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  • 601. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for scalar top quark pair production in natural gauge mediated supersymmetry models with the ATLAS detector in pp collisions at root s=7 TeV2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 714, no 1-3, p. 44-60Article in journal (Refereed)
    Abstract [en]

    The results of a search for pair production of the lighter scalar partners of top quarks ((t) over bar (1)) in 2.05 fb(-1) of pp collisions at root s = 7 TeV using the ATLAS experiment at the LHC are reported. Scalar top quarks are searched for in events with two same flavour opposite-sign leptons (e, mu) with invariant mass consistent with the Z boson mass, large missing transverse momentum and jets in the final state. At least one of the jets is identified as originating from a b-quark. No excess over Standard Model expectations is found. The results are interpreted in the framework of R-parity conserving, gauge mediated Supersymmetry breaking 'natural' scenarios, where the neutralino ((chi) over bar (0)(1)) is the next-to-lightest supersymmetric particle. Scalar top quark masses up to 310 GeV are excluded for 115 GeV m(<(chi) over bar1)(0) 230 GeV at 95% confidence level, reaching an exclusion of m(<(t) over bar1) 330 GeV for m(<(chi) over bar1)(0) = 190 GeV. Scalar top quark masses below 240 GeV are excluded for all values of m((chi) over bar1)(0) > m(z).

  • 602. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for second generation scalar leptoquarks in pp collisions at root s=7 TeV with the ATLAS detector2012In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 72, no 9, p. 2151-Article in journal (Refereed)
    Abstract [en]

    The results of a search for the production of second generation scalar leptoquarks are presented for final states consisting of either two muons and at least two jets or a muon plus missing transverse momentum and at least two jets. A total of 1.03 fb(-1) integrated luminosity of proton-proton collision data produced by the Large Hadron Collider at root s = 7 TeV and recorded by the ATLAS detector is used for the search. The event yields in the signal regions are found to be consistent with the Standard Model background expectations. The production of second generation leptoquarks is excluded for a leptoquark mass m(LQ) < 594 (685) GeV at 95 % confidence level, for a branching ratio of 0.5 (1.0) for leptoquark decay to a muon and a quark.

  • 603. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for single b*-quark production with the ATLAS detector at root s=7 TeV2013In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 721, no 4-5, p. 171-189Article in journal (Refereed)
    Abstract [en]

    The results of a search for an excited bottom-quark b* in pp collisions at root s = 7 TeV, using 4.7 fb(-1) of data collected by the ATLAS detector at the LHC are presented. In the model studied, a single b*-quark is produced through a chromomagnetic interaction and subsequently decays to a W boson and a top quark. The search is performed in the dilepton and lepton + jets final states, which are combined to set limits on b*-quark couplings for a range of b*-quark masses. For a benchmark with unit size chromomagnetic and Standard Model-like electroweak b* couplings, b* quarks with masses less than 870 GeV are excluded at the 95% credibility level.

  • 604. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using 4:7 fb(-1) of root s=7 TeV proton-proton collision data2013In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 87, no 1, p. 012008-Article in journal (Refereed)
    Abstract [en]

    A search for squarks and gluinos in final states containing jets, missing transverse momentum and no high-p(T) electrons or muons is presented. The data represent the complete sample recorded in 2011 by the ATLAS experiment in 7 TeV proton-proton collisions at the Large Hadron Collider, with a total integrated luminosity of 4.7 fb(-1). No excess above the Standard Model background expectation is observed. Gluino masses below 860 GeV and squark masses below 1320 GeV are excluded at the 95% confidence level in simplified models containing only squarks of the first two generations, a gluino octet and a massless neutralino, for squark or gluino masses below 2 TeV, respectively. Squarks and gluinos with equal masses below 1410 GeV are excluded. In minimal supergravity/constrained minimal supersymmetric Standard Model models with tan beta = 10, A(0) = 0 and mu > 0, squarks and gluinos of equal mass are excluded for masses below 1360 GeV. Constraints are also placed on the parameter space of supersymmetric models with compressed spectra. These limits considerably extend the region of supersymmetric parameter space excluded by previous measurements with the ATLAS detector.

  • 605. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for supersymmetry in events with large missing transverse momentum, jets, and at least one tau lepton in 7 TeV proton-proton collision data with the ATLAS detector2012In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 72, no 11, p. 2215-Article in journal (Refereed)
    Abstract [en]

    A search for supersymmetry (SUSY) in events with large missing transverse momentum, jets, and at least one hadronically decaying tau lepton, with zero or one additional light lepton (e/mu), has been performed using 4.7 fb(-1) of proton-proton collision data at root s = 7 TeV recorded with the ATLAS detector at the Large Hadron Collider. No excess above the Standard Model background expectation is observed and a 95 % confidence level visible cross-section upper limit for new phenomena is set. In the framework of gauge-mediated SUSY-breaking models, lower limits on the mass scale. are set at 54 TeV in the regions where the (tau) over tilde (1) is the next-to-lightest SUSY particle (tan beta > 20). These limits provide the most stringent tests to date of GMSB models in a large part of the parameter space considered.

  • 606. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for supersymmetry in events with photons, bottom quarks, and missing transverse momentum in proton-proton collisions at a centre-of-mass energy of 7 TeV with the ATLAS detector2013In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 719, no 4-5, p. 261-279Article in journal (Refereed)
    Abstract [en]

    A search has been performed for the experimental signature of an isolated photon with high transverse momentum, at least one jet identified as originating from a bottom quark, and high missing transverse momentum. Such a final state may originate from supersymmetric models with gauge-mediated supersymmetry breaking in events in which one of a pair of higgsino-like neutralinos decays into a photon and a gravitino while the other decays into a Higgs boson and a gravitino. The search is performed using the full dataset of 7 TeV proton-proton collisions recorded with the ATLAS detector at the LHC in 2011, corresponding to an integrated luminosity of 4.7 fb(-1). A total of 7 candidate events are observed while 7.5 +/- 2.2 events are expected from the Standard Model background. The results of the search are interpreted in the context of general gauge mediation to exclude certain regions of a benchmark plane for higgsino-like neutralino production.

