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  • 101. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for Higgs boson decays to a photon and a Z boson in pp collisions at root s=7 and 8 TeV with the ATLAS detector2014Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 732, s. 8-27Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search is reported for a neutral Higgs boson in the decay channel H -> Z gamma, Z -> l(+)l(-) (l = e, mu), using 4.5 fb(-1) of pp collisions at root s = 7 TeV and 20.3 fb(-1) of pp collisions at root s = 8 TeV, recorded by the ATLAS detector at the CERN Large Hadron Collider. The observed distribution of the invariant mass of the three final-state particles, m(ll gamma), is consistent with the Standard Model hypothesis in the investigated mass range of 120-150 GeV. For a Higgs boson with a mass of 125.5 GeV, the observed upper limit at the 95% confidence level is 11 times the Standard Model expectation. Upper limits are set on the cross section times branching ratio of a neutral Higgs boson with mass in the range 120-150 GeV between 0.13 and 0.5 pb for root s = 8 TeV at 95% confidence level.

  • 102. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for Higgs Boson Pair Production in the gamma gamma b(b)over-bar Final State Using pp Collision Data at root s=8 TeV from the ATLAS Detector2015Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 114, nr 8, artikkel-id 081802Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Searches are performed for resonant and nonresonant Higgs boson pair production in the gamma gamma b (b) over bar final state using 20 fb(-1) of proton-proton collisions at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the CERN Large Hadron Collider. A 95% confidence level upper limit on the cross section times branching ratio of nonresonant production is set at 2.2 pb, while the expected limit is 1.0 pb. The difference derives from a modest excess of events, corresponding to 2.4 standard deviations from the background-only hypothesis. The limit observed in the search for a narrow X -> hh resonance ranges between 0.7 and 3.5 pb as a function of the resonance mass.

  • 103. Aad, G
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for high-mass diphoton resonances in pp collisions at pffisffi root s=8 TeV with the ATLAS detector2015Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 92, nr 3, artikkel-id 032004Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article describes a search for high-mass resonances decaying to a pair of photons using a sample of 20.3 fb(-1) of pp collisions at root s = 8 TeV recorded with the ATLAS detector at the Large Hadron Collider. The data are found to be in agreement with the Standard Model prediction, and limits are reported in the framework of the Randall-Sundrum model. This theory leads to the prediction of graviton states, the lightest of which could be observed at the Large Hadron Collider. A lower limit of 2.66 (1.41) TeV at 95% confidence level is set on the mass of the lightest graviton for couplings of k/(M) over bar (Pl) = 0.1 (0.01).

  • 104. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for invisible particles produced in association with single-top-quarks in proton–proton collisions at √s = 8 Tev with the ATLAS detector2015Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 75, nr 2, artikkel-id 79Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for the production of single-top-quarks in association with missing energy is performed in proton–proton collisions at a centre-of-mass energy of √s = 8 Tev with the ATLAS experiment at the large hadron collider using data collected in 2012, corresponding to an integrated luminosity of 20.3 fb-1. In this search, the W boson from the top quark is required to decay into an electron or a muon and a neutrino. No deviation from the standard model prediction is observed, and upper limits are set on the production cross-section for resonant and non-resonant production of an invisible exotic state in association with a right-handed top quark. In the case of resonant production, for a spin-0 resonance with a mass of 500 GeV, an effective coupling strength above 0.15 confidence level for the top quark and an invisible spin-1/2 state with mass between 0 and 100 GeV. In the case of non-resonant production, an effective coupling strength above 0.2 is excluded at 95% confidence level for the top quark and an invisible spin-1 state with mass between 0 and 657 GeV.

  • 105. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for long-lived stopped R-hadrons decaying out of time with pp collisions using the ATLAS detector2013Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 88, nr 11, s. 112003-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An updated search is performed for gluino, top squark, or bottom squark R-hadrons that have come to rest within the ATLAS calorimeter, and decay at some later time to hadronic jets and a neutralino, using 5.0 and 22.9 fb -1 of pp collisions at 7 and 8 TeV, respectively. Candidate decay events are triggered in selected empty bunch crossings of the LHC in order to remove pp collision backgrounds. Selections based on jet shape and muon system activity are applied to discriminate signal events from cosmic ray and beam-halo muon backgrounds. In the absence of an excess of events, improved limits are set on gluino, stop, and sbottom masses for different decays, lifetimes, and neutralino masses. With a neutralino of mass 100 GeV, the analysis excludes gluinos with mass below 832 GeV (with an expected lower limit of 731 GeV), for a gluino lifetime between 10 μs and 1000 s in the generic R-hadron model with equal branching ratios for decays to qq̄χËœ0 and gχËœ0. Under the same assumptions for the neutralino mass and squark lifetime, top squarks and bottom squarks in the Regge R-hadron model are excluded with masses below 379 and 344 GeV, respectively.

