Constructing Dimension-8 SMEFT from Conserved Currents

TL;DR

This paper introduces the Kinematically Diagonalized Current Basis (KDCB), a new operator basis for dimension-8 SMEFT that simplifies amplitude analysis, enhances interpretability, and facilitates the application of positivity bounds and UV diagnostics.

Contribution

The paper develops a novel operator basis from conserved currents that resolves kinematic mixing issues in dimension-8 SMEFT, improving analysis and interpretation of collider data.

Findings

Operators map to unique energy scalings in amplitudes

Enables manifest positivity bounds in S-matrix analysis

Provides a stable framework for Monte Carlo simulations

Abstract

Effective Field Theories (EFTs) are the primary tool for interpreting precision collider data in the absence of new resonances. However, in the dimension-8 Standard Model Effective Field Theory (SMEFT), the utility of traditional algebraically minimal bases is fundamentally limited by kinematic mixing: multiple operators contribute to a single high-energy amplitude, creating degeneracies that obscure ultraviolet interpretations and complicate the application of theoretical constraints. We introduce a generative framework that resolves this by constructing operators directly from the conserved Noether currents of the Standard Model. The resulting Kinematically Diagonalized Current Basis (KDCB) ensures that each operator maps to a unique asymptotic energy scaling ($E^4$, $E^2$, $E^0$) in scattering amplitudes. This organization makes S-matrix positivity bounds manifest, enables a stable auxiliary-field formulation for Monte Carlo simulation, and provides direct diagnostics for universal versus non-universal ultraviolet completions through current decomposition. By rotating the operator space into physically interpretable sectors, the KDCB offers a transformative framework for global fits and a clear pathway from high-energy data to the structure of new physics.