  • 607. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for supersymmetry in pp collisions at root s=7 Te V in final states with missing transverse momentum and b-jets with the ATLAS detector2012In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 85, no 11, p. 112006-Article in journal (Refereed)
    Abstract [en]

    The results of a search for supersymmetry in events with large missing transverse momentum and heavy-flavor jets using an integrated luminosity corresponding to 2.05 fb(-1) of pp collisions at root s = 7 TeV recorded with the ATLAS detector at the Large Hadron Collider are reported. No significant excess is observed with respect to the prediction for standard model processes. Results are interpreted in a variety of R-parity conserving models in which scalar bottoms and tops are the only scalar quarks to appear in the gluino decay cascade, and in an SO(10) model framework. Gluino masses up to 600-900 GeV are excluded, depending on the model considered.

  • 608. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for supersymmetry with jets, missing transverse momentum and at least one hadronically decaying tau lepton in proton-proton collisions at root s=7 TeV with the ATLAS detector ATLAS Collaboration2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 714, no 2-5, p. 197-214Article in journal (Refereed)
    Abstract [en]

    A search for production of supersymmetric particles in final states containing jets, missing transverse momentum, and at least one hadronically decaying tau lepton is presented. The data were recorded by the ATLAS experiment in root s = 7 TeV proton-proton collisions at the Large Hadron Collider. No excess above the Standard Model background expectation was observed in 2.05 fb(-1) of data. The results are interpreted in the context of gauge mediated supersymmetry breaking models with M-mess = 250 TeV, N-5 = 3, mu > 0, and C-grav = 1. The production of supersymmetric particles is excluded at 95% C.L. up to a supersymmetry breaking scale Lambda = 30 TeV, independent of tan beta, and up to Lambda = 43 TeV for large tan beta.

  • 609. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for tb Resonances in Proton-Proton Collisions at root s=7 TeV with the ATLAS Detector2012In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 109, no 8, p. 081801-Article in journal (Refereed)
    Abstract [en]

    This Letter presents a search for tb resonances in 1.04 fb(-1) of LHC proton-proton collision data collected by the ATLAS detector at a center-of-mass energy of 7 TeV. Events with a lepton, missing transverse momentum, and two jets are selected and the invariant mass of the corresponding final state is reconstructed. The search exploits the shape of the tb invariant mass distribution compared to the expected standard model backgrounds. The model of a right-handed W'(R) with standard model-like couplings is chosen as the benchmark model for this search. No statistically significant excess of events is observed in the data, and upper limits on the cross section times the branching ratio of W'(R) resonances at 95% C.L. lie in the range of 6.1-1.0 pb for W'(R) masses ranging from 0.5 to 2.0 TeV. These limits are translated into a lower bound on the allowed right-handed W'(R) mass, giving mW'(R) > 1.13 TeV at 95% C.L.

  • 610. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for TeV-scale gravity signatures in final states with leptons and jets with the ATLAS detector at root s=7 TeV2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 716, no 1, p. 122-141Article in journal (Refereed)
    Abstract [en]

    The production of events with multiple high transverse momentum particles including charged leptons and jets is measured, using 1.04 fb(-1) of proton-proton collision data recorded by the ATLAS detector during the first half of 2011 at root s = 7 TeV. No excess beyond Standard Model expectations is observed, and upper limits on the fiducial cross sections for non-Standard Model production of these final states are set. Using models for string ball and black hole production and decay, exclusion contours are determined as a function of mass threshold and the fundamental gravity scale.

  • 611. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for the decay B-s(0) -> mu(+)mu(-) with the ATLAS detector2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 713, no 4-5, p. 387-407Article in journal (Refereed)
    Abstract [en]

    A blind analysis searching for the decay B-s(0) -> mu(+)mu(-) has been performed using proton-proton collisions at a centre-of-mass energy of 7 TeV recorded with the ATLAS detector at the LHC. With an integrated luminosity of 2.4 fb(-1) no excess of events over the background expectation is found and an upper limit is set on the branching fraction BR(B-s(0) -> mu(+)mu(-)) <2.2(1.9) x 10(-8) at 95% (90%) confidence level.

  • 612. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for the Higgs boson in the H -> WW -> lvjj decay channel at root s=7 TeV with the ATLAS detector2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 718, no 2, p. 391-410Article in journal (Refereed)
    Abstract [en]

    A search for the Standard Model Higgs boson has been performed in the H -> WW -> lvjj channel using 4.7 fb(-1) of pp collision data recorded at a centre-of-mass energy of root s = 7 TeV with the ATLAS detector at the Large Hadron Collider. Higgs boson candidates produced in association with zero, one or two jets are included in the analysis to maximize the acceptance for both gluon fusion and weak boson fusion Higgs boson production processes. No significant excess of events is observed over the expected background and limits on the Higgs boson production cross section are derived for a Higgs boson mass in the range 300 GeV < m(H) < 600 GeV. The best sensitivity is reached for m(H) = 400 GeV, where the observed (expected) 95% confidence level upper bound on the cross section for H -> WW produced in association with zero or one jet is 2.2 pb (1.9 pb), corresponding to 1.9 (1.6) times the Standard Model prediction. In the Higgs boson plus two jets channel, which is more sensitive to the weak boson fusion process, the observed (expected) 95% confidence level upper bound on the cross section for H -> WW production with m(H) = 400 GeV is 0.7 pb (0.6 pb), corresponding to 7.9 (6.5) times the Standard Model prediction.

  • 613. Aad, G
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for the neutral Higgs bosons of the minimal supersymmetric standard model in pp collisions at root s=7 TeV with the ATLAS detector2013In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 2, p. 095-Article in journal (Refereed)
    Abstract [en]

    A search for neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) is reported. The analysis is based on a sample of proton-proton collisions at a centre-of-mass energy of 7 TeV recorded with the ATLAS detector at the Large Hadron Collider. The data were recorded in 2011 and correspond to an integrated luminosity of 4.7 fb(-1) to 4.8 fb(-1). Higgs boson decays into oppositely-charged in muon or tau lepton pairs are considered for final states requiring either the presence or absence of b-jets. No statistically significant excess over the expected background is observed and exclusion limits at the 95% confidence level are derived. The exclusion limits are for the production cross-section of a generic neutral Higgs boson, phi, as a function of the Higgs boson mass and for h/A/H production in the MSSM as a function of the parameters m(A) and tan beta in the m(h)(max) scenario for m(A) in the range of 90 GeV to 500 GeV.

