The coupling of the Higgs boson to other particles is probed by measuring the production cross sections at the Large Hadron Collider using the ATLAS detector. The present measurement is performed using the H->ZZ*->4l decay channel, with l= electron or muon and with datasets corresponding to various integrated luminosities. The inclusive production cross section is measured to be 1.34 +/- 0.12 pb, which is in good agreement with the predicted value of 1.33 +/- 0.08 pb. The gluon-gluon fusion, the vector boson fusion, the vector boson associated and the top associated production cross sections are measured to be 1.12 +/- 0.12 pb, 110 +/- 40 fb, 75 +61 -49 fb and 27 +26 -17 fb, respectively. The differential production cross sections are also measured using the Simplified Template cross sections framework. All measurements are in good agreement with the Standard Model predictions. These results are used to measure the Higgs boson coupling to fermions and vector bosons using the kappa-framework and to derive constraints on contributions from beyond the Standard Model physics using an effective field theory approach. No significant deviations from the Standard Model are observed.

Studies of the spin, parity and tensor couplings of the Higgs boson in the H→ZZ*→4l, H→WW*→e[nu][mu][nu] and H→[gamma][gamma] decay processes at the LHC are presented. The investigations are based on 25fb-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 JP=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→ZZ*→4l and H→WW*→e[nu][mu][nu] 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.

During Run 2 of the Large Hadron Collider, the ATLAS experiment recorded proton-proton collision events at 13 TeV, the highest energy ever achieved in a collider. Analysis of this dataset has provided new opportunities for precision measurements of the Higgs boson, including its interaction with the top quark. The Higgs-top coupling can be directly probed through the production of a Higgs boson in association with a top-antitop quark pair (ttH). The Higgs to diphoton decay channel is among the most sensitive for ttH measurements due to the excellent diphoton mass resolution of the ATLAS detector and the clean signature of this decay. Event selection criteria were developed using novel Machine Learning techniques to target ttH events, yielding a precise measurement of the ttH cross section in the diphoton channel and a 6.3 $\sigma$ observation of the ttH process in combination with other decay channels, as well as stringent limits on CP violation in the Higgs-top coupling.