Adding Flavor to the SMEFT

TL;DR

This paper explores the flavor structure of dimension-6 operators in SMEFT, proposing various flavor symmetries and providing tools for phenomenological analysis of UV dynamics beyond the Standard Model.

Contribution

It introduces multiple flavor symmetry hypotheses in SMEFT, constructs operator sets under these symmetries, and offers a Mathematica package for further analysis.

Findings

Defined several flavor symmetries and symmetry-breaking patterns.

Constructed and counted operators for each flavor hypothesis.

Provided a Mathematica package for flavor analysis.

Abstract

We study the flavor structure of the lepton and baryon number--conserving dimension-6 operators in the Standard Model effective field theory (SMEFT). Building on the work of [1], we define several well-motivated flavor symmetries and symmetry-breaking patterns that serve as competing hypotheses about the ultraviolet (UV) dynamics beyond the SM, not far above the TeV scale. In particular, we consider four different structures in the quark sector and seven in the charged lepton sector. The set of flavor-breaking spurions is (almost) always taken to be the minimal one needed to reproduce the observed charged fermion masses and mixings. For each case, we explicitly construct and count the operators to the first few orders in the spurion expansion, providing ready-for-use setups for phenomenological studies and global fits. We provide a Mathematica package SMEFTflavor to facilitate similar analyses for flavor symmetries not covered in this work.