  • 614. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for the Standard Model Higgs boson in the decay channel H -> ZZ((*)) -> 4l with 4.8 fb(-1) of pp collision data at root s=7 TeV with ATLAS2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 710, no 3, p. 383-402Article in journal (Refereed)
    Abstract [en]

    This Letter presents a search for the Standard Model Higgs boson in the decay channel H -> ZZ((*)) -> l(+)l(-)l(-)+l(')-, where l,l' = e or mu, using proton-proton collisions at root s = 7 TeV recorded with the ATLAS detector and corresponding to an integrated luminosity of 4.8 fb(-1). 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.

  • 615. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for the Standard Model Higgs boson in the H -> tau(+)tau(-) decay mode in root s=7 TeV pp collisions with ATLAS2012In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 9, p. 070-Article in journal (Refereed)
    Abstract [en]

    A search for the Standard Model Higgs boson decaying into a pair of tau leptons is reported. The analysis is based on a data sample of proton-proton collisions collected by the ATLAS experiment at the LHC and corresponding to an integrated luminosity of 4.7 fb(-1). No significant excess over the expected background is observed in the Higgs boson mass range of 100-150GeV. The observed (expected) upper limits on the cross section times the branching ratio for H -> tau(+)tau(-) are found to be between 2.9 (3.4) and 11.7 (8.2) times the Standard Model prediction for this mass range.

  • 616. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for the Standard Model Higgs boson produced in association with a vector boson and decaying to a b-quark pair with the ATLAS detector2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 718, no 2, p. 369-390Article in journal (Refereed)
    Abstract [en]

    This Letter presents the results of a direct search with the ATLAS detector at the LHC for a Standard Model Higgs boson of mass 110 <= m(H) <= 130 GeV produced in association with a W or Z boson and decaying to b (b) over bar. Three decay channels are considered: ZH -> l(+)l(-)b (b) over bar, WH -> lvbb (b) over bar and ZH -> v (v) over bar(b) over bar where l corresponds to an electron or a muon. No evidence for Higgs boson production is observed in a dataset of 7 TeV pp collisions corresponding to 4.7 fb(-1) of integrated luminosity collected by ATLAS in 2011. Exclusion limits on Higgs boson production, at the 95% confidence level, of 2.5 to 5.5 times the Standard Model cross section are obtained in the mass range 110-130 GeV. The expected exclusion limits range between 2.5 and 4.9 for the same mass interval.

  • 617. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for third generation scalar leptoquarks in pp collisions at root s=7 TeV with the ATLAS detector2013In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 6, p. 033-Article in journal (Refereed)
    Abstract [en]

    A search for pair-produced third generation scalar leptoquarks is presented, using proton-proton collisions at root s = 7 TeV at the LHC. The data were recorded with the ATLAS detector and correspond to an integrated luminosity of 4.7 fb(-1). Each leptoquark is assumed to decay to a tau lepton and a b-quark with a branching fraction equal to 100%. No statistically significant excess above the Standard Model expectation is observed. Third generation leptoquarks are therefore excluded at 95% confidence level for masses less than 534 GeV.

  • 618. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for top and bottom squarks from gluino pair production in final states with missing transverse energy and at least three b-jets with the ATLAS detector2012In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 72, no 10, p. 2174-Article in journal (Refereed)
    Abstract [en]

    This letter reports the results of a search for top and bottom squarks from gluino pair production in 4.7 fb(-1) of pp collisions at root s = 7 TeV using the ATLAS detector at the LHC. The search is performed in events with large missing transverse momentum and at least three jets identified as originating from a b-quark. Exclusion limits are presented for a variety of gluino-mediated models with gluino masses up to 1 TeV excluded.

  • 619. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for t(t)over-bar resonances in the lepton plus jets final state with ATLAS using 4.7 fb(-1) of pp collisions at root s=7 TeV2013In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 88, no 1, p. 012004-Article in journal (Refereed)
    Abstract [en]

    A search for new particles that decay into top quark pairs (t (t) over bar) is performed with the ATLAS experiment at the LHC using an integrated luminosity of 4.7 fb(-1) of proton-proton (pp) collision data collected at a center-of-mass energy root s = 7 TeV. In the t (t) over bar) -> WbWb decay, the lepton plus jets final state is used, where one W boson decays leptonically and the other hadronically. The t (t) over bar) system is reconstructed using both small-radius and large-radius jets, the latter being supplemented by a jet substructure analysis. A search for local excesses in the number of data events compared to the Standard Model expectation in the t (t) over bar) invariant mass spectrum is performed. No evidence for a t (t) over bar) resonance is found and 95% credibility-level limits on the production rate are determined for massive states predicted in two benchmark models. The upper limits on the cross section times branching ratio of a narrow Z' resonance range from 5.1 pb for a boson mass of 0.5 TeV to 0.03 pb for a mass of 3 TeV. A narrow leptophobic topcolor Z' resonance with a mass below 1.74 TeV is excluded. Limits are also derived for a broad color-octet resonance with m 15.3%. A Kaluza-Klein excitation of the gluon in a Randall-Sundrum model is excluded for masses below 2.07 TeV.

  • 620. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for WH production with a light Higgs boson decaying to prompt electron-jets in proton-proton collisions at root s=7 TeV with the ATLAS detector2013In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 15, p. 043009-Article in journal (Refereed)
    Abstract [en]

    A search is performed for WH production with a light Higgs boson decaying to hidden-sector particles resulting in clusters of collimated electrons, known as electron-jets. The search is performed with 2.04 fb(-1) of data collected in 2011 with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at root s = 7 TeV. One event satisfying the signal selection criteria is observed, which is consistent with the expected background rate. Limits on the product of the WH production cross section and the branching ratio of a Higgs boson decaying to prompt electron-jets are calculated as a function of a Higgs boson mass in the range from 100 to 140 GeV.

