Test of CP invariance in vector-boson fusion production of the Higgs boson in the H → ττ channel in proton–proton collisions at [Formula presented] with the ATLAS detector

Author(s): Aad, G; Abbott, B; Abbott, DC; Abed Abud, A; Abeling, K; Abhayasinghe, DK; Abidi, SH; AbouZeid, OS; Abraham, NL; Abramowicz, H; Abreu, H; Abulaiti, Y; Acharya, BS; Achkar, B; Adachi, S; Adam, L; Adam Bourdarios, C; Adamczyk, L; Adamek, L; Adelman, J; Adersberger, M; Adiguzel, A; Adorni, S; Adye, T; Affolder, AA; Afik, Y; Agapopoulou, C; Agaras, MN; Aggarwal, A; Agheorghiesei, C; Aguilar-Saavedra, JA; Ahmadov, F; Ahmed, WS; Ai, X; Aielli, G; Akatsuka, S; Akesson, TPA; Akilli, E; Akimov, AV; Al Khoury, K; Alberghi, GL; Albert, J; Alconada Verzini, MJ; Alderweireldt, S; Aleksa, M; Aleksandrov, IN; Alexa, C; Alexopoulos, T; Alfonsi, A; Alfonsi, F; Alhroob, M; Ali, B; Aliev, M; Alimonti, G; Allaire, C; Allbrooke, BMM; Allen, BW; Allport, PP; Aloisio, A; Alonso, F; Alpigiani, C; Alshehri, AA; Alunno Camelia, E; Alvarez Estevez, M; Alviggi, MG; Amaral Coutinho, Y; Ambler, A; Ambroz, L; Amelung, C; Amidei, D; Amor Dos Santos, SP; Amoroso, S; Amrouche, CS; An, F; Anastopoulos, C; Andari, N; Andeen, T; Anders, CF; Anders, JK; Andreazza, A; Andrei, V; Anelli, CR; Angelidakis, S; Angerami, A; Anisenkov, AV | Abstract: © 2020 The Author(s) A test of CP invariance in Higgs boson production via vector-boson fusion is performed in the H→ττ decay channel. This test uses the Optimal Observable method and is carried out using 36.1fb−1 of s=13TeV proton–proton collision data collected by the ATLAS experiment at the LHC. Contributions from CP-violating interactions between the Higgs boson and electroweak gauge bosons are described by an effective field theory, in which the parameter d˜ governs the strength of CP violation. No sign of CP violation is observed in the distributions of the Optimal Observable, and d˜ is constrained to the interval [−0.090, 0.035] at the 68% confidence level (CL), compared to an expected interval of d˜∈[−0.035,0.033] based upon the Standard Model prediction. No constraints can be set on d˜ at 95% CL, while an expected 95% CL interval of d˜∈[−0.21,0.15] for the Standard Model hypothesis was expected.