Renormalization of the Standard Model effective field theory to dimension eight

TL;DR

This paper systematically constructs and renormalizes dimension-eight operators in SMEFT, providing essential tools for high-precision phenomenology and extending the theoretical framework beyond dimension-six effects.

Contribution

It introduces a complete operator basis at dimension eight and computes the one-loop renormalisation group equations involving these operators.

Findings

Constructed a systematic basis for dimension-eight bosonic operators.

Calculated the complete one-loop RGEs for operators up to dimension eight.

Applied results to positivity bounds and oblique parameters.

Abstract

The Standard Model Effective Field Theory (SMEFT) provides a powerful, model-independent framework to explore deviations from the Standard Model (SM) by parametrising potential new physics through higher-dimensional operators. This thesis investigates the renormalisation structure of SMEFT, focusing on dimension-eight operators, which are increasingly relevant in precision analyses and in models where dimension-six effects are suppressed. We review renormalisation in quantum field theory, emphasising dimensional regularisation and the $\overline{\text{MS}}$ scheme, and outline the conceptual foundations of EFTs. One of the central results of this work is the systematic construction and classification of bosonic operators in SMEFT at dimension eight, employing Group Theory techniques and removing redundancies by working in momentum space. Building on this operator basis, we compute the complete one-loop renormalisation group equations (RGEs) involving insertions of dimension-eight-or-lower operators. This includes pure dimension-eight effects, pairs of dimension-six operators and lepton-number-violating sectors. Our calculations use an off-shell Green's function basis and leverage algebraic simplifications derived from symmetry and gauge invariance. These results are applied to positivity bounds and oblique parameters, providing essential tools for consistent SMEFT analyses across energy scales. The findings extend SMEFT's theoretical reach and support its use in high-precision phenomenology.