  • 621. Aad, G
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Searches for heavy long-lived sleptons and R-hadrons with the ATLAS detector in pp collisions at root s=7 TeV2013In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 720, no 4-5, p. 277-308Article in journal (Refereed)
    Abstract [en]

    A search for long-lived particles is performed using a data sample of 4.7 fb(-1) from proton-proton collisions at a centre-of-mass energy. root s = 7 TeV collected by the ATLAS detector at the LHC. No excess is observed above the estimated background and lower limits, at 95% confidence level, are set on the mass of the long-lived particles in different scenarios, based on their possible interactions in the inner detector, the calorimeters and the muon spectrometer. Long-lived staus in gauge-mediated SUSY-breaking models are excluded up to a mass of 300 GeV for tan beta = 5-20. Directly produced long-lived sleptons are excluded up to a mass of 278 GeV. R-hadrons, composites of gluino (stop, sbottom) and light quarks, are excluded up to a mass of 985 GeV (683 GeV, 612 GeV) when using a generic interaction model. Additionally two sets of limits on R-hadrons are obtained that are less sensitive to the interaction model for R-hadrons. One set of limits is obtained using only the inner detector and calorimeter observables, and a second set of limits is obtained based on the inner detector alone.

  • 622. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC2013In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 73, no 3, p. 2305-Article in journal (Refereed)
    Abstract [en]

    The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of root s = 900 GeV and 7 TeV collected during 2009 and 2010. Then, using the decay of K-s and Lambda particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5 % for central isolated hadrons and 1-3 % for the final calorimeter jet energy scale.

  • 623. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Study of heavy-flavor quarks produced in association with top-quark pairs at root s=7 TeV using the ATLAS detector2014In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 89, no 7, p. 072012-Article in journal (Refereed)
    Abstract [en]

    Using a sample of dilepton top-quark pair ((tt) over bar) candidate events, a study is performed of the production of top-quark pairs together with heavy-flavor (HF) quarks, the sum of (tt) over bar + b + X and (tt) over bar + c + X, collectively referred to as (tt) over bar + HF. The data set used corresponds to an integrated luminosity of 4.7 fb(-1) of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The presence of additional HF (b or c) quarks in the (tt) over bar sample is inferred by looking for events with at least three b-tagged jets, where two are attributed to the b quarks from the (tt) over bar decays and the third to additional HF production. The dominant background to (tt) over bar + HF in this sample is (tt) over bar + jet events in which a light-flavor jet is misidentified as a heavy-flavor jet. To determine the heavy-and light-flavor content of the additional b-tagged jets, a fit to the vertex mass distribution of b-tagged jets in the sample is performed. The result of the fit shows that 79 +/- 14 (stat) +/- 22 (syst) of the 105 selected extra b-tagged jets originate from HF quarks, 3 standard deviations away from the hypothesis of zero (tt) over bar + HF production. The result for extra HF production is quoted as a ratio (R-HF) of the cross section for (tt) over bar + HF production to the cross section for (tt) over bar production with at least one additional jet. Both cross sections are measured in a fiducial kinematic region within the ATLAS acceptance. R-HF is measured to be [6.2 +/- 1.1(stat) +/- 1.8 (syst)]% for jets with p(T) > 25 GeV and vertical bar eta vertical bar < 2.5, in agreement with the expectations from Monte Carlo generators.

  • 624. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    The differential production cross section of the phi(1020) meson in root s=7 TeV pp collisions measured with the ATLAS detector2014In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 74, no 7, p. 2895-Article in journal (Refereed)
    Abstract [en]

    A measurement is presented of the phi x BR(phi -> K+ K-) production cross section at root s = 7 TeV using pp collision data corresponding to an integrated luminosity of 383 mu b(-1), collected with the ATLAS experiment at the LHC. Selection of phi(1020) mesons is based on the identification of charged kaons by their energy loss in the pixel detector. The differential cross section is measured as a function of the transverse momentum, pT, phi, and rapidity, y(phi), of the phi(1020) meson in the fiducial region 500 < pT,phi < 1200MeV, vertical bar y phi| < 0.8, kaon p(T), (K) > 230 MeV and kaon momentum p(K) < 800 MeV. The integrated phi(1020)-meson production cross section in this fiducial range is measured to be sigma(phi) x BR(phi -> K+ K-) = 570 +/- 8 (stat) +/- 66 (syst) +/- 20 (lumi) mu b.

  • 625. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Time-dependent angular analysis of the decay B-s(0) -> J/psi phi and extraction of Delta Gamma(s) and the CP-violating weak phase phi(s) by ATLAS2012In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 12, p. 072-Article in journal (Refereed)
    Abstract [en]

    A measurement of B-s(0) -> J/psi phi decay parameters, including the CP-violating weak phase phi(s) and the decay width difference Delta Gamma(s) is reported, using 4.9 fb(-1) of integrated luminosity collected in 2011 by the ATLAS detector from LHC pp collisions at a centre-of-mass energy root s = 7 TeV. The mean decay width Gamma(s) and the transversity amplitudes vertical bar A(0)(0)vertical bar(2) and vertical bar A(parallel to)(0)vertical bar(2) are also measured. The values reported for these parameters are: phi(s) = 0.22 +/- 0.41 (stat.) +/- 0.10 (syst.) rad Delta Gamma(s) = 0.053 +/- 0.021 (stat.) +/- 0.010 (syst.) ps(-1) Gamma(s) = 0.677 +/- 0.007 (stat.) +/- 0.004 (syst.) ps(-1) vertical bar A(0)(0)vertical bar(2) = 0.528 +/- 0.006 (stat.) +/- 0.009 (syst.) vertical bar A(parallel to)(0)vertical bar(2) = 0.220 +/- 0.008 (stat.) +/- 0.007 (syst.) where the values quoted for phi(s) and Delta Gamma(s) correspond to the solution compatible with the external measurements to which the strong phase delta(perpendicular to) is constrained and where is Delta Gamma(s) constrained to be positive. The fraction of S-wave KK or f(0) contamination through the decays B-s(0) -> J/psi K+K- (f(0)) is measured as well and is found to be consistent with zero. Results for phi(s) and Delta Gamma(s) are also presented as 68%, 90% and 95% likelihood contours, which show agreement with Standard Model expectations.

