Engineering topics
Aliyev, M.
Publications and source records attributed to Aliyev, M..
Measurement of the production cross section for Z / γ * in association with jets in p p collisions at s = 7 TeV with the ATLAS detector
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Measurement of the cross section for the production of a W boson in association with b-jets in pp collisions at root s=7 TeV with the ATLAS detector
A measurement is presented of the cross section for the production of a W boson with one or two jets, of which at least one must be a b-jet, in pp collisions at {radical}s = 7 TeV. Production via top decay is not included in the signal definition. The measurement is based on 35 pb{sup -1} of data collected with the ATLAS detector at the LHC. The W + b-jet cross section is defined for jets reconstructed with the anti-kt clustering algorithm with transverse momentum above 25 GeV and rapidity within {+-}2.1. The b-jets are identified by reconstructing secondary vertices. The fiducial cross section is measured both for the electron and muon decay channel of the W boson and is found to be 10.2 {+-} 1.9(stat) {+-} 2.6(syst) pb for one lepton flavour. The results are compared with next-to-leading order QCD calculations, which predict a cross section smaller than, though consistent with, the measured value.
Measurements of the electron and muon inclusive cross-sections in proton-proton collisions at root s=7 TeV with the ATLAS detector
This Letter presents measurements of the differential cross-sections for inclusive electron and muon production in proton-proton collisions at a centre-of-mass energy of {radical}s = 7 TeV, using data collected by the ATLAS detector at the LHC. The muon cross-section is measured as a function of pT in the range 4 < pT < 100 GeV and within pseudorapidity |{eta}| < 2.5. In addition the electron and muon cross-sections are measured in the range 7 < pT < 26 GeV and within |{eta}| < 2.0, excluding 1.37 < |{eta}| < 1.52. Integrated luminosities of 1.3 pb{sup -1} and 1.4 pb{sup -1} are used for the electron and muon measurements, respectively. After subtraction of the W/Z/{gamma}{sm_bullet} contribution, the differential cross-sections are found to be in good agreement with theoretical predictions for heavy-flavour production obtained from Fixed Order NLO calculations with NLL high-pT resummation, and to be sensitive to the effects of NLL resummation.
Measurement of the top quark pair production cross section in pp collisions at root s=7 TeV in dilepton final states with ATLAS
A measurement of the production cross section of top quark pairs (t{bar t}) in proton-proton collisions at a center-of-mass energy of 7 TeV recorded with the ATLAS detector at the Large Hadron Collider is reported. Candidate events are selected in the dilepton topology with large missing transverse energy and at least two jets. Using a data sample corresponding to an integrated luminosity of 35 pb{sup -1}, a t{bar t} production cross section {sigma}{sub t{bar t}} = 177 {+-} 20(stat.) {+-} 14(syst.) {+-} 7(lum.) pb is measured for an assumed top quark mass of mt = 172.5 GeV. A second measurement requiring at least one jet identified as coming from a b quark yields a comparable result, demonstrating that the dilepton final states are consistent with being accompanied by b-quark jets. These measurements are in good agreement with Standard Model predictions.
Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS
We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb{sup -1} collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.
Search for new physics in the dijet mass distribution using 1 fb⁻¹ of pp collision data at √s = 7 TeV collected by the ATLAS detector
Invariant mass distributions of jet pairs (dijets) produced in LHC proton–proton collisions at a centre-of-mass energy √s = 7 TeV have been studied using a data set corresponding to an integrated luminosity of 1.0 fb⁻¹ recorded in 2011 by ATLAS. Dijet masses up to ~4 TeV are observed in the data, and no evidence of resonance production over background is found. Limits are set at 95% C.L. for several new physics hypotheses: excited quarks are excluded for masses below 299 TeV, axigluons are excluded for masses below 3.32 TeV, and colour octet scalar resonances are excluded for masses below 1.92 TeV.
