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

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SUMMARY

The mass of the singlet meson is significantly higher than that of the octet mesons in Quantum Chromodynamics (QCD) due to the presence of a spin-spin interaction. This interaction affects the mass differences between the pseudoscalar and vector mesons, leading to distinct mass characteristics. Specifically, the eta prime and eta mesons exhibit considerable mass variation, which can be attributed to their differing quark compositions and interactions. Understanding these mass differences is crucial for deeper insights into QCD and meson classification.

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  • Group theory applications in particle physics
  • Quark model and meson classification
  • Spin-spin interactions in quantum systems
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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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