Probing the Higgs boson CP properties in vector-boson fusion production in the $H\to \ddot{I}{„}^{+}\ddot{I}{„}^{-}$ channel with the ATLAS detector

Abstract

The CP properties of the Higgs boson are studied in the vector-boson fusion production mode. The analysis exploits the decay mode of the Higgs boson into two $\ddot{I}„$-leptons using 140 fb${}^{-1}$ of proton-proton collision data at $\sqrt{s}=13$ TeV collected by the ATLAS experiment at the Large Hadron Collider. Results are obtained using the Optimal Observable method. CP-violating interactions between the Higgs boson and electroweak gauge bosons are considered in the effective field theory framework, with the interaction strength described in the HISZ basis by $\tilde{d}$, and in the Warsaw basis by $c_{H\tilde{W}}$, $c_{H\tilde{B}}$, and $c_{H\tilde{W}B}$. No deviations relative to the Standard Model are observed, and limits are obtained on the strength parameters. The $\tilde{d}$ parameter is constrained to the interval [$-0.012,0.044$] at the 95% confidence level while $c_{H\tilde{W}}$ is constrained to [$-0.24,0.83$], when considering both linear and quadratic effects of physics beyond the Standard Model.

53 pages in total, author list starting page 36, 7 figures, 9 tables, published in JHEP 10 (2025) 92. All figures and tables including auxiliary figures and tables are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGP-2024-09/