  • 626. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Triggers for displaced decays of long-lived neutral particles in the ATLAS detector2013In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 8, p. P07015-Article in journal (Refereed)
    Abstract [en]

    A set of three dedicated triggers designed to detect long-lived neutral particles decaying throughout the ATLAS detector to a pair of hadronic jets is described. The efficiencies of the triggers for selecting displaced decays as a function of the decay position are presented for simulated events. The effect of pile-up interactions on the trigger efficiencies and the dependence of the trigger rate on instantaneous luminosity during the 2012 data-taking period at the LHC are discussed.

  • 627. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Underlying event characteristics and their dependence on jet size of charged-particle jet events in pp collisions at root(s)=7 TeV with the ATLAS detector2012In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 86, no 7, p. 072004-Article in journal (Refereed)
    Abstract [en]

    Distributions sensitive to the underlying event are studied in events containing one or more chargedparticle jets produced in pp collisions at root s = 7 TeV with the ATLAS detector at the Large Hadron Collider (LHC). These measurements reflect 800 mu b(-1) of data taken during 2010. Jets are reconstructed using the anti-k(t) algorithm with radius parameter R varying between 0.2 and 1.0. Distributions of the charged-particle multiplicity, the scalar sum of the transverse momentum of charged particles, and the average charged-particle p(T) are measured as functions of p(T)(jet) in regions transverse to and opposite the leading jet for 4 GeV < p(T)(jet) < 100 GeV. In addition, the R dependence of the mean values of these observables is studied. In the transverse region, both the multiplicity and the scalar sum of the transverse momentum at fixed p(T)(jet) vary significantly with R, while the average charged- particle transverse momentum has a minimal dependence on R. Predictions from several Monte Carlo tunes have been compared to the data; the predictions from Pythia 6, based on tunes that have been determined using LHC data, show reasonable agreement with the data, including the dependence on R. Comparisons with other generators indicate that additional tuning of soft-QCD parameters is necessary for these generators. The measurements presented here provide a testing ground for further development of the Monte Carlo models.

  • 628. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for the Standard Model Higgs boson in the H -> WW(*()) -> lvlv decay mode with 4.7 fb(-1) of ATLAS data at root s=7 TeV2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 716, no 1, p. 62-81Article in journal (Refereed)
    Abstract [en]

    A search for the Standard Model Higgs boson in the H -> WW(*()) -> lvlv (l = e.mu) decay mode is presented. The search is performed using proton-proton collision data corresponding to an integrated luminosity of 4.7 fb(-1) at a centre-of-mass energy of 7 TeV collected during 2011 with the ATLAS detector at the Large Hadron Collider. No significant excess of events over the expected background is observed. An upper bound is placed on the Higgs boson production cross section as a function of its mass. A Standard Model Higgs boson with mass in the range between 133 GeV and 261 GeV is excluded at 95% confidence level, while the expected exclusion range is from 127 GeV to 233 GeV.

  • 629. Aad, G
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Morley, Anthony
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for Scalar Diphoton Resonances in the Mass Range 65-600 GeV with the ATLAS Detector in pp Collision Data at root s=8 TeV2014In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 113, no 17Article in journal (Refereed)
    Abstract [en]

    A search for scalar particles decaying via narrow resonances into two photons in the mass range 65-600 GeV is performed using 20.3 fb(-1) of root s = 8 TeV pp collision data collected with the ATLAS detector at the Large Hadron Collider. The recently discovered Higgs boson is treated as a background. No significant evidence for an additional signal is observed. The results are presented as limits at the 95% confidence level on the production cross section of a scalar boson times branching ratio into two photons, in a fiducial volume where the reconstruction efficiency is approximately independent of the event topology. The upper limits set extend over a considerably wider mass range than previous searches.

  • 630. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Morley, Anthony
    KTH, School of Engineering Sciences (SCI), Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Evidence for the spin-0 nature of the Higgs boson using ATLAS data2013In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 726, no 1-3, p. 120-144Article in journal (Refereed)
    Abstract [en]

    Studies of the spin and parity quantum numbers of the Higgs boson are presented, based on proton-proton collision data collected by the ATLAS experiment at the LHC. The Standard Model spin-parity JP=0+ hypothesis is compared with alternative hypotheses using the Higgs boson decays H→γγ, H→ZZ*→4ℓ and H→WW*→ℓνℓν, as well as the combination of these channels. The analysed dataset corresponds to an integrated luminosity of 20.7 fb-1 collected at a centre-of-mass energy of s=8TeV. For the H→ZZ*→4ℓ decay mode the dataset corresponding to an integrated luminosity of 4.6 fb-1 collected at s=7TeV is included. The data are compatible with the Standard Model JP=0+ quantum numbers for the Higgs boson, whereas all alternative hypotheses studied in this Letter, namely some specific JP=0-, 1+, 1-, 2+ models, are excluded at confidence levels above 97.8%. This exclusion holds independently of the assumptions on the coupling strengths to the Standard Model particles and in the case of the JP=2+ model, of the relative fractions of gluon-fusion and quark-antiquark production of the spin-2 particle. The data thus provide evidence for the spin-0 nature of the Higgs boson, with positive parity being strongly preferred.

  • 631. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Morley, Anthony K.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Measurements of Higgs boson production and couplings in the four-lepton channel in pp collisions at center-of-mass energies of 7 and 8 TeV with the ATLAS detector2015In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 91, no 1, article id 012006Article in journal (Refereed)
    Abstract [en]

    The final ATLAS Run 1 measurements of Higgs boson production and couplings in the decay channel H -> ZZ* -> l(+)l(-)l(+)l'(-), where l, l' = e or mu, are presented. These measurements were performed using pp collision data corresponding to integrated luminosities of 4.5 and 20.3 fb(-1) at center-of-mass energies of 7 and 8 TeV, respectively, recorded with the ATLAS detector at the LHC. The H -> ZZ* -> 4l signal is observed with a significance of 8.1 standard deviations, with an expectation of 6.2 standard deviations, at m(H) = 125.36 GeV, the combined ATLAS measurement of the Higgs boson mass from the H -> gamma gamma and H -> ZZ* -> 4l channels. The production rate relative to the Standard Model expectation, the signal strength, is measured in four different production categories in the H -> ZZ* -> 4l channel. The measured signal strength, at this mass, and with all categories combined, is 1.44(-0.33)(+0.40). The signal strength for Higgs boson production in gluon fusion or in association with (tt) over bar or (bb) over bar pairs is found to be 1.7(-0.4)(+0.5), while the signal strength for vector-boson fusion combined with WH/ZH associated production is found to be 0.3(-0.9)(+1.6).

