String compactification, QCD axion and axion-photon-photon coupling

Kang Sin Choi, Lan Woo Kim, Jihn E. Kim

Research output: Contribution to journalArticlepeer-review

40 Scopus citations


It is pointed out that there exist a few problems to be overcome toward an observable sub-eV QCD axion in superstring compactification. We give a general expression for the axion decay constant. For a large domain wall number Now, the axion decay constant can be substantially lowered from a generic value of a scalar singlet VEV. The Yukawa coupling structure in the recent Z12-1 model is studied completely, including the needed nonrenormalizable terms toward realistic quark and lepton masses. In this model we find an approximate global symmetry and vacuum so that a QCD axion results but its decay constant is at the GUT scale. The axion-photon-photon coupling is calculated with a reasonable assumption on a realistic vacuum satisfying the quark and lepton mass matrix conditions. It is the first time calculation of c αγγ in realistic string compactifications: C αγγ= 5/3- 1.93 ≃ -0.26.

Original languageEnglish
JournalJournal of High Energy Physics
Issue number3
StatePublished - 1 Mar 2007


  • GUT
  • Global symmetries compactification and string models
  • Quark masses and SM parameters


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