A measurement of the ratio of the W and Z cross sections with exactly one associated jet in pp collisions at s = 7 TeV with ATLAS
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Search for New Phenomena in tt¯ Events with Large Missing Transverse Momentum in Proton-Proton Collisions at √s=7 TeV with the ATLAS Detector
A search for new phenomena in tt¯ events with large missing transverse momentum in proton-proton collisions at a center-of-mass energy of 7 TeV is presented. The measurement is based on 1.04 fb⁻¹ of data collected with the ATLAS detector at the LHC. Contributions to this final state may arise from a number of standard model extensions. The results are interpreted in terms of a model where new top-quark partners are pair produced and each decay to an on-shell top (or antitop) quark and a long-lived undetected neutral particle. The data are found to be consistent with standard model expectations. A limit at 95% confidence level is set excluding a cross section times branching ratio of 1.1 pb for a top-partner mass of 420 GeV and a neutral particle mass less than 10 GeV. In a model of exotic fourth generation quarks, top-partner masses are excluded up to 420 GeV and neutral particle masses up to 140 GeV.
Measurement of the Z Z Production Cross Section and Limits on Anomalous Neutral Triple Gauge Couplings in Proton-Proton Collisions at s = 7 TeV with the ATLAS Detector
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Measurement of the transverse momentum distribution of W bosons in p p collisions at s = 7 TeV with the ATLAS detector
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Search for supersymmetry in final states with jets, missing transverse momentum and one isolated lepton in s = 7 TeV pp collisions using 1 fb − 1 of ATLAS data
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Measurement of the isolated diphoton cross section in p p collisions at s = 7 TeV with the ATLAS detector
Here, the ATLAS experiment has measured the production cross section of events with two isolated photons in the final state, in proton-proton collisions at √s = 7 TeV. The full data set acquired in 2010 is used, corresponding to an integrated luminosity of 37 pb –1 . The background, consisting of hadronic jets and isolated electrons, is estimated with fully data-driven techniques and subtracted. The differential cross sections, as functions of the di-photon mass (m γγ ), total transverse momentum (pT, γγ ), and azimuthal separation (ΔΦ γγ ), are presented and compared to the predictions of next-to-leading-order QCD.
Search for a heavy Standard Model Higgs boson in the channel H → Z Z → ℓ ⁺ ℓ ⁻ q q ¯ using the ATLAS detector
A search for a heavy Standard Model Higgs boson decaying via H → ZZ → ℓ⁺ℓ⁻qq¯, where ℓ = e,μ, is presented. The search is performed using a data set of pp collisions at √s = 7 TeV, corresponding to an integrated luminosity of 1.04 fb⁻¹ collected in 2011 by the ATLAS detector at the CERN LHC collider. No significant excess of events above the estimated background is found. Upper limits at 95% confidence level on the production cross section (relative to that expected from the Standard Model) of a Higgs boson with a mass in the range between 200 and 600 GeV are derived. Within this mass range, there is at present insufficient sensitivity to exclude a Standard Model Higgs boson. For a Higgs boson with a mass of 360 GeV, where the sensitivity is maximal, the observed and expected cross section upper limits are factors of 1.7 and 2.7, respectively, larger than the Standard Model prediction.
Measurement of the W → τ ν τ cross section in pp collisions at s = 7 TeV with the ATLAS experiment
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Measurement of the cross-section for b-jets produced in association with a Z boson at s = 7 TeV with the ATLAS detector
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Search for Dilepton Resonances in pp Collisions at {radical}(s)=7 TeV with the ATLAS Detector
This Letter reports on a search for narrow high-mass resonances decaying into dilepton final states. The data were recorded by the ATLAS experiment in pp collisions at {radical}(s)=7 TeV at the Large Hadron Collider and correspond to a total integrated luminosity of 1.08 (1.21) fb{sup -1} in the e{sup +}e{sup -} ({mu}{sup +}{mu}{sup -}) channel. No statistically significant excess above the standard model expectation is observed and upper limits are set at the 95% C.L. on the cross section times branching fraction of Z{sup '} resonances and Randall-Sundrum gravitons decaying into dileptons as a function of the resonance mass. A lower mass limit of 1.83 TeV on the sequential standard model Z{sup '} boson is set. A Randall-Sundrum graviton with coupling k/M{sub Pl}=0.1 is excluded at 95% C.L. for masses below 1.63 TeV.