| 1. |
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| 2. |
- Abulaiti, Yiming, et al.
(författare)
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Search for heavy long-lived charged R-hadrons with the ATLAS detector in 3.2 fb(-1) of proton-proton collision data at root s=13 TeV
- 2016
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 760, s. 647-665
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Tidskriftsartikel (refereegranskat)abstract
- A search for heavy long-lived charged R-hadronsis reported using a data sample corresponding to 3.2fb(-1)of proton-proton collisions at root s = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider at CERN. The search is based on observables related to large ionisation losses and slow propagation velocities, which are signatures of heavy charged particles travelling significantly slower than the speed of light. No significant deviations from the expected background are observed. Upper limits at 95% confidence level are provided on the production cross section of long-lived R-hadronsin the mass range from 600 GeV to 2000 GeV and gluino, bottom and top squark masses are excluded up to 1580 GeV, 805 GeV and 890 GeV, respectively.
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| 3. |
- Abulaiti, Yiming, et al.
(författare)
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Search for TeV-scale gravity signatures in high-mass final states with leptons and jets with the ATLAS detector at root s=13 TeV
- 2016
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 760, s. 520-537
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Tidskriftsartikel (refereegranskat)abstract
- A search for physics beyond the Standard Model, in final states with at least one high transverse momentum charged lepton (electron or muon) and two additional high transverse momentum leptons or jets, is performed using 3.2 fb (1) of proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015 at root s = 13 TeV. The upper end of the distribution of the scalar sum of the transverse momenta of leptons and jets is sensitive to the production of high-mass objects. No excess of events beyond Standard Model predictions is observed. Exclusion limits are set for models of microscopic black holes with two to six extra dimensions.
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| 4. |
- Aad, G, et al.
(författare)
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Beam-induced and cosmic-ray backgrounds observed in the ATLAS detector during the LHC 2012 proton-proton running period
- 2016
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Ingår i: Journal of Instrumentation. - : IOP PUBLISHING LTD. - 1748-0221. ; 11:5
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Tidskriftsartikel (refereegranskat)abstract
- This paper discusses various observations on beam-induced and cosmic-ray backgrounds in the ATLAS detector during the LHC 2012 proton-proton run. Building on published results based on 2011 data, the correlations between background and residual pressure of the beam vacuum are revisited. Ghost charge evolution over 2012 and its role for backgrounds are evaluated. New methods to monitor ghost charge with beam-gas rates are presented and observations of LHC abort gap population by ghost charge are discussed in detail. Fake jets from colliding bunches and from ghost charge are analysed with improved methods, showing that ghost charge in individual radio-frequency buckets of the LHC can be resolved. Some results of two short periods of dedicated cosmic-ray background data-taking are shown; in particular cosmic-ray muon induced fake jet rates are compared to Monte Carlo simulations and to the fake jet rates from beam background. A thorough analysis of a particular LHC fill, where abnormally high background was observed, is presented. Correlations between backgrounds and beam intensity losses in special fills with very high β∗ are studied. © 2016 CERN for the benefit of the ATLAS collaboration.
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| 5. |
- Aad, G, et al.
(författare)
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Measurement of the ZZ production cross section in pp collisions at √s = 13 TeV with the ATLAS detector
- 2016
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Ingår i: Physical Review Letters. - : American Physical Society. - 1079-7114 .- 0031-9007. ; 116:10
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Tidskriftsartikel (refereegranskat)abstract
- The ZZ production cross section in proton-proton collisions at 13 TeV center-of-mass energy is measured using 3.2 fb-1 of data recorded with the ATLAS detector at the Large Hadron Collider. The considered Z boson candidates decay to an electron or muon pair of mass 66-116 GeV. The cross section is measured in a fiducial phase space reflecting the detector acceptance. It is also extrapolated to a total phase space for Z bosons in the same mass range and of all decay modes, giving 16.7-2.0+2.2(stat)+0.9-0.7(syst)+1.0-0.7(lumi) pb. The results agree with standard model predictions. © 2016 CERN. Published by the American Physical Society under the terms of the "http://creativecommons.org/licenses/by/3.0/" Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
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| 6. |
- Abulaiti, Yiming, et al.
