Extending the Standard Model Effective Field Theory with the Complete Set of Dimension-7 Operators

TL;DR

This paper provides a complete classification of dimension-7 operators in the Standard Model Effective Field Theory, highlighting their structure, gauge invariance, and implications for lepton and baryon number violation.

Contribution

It introduces the full set of 20 independent dimension-7 operators in SMEFT, expanding the theoretical framework for exploring physics beyond the Standard Model.

Findings

20 independent dimension-7 operators identified

All operators contain fermions and violate lepton number

7 operators also violate baryon number

Abstract

We present a complete list of the independent dimension-7 operators that are constructed using the Standard Model degrees of freedom and are invariant under the Standard Model gauge group. This list contains only 20 independent operators; far fewer than the 63 operators available at dimension 6. All of these dimension-7 operators contain fermions and violate lepton number, and 7 of the 20 violate baryon number as well. This result extends the Standard Model Effective Field Theory (SMEFT) and allows a more detailed exploration of the structure and properties of possible deformations from the Standard Model Lagrangian.