395 research outputs found
Muon detector description as built and its simulation for the ATLAS experiment
No full textThe ATLAS detector is designed to exploit the full potential of the LHC, identifying and providing highly accurate energy and momentum measurements of particles emerging from the LHC proton–proton collisions. High-momentum final-state muons are among the most promising signatures at the LHC, thanks to a high-resolution Muon Spectrometer with standalone triggering and momentum measurement. The Muon Spectrometer is a large and complex system of gaseous detectors, requiring a detailed simulation to exploit its full capabilities. Over the last few years these systems have been described in terms of a set of geometrical primitives known as GeoModel. This description is now used in the GEANT4-based simulation program, which is fully operational and integrated into the ATLAS common analysis framework
Search for Pair Production of a New b′ Quark that Decays into a Z Boson and a Bottom Quark with the ATLAS Detector
No full textA search is reported for the pair production of a new quark b′ with at least one b′ decaying to a Z boson and a bottom quark. The data, corresponding to 2.0 fb[superscript -1] of integrated luminosity, were collected from pp collisions at √s=7 TeV with the ATLAS detector at the CERN Large Hadron Collider. Using events with a b-tagged jet and a Z boson reconstructed from opposite-charge electrons, the mass distribution of large transverse momentum b′ candidates is tested for an enhancement. No evidence for a b′ signal is detected in the observed mass distribution, resulting in the exclusion at a 95% confidence level of b′ quarks with masses m[subscript b′]<400 GeV that decay entirely via b′→Z+b. In the case of a vectorlike singlet b′ mixing solely with the third standard model generation, masses m[subscript b′]<358 GeV are excluded
Search for Pair Production of a Heavy Up-Type Quark Decaying to a W Boson and a b Quark in the lepton+jets Channel with the ATLAS Detector
No full textA search is presented for production of a heavy up-type quark (t′) together with its antiparticle, assuming subsequent decay to a W boson and a b quark, t′t̅ ′-->W[superscript+]bW[superscript -]b̅ . The search is based on 1.04 fb-1 of proton-proton collisions at √s=7 TeV collected by the ATLAS detector at the CERN Large Hadron Collider. Data are analyzed in the lepton+jets final state, characterized by a high transverse momentum isolated electron or muon, high missing transverse momentum, and at least three jets. No significant excess of events above the background expectation is observed. A 95% C.L. lower limit of 404 GeV is set for the mass of the t′ quark.United States. Dept. of Energy.National Science Foundation (U.S.)
Search for a heavy gauge boson decaying to a charged lepton and a neutrino in 1 fb(-1) of pp collisions at root s=7 TeV using the ATLAS detector
No full textThe ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge bosons (<i>W</i>′), decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 1.04 fb<sup>−1</sup>. No excess above Standard Model expectations is observed. A <i>W</i> with Sequential Standard Model couplings is excluded at the 95% confidence level for masses up to 2.15 TeV
Search for a Heavy Particle Decaying into an Electron and a Muon with the ATLAS Detector in √s=7 TeV pp collisions at the LHC
No full textThis Letter presents the first search for a heavy particle decaying into an e[superscript ±]μ[superscript ∓] final state in √s=7 TeV pp collisions at the LHC. The data were recorded by the ATLAS detector during 2010 and correspond to a total integrated luminosity of 35 pb[superscript -1]. No excess above the standard model background expectation is observed. Exclusions at 95% confidence level are placed on two representative models. In an R-parity violating supersymmetric model, tau sneutrinos with a mass below 0.75 TeV are excluded, assuming all R-parity violating couplings are zero except λ[subscript 311][superscript ′]=0.11 and λ[subscript 312]=0.07. In a lepton flavor violating model, a Z[superscript ′]-like vector boson with masses of 0.70–1.00 TeV and corresponding cross sections times branching ratios of 0.175–0.183 pb is excluded. These results extend to higher mass R-parity violating sneutrinos and lepton flavor violating Z’s than previous constraints from the Tevatron
Search for a fermiophobic Higgs boson in the diphoton decay channel with the ATLAS detector
No full textA search for a fermiophobic Higgs boson using diphoton events produced in proton-proton collisions at a centre-of-mass energy of s=7 TeV is performed using data corresponding to an integrated luminosity of 4.9 fb−1 collected by the ATLAS experiment at the Large Hadron Collider. A specific benchmark model is considered where all the fermion couplings to the Higgs boson are set to zero and the bosonic couplings are kept at the Standard Model values (fermiophobic Higgs model). The largest excess with respect to the background-only hypothesis is found at 125.5 GeV, with a local significance of 2.9 standard deviations, which reduces to 1.6 standard deviations when taking into account the look-elsewhere effect. The data exclude the fermiophobic Higgs model in the ranges 110.0–118.0 GeV and 119.5–121.0 GeV at 95 % confidence level
A search for flavour changing neutral currents in top-quark decays in pp collision data collected with the ATLAS detector at √<span style="text-decoration:overline">s</span>=7 TeV
No full textContains fulltext :
103521.pdf (Publisher’s version ) (Open Access
Search for a heavy neutral particle decaying into an electron and a muon using 1 fb−1 of ATLAS data
No full textA search is presented for a high mass neutral particle that decays directly to the e ± μ ∓ final state. The data sample was recorded by the ATLAS detector in √s=7 TeV pp collisions at the LHC from March to June 2011 and corresponds to an integrated luminosity of 1.07 fb−1. The data are found to be consistent with the Standard Model background. The high e ± μ ∓ mass region is used to set 95% confidence level upper limits on the production of two possible new physics processes: tau sneutrinos in an R-parity violating supersymmetric model and Z′-like vector bosons in a lepton flavor violating model
Sag Compensation System for Assembly of MDT-Chambers for the ATLAS Experiment
No full textThe description of a system of the devices created for compensation of the gravitational deflection of the drift chamber during its assembly is presented. By means of this system during stage-by-stage gluing of layers of tube drift detectors to the chamber the transversal deflection considerably decreases and by that high accuracy of mutual position of separate tubes is provided. The devices were applied at assembly of 74 MDT-chambers of the ATLAS experiment. Design values of deformation of the chambers as well as the results of measurement of transversal deflections obtained during the assembly with the use of the system of sag compensation are given. Testing of chambers on the X-ray tomograph at CERN has shown that the accuracy of the positions of separate signal wires inside the assembled chambers is within the limits of the required 20 m
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