Baryon Number, Lepton Number, and Operator Dimension in the SMEFT with Flavor Symmetries

TL;DR

This paper explores how flavor symmetries in the SMEFT framework elevate the operator dimension for baryon and lepton number violation to nine, thereby suppressing related processes and lowering the proton decay scale.

Contribution

It identifies the lowest-dimensional baryon- and lepton-number violating operators in SMEFT with flavor symmetry as dimension 9, highlighting their impact on process suppression.

Findings

Operators are of dimension 9 under flavor symmetries.

Proton decay scale can be as low as 10^5 GeV.

Flavor symmetries suppress baryon and lepton number violation.

Abstract

For a large set of flavor symmetries, the lowest-dimensional baryon- or lepton-number violating operators in the Standard Model effective field theory (SMEFT) with flavor symmetry are of mass dimension 9. As a consequence, baryon- and lepton-number violating processes are further suppressed with the introduction of flavor symmetries, e.g., the allowed scale associated with proton decay is typically lowered to $10^5$ GeV, which is significantly lower than the GUT scale. To illustrate these features, we discuss Minimal Flavor Violation for the Standard Model augmented by sterile neutrinos.