C. Topfel

Measurement of the cross section for the production of a W boson in association with b-jets in pp collisions at View the MathML source with the ATLAS detector

A measurement is presented of the cross section for the produ cti n of aW boson with one or two jets, of which at least one must be a b-jet, in pp collisions at √ s = 7 TeV. Production via top decay is not included in the signal definition. The measurement is based on 35 pb −1of 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. Theb-jets are identified by reconstructing secondary vertices. The fiducial cross section is measured both for the electron and muon decay chan nel of theW 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 wit h, the measured value.

Measurement of the cross-section for b-jets produced in association with a Z boson at View the MathML source with the ATLAS detector

A measurement is presented of the inclusive cross-section f or b-jet production in association with a Z boson inpp collisions at a centre-of-mass energy of √ s = 7 TeV. The analysis uses the data sample collected by the ATLA S experiment in 2010, corresponding to an integrated luminosity of approximately 36 pb −1. The event selection requires a Z boson decaying into highpT electrons or muons, and at least one b-jet, identified by its displaced vertex, with transverse mo mentumpT > 25 GeV and rapidity|y| < 2.1. After subtraction of background processes, the yield is ext racted from the vertex mass distribution of the candidate b-jets. The ratio of this cross-section to the inclusive Z cross-section (the average number of b-jets perZ event) is also measured. Both results are found to be in good agreement with perturbative QCD predicti ons at next-to-leading order.

Measurement of the W±Z production cross section and limits on anomalous triple gauge couplings in proton–proton collisions at View the MathML source with the ATLAS detector

This Letter presents a measurement of W(+/-)Z production in 1.02 fb(-1) of pp collision data at root s = 7 TeV collected by the ATLAS experiment in 2011. Doubly leptonic decay events are selected w ...This Letter presents a measurement of W(+/-)Z production in 1.02 fb(-1) of pp collision data at root s = 7 TeV collected by the ATLAS experiment in 2011. Doubly leptonic decay events are selected w ...

Search for long-lived, heavy particles in final states with a muon and multi-track displaced vertex in proton–proton collisions at View the MathML sources=7 TeV with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of √ s = 7 TeV proton-proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results. Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √ s =7TeV pp collisions with theA search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb(-1) of root s = 7 TeV proton-proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results.

Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using 4.7 fb⁻¹ of sqrts=7 TeV proton-pro collision data

Weak scale supersymmetry is one of the best motivated and studied Standard Model extensions. It predicts the existence of new heavy coloured particles called squarks and gluinos which are the supersymmetric partners of the quarks and gluons, respectively. The poster summarises results on inclusive searches for supersymmetric squarks and gluinos in events containing jets and missing transverse momentum without leptons. The searches use the full data sample recorded in 2012 at √ s=8 TeV centre-of-mass energy by the ATLAS experiment at the LHC.

Search for first generation scalar leptoquarks in pp collisions at View the MathML source with the ATLAS detector

We report a search for first generation scalar leptoquarks us ing 1.03 fb−1 of proton-proton collisions data produced by the Large Hadron Collider at √ s = 7 TeV and recorded by the ATLAS experiment. Leptoquarks are s ought via their decay into an electron or neutrino and a quark, producing events with two oppositel y charged electrons and at least two jets, or events with an el ectron, missing transverse momentum and at least two jets. Control d ata samples are used to validate background predictions fro m M nte Carlo simulation. In the signal region, the observed event y ields are consistent with the background expectations. We e xclude at 95% confidence level the production of first generation scala r leptoquark with masses mLQ < 660 (607) GeV when assuming the branching fraction of a leptoquark to a charged lepton is equ al to 1.0 (0.5).We report a search for first generation scalar leptoquarks using 1.03 fb(-1) of proton-proton collisions data produced by the Large Hadron Collider at root s = 7 TeV and recorded by the ATLAS experiment. Leptoquarks are sought via their decay into an electron or neutrino and a quark, producing events with two oppositely charged electrons and at least two jets, or events with an electron, missing transverse momentum and at least two jets. Control data samples are used to validate background predictions from Monte Carlo simulation. In the signal region, the observed event yields are consistent with the background expectations. We exclude at 95% confidence level the production of first generation scalar leptoquark with masses m(LQ) < 660 (607) GeV when assuming the branching fraction of a leptoquark to a charged lepton is equal to 1.0 (0.5)

Measurement of the t-channel single top-quark production cross section in pp collisions at View the MathML source with the ATLAS detector

