I will describe a state-of-the-art functional integration approach to integrate out heavy fields of beyond Standard Model (BSM) theories at one-loop level.
The operators of the resulting effective field theory (EFT) encode the effects of the heavy loops in their Wilson coefficients.
The method is based on the background-field formalism and the expansion by regions.
As an illustrative example I will discuss the matching of a singlet extension of the Standard Model onto the Standard Model EFT (SMEFT).
I will particularly focus on issues related to the mixing of Higgs fields in the BSM model.
In this context a proper scheme choice for the renormalization of tad poles and mixing angles turns out to be crucial.
Maximilian Stahlhofen (Freiburg): Integrating out heavy fields in the path integral using the background-field method
