CP-violating axion interactions in effective field theory

Understand

Axions are introduced to explain the observed smallness of the $\bar \theta $ term of QCD.

• Standard Model extensions typically contain new sources of CP violation, for instance to account for the baryon asymmetry of the universe.
• In the presence of additional CP-violating sources a Peccei-Quinn mechanism does not remove all CP violation, leading to CP-odd interactions among axions and Standard Model fields.
• In this work, we use effective field theory to parametrize generic sources of beyond-the-Standard-Model CP violation.