On $\gamma_5$ schemes and the interplay of SMEFT operators in the Higgs-gluon coupling

TL;DR

This paper investigates the effects of four-top quark operators on Higgs production via gluon fusion within the Standard Model Effective Field Theory, highlighting the importance of $oldsymbol{oldsymbol{ ext{γ}_5}}$ schemes and operator interplay at two-loop level.

Contribution

It introduces the first calculation of four-top operator contributions to Higgs-gluon coupling at two loops, considering different $oldsymbol{ ext{γ}_5}}$ schemes and their impact on operator mixing.

Findings

Two different $ ext{γ}_5$ schemes lead to consistent results with a clear parameter mapping.

Four-top operators influence Higgs production through loop-level operator interplay.

Results validated by matching onto UV models.

Abstract

We calculate the four-top quark operator contributions to Higgs production via gluon fusion in the Standard Model Effective Field Theory. The four-top operators enter for the first time via two-loop diagrams. Due to their chiral structure they contain $\gamma_5$, so special care needs to be taken when using dimensional regularisation for the loop integrals. We use two different schemes for the continuation of $\gamma_5$ to $D$ space-time dimensions in our calculations and present a mapping for the parameters in the two schemes. This generically leads to an interplay of different operators, such as four-top operators, chromomagnetic operators or Yukawa-type operators at the loop level. We validate our results by examples of matching onto UV models.