(författare)
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A measurement of material in the ATLAS tracker using secondary hadronic interactions in 7 TeV p p collisions
- 2016
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Ingår i: Journal of Instrumentation. - : IOP PUBLISHING LTD. - 1748-0221 .- 1748-0221. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge of the material in the ATLAS inner tracking detector is crucial in under-standing the reconstruction of charged-particle tracks, the performance of algorithms that identify jets containing b-hadrons and is also essential to reduce background in searches for exotic particles that can decay within the inner detector volume. Interactions of primary hadrons produced in pp collisions with the material in the inner detector are used to map the location and amount of this material. The hadronic interactions of primary particles may result in secondary vertices, which in this analysis are reconstructed by an inclusive vertex-finding algorithm. Data were collected using minimum-bias triggers by the ATLAS detector operating at the LHC during 2010 at centre-of-mass energy root s = 7 TeV, and correspond to an integrated luminosity of 19 nb(-1). Kinematic properties of these secondary vertices are used to study the validity of the modelling of hadronic interactions in simulation. Secondary-vertex yields are compared between data and simulation over a volume of about 0.7m(3) around the interaction point, and agreement is found within overall uncertainties.
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| 7. |
- Abulaiti, Yiming, et al.
(författare)
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A search for top squarks with R-parity-violating decays to all-hadronic final states with the ATLAS detector in root s=8 TeV proton-proton collisions
- 2016
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :6
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Tidskriftsartikel (refereegranskat)abstract
- A search for the pair production of top squarks, each with R-parity-violating decays into two Standard Model quarks, is performed using 17.4 fb(-1) of root s = 8 TeV proton-proton collision data recorded by the ATLAS experiment at the LITC. Each top squark is assumed to decay to a b- and an 8-quark, leading to four quarks in the final state. Background discrimination is achieved with the use of b-tagging and selections on the mass and substructure of large-radius jets, providing sensitivity to top squark masses as low as 100 GeV. No evidence of an excess beyond the Standard Model background prediction is observed and top squalls decaying to bs are excluded for top squark masses in the range 100 <= m((t) over tilde) <= 315 GeV at 95% confidence level.
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| 8. |
- Abulaiti, Yiming, et al.
(författare)
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Charged-particle distributions in root s=13 TeV pp interactions measured with the ATLAS detector at the LHC
- 2016
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 758, s. 67-88
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Tidskriftsartikel (refereegranskat)abstract
- Charged-particle distributions are measured in proton-proton collisions at a centre-of-mass energy of 13 TeV, using a data sample of nearly 9 million events, corresponding to an integrated luminosity of 170 mu b(-1), recorded by the ATLAS detector during a special Large Hadron Collider fill. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the dependence of the mean transverse momentum on the charged-particle multiplicity are presented. The measurements are performed with charged particles with transverse momentum greater than 500 MeV and absolute pseudorapidity less than 2.5, in events with at least one charged particle satisfying these kinematic requirements. Additional measurements in a reduced phase space with absolute pseudorapidity less than 0.8 are also presented, in order to compare with other experiments. The results are corrected for detector effects, presented as particle-level distributions and are compared to the predictions of various Monte Carlo event generators.
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| 9. |
- Abulaiti, Yiming, et al.
(författare)
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Dark matter interpretations of ATLAS searches for the electroweak production of supersymmetric particles in root s=8 TeV proton-proton collisions
- 2016
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :9
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Tidskriftsartikel (refereegranskat)abstract
- A selection of searches by the ATLAS experiment at the LHC for the electroweak production of SUSY particles are used to study their impact on the constraints on dark matter candidates. The searches use 20 fb(-1) of proton-proton collision data at root s = 8 TeV. A likelihood-driven scan of a five-dimensional effective model focusing on the gaugino-higgsino and Higgs sector of the phenomenological minimal supersymmetric Standard Model is performed. This scan uses data from direct dark matter detection experiments, the relic dark matter density and precision flavour physics results. Further constraints from the ATLAS Higgs mass measurement and SUSY searches at LEP are also applied. A subset of models selected from this scan are used to assess the impact of the selected ATLAS searches in this five-dimensional parameter space. These ATLAS searches substantially impact those models for which the mass m((chi) over tilde (0)(1)) of the lightest neutralino is less than 65 GeV, excluding 86% of such models. The searches have limited impact on models with larger m((chi) over tilde (0)(1)) due to either heavy electroweakinos or compressed mass spectra where the mass splittings between the produced particles and the lightest supersymmetric particle is small.
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| 10. |
- Abulaiti, Yiming, et al.
(författare)
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Luminosity determination in pp collisions at root s=8 TeV using the ATLAS detector at the LHC
- 2016
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 76:12
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Tidskriftsartikel (refereegranskat)abstract
- The luminosity determination for the ATLAS detector at the LHC during pp collisions at root s = 8 TeV in 2012 is presented. The evaluation of the luminosity scale is performed using several luminometers, and comparisons between these luminosity detectors are made to assess the accuracy, consistency and long-term stability of the results. A luminosity uncertainty of delta L/L = +/- 1.9% is obtained for the 22.7 fb(-1) of pp collision data delivered to ATLAS at root s = 8 TeV in 2012.
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