From axion quality and naturalness problems to a high-quality <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi mathvariant="double-struck">Z</mml:mi><mml:mi>N</mml:mi></mml:msub></mml:math> QCD relaxion

Abstract

We highlight general issues associated with quality and naturalness problems in theories of light QCD axions, axionlike particles, and relaxions. We show that the presence of Planck-suppressed operators generically lead to scalar coupling of axions with the Standard Model. We present a new class of ${\mathbb{Z}}_{N}$ QCD relaxion models that can address both the QCD relaxion $CP$ problem as well as its quality problem. This new class of models also leads to interesting experimental signatures, which can be searched for at the precision frontier.

Topics & Concepts