  • 106. Aad, G
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L
    et, al.
    Search for massive supersymmetric particles decaying to many jets using the ATLAS detector in pp collisions at root s=8 TeV2015Inngår i: PHYSICAL REVIEW D, ISSN 1550-2368, Vol. 91, nr 11, artikkel-id 112016Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Results of a search for decays of massive particles to fully hadronic final states are presented. This search uses 20.3 fb(-1) of data collected by the ATLAS detector in root s = 8 TeV proton-proton collisions at the LHC. Signatures based on high jet multiplicities without requirements on the missing transverse momentum are used to search for R-parity-violating supersymmetric gluino pair production with subsequent decays to quarks. The analysis is performed using a requirement on the number of jets, in combination with separate requirements on the number of b-tagged jets, as well as a topological observable formed from the scalar sum of the mass values of large-radius jets in the event. Results are interpreted in the context of all possible branching ratios of direct gluino decays to various quark flavors. No significant deviation is observed from the expected Standard Model backgrounds estimated using jet counting as well as data-driven templates of the total-jet-mass spectra. Gluino pair decays to ten or more quarks via intermediate neutralinos are excluded for a gluino with mass m((g) over tilde) < 1 TeV for a neutralino mass m(<(chi)over tilde>10) = 500 GeV. Direct gluino decays to six quarks are excluded for m((g) over tilde) < 917 GeV for light-flavor final states, and results for various flavor hypotheses are presented.

  • 107. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for microscopic black holes and string balls in final states with leptons and jets with the ATLAS detector at root s=8 TeV2014Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 8, s. 103-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for an excess of events with multiple high transverse momentum objects including charged leptons and jets is presented, using 20.3 fb(-1) of proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2012 at a centre-of-mass energy of root s = 8 TeV. No excess of events beyond Standard Model expectations is observed. Using extra-dimensional models for black hole and string ball production and decay, exclusion contours are determined as a function of the mass threshold for production and the fundamental gravity scale for two, four and six extra dimensions. For six extra dimensions, mass thresholds of 4.8-6.2 TeV are excluded at 95 % confidence level, depending on the fundamental gravity scale and model assumptions. Upper limits on the fiducial cross-sections for non-Standard Model production of these final states are set.

  • 108. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for microscopic black holes in a like-sign dimuon final state using large track multiplicity with the ATLAS detector2013Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 88, nr 7, s. 072001-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search is presented for microscopic black holes in a like-sign dimuon final state in proton-proton collisions at root s = 8 TeV. The data were collected with the ATLAS detector at the Large Hadron Collider in 2012 and correspond to an integrated luminosity of 20.3 fb(-1). Using a high track multiplicity requirement, 0.6 +/- 0.2 background events from Standard Model processes are predicted and none observed. This result is interpreted in the context of low-scale gravity models and 95% C.L. lower limits on microscopic black hole masses are set for different model assumptions.

  • 109. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for neutral Higgs bosons of the minimal supersymmetric standard model in pp collisions at root s=8 TeV with the ATLAS detector2014Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 11, artikkel-id 056Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for the neutral Higgs bosons predicted by the Minimal Supersymmetric Standard Model (MSSM) is reported. The analysis is performed on data from proton-proton collisions at a centre-of-mass energy of 8 TeV collected with the ATLAS detector at the Large Hadron Collider. The samples used for this search were collected in 2012 and correspond to integrated luminosities in the range 19.5-20.3 fb(-1). The MSSM Higgs bosons are searched for in the tau tau final state. No significant excess over the expected background is observed, and exclusion limits are derived for the production cross section times branching fraction of a scalar particle as a function of its mass. The results are also interpreted in the MSSM parameter space for various benchmark scenarios.

