A search is performed for top-quark pairs (tt¯) produced together with a photon (γ) with transverse energy greater than 20 GeV using a sample of tt¯ candidate events in final states with jets, missing trans...
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A search is performed for top-quark pairs (tt¯) produced together with a photon (γ) with transverse energy greater than 20 GeV using a sample of tt¯ candidate events in final states with jets, missing transverse momentum, and one isolated electron or muon. The data set used corresponds to an integrated luminosity of 4.59 fb−1 of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. In total, 140 and 222 tt¯γ candidate events are observed in the electron and muon channels, to be compared to the expectation of 79±26 and 120±39 non-tt¯γ background events, respectively. The production of tt¯γ events is observed with a significance of 5.3 standard deviations away from the null hypothesis. The tt¯γ production cross section times the branching ratio (bR) of the single-lepton decay channel is measured in a fiducial kinematic region within the ATLAS acceptance. The measured value is σtt¯γfid×bR=63±8(stat)−13+17(syst)±1(lumi) fb per lepton flavor, in good agreement with the leading-order theoretical calculation normalized to the next-to-leading-order theoretical prediction of 48±10 fb.
The final ATLAS Run 1 measurements of Higgs boson production and couplings in the decay channel H→ZZ*→ℓ+ℓ−ℓ′+ℓ′−, where ℓ, ℓ′=e or μ, are presented. These measurements were performed using pp collision data corr...
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The final ATLAS Run 1 measurements of Higgs boson production and couplings in the decay channel H→ZZ*→ℓ+ℓ−ℓ′+ℓ′−, where ℓ, ℓ′=e or μ, are presented. These measurements were performed using pp collision data corresponding to integrated luminosities of 4.5 and 20.3 fb−1 at center-of-mass energies of 7 and 8 TeV, respectively, recorded with the ATLAS detector at the LHC. The H→ZZ*→4ℓ signal is observed with a significance of 8.1 standard deviations, with an expectation of 6.2 standard deviations, at mH=125.36 GeV, the combined ATLAS measurement of the Higgs boson mass from the H→γγ and H→ZZ*→4ℓ channels. The production rate relative to the Standard Model expectation, the signal strength, is measured in four different production categories in the H→ZZ*→4ℓ channel. The measured signal strength, at this mass, and with all categories combined, is 1.44−0.33+0.40. The signal strength for Higgs boson production in gluon fusion or in association with tt¯ or bb¯ pairs is found to be 1.7−0.4+0.5, while the signal strength for vector-boson fusion combined with WH/ZH associated production is found to be 0.3−0.9+1.6.
The transverse polarization of Λ and Λ¯ hyperons produced in proton-proton collisions at a center-of-mass energy of 7 TeV is measured. The analysis uses 760 μb−1 of minimum bias data collected by the ATLAS de...
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The transverse polarization of Λ and Λ¯ hyperons produced in proton-proton collisions at a center-of-mass energy of 7 TeV is measured. The analysis uses 760 μb−1 of minimum bias data collected by the ATLAS detector at the LHC in the year 2010. The measured transverse polarization averaged over Feynman xF from 5×10−5 to 0.01 and transverse momentum pT from 0.8 to 15 GeV is −0.010±0.005(stat)±0.004(syst) for Λ and 0.002±0.006(stat)±0.004(syst) for Λ¯. It is also measured as a function of xF and pT, but no significant dependence on these variables is observed. Prior to this measurement, the polarization was measured at fixed-target experiments with center-of-mass energies up to about 40 GeV. The ATLAS results are compatible with the extrapolation of a fit from previous measurements to the xF range covered by this measurement.
We report the observation of Higgs boson decays to WW* based on an excess over background of 6.1 standard deviations in the dilepton final state, where the Standard Model expectation is 5.8 standard deviations. Eviden...
