Explore the vast range of titles available.

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) The luminosity calibration for the ATLAS detector at the LHC during pp collisions at ... in 2010 and 2011 is presented. Evaluation of the luminosity scale is performed using several luminosity-sensitive detectors, and comparisons are made of the long-term stability and accuracy of this calibration applied to the pp collisions at ... A luminosity uncertainty of ... is obtained for the 47 pb^sup -1^ of data delivered to ATLAS in 2010, and an uncertainty of ... is obtained for the 5.5 fb^sup -1^ delivered in 2011.

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of ... corresponding to an integrated luminosity of 38 pb^sup -1^. Jets are reconstructed with the anti-k ^sub t^ algorithm with distance parameters R=0.4 or R=0.6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta p ^sub T^[greater than or equal to]20 GeV and pseudorapidities |[eta]|<4.5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2.5 % in the central calorimeter region (|[eta]|<0.8) for jets with 60[less than or equal to]p ^sub T^<800 GeV, and is maximally 14 % for p ^sub T^<30 GeV in the most forward region 3.2[less than or equal to]|[eta]|<4.5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon p ^sub T^, the sum of the transverse momenta of tracks associated to the jet, or a system of low-p ^sub T^ jets recoiling against a high-p ^sub T^ jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-p ^sub T^ jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined.

Detailed measurements of the electron performance of the ATLAS detector at the LHC are reported, using decays of the Z , W and J / ψ particles. Data collected in 2010 at are used, corresponding to an integrated luminosity of almost 40 pb −1 . The inter-alignment of the inner detector and the electromagnetic calorimeter, the determination of the electron energy scale and resolution, and the performance in terms of response uniformity and linearity are discussed. The electron identification, reconstruction and trigger efficiencies, as well as the charge misidentification probability, are also presented.

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) The measurement of the jet energy resolution is presented using data recorded with the ATLAS detector in proton-proton collisions at ... The sample corresponds to an integrated luminosity of 35 pb^sup -1^. Jets are reconstructed from energy deposits measured by the calorimeters and calibrated using different jet calibration schemes. The jet energy resolution is measured with two different in situ methods which are found to be in agreement within uncertainties. The total uncertainties on these measurements range from 20 % to 10 % for jets within |y|<2.8 and with transverse momenta increasing from 30 GeV to 500 GeV. Overall, the Monte Carlo simulation of the jet energy resolution agrees with the data within 10 %.

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) The inclusive jet cross-section has been measured in proton-proton collisions at ... in a dataset corresponding to an integrated luminosity of ... collected with the ATLAS detector at the Large Hadron Collider in 2011. Jets are identified using the anti-k ^sub t^ algorithm with two radius parameters of 0.4 and 0.6. The inclusive jet double-differential cross-section is presented as a function of the jet transverse momentum p ^sub T^ and jet rapidity y, covering a range of 20[less than or equal to]p ^sub T^<430 GeV and |y|<4.4. The ratio of the cross-section to the inclusive jet cross-section measurement at ..., published by the ATLAS Collaboration, is calculated as a function of both transverse momentum and the dimensionless quantity ..., in bins of jet rapidity. The systematic uncertainties on the ratios are significantly reduced due to the cancellation of correlated uncertainties in the two measurements. Results are compared to the prediction from next-to-leading order perturbative QCD calculations corrected for non-perturbative effects, and next-to-leading order Monte Carlo simulation. Furthermore, the ATLAS jet cross-section measurements at ... and ... are analysed within a framework of next-to-leading order perturbative QCD calculations to determine parton distribution functions of the proton, taking into account the correlations between the measurements.

A bstract A search for new phenomena in events with a high-energy jet and large missing transverse momentum is performed using data from proton-proton collisions at TeV with the ATLAS experiment at the Large Hadron Collider. Four kinematic regions are explored using a dataset corresponding to an integrated luminosity of 4.7 fb −1 . No excess of events beyond expectations from Standard Model processes is observed, and limits are set on large extra dimensions and the pair production of dark matter particles.

A search for doubly charged Higgs bosons decaying to pairs of electrons and/or muons is presented. The search is performed using a data sample corresponding to an integrated luminosity of 4.7 fb −1 of pp collisions at √s = 7 TeV collected by the ATLAS detector at the LHC. Pairs of prompt, isolated, high-pT leptons with the same electric charge (e ± e ± , e ± μ ± , μ ± μ ± ) are selected, and their invariant mass distribution is searched for a narrow resonance. No significant excess over Standard Model background expectations is observed, and limits are placed on the cross section times branching ratio for pair production of doubly charged Higgs bosons. The masses of doubly charged Higgs bosons are constrained depending on the branching ratio into these leptonic final states. Assuming pair production, coupling to left-handed fermions, and a branching ratio of 100% for each final state, masses below 409 GeV, 375 GeV, and 398 GeV are excluded for e ± e ± , e ± μ ± , and μ ± μ ± , respectively.

A measurement of the production cross-section for top quark pairs ( bar{t} ) in pp collisions at s=7 TeV is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in two different topologies: single lepton (electron e or muon mu ) with large missing transverse energy and at least four jets, and dilepton (ee, mu mu or e mu ) with large missing transverse energy and at least two jets. In a data sample of 2.9 pb super(-1), 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding expected backgrounds from non- t Standard Model processes are estimated using data-driven methods and determined to be 12.2 plus or minus 3.9 events and 2.5 plus or minus 0.6 events, respectively. The kinematic properties of the selected events are consistent with SM t production. The inclusive top quark pair production cross-section is measured to be sigma_t=145\\pm31. The measurement agrees with perturbative QCD calculations.

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Abstract Mass and angular distributions of dijets produced in LHC proton-proton collisions at a centre-of-mass energy ...TeV have been studied with the ATLAS detector using the full 2011 data set with an integrated luminosity of 4.8 fb^sup -1^. Dijet masses up to ~ 4.0 TeV have been probed. No resonance-like features have been observed in the dijet mass spectrum, and all angular distributions are consistent with the predictions of QCD. Exclusion limits on six hypotheses of new phenomena have been set at 95% CL in terms of mass or energy scale, as appropriate. These hypotheses include excited quarks below 2.83 TeV, colour octet scalars below 1.86 TeV, heavy W bosons below 1.68 TeV, string resonances below 3.61 TeV, quantum black holes with six extra space-time dimensions for quantum gravity scales below 4.11 TeV, and quark contact interactions below a compositeness scale of 7.6 TeV in a destructive interference scenario.[Figure not available: see fulltext.]

The dependence of the rate of proton–proton interactions on the centre-of-mass collision energy, √ s , is of fundamental importance for both hadron collider physics and particle astrophysics. The dependence cannot yet be calculated from first principles; therefore, experimental measurements are needed. Here we present the first measurement of the inelastic proton–proton interaction cross-section at a centre-of-mass energy, √ s , of 7 TeV using the ATLAS detector at the Large Hadron Collider. Events are selected by requiring hits on scintillation counters mounted in the forward region of the detector. An inelastic cross-section of 60.3±2.1 mb is measured for ξ>5×10 −6 , where ξ is calculated from the invariant mass, M X , of hadrons selected using the largest rapidity gap in the event. For diffractive events, this corresponds to requiring at least one of the dissociation masses to be larger than 15.7 GeV. The measurement of the total cross-section of proton–proton collisions is of fundamental importance for particle physics. Here, the first measurement of the inelastic cross-section is presented for proton–proton collisions at an energy of 7 teraelectronvolts using the ATLAS detector at the Large Hadron Collider.