γ5 schemes and the interplay of SMEFT operators in the Higgs-gluon coupling

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. Owing to their chiral structure they contain <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msub><a:mi>γ</a:mi><a:mn>5</a:mn></a:msub></a:math>, so special care needs to be taken when using dimensional regularization for the loop integrals. We use two different schemes for the continuation of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:msub><c:mi>γ</c:mi><c:mn>5</c:mn></c:msub></c:math> to <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>D</e:mi></e:math> 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.