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Aliyev, M.

Publications and source records attributed to Aliyev, M..

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Properties of jets measured from tracks in proton-proton collisions at center-of-mass energy √s=7 TeV with the ATLAS detector

Jets are identified and their properties studied in center-of-mass energy √s=7 TeV proton-proton collisions at the Large Hadron Collider using charged particles measured by the ATLAS inner detector. Events are selected using a minimum bias trigger, allowing jets at very low transverse momentum to be observed and their characteristics in the transition to high-momentum fully perturbative jets to be studied. Jets are reconstructed using the anti-k t algorithm applied to charged particles with two radius parameter choices, 0.4 and 0.6. An inclusive charged jet transverse momentum cross section measurement from 4 GeV to 100 GeV is shown for four ranges in rapidity extending to 1.9 and corrected to charged particle-level truth jets. The transverse momenta and longitudinal momentum fractions of charged particles within jets are measured, along with the charged particle multiplicity and the particle density as a function of radial distance from the jet axis. Comparison of the data with the theoretical models implemented in existing tunings of Monte Carlo event generators indicates reasonable overall agreement between data and Monte Carlo. These comparisons are sensitive to Monte Carlo parton showering, hadronization, and soft physics models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Limits on the production of the standard model Higgs boson in pp collisions at $\sqrt{s} = 7$ TeV with the ATLAS detector

A search for the Standard Model Higgs boson at the Large Hadron Collider (LHC) running at a centre-of-mass energy of 7 TeV is reported, based on a total integrated luminosity of up to 40 pb -1 collected by the ATLAS detector in 2010. Several Higgs boson decay channels: H→γγ, H→ZZ (*) →ℓℓℓℓ, H→ZZ→ℓℓνν, H→ZZ→ℓℓqq, H→WW (*) →ℓνℓν and H→WW→ℓνqq (ℓ is e, μ) are combined in a mass range from 110 GeV to 600 GeV. The highest sensitivity is achieved in the mass range between 160 GeV and 170 GeV, where the expected 95% CL exclusion sensitivity is at Higgs boson production cross sections 2.3 times the Standard Model prediction. Upper limits on the cross section for its production are determined. Models with a fourth generation of heavy leptons and quarks with Standard Model-like couplings to the Higgs boson are also investigated and are excluded at 95% CL for a Higgs boson mass in the range from 140 GeV to 185 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Measurement of Wγ and Zγ production in proton-proton collisions at $ \sqrt {s} = 7 $ TeV with the ATLAS detector

We present studies of W and Z bosons with associated high energy photons produced in pp collisions at √s = 7TeV. The analysis uses 35 pb -1 of data collected by the ATLAS experiment in 2010. The event selection requires W and Z bosons decaying into high p T leptons (electrons or muons) and a photon with E T > 15 GeV separated from the lepton(s) by a distance ΔR(l,γ) > 0.7 in η-Φ space. A total of 95 (97) pp → e ± νγ + X(pp → μ ± νγ + X) and 25 (23) pp → e + e - γ + X(pp → μ + μ - γ+X) event candidates are selected. The kinematic distributions of the leptons and photons and the production cross sections are measured. The data are found to agree with Standard Model predictions that include next-to-leading-order O(αα s ) contributions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Measurement of dijet production with a veto on additional central jet activity in pp collisions at $ \sqrt {s} = 7 $ TeV using the ATLAS detector

A measurement of jet activity in the rapidity interval bounded by a dijet system is presented. Events are vetoed if a jet with transverse momentum greater than 20 GeV is found between the two boundary jets. The fraction of dijet events that survive the jet veto is presented for boundary jets that are separated by up to six units of rapidity and with mean transverse momentum 50 < p¯ T < 500 GeV. The mean multiplicity of jets above the veto scale in the rapidity interval bounded by the dijet system is also presented as an alternative method for quantifying perturbative QCD emission. The data are compared to a next-to-leading order plus parton shower prediction from the powheg-box, an all-order resummation using the hej calculation and the pythia, herwig++ and alpgen event generators. In conclusion, the measurement was performed using pp collisions at √s = 7 TeV using data recorded by the ATLAS detector in 2010.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Measurement of the W⁺W⁻ Cross Section in √s=7 TeV pp Collisions with ATLAS

This Letter presents a measurement of the W⁺W⁻ production cross section in √s=7 TeV pp collisions by the ATLAS experiment, using 34 pb⁻¹ of integrated luminosity produced by the Large Hadron Collider at CERN. Selecting events with two isolated leptons, each either an electron or a muon, 8 candidate events are observed with an expected background of 1.7±0.6 events. The measured cross section is 41 +20 -16 (stat)±5(syst)±1(lumi) pb, which is consistent with the standard model prediction of 44±3 pb calculated at next-to-leading order in QCD.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Search for an excess of events with an identical flavour lepton pair and significant missing transverse momentum in $\sqrt{s}=7$ TeV proton–proton collisions with the ATLAS detector

