Measurement of the production cross section of prompt J/ψ mesons in association with a W ± boson in pp collisions at √s = 7 TeV with the ATLAS detector

The process pp → W ± J/ψ provides a powerful probe of the production mechanism of charmonium in hadronic collisions, and is also sensitive to multiple parton interactions in the colliding protons. Using the 2011 ATLAS dataset of 4.5 fb−1 of s√ = 7 TeV pp collisions at the LHC, the first observation is made of the production of W ± + prompt J/ψ events in hadronic collisions, using W ± → μν μ and J/ψ → μ + μ −. A yield of 27.4+7.5−6.5 W ± + prompt J/ψ events is observed, with a statistical significance of 5.1σ. The production rate as a ratio to the inclusive W ± boson production rate is measured, and the double parton scattering contribution to the cross section is estimate

Search for a Standard Model Higgs boson in the mass range 200-600GeV in the H→ZZ→ℓ+ℓqq̄ decay channel with the ATLAS detector

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Search for Direct Top Squark Pair Production in Final States with One Isolated Lepton, Jets, and Missing Transverse Momentum in s = 7 TeV p p Collisions Using 4.7 fb − 1 of ATLAS Data

A search is presented for direct top squark pair production in final states with one isolated electron or muon, jets, and missing transverse momentum in proton-proton collisions at root s = 7 TeV. ..

Search for a standard model Higgs boson in the H→ZZ→ ℓ+ ℓ−ν ̄ν decay channelusing 4.7fb−1of√s=7 TeV data with the ATLAS detector

A search for a Standard Model Higgs boson decaying via H→ZZ→ ℓ+ ℓ−ν ̄ν, where ℓ represents electrons or muons, is presented. It is based on proton-proton collision data at √s=7 TeV, collected by the ATLAS experiment at the LHC during 2011 and corresponding to an integrated luminosity of 4.7fb−1. The data agree with the expected Standard Model backgrounds. Upper limits on the Higgs boson production crosssection are derived for Higgs boson masses between 200 GeV and 600 GeV and the production of a Standard Model Higgs boson with a mass in the range 319–558 GeV is excluded at the 95% confidence leve

Study of jet shapes in inclusive jet production in pppp collisions at =7\sqrt{}=7 TeVTeV using the ATLAS detector

Jet shapes have been measured in inclusive jet production in proton-proton collisions at $\sqrt{}=7$  $TeV$ using $3  pb^{−1}$ of data recorded by the ATLAS experiment at the LHC. Jets are reconstructed using the anti-$k_t$ algorithm with transverse momentum $30  GeV<<600  GeV$ and rapidity in the region $|y|<2.8$. The data are corrected for detector effects and compared to several leading-order QCD matrix elements plus parton shower Monte Carlo predictions, including different sets of parameters tuned to model fragmentation processes and underlying event contributions in the final state. The measured jets become narrower with increasing jet transverse momentum and the jet shapes present a moderate jet rapidity dependence. Within QCD, the data test a variety of perturbative and nonperturbative effects. In particular, the data show sensitivity to the details of the parton shower, fragmentation, and underlying event models in the Monte Carlo generators. For an appropriate choice of the parameters used in these models, the data are well described