| Details of the discovery of a Higgs Boson and its mass and coupling measurements using up to 25 fb-1 of collision data measured with the ATLAS detector at the LHC are presented. The measured mass is mH = 125.5 +/-0.2(stat) +0.5-0.6(sys) using the H→gammagamma and H→ZZ*→4ℓ channels. A combination of H→gammagamma, H→ZZ*→4ℓ, H→WW*→lnulnu, H→tautau and H→bb yields an observed signal strength of mu = 1.30 +/-0.12(stat)+0.14-0.11(sys) at a Higgs Boson mass of 125.5 GeV. The evidence for Higgs production through Vector Boson Fusion is confirmed at the 4.1sigma level. The coupling to fermions is established at the 3.7sigma level with a fermionic signal strength mu tautau,bb = 1.09 +/-0.24(stat) +0.27 -0.21(sys). Couplings of the Higgs Boson to other particles are explored under a set of benchmark scenarios where no deviation from the Standard Model was found.;Modeling and statistics techniques are discussed thoroughly throughout. The channel H→ZZ*→4ℓ is described in detail with special attention on contributions to background estimates from objects that are falsely identified as leptons. A novel technique for the interpolation of outputs from large simulations using k-d trees, B-splines and kernel density estimates for the mass measurement in high resolution channels is presented. For the presentation of future results, it is desirable to factor out theoretical uncertainties. A framework for the construction of effective likelihoods free of theoretical uncertainties and for deriving physics results from those is explained in detail. |
