What is so Special About Eta-Meson Physics

  • B. M. K. Nefkens
Part of the Few-Body Systems book series (FEWBODY, volume 9)


The η is a remarkable particle as regards its production, interaction, and its various suppressed, rare and forbidden decay modes. Eta production is always large; near threshold it is dominated by 3 special S-wave resonances. The ηN and ηΛ scattering lengths are attractive and large; this has generated speculations about the possible existence of a new type of nuclear matter, bound or quasi bound eta-mesic nuclei and eta-mesic hypernuclei. η is an isospin singlet, η production is therefore an isospin selective reaction which is particularly helpful in baryon spectroscopy. π0η mixing causes intrinsic (non Coulombic) violation of charge symmetry, which allows for new measurements of the mass difference between the up and down quarks at different four-momentum transfers. The η is a Goldstone boson; this provides opportunities for unique probes of chiral perturbation theory. Finally, the η is an eigenstate of the charge-conjunction and CP operators; this makes possible a variety of tests of C and CP invariance of flavor-non-changing strong/electromagnetic interactions.


Nuclear Matter Goldstone Boson Chiral Perturbation Theory Massless Quark Charge Symmetry 
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Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • B. M. K. Nefkens
    • 1
  1. 1.Department of Physics and AstronomyUCLALos AngelesUSA

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