Study of the spin and parity of the Higgs boson in diboson decays with the ATLAS detector

Studies of the spin, parity and tensor couplings of the Higgs boson in the H → Z Z ∗ → 4 ℓ , H → W W ∗ → e ν μ ν and H → γ γ decay processes at the LHC are presented. The investigations are based on 25 fb - 1 of pp collision data collected by the ATLAS experiment at s = 7 TeV and s = 8 TeV. The Standard Model (SM) Higgs boson hypothesis, corresponding to the quantum numbers J P = 0 + , is tested against several alternative spin scenarios, including non-SM spin-0 and spin-2 models with universal and non-universal couplings to fermions and vector bosons. All tested alternative models are excluded in favour of the SM Higgs boson hypothesis at more than 99.9 % confidence level. Using the H → Z Z ∗ → 4 ℓ and H → W W ∗ → e ν μ ν decays, the tensor structure of the interaction between the spin-0 boson and the SM vector bosons is also investigated. The observed distributions of variables sensitive to the non-SM tensor couplings are compatible with the SM predictions and constraints on the non-SM couplings are derived.