Enhanced photon coupling of ALP dark matter adiabatically converted from the QCD axion

Shu Yu Ho, Ken'Ichi Saikawa, Fuminobu Takahashi

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


We revisit the adiabatic conversion between the QCD axion and axion-like particle (ALP) at level crossing, which can occur in the early universe as a result of the existence of a hypothetical mass mixing. This is similar to the Mikheyev-Smirnov-Wolfenstein effect in neutrino oscillations. After refining the conditions for the adiabatic conversion to occur, we focus on a scenario where the ALP produced by the adiabatic conversion of the QCD axion explains the observed dark matter abundance. Interestingly, we find that the ALP decay constant can be much smaller than the ordinary case in which the ALP is produced by the realignment mechanism. As a consequence, the ALP-photon coupling is enhanced by a few orders of magnitude, which is advantageous for the future ALP and axion-search experiments using the ALP-photon coupling.

Original languageEnglish
Article number042
JournalJournal of Cosmology and Astroparticle Physics
Issue number10
Publication statusPublished - 2018 Oct 22


  • axions
  • dark matter theory
  • particle physics - cosmology connection
  • physics of the early universe


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