Baryon and lepton number intricacies in axion models

TL;DR

This paper explores the complex relationship between axion models and baryon/lepton number violations, analyzing their compatibility, effects on axion properties, and identifying interactions that do not affect axion phenomenology.

Contribution

It provides a detailed analysis of how B and L violating effects interact with axion models and identifies classes of interactions that do not impact axion phenomenology.

Findings

Compatibility of axion models with B and L violation effects analyzed

Quantification of simultaneous B and L violating effects and their impact on axion properties

Identification of B and L violating interactions that do not affect axion phenomenology

Abstract

Because the Peccei-Quinn (PQ) symmetry has to be anomalous to solve the strong CP puzzle, some colored and chiral fermions have to transform non-trivially under this symmetry. But when the SM fermions are charged, as in the PQ or DFSZ models, this symmetry ends up entangled with the SM global symmetries, baryon (B) and lepton (L) numbers. This raises several questions addressed in this paper. First, the compatibility of axion models with some explicit B and/or L violating effects is analyzed, including those arising from seesaw mechanisms, electroweak instanton interactions, or explicit B and L violating effective operators. Second, how many of these effects can be simultaneously present is quantified, along with the consequences for the axion mass and vacuum alignment if too many of them are introduced. Finally, large classes of B and/or L violating interactions without impact on axion phenomenology are identified, like for example the various implementations of the type I and II seesaw mechanisms in the DFSZ context.