We report a measurement of the cross section of single top-quark production in the t-channel using 1.04 fb−1 of pp collision data at √ s = 7 TeV recorded with the ATLAS detector at the LHC. Selected events feature one electron or muon, missing transverse momentum, and two or three jets, exactly one of them identified as originating from a b quark. The cross section is measured by fitting the distribution of a multivariate discriminant constructed with a neural network, yielding σt = 83± 4 (stat .) +20 −19 (syst.) pb, which is in good agreement with the prediction of the Standard Model. Using the ratio of the measured to the theoretically predicted cross section and assuming that the top-quarkrelated CKM matrix elements obey the relation |Vtb| ≫ |Vts|, |Vtd |, the coupling strength at the W-t-b vertex is determined to be |Vtb| = 1.13+0.14 −0.13. If it is assumed that |Vtb| ≤ 1 a lower limit of |Vtb| > 0.75 is obtained at the 95% confidence level. Measurement of the t-channel single top-quark production c r ss section inpp collisions at √ s = 7 TeV with the ATLAS detector The ATLAS Collaboration

Measurement of the WW cross section in View the MathML sourcepp collisions with the ATLAS detector and limits on anomalous gauge couplings

This Letter reports a measurement of the WW production cross section in √ s = 7 TeV pp collisions using data corresponding to an integrated luminosity of 1.02 fb−1 collected with the ATLAS detector. Using leptonic decays of oppositely charged W bosons, the total measured cross section is σ(pp → WW) = 54.4 ± 4.0 (stat.) ± 3.9 (syst.) ± 2.0 (lumi.) pb, consistent with the Standard Model prediction of σ(pp → WW) = 44.4 ± 2.8 pb. Limits on anomalous electroweak triple-gauge couplings are extracted from a fit to the transverse-momentum distribution of the leading charged lepton in the event. ar X iv :1 20 3. 62 32 v2 [ he pex ] 7 M ay 2 01 2 Measurement of the WW cross section in √ s = 7 TeV pp collisions with the ATLAS detector and limits on anomalous gauge couplings The ATLAS Collaboration

Measurement of Wγ and Zγ production cross sections in pp collisions at View the MathML source and limits on anomalous triple gauge couplings with the ATLAS detector

This Letter presents measurements of l±νγ and l+l−γ (l = e, μ) production in 1.02 fb−1 of pp collision data recorded at √ s = 7 TeV with the ATLAS detector at the LHC during 2011. Events dominated by Wγ and Zγ production with leptonic decays of the W and Z bosons are selected, and their production cross sections and kinematic properties are measured in several ranges of the photon transverse energy. The results are compared to Standard Model predictions and are used to determine limits on anomalous WWγ and ZZγ/Zγγ couplings. ar X iv :1 20 5. 25 31 v1 [ he pex ] 1 1 M ay 2 01 2 Measurement of Wγ and Zγ production cross sections in pp collisions at √ s = 7 TeV and limits on anomalous triple gauge couplings with the ATLAS detector (ATLAS Collaboration) (Dated: May 11, 2012) This Letter presents measurements of l±νγ and l+l−γ (l = e, μ) production in 1.02 fb−1 of pp collision data recorded at √ s = 7 TeV with the ATLAS detector at the LHC during 2011. Events dominated by Wγ and Zγ production with leptonic decays of the W and Z bosons are selected, and their production cross sections and kinematic properties are measured in several ranges of the photon transverse energy. The results are compared to Standard Model predictions and are used to determine limits on anomalous WWγ and ZZγ/Zγγ couplings.

Search for the Standard Model Higgs boson in the decay channel H→ZZ(⁎)→4ℓ with 4.8 fb−1 of pp collision data at View the MathML source with ATLAS

This Letter presents a search for the Standard Model Higgs boson in the decay channel H → ZZ → lll ′+l ′ −, where l, l ′ = e or μ, using proton-proton collisions at √ s = 7 TeV recorded with the ATLAS detector and corresponding to an integrated luminosity of 4.8 fb. The four-lepton invariant mass distribution is compared with Standard Model background expectations to derive upper limits on the cross section of a Standard Model Higgs boson with a mass between 110 GeV and 600 GeV. The mass ranges 134−156 GeV, 182−233 GeV, 256−265 GeV and 268−415 GeV are excluded at the 95% confidence level. The largest upward deviations from the background-only hypothesis are observed for Higgs boson masses of 125 GeV, 244 GeV and 500 GeV with local significances of 2.1, 2.2 and 2.1 standard deviations, respectively. Once the look-elsewhere effect is considered, none of these excesses are significant.