We report the observation of Higgs boson decays to WW* based on an excess over background of 6.1 standard deviations in the dilepton final state, where the Standard Model expectation is 5.8 standard deviations. Evidence for the vector-boson fusion (VbF) production process is obtained with a significance of 3.2 standard deviations. The results are obtained from a data sample corresponding to an integrated luminosity of 25 fb−1 from s=7 and 8 TeV pp collisions recorded by the ATLAS detector at the LHC. For a Higgs boson mass of 125.36 GeV, the ratio of the measured value to the expected value of the total production cross section times branching fraction is 1.09−0.15+0.16(stat)−0.14+0.17(syst). The corresponding ratios for the gluon fusion and vector-boson fusion production mechanisms are 1.02±0.19(stat)−0.18+0.22(syst) and 1.27−0.40+0.44(stat)−0.21+0.30(syst), respectively. At s=8 TeV, the total production cross sections are measured to be σ(gg→H→WW*)=4.6±0.9(stat)−0.7+0.8(syst) pb and σ(VbF H→WW*)=0.51−0.15+0.17(stat)−0.08+0.13(syst) pb. The fiducial cross section is determined for the gluon-fusion process in exclusive final states with zero or one associated jet.
Service-Oriented Architecture (SOA) is now one of the most acknowledged paradigms to design and realize scalable ubiquitous systems. However, the emergence of various versatile service technologies (WS, UPnP, DPWS, OS...
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Recent advances in technology and wireless sensor networks made new trends to emerge in agriculture sector. One such new trend is Precision Agriculture(PA). This paper presents an automatic Irrigation Controller for p...
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A search is presented for dark matter pair production in association with a W or Z boson in pp collisions representing 20.3 fb−1 of integrated luminosity at s=8 TeV using data recorded with the ATLAS detector at the...
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A search is presented for dark matter pair production in association with a W or Z boson in pp collisions representing 20.3 fb−1 of integrated luminosity at s=8 TeV using data recorded with the ATLAS detector at the Large Hadron Collider. Events with a hadronic jet with the jet mass consistent with a W or Z boson, and with large missing transverse momentum are analyzed. The data are consistent with the standard model expectations. Limits are set on the mass scale in effective field theories that describe the interaction of dark matter and standard model particles, and on the cross section of Higgs production and decay to invisible particles. In addition, cross section limits on the anomalous production of W or Z bosons with large missing transverse momentum are set in two fiducial regions.
A search for evidence of invisible-particle decay modes of a Higgs boson produced in association with a Z boson at the Large Hadron Collider is presented. No deviation from the standard model expectation is observed i...
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A search for evidence of invisible-particle decay modes of a Higgs boson produced in association with a Z boson at the Large Hadron Collider is presented. No deviation from the standard model expectation is observed in 4.5 fb−1 (20.3 fb−1) of 7 (8) TeV pp collision data collected by the ATLAS experiment. Assuming the standard model rate for ZH production, an upper limit of 75%, at the 95% confidence level is set on the branching ratio to invisible-particle decay modes of the Higgs boson at a mass of 125.5 GeV. The limit on the branching ratio is also interpreted in terms of an upper limit on the allowed dark matter-nucleon scattering cross section within a Higgs-portal dark matter scenario. Within the constraints of such a scenario, the results presented in this Letter provide the strongest available limits for low-mass dark matter candidates. Limits are also set on an additional neutral Higgs boson, in the mass range 110boson and decaying to invisible particles.
This Letter presents the first study of W±W±jj, same-electric-charge diboson production in association with two jets, using 20.3 fb−1 of proton-proton collision data at s=8 TeV recorded by the ATLAS detect...
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This Letter presents the first study of W±W±jj, same-electric-charge diboson production in association with two jets, using 20.3 fb−1 of proton-proton collision data at s=8 TeV recorded by the ATLAS detector at the Large Hadron Collider. Events with two reconstructed same-charge leptons (e±e±, e±μ±, and μ±μ±) and two or more jets are analyzed. Production cross sections are measured in two fiducial regions, with different sensitivities to the electroweak and strong production mechanisms. First evidence for W±W±jj production and electroweak-only W±W±jj production is observed with a significance of 4.5 and 3.6 standard deviations, respectively. The measured production cross sections are in agreement with standard model predictions. Limits at 95% confidence level are set on anomalous quartic gauge couplings.
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