Investigation of the CP properties of VBF Higgs production using the decay to a pair of tau leptons with the ATLAS detector

Recent studies at the LHC have led to the observation of the Higgs boson decay to tau leptons, with a rate compatible with the Standard Model expectation. The observation opens the way to a more in-depth investigation of the properties of the production and decay of a Higgs boson into tau leptons, including whether or not the Higgs boson couplings involved in this process violate CP conservation. The analysis presented in these proceedings focuses on events where Higgs bosons are produced via vector boson fusion in order to investigate the tensor structure of their coupling to electroweak gauge bosons. For this, a profile likelihood fit using a matrix-element observable is employed in the decay to tau leptons to test whether a CP-odd component is present in the coupling. A measurement of a non-zero value would be an indication of CP-violation in the Higgs sector. No evidence of CP violation was found.