A search for the Standard Model Higgs boson in proton–proton collisions with the ATLAS detector at the LHC is presented. The datasets used correspond to integrated luminosities of approximately 4.8 fb−1 collected at √s=7 TeV in 2011 and 5.8 fb−1 at √s=8 TeV in 2012. Individual searches in the channels H→ZZ(⁎)→4ℓ, H→γγ and H→WW(⁎)→eνμν in the 8 TeV data are combined with previously published results of searches for H→ZZ(⁎), WW(⁎), bb and τ+τ− in the 7 TeV data and results from improved analyses of the H→ZZ(⁎)→4ℓ and H→γγ channels in the 7 TeV data. Clear evidence for the production of a neutral boson with a measured mass of 126.0±0.4(stat)±0.4(sys) GeV is presented. This observation, which has a significance of 5.9 standard deviations, corresponding to a background fluctuation probability of 1.7×10−9, is compatible with the production and decay of the Standard Model Higgs boson

The simulation software for the ATLAS Experiment at the Large Hadron Collider is being used for largescale production of events on the LHC Computing Grid. This simulation requires many components, from the generators that simulate particle collisions, through packages simulating the response of the various detectors and triggers. All of these components come together under the AT-LAS simulation infrastructure. In this paper, that infrastructure is discussed, including that supporting the detector description, interfacing the event generation, and combining the GEANT4 simulation of the response of the individual detectors. Also described are the tools allowing the software validation, performance testing, and the validation of the simulated output against known physics processes.

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IntroductionThe discovery of a new particle of mass about 125 GeV in the search for the Standard Model This Letter presents measurements of several properties of the newly observed particle, including its mass, production strengths and couplings to fermions and bosons, using diboson final states 1 : Monte Carlo (MC) samples used to model signal and background processes. The analyses of the three decay channels are presented in Sections 4-6. Measurements of the Higgs boson mass, production properties and couplings are discussed in Section 7. Section 8 is devoted to the conclusions. Data sample and event reconstructionAfter data quality requirements, the integrated luminosities of the samples used for the studies reported here are about 4.7 fb −1 in 2011 and 20.7 fb −1 in 2012, with uncertainties given in Table 1 (determined as described in Ref. [13]). Because of the high LHC peak luminosity (up to 7.7 × 10 33 cm −2 s −1 in 2012) and the 50 ns bunch spacing, the number of proton-proton interactions occurring in the same bunch crossing is large (on average 20.7, up to about 40). This "pile-up" of events requires the use of dedicated algorithms and corrections to mitigate its impact on the reconstruction of e.g. leptons, photons and jets. 0370-2693/