Light Higgsino from axion dark radiation

Kwang Sik Jeong, Fuminobu Takahashi

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


The recent observations imply that there is an extra relativistic degree of freedom coined dark radiation. We argue that the QCD axion is a plausible candidate for the dark radiation, not only because of its extremely small mass, but also because in the supersymmetric extension of the Peccei-Quinn mechanism the saxion tends to dominate the Universe and decays into axions with a sizable branching fraction. We show that the Higgsino mixing parameter μ is bounded from above when the axions produced at the saxion decays constitute the dark radiation: μ 300 GeV for a saxion lighter than 2 mW, and μ less than the saxion mass otherwise. Interestingly, the Higgsino can be light enough to be within the reach of LHC and/or ILC even when the other superparticles are heavy with mass about 1 TeV or higher. We also estimate the abundance of axino produced by the decays of Higgsino and saxion.

Original languageEnglish
Article number17
JournalJournal of High Energy Physics
Issue number8
Publication statusPublished - 2012


  • Cosmology of Theories beyond the SM
  • Supersymmetric Standard Model

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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