Results are presented of a search for supersymmetric particles decaying into final states with significant missing transverse momentum and exactly two identical flavour leptons (e, μ) of opposite charge in √s = 7 TeV collisions at the Large Hadron Collider. This channel is particularly sensitive to supersymmetric particle cascade decays producing flavour correlated lepton pairs. Flavour uncorrelated backgrounds are subtracted using a sample of opposite flavour lepton pair events. Observation of an excess beyond Standard Model expectations following this subtraction procedure would offer one of the best routes to measuring the masses of supersymmetric particles. In a data sample corresponding to an integrated luminosity of 35 pb⁻¹ no such excess is observed. Model-independent limits are set on the contribution to these final states from new physics and are used to exclude regions of a phenomenological supersymmetric parameter space.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Search for supersymmetric particles in events with lepton pairs and large missing transverse momentum in $\sqrt{s}=7~\mbox{TeV}$ proton–proton collisions with the ATLAS experiment

Results are presented of searches for the production of supersymmetric particles decaying into final states with missing transverse momentum and exactly two isolated leptons in √s = 7 TeV proton-proton collisions at the Large Hadron Collider. Search strategies requiring lepton pairs with identical-sign or opposite-sign electric charges are described. In a data sample corresponding to an integrated luminosity of 35 pb -1 collected with the ATLAS detector, no significant excesses are observed. Based on specific benchmark models, limits are placed on the squark mass between 450 and 690 GeV for squarks approximately degenerate in mass with gluinos, depending on the supersymmetric mass hierarchy considered.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Search for contact interactions in dimuon events from pp collisions at &radic;s=7 TeV with the ATLAS detector

A search for contact interactions has been performed using dimuon events recorded with the ATLAS detector in proton-proton collisions at √s=7 TeV. The data sample corresponds to an integrated luminosity of 42 pb⁻¹. No significant deviation from the standard model is observed in the dimuon mass spectrum, allowing the following 95% C.L. limits to be set on the energy scale of contact interactions: Λ>4.9 TeV (4.5 TeV) for constructive (destructive) interference in the left-left isoscalar compositeness model. These limits are the most stringent to date for μμqq contact interactions.

Aad, G.↗
DOE OSTI2011

Search for pair production of first or second generation leptoquarks in proton-proton collisions at √s=7 TeV using the ATLAS detector at the LHC

This paper describes searches for the pair production of first or second generation scalar leptoquarks using 35 pb⁻¹ of proton-proton collision data recorded by the ATLAS detector at s√=7 TeV. Leptoquarks are searched in events with two oppositely-charged muons or electrons and at least two jets, and in events with one muon or electron, missing transverse momentum and at least two jets. After event selection, the observed yields are consistent with the predicted backgrounds. Leptoquark production is excluded at the 95% CL for masses M LQ <376 (319) GeV and M LQ <422 (362) GeV for first and second generation scalar leptoquarks, respectively, when assuming the branching fraction of a leptoquark to a charged lepton is equal to 1.0 (0.5).

Aad, G.↗
DOE OSTI2011

Measurement of underlying event characteristics using charged particles in pp collisions at {radical}(s)=900 GeV and 7 TeV with the ATLAS detector

Measurements of charged particle distributions, sensitive to the underlying event, have been performed with the ATLAS detector at the LHC. The measurements are based on data collected using a minimum-bias trigger to select proton-proton collisions at center-of-mass energies of 900 GeV and 7 TeV. The 'underlying event' is defined as those aspects of a hadronic interaction attributed not to the hard scattering process, but rather to the accompanying interactions of the rest of the proton. Three regions are defined in azimuthal angle with respect to the highest transverse momentum charged particle in the event, such that the region transverse to the dominant momentum-flow is most sensitive to the underlying event. In each of these regions, distributions of the charged particle multiplicity, transverse momentum density, and average p{sub T} are measured. The data show generally higher underlying event activity than that predicted by Monte Carlo models tuned to pre-LHC data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

A search for new physics in dijet mass and angular distributions in pp collisions at $\sqrt{s}$=7 TeV measured with the ATLAS detector

A search for new interactions and resonances produced in LHC proton-proton ( pp ) collisions at a centre-of-mass energy $\sqrt{s}$= 7 TeV has been performed with the ATLAS detector. Using a data set with an integrated luminosity of 36 pb -1 dijet mass and angular distributions have been measured up to dijet masses of ~3.5 TeV and found to be in good agreement with Standard Model predictions. This analysis sets limits at 95% C.L. on various models for new physics: an excited quark is excluded with mass between 0.60 and 2.64 TeV, an axigluon hypothesis is excluded for axigluon masses between 0.60 and 2.10 TeV and Randall-Meade quantum black holes are excluded in models with six extra space-time dimensions for quantum gravity scales between 0.75 and 3.67 TeV. Production cross section limits as a function of dijet mass are set using a simplified Gaussian signal model to facilitate comparisons with other hypotheses. In conclusion, analysis of the dijet angular distribution using a novel technique 18 simultaneously employing the dijet mass excludes quark contact interactions with a compositeness scale ${\Lambda}$ below 9.5 TeV.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