  • 632. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Morley, Anthony K.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Monitoring and data quality assessment of the ATLAS liquid argon calorimeter2014In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 9, no 7Article in journal (Refereed)
    Abstract [en]

    The liquid argon calorimeter is a key component of the ATLAS detector installed at the CERN Large Hadron Collider. The primary purpose of this calorimeter is the measurement of electron and photon kinematic properties. It also provides a crucial input for measuring jets and missing transverse momentum. An advanced data monitoring procedure was designed to quickly identify issues that would affect detector performance and ensure that only the best quality data are used for physics analysis. This article presents the validation procedure developed during the 2011 and 2012 LHC data-taking periods, in which more than 98% of the proton-proton luminosity recorded by ATLAS at a centre-of-mass energy of 7-8 TeV had calorimeter data quality suitable for physics analysis.

  • 633. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Morley, Anthony K.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for high-mass dilepton resonances in pp collisions at root s = 8 TeV with the ATLAS detector2014In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 90, no 5, p. 052005-Article in journal (Refereed)
    Abstract [en]

    The ATLAS detector at the Large Hadron Collider is used to search for high-mass resonances decaying to dielectron or dimuon final states. Results are presented from an analysis of proton-proton (pp) collisions at a center-of-mass energy of 8 TeV corresponding to an integrated luminosity of 20.3 fb(-1) in the dimuon channel. A narrow resonance with Standard Model Z couplings to fermions is excluded at 95% confidence level for masses less than 2.79 TeV in the dielectron channel, 2.53 TeV in the dimuon channel, and 2.90 TeV in the two channels combined. Limits on other model interpretations are also presented, including a grand-unification model based on the E-6 gauge group, Z* bosons, minimal Z' models, a spin-2 graviton excitation from Randall-Sundrum models, quantum black holes, and a minimal walking technicolor model with a composite Higgs boson.

  • 634. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Morley, Anthony K.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for new phenomena in events with a photon and missing transverse momentum in pp collisions at root s = 8 TeV with the ATLAS detector2015In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 91, no 1, article id 012008Article in journal (Refereed)
    Abstract [en]

    Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum with the ATLAS experiment at the LHC are reported. Data were collected in proton-proton collisions at a center-of-mass energy of 8 TeVand correspond to an integrated luminosity of 20.3 fb(-1). The observed data are well described by the expected Standard Model backgrounds. The expected (observed) upper limit on the fiducial cross section for the production of events with a photon and large missing transverse momentum is 6.1 (5.3) fb at 95% confidence level. Exclusion limits are presented on models of new phenomena with large extra spatial dimensions, supersymmetric quarks, and direct pair production of dark-matter candidates.

  • 635. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Morley, Anthony K.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for pair-produced long-lived neutral particles decaying to jets in the ATLAS hadronic calorimeter in pp collisions at root s=8 TeV2015In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 743, p. 15-34Article in journal (Refereed)
    Abstract [en]

    The ATLAS detector at the Large Hadron Collider at CERN is used to search for the decay of a scalar boson to a pair of long-lived particles, neutral under the Standard Model gauge group, in 20.3 fb(-1) of data collected in proton-proton collisions at root s = 8 TeV. This search is sensitive to long-lived particles that decay to Standard Model particles producing jets at the outer edge of the ATLAS electromagnetic calorimeter or inside the hadronic calorimeter. No significant excess of events is observed. Limits are reported on the product of the scalar boson production cross section times branching ratio into long-lived neutral particles as a function of the proper lifetime of the particles. Limits are reported for boson masses from 100 GeV to 900 GeV, and a long-lived neutral particle mass from 10 GeV to 150 GeV.

  • 636. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Morley, Anthony K.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for pair-produced third-generation squarks decaying via charm quarks or in compressed supersymmetric scenarios in pp collisions at root s = 8 TeV with the ATLAS detector2014In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 90, no 5Article in journal (Refereed)
    Abstract [en]

    Results of a search for supersymmetry via direct production of third-generation squarks are reported, using 20.3 fb(-1) of proton-proton collision data at root s = 8 TeV recorded by the ATLAS experiment at the LHC in 2012. Two different analysis strategies based on monojetlike and c-tagged event selections are carried out to optimize the sensitivity for direct top squark-pair production in the decay channel to a charm quark and the lightest neutralino ((t) over tilde (1) -> c + (chi) over tilde (0)(1)) across the top squark-neutralino mass parameter space. No excess above the Standard Model background expectation is observed. The results are interpreted in the context of direct pair production of top squarks and presented in terms of exclusion limits in the (m((t) over tilde1), m((chi) over tilde 10)) parameter space. A top squark of mass up to about 240 GeV is excluded at 95% confidence level for arbitrary neutralino masses, within the kinematic boundaries. Top squark masses up to 270 GeV are excluded for a neutralino mass of 200 GeV. In a scenario where the top squark and the lightest neutralino are nearly degenerate in mass, top squark masses up to 260 GeV are excluded. The results from the monojetlike analysis are also interpreted in terms of compressed scenarios for top squark-pair production in the decay channel (t) over tilde (1) -> b + ff' + (chi) over tilde (0)(1) and sbottom pair production with (b) over tilde -> b + (chi) over tilde (0)(1), leading to a similar exclusion for nearly mass-degenerate third-generation squarks and the lightest neutralino. The results in this paper significantly extend previous results at colliders.

