The SMEFTsim package, theory and tools

Abstract

We report codes for the Standard Model Effective Field Theory (SMEFT) in FeynRules — the SMEFTsim package. The codes enable theoretical predictions for dimension six operator corrections to the Standard Model using numerical tools, where predictions can be made based on either the electroweak input parameter set $$ \left\{{\widehat{\alpha}}_{ew},{\widehat{m}}_Z,{\widehat{G}}_F\right\} $$ or $$ \left\{{\widehat{m}}_W,{\widehat{m}}_Z,{\widehat{G}}_F\right\} $$ . All of the baryon and lepton number conserving operators present in the SMEFT dimension six Lagrangian, defined in the Warsaw basis, are included. A flavour symmetric U(3)5 version with possible non-SM CP violating phases, a (linear) minimal flavour violating version neglecting such phases, and the fully general flavour case are each implemented. The SMEFTsim package allows global constraints to be determined on the full Wilson coefficient space of the SMEFT. As the number of parameters present is large, it is important to develop global analyses on reduced sets of parameters minimizing any UV assumptions and relying on IR kinematics of scattering events and symmetries. We simultaneously develop the theoretical framework of a “W-Higgs-Z pole parameter” physics program that can be pursued at the LHC using this approach and the SMEFTsim package. We illustrate this methodology with several numerical examples interfacing SMEFTsim with MadGraph5. The SMEFTsim package can be downloaded at https://feynrules.irmp.ucl.ac.be/wiki/SMEFT .