V. Gallo

Improved luminosity determination in pp collisions at sqrts = 7 TeV using the ATLAS detector at the LHC

The luminosity calibration for the ATLAS detector at the LHC during pp collisions at √ s = 7 TeV in 2010 and 2011 is presented. Evaluation of the luminosity scale is performed using several luminositysensitive detectors, and comparisons are made of the long-term stability and accuracy of this calibration applied to the pp collisions at √ s = 7 TeV. A luminosity uncertainty of δL /L =±3.5% is obtained for the 47pb−1 of data delivered to ATLAS in 2010, and an uncertainty of δL /L =±1.8% is obtained for the 5.5fb−1 delivered in 2011. ar X iv :1 30 2. 43 93 v2 [ he pex ] 8 J ul 2 01 3 Eur. Phys. J. C manuscript No. (will be inserted by the editor) Improved luminosity determination in pp collisions at √ s = 7 TeV using the ATLAS detector at the LHC The ATLAS Collaboration 1CERN, 1211 Geneve 23, Switzerland Received: date / Accepted: date Abstract The luminosity calibration for the ATLAS detector at the LHC during pp collisions at √ s = 7 TeV 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 √ s = 7 TeV. A luminosity uncertainty of δL /L =±3.5% is obtained for the 47pb−1 of data delivered to ATLAS in 2010, and an uncertainty of δL /L = ±1.8% is obtained for the 5.5fb−1 delivered in 2011.The luminosity calibration for the ATLAS detector at the LHC during pp collisions at √ s = 7 TeV 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 √ s = 7 TeV. A luminosity uncertainty of δL /L =±3.5% is obtained for the 47pb−1 of data delivered to ATLAS in 2010, and an uncertainty of δL /L = ±1.8% is obtained for the 5.5fb−1 delivered in 2011. PACS 29.27.-a Charged-particle beams in accelerators · 13.75.Cs, 13.85.-t Proton-proton interactions

Search for supersymmetry at √8=8 TeV in final states with jets and two same-sign leptons or three leptons with the ATLAS detector

A bstractA search for strongly produced supersymmetric particles is conducted using signatures involving multiple energetic jets and either two isolated leptons (e or μ) with the same electric charge, or at least three isolated leptons. The search also utilises jets originating from b-quarks, missing transverse momentum and other observables to extend its sensitivity. The analysis uses a data sample corresponding to a total integrated luminosity of 20.3 fb−1 of

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

\sqrt{s}

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

= 8 TeV proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider in 2012. No deviation from the Standard Model expectation is observed. New or significantly improved exclusion limits are set on a wide variety of supersymmetric models in which the lightest squark can be of the first, second or third generations, and in which R-parity can be conserved or violated.

Search for a heavy narrow resonance decaying to eμ, eτ, or μτ with the ATLAS detector in View the MathML sourcepp collisions at the LHC

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 ℤℤ production in pp collisions at sqrts=7 TeV and limits on anomalous ℤℤℤ ℤℤgamma couplings 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.

Search for new phenomena in events with three charged leptons at a center-of-mass energy of 7 TeV with the ATLAS detector

This Letter presents the results of a search for a heavy particle decaying into an e(+/-)mu(+/-), e(+/-)tau(+/-), or mu(+/-)tau(+/-) final state in pp collisions at root s = 7 TeV. The data were recorded with the ATLAS detector at the LHC during 2011 and correspond to an integrated luminosity of 4.6 fb(-1). No significant excess above the Standard Model expectation is observed, and exclusions at 95% confidence level are placed on the cross section times branching ratio for the production of an R-parity-violating supersymmetric tau sneutrino. For a sneutrino mass of 500 (2000) GeV, the observed limits on the production cross section times branching ratio are 3.2 (1.4) fb, 42 (17) fb, and 40 (18) fb for the e mu, e tau, and mu tau modes, respectively. These results considerably extend constraints from Tevatron experiments.

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

A bstractA measurement of the ZZ production cross section in proton-proton collisions at

Search for non-pointing photons in the diphoton and

\sqrt{s}=7

E_T^{miss}

TeV using data recorded by the ATLAS experiment at the Large Hadron Collider is presented. In a data sample corresponding to an integrated luminosity of 4.6 fb−1 collected in 2011, events are selected that are consistent either with two Z bosons decaying to electrons or muons or with one Z boson decaying to electrons or muons and a second Z boson decaying to neutrinos. The ZZ(*) → ℓ+ℓ−ℓ′+ℓ′− and