Aad, G; Abbott, B; Abdinov, O; Abdallah, J; Abeloos, B; Aben, R; Abolins, M; Aben, R; Abolins, M; AbouZeid, OS; Abraham, NL; Abramowicz, H; Abreu, H; Abreu, R; Abulaiti, Y; Acharya, BS; Adamczyk, L; Adams, DL; Adelman, J; Adomeit, S; Adye, T; Affolder, AA; Agatonovic-Jovin, T; Agricola, J; Aguilar-Saavedra, JA; Ahlen, SP; Ahmadov, F; Aielli, G; Akerstedt, H; Åkesson, TPA; Akimov, AV; Alberghi, GL; Albert, J; Albrand, S; Verzini, MJA; Aleksa, M; Aleksandrov, IN; Alexa, C; Alexander, G et al., *Test of CP invariance in vector-boson fusion production of the Higgs boson using the Optimal Observable method in the ditau decay channel with the ATLAS detector.*,
The European Physical Journal C - Particles and Fields, vol. 76 no. 12
(January, 2016),
pp. 658 [doi] .
**Abstract:**

*A test of CP invariance in Higgs boson production via vector-boson fusion using the method of the Optimal Observable is presented. The analysis exploits the decay mode of the Higgs boson into a pair of [Formula: see text] leptons and is based on 20.3 [Formula: see text] of proton-proton collision data at [Formula: see text] = 8 [Formula: see text] collected by the ATLAS experiment at the LHC. Contributions from CP-violating interactions between the Higgs boson and electroweak gauge bosons are described in an effective field theory framework, in which the strength of CP violation is governed by a single parameter [Formula: see text]. The mean values and distributions of CP-odd observables agree with the expectation in the Standard Model and show no sign of CP violation. The CP-mixing parameter [Formula: see text] is constrained to the interval [Formula: see text] at 68% confidence level, consistent with the Standard Model expectation of [Formula: see text].*