  • 637. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Morley, Anthony K.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for resonant diboson production in the llq(q)over-bar final state in pp collisions at root s=8 TeV with the ATLAS detector2015In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 75, no 2, article id 69Article in journal (Refereed)
    Abstract [en]

    This paper reports on a search for narrow resonances in diboson production in the llq (q) over bar final state using pp collision data corresponding to an integrated luminosity of 20 fb(-1) collected at root s = 8 TeV with the ATLAS detector at the Large Hadron Collider. No significant excess of data events over the Standard Model expectation is observed. Upper limits at the 95 % confidence level are set on the production cross section times branching ratio for Kaluza-Klein gravitons predicted by the Randall-Sundrum model and for Extended Gauge Model W' bosons. These results lead to the exclusion of mass values below 740 and 1590 GeV for the graviton and W' boson respectively.

  • 638. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Morley, Anthony K.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for Scalar Charm Quark Pair Production in pp Collisions at root s=8 TeV with the ATLAS Detector2015In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 114, no 16, article id UNSP 161801Article in journal (Refereed)
    Abstract [en]

    The results of a dedicated search for pair production of scalar partners of charm quarks are reported. The search is based on an integrated luminosity of 20.3 fb(-1) of pp collisions at root s = 8 TeV recorded with the ATLAS detector at the LHC. The search is performed using events with large missing transverse momentum and at least two jets, where the two leading jets are each tagged as originating from c quarks. Events containing isolated electrons or muons are vetoed. In an R-parity-conserving minimal super-symmetric scenario in which a single scalar-charm state is kinematically accessible, and where it decays exclusively into a charm quark and a neutralino, 95% confidence-level upper limits are obtained in the scalar-charm-neutralino mass plane such that, for neutralino masses below 200 GeV, scalar-charm masses up to 490 GeV are excluded.

  • 639. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Morley, Anthony K.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at root s=8 TeV with the ATLAS detector2015In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 4, article id UNSP 116Article in journal (Refereed)
    Abstract [en]

    The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. The search is based on proton-proton collision data at a centre-of-mass energy root s = 8 TeV collected in 2012, corresponding to an integrated luminosity of 20 fb(-1). No significant excess above the Standard Model expectation is observed. Limits are set on supersymmetric particle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV. Limits are also set on the parameters of a minimal universal extra dimension model, excluding a compactification radius of 1/R-c = 950 GeV for a cut-off scale times radius (Lambda R-c) of approximately 30.

  • 640. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Morley, Anthony K.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for strong production of supersymmetric particles in final states with missing transverse momentum and at least three b-jets at root s=8 TeV proton-proton collisions with the ATLAS detector2014In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 10, p. UNSP 024-Article in journal (Refereed)
    Abstract [en]

    This paper reports the results of a search for strong production of supersymmetric particles in 20.1 fb(-1) of proton-proton collisions at a centre-of-mass energy of 8 TeV using the ATLAS detector at the LHC. The search is performed separately in events with either zero or at least one high-p (T) lepton (electron or muon), large missing transverse momentum, high jet multiplicity and at least three jets identified as originated from the fragmentation of a b-quark. No excess is observed with respect to the Standard Model predictions. The results are interpreted in the context of several supersymmetric models involving gluinos and scalar top and bottom quarks, as well as a mSUGRA/CMSSM model. Gluino masses up to 1340 GeV are excluded, depending on the model, significantly extending the previous ATLAS limits.

  • 641. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Morley, Anthony K.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for top squark pair production in final states with one isolated lepton, jets, and missing transverse momentum in root s=8 TeV pp collisions with the ATLAS detector2014In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 11, article id UNSP 118Article in journal (Refereed)
    Abstract [en]

    The results of a search for top squark (stop) pair production in final states with one isolated lepton, jets, and missing transverse momentum are reported. The analysis is performed with proton-proton collision data at root s = 8 TeV collected with the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of 20 fb(-1). The lightest supersymmetric particle (LSP) is taken to be the lightest neutralino which only interacts weakly and is assumed to be stable. The stop decay modes considered are those to a top quark and the LSP as well as to a bottom quark and the lightest chargino, where the chargino decays to the LSP by emitting a W boson. A wide range of scenarios with different mass splittings between the stop, the lightest neutralino and the lightest chargino are considered, including cases where the W bosons or the top quarks are off-shell. Decay modes involving the heavier charginos and neutralinos are addressed using a set of phenomenological models of supersymmetry. No significant excess over the Standard Model prediction is observed. A stop with a mass between 210 and 640 GeV decaying directly to a top quark and a massless LSP is excluded at 95% confidence level, and in models where the mass of the lightest chargino is twice that of the LSP, stops are excluded at 95% confidence level up to a mass of 500 GeV for an LSP mass in the range of 100 to 150 GeV. Stringent exclusion limits are also derived for all other stop decay modes considered, and model-independent upper limits are set on the visible cross-section for processes beyond the Standard Model.

  • 642. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics.
    Morley, Anthony K.
    KTH, School of Engineering Sciences (SCI), Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics.
    Zwalinski, Lukasz
    et al,
    Search for long-lived neutral particles decaying into lepton jets in proton-proton collisions at √s= 8TeV with the ATLAS detector2014In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2014, no 11, p. 48p-Article in journal (Refereed)
    Abstract [en]

    Abstract: Several models of physics beyond the Standard Model predict neutral particles that decay into final states consisting of collimated jets of light leptons and hadrons (so-called “lepton jets”). These particles can also be long-lived with decay length comparable to, or even larger than, the LHC detectors’ linear dimensions. This paper presents the results of a search for lepton jets in proton-proton collisions at the centre-of-mass energy of √s= 8TeV in a sample of 20.3 fb−1 collected during 2012 with the ATLAS detector at the LHC. Limits on models predicting Higgs boson decays to neutral long-lived lepton jets are derived as a function of the particle’s proper decay length.

  • 643. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Morley, Anthony
    KTH, School of Engineering Sciences (SCI), Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC2013In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 726, no 1-3, p. 88-119Article in journal (Refereed)
    Abstract [en]

    Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H→γγ, H→ZZ*→4ℓ and H→WW*→ℓνℓν. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of s=7 TeV and s=8 TeV, corresponding to an integrated luminosity of about 25 fb-1. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson.

  • 644. Aad, G
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L
    Measurement of the W W cross section in root s=7 TeV pp collisions with the ATLAS detector and limits on anomalous gauge couplings2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 712, no 4-5, p. 289-308Article in journal (Refereed)
    Abstract [en]

    This Letter reports a measurement of the W W production cross section in root 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 sigma (pp -> W W) = 54.4 +/- 4.0 (stat.) +/- 3.9 (syst.) +/- 2.0 (lumi.) pb, consistent with the Standard Model prediction of sigma (pp -> W W)= 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.

