Approaching robust EFT limits for CP-violation in the Higgs sector

Understand

Constraining CP-violating interactions in effective field theory (EFT) of dimension six faces two challenges.

• Firstly, degeneracies in the multi-dimensional space of Wilson coefficients have to be lifted.
• Secondly, quadratic contributions of CP-odd dimension six operators are difficult to disentangle from squared contributions of CP-even dimension six operators and from linear contributions of dimension eight operators.
• Both of these problems are present when new sources of CP-violation are present in the interactions between the Higgs boson and heavy strongly-interacting fermions.