state we get 9 pseudoscalar mesons and 9 vector mesons. The difference in masses between the 2 classes is explained by the existence of a spin-spin interaction, which seems like a reasonable argument. However they don't say anything about the fact that the mass of the singlet in each case (the 9 mesons are grouped in an octet and a singlet) is significantly higher than the masses of the mesons in the octet. What is the reason for that? Thank you!
 
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How does this connect to the title? (Title has now been changed, removing confusion)
 
Last edited:
In case of scalar mesons: what is the reason eta prime and eta mesons are at much different masses, rather than close?
 
Malamala said:
mass of the singlet in each case...is significantly higher than the masses of the mesons in the octet

Which particle do you think is the singlet? Why? Please write down the wavefunction of the particle you think is the singlet and also the wavefunction of a singlet.
 

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