After the discovery of the Higgs boson, one of the major questions about its properties is how it behaves under charge and parity (CP) conjugation. Our group played a crucial role in the first measurement of the CP properties of the Higgs boson in its decays to τ leptons. The analysis was done in the H→ττ→μτ_h final state. The combination with the H→ττ→τ_hτ_h final state allowed to put limits on a possible deviation from a pure CP-even state. In particular a pure CP-odd state could be excluded with more than 3σ.
Currently, the group is involved in adding the H→ττ→eτ_h channel to the measurement to further constrain the existence of a CP-odd component in the Yukawa interaction.