  • 645. Aad, G
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L
    Search for new particles decaying to ZZ using final states with leptons and jets with the ATLAS detector in root s=7 TeV proton-proton collisions2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 712, no 4-5, p. 331-350Article in journal (Refereed)
    Abstract [en]

    A search is presented for a narrow resonance decaying to a pair of Z bosons using data corresponding to 1.02 fb(-1) of integrated luminosity collected by the ATLAS experiment from pp collisions at root s= 7 TeV. Events containing either four charged leptons (llll) or two charged leptons and two jets (lljj) are analyzed and found to be consistent with the Standard Model background expectation. Lower limits on a resonance mass are set using the Randall-Sundrum (RS1) graviton model as a benchmark. Using both llll and lljj events, an RS1 graviton with k/(m) over bar (pl) = 0.1 and mass between 325 and 845 GeV is excluded at 95% confidence level. In addition, the llll events are used to set a model-independent fiducial cross section limit of sigma(fid)(pp -> X -> ZZ) < 0.92 pb at 95% confidence level for any new sources of ZZ production with m(ZZ) greater than 300 GeV.

  • 646. Aad, G
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L
    Search for resonant WZ production in the WZ -> lvl ' l ' channel in root(s)=7 TeV pp collisions with the ATLAS detector2012In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 85, no 11, p. 112012-Article in journal (Refereed)
    Abstract [en]

    A generic search is presented for a heavy particle decaying to WZ -> lvl'l' (l, l' = e, mu) final states. The data were recorded by the ATLAS detector in root s = 7 TeV pp collisions at the Large Hadron Collider and correspond to an integrated luminosity of 1.02 fb(-1). The transverse mass distribution of the selected WZ candidates is found to be consistent with the standard model expectation. Upper limits on the production cross section times branching ratio are derived using two benchmark models predicting a heavy particle decaying to a WZ pair.

  • 647. Aad, G
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L
    Search for Supersymmetry in Events with Three Leptons and Missing Transverse Momentum in root s=7 TeV pp Collisions with the ATLAS Detector2012In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 108, no 26, p. 261804-Article in journal (Refereed)
    Abstract [en]

    A search for the weak production of charginos and neutralinos decaying to a final state with three leptons (electrons or muons) and missing transverse momentum is presented. The analysis uses 2.06 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 two 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 and simplified models. For the simplified models, degenerate lightest chargino and next-to-lightest neutralino masses up to 300 GeV are excluded for mass differences from the lightest neutralino up to 300 GeV.

  • 648. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Combined search for the Standard Model Higgs boson using up to 4.9 fb(-1) of pp collision data at root s=7 TeV with the ATLAS detector at the LHC2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 710, no 1, p. 49-66Article in journal (Refereed)
    Abstract [en]

    A combined search for the Standard Model Higgs boson with the ATLAS experiment at the LHC using datasets corresponding to integrated luminosities from 1.04 fb(-1) to 4.9 fb(-1) of pp collisions collected at root s = 7 TeV is presented. The Higgs boson mass ranges 112.9-115.5 GeV, 131-238 GeV and 251-466 GeV are excluded at the 95% confidence level (CL), while the range 124-519 GeV is expected to be excluded in the absence of a signal. An excess of events is observed around m(H) similar to 126 GeV with a local significance of 3.5 standard deviations (sigma). The local significances of H -> gamma, H -> ZZ(()*()) -> l(+)l(-)l'(+)l'(-) and H -> WW(*()) l(+)nu l'(-)(nu) over bar, the three most sensitive channels in this mass range, are 2.8 sigma, 2.1 sigma and 1.4 sigma. respectively. The global probability for the background to produce such a fluctuation anywhere in the explored Higgs boson mass range 110-600 GeV is estimated to be similar to 1.4% or, equivalently, 2.2 sigma.

  • 649. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Measurement of W+W- production in pp collisions at root s=7 TeV with the ATLAS detector and limits on anomalous WWZ and WW gamma couplings2013In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 87, no 11, p. 112001-1-112001-29Article in journal (Refereed)
    Abstract [en]

    This paper presents a measurement of the W+W- production cross section in pp collisions at root s = 7 TeV. The leptonic decay channels are analyzed using data corresponding to an integrated luminosity of 4: 6 fb(-1) collected with the ATLAS detector at the Large Hadron Collider. The W+W- production cross section sigma(pp -> W+W- + X) is measured to be 51.9 +/- 2.0(stat) +/- 3.9(syst) +/- 2.0(lumi) pb, compatible with the Standard Model prediction of 44.7(-1.9)(+2.1) pb. A measurement of the normalized fiducial cross section as a function of the leading lepton transverse momentum is also presented. The reconstructed transverse momentum distribution of the leading lepton is used to extract limits on anomalous WWZ and WW gamma couplings.

  • 650. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kuwertz, Emma S.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Measurements of W gamma and Z gamma production in pp collisions at root s=7 TeV with the ATLAS detector at the LHC2013In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 87, no 11, p. 112003-Article in journal (Refereed)
    Abstract [en]

    The integrated and differential fiducial cross sections for the production of a W or Z boson in association with a high-energy photon are measured using pp collisions at root s = 7 TeV. The analyses use a data sample with an integrated luminosity of 4.6 fb(-1) collected by the ATLAS detector during the 2011 LHC data-taking period. Events are selected using leptonic decays of the W and Z bosons [W(e nu, mu nu) and Z(e(+)e(-), mu(+)mu(-), nu(nu) over bar)] with the requirement of an associated isolated photon. The data are used to test the electroweak sector of the Standard Model and search for evidence for new phenomena. The measurements are used to probe the anomalous WW gamma, ZZ gamma, and Z gamma gamma triple-gauge-boson couplings and to search for the production of vector resonances decaying to Z gamma and W gamma. No deviations from Standard Model predictions are observed and limits are placed on anomalous triple-gauge-boson couplings and on the production of new vector meson resonances.

10111213141516 601 - 650 of 124192
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