Probing the Higgs boson CP properties in vector-boson fusion production in the H → τ+τ− 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 τ -leptonsusing 140 fb-1 of proton-proton collision data at SQUARE ROOTs = 13TeV collected by the ATLASexperiment at the Large Hadron Collider. Results are obtained using the Optimal Observablemethod. CP-violating interactions between the Higgs boson and electroweak gauge bosons areconsidered in the effective field theory framework, with the interaction strength described inthe HISZ basis by ~ d, and in the Warsaw basis by cH ~W , cH~B, and cH ~W B. No deviations relativeto the Standard Model are observed, and limits are obtained on the strength parameters.The ~ d parameter is constrained to the interval [-0.012, 0.044] at the 95% confidence levelwhile cH ~W is constrained to [-0.24, 0.83], when considering both linear and quadratic effects of physics beyond the Standard Model.