  • 110. Aad, G
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at root s=8 TeV with the ATLAS detector2015Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 75, nr 7, artikkel-id 299Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb(-1) of root s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between E-T(miss) > 150 GeV and E-T(miss) > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presented.

  • 111. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for new phenomena in final states with large jet multiplicities and missing transverse momentum at root s=8 TeV proton-proton collisions using the ATLAS experiment2013Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 10, s. 130-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search is presented for new particles decaying to large numbers (7 or more) of jets, with missing transverse momentum and no isolated electrons or muons. This analysis uses 20.3 fb(-1) of p p collision data at root s = 8 TeV collected by the ATLAS experiment at the Large Hadron Collider. The sensitivity of the search is enhanced by considering the number of b-tagged jets and the scalar sum of masses of large-radius jets in an event. No evidence is found for physics beyond the Standard Model. The results are interpreted in the context of various simplified supersymmetry-inspired models where gluinos are pair produced, as well as an mSUGRA/CMSSM model.

  • 112. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for new phenomena in photon plus jet events collected in proton-proton collisions at root s=8 TeV with the ATLAS detector2014Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 728, s. 562-578Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This Letter describes a model-independent search for the production of new resonances in photon + jet (gamma + jet) events using 20 fb(-1) of proton-proton LHC data recorded with the ATLAS detector at a centre-of-mass energy of root s = 8 TeV. The gamma + jet mass distribution is compared to a background model fit from data; no significant deviation from the background-only hypothesis is found. Limits are set at 95% credibility level on generic Gaussian-shaped signals and two benchmark phenomena beyond the Standard Model: non-thermal quantum black holes and excited quarks. Non-thermal quantum black holes are excluded below masses of 4.6 TeV and excited quarks are excluded below masses of 3.5 TeV.

  • 113. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for new phenomena in the dijet mass distribution using pp collision data at root s=8 TeV with the ATLAS detector2015Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 91, nr 5, artikkel-id 052007Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dijet events produced in LHC proton-proton collisions at a center-of-mass energy root s = 8 TeV are studied with the ATLAS detector using the full 2012 data set, with an integrated luminosity of 20.3 fb(-1). Dijet masses up to about 4.5 TeV are probed. No resonancelike features are observed in the dijet mass spectrum. Limits on the cross section times acceptance are set at the 95% credibility level for various hypotheses of new phenomena in terms of mass or energy scale, as appropriate. This analysis excludes excited quarks with a mass below 4.06 TeV, color-octet scalars with a mass below 2.70 TeV, heavy W' bosons with a mass below 2.45 TeV, chiral W* bosons with a mass below 1.75 TeV, and quantum black holes with six extra space-time dimensions with threshold mass below 5.66 TeV.

  • 114. Aad, G
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for new resonances in W gamma and Z gamma final states in pp collisions at root s=8 TeV with the ATLAS detector2014Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 738, s. 428-447Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This Letter presents a search for new resonances decaying to final states with a vector boson produced in association with a high transverse momentum photon, V gamma, with V = W(-> l nu) or Z(-> l(+)l(-)), where l = mu or mu. The measurements use 20.3fb(-1) of proton-proton collision data at a center-of-mass energy of root s = 8 TeV recorded with the ATLAS detector. No deviations from the Standard Model expectations are found, and production cross section limits are set at 95% confidence level. Masses of the hypothetical a(T) and omega(T) states of a benchmark Low Scale Technicolor model are excluded in the ranges [275, 960] GeV and [200, 700]boolean OR[750, 890] GeV, respectively. Limits at 95% confidence level on the production cross section of a singlet scalar resonance decaying to Z gamma final states have also been obtained for masses below 1180GeV.

  • 115. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Zwalinski, L.
    et al,
    Search for nonpointing and delayed photons in the diphoton and missing transverse momentum final state in 8 TeV pp collisions at the LHC using the ATLAS detector2014Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 90, nr 11Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search has been performed, using the full 20.3fb-1 data sample of 8 TeV proton-proton collisions collected in 2012 with the ATLAS detector at the LHC, for photons originating from a displaced vertex due to the decay of a neutral long-lived particle into a photon and an invisible particle. The analysis investigates the diphoton plus missing transverse momentum final state, and is therefore most sensitive to pair production of long-lived particles. The analysis technique exploits the capabilities of the ATLAS electromagnetic calorimeter to make precise measurements of the flight direction, as well as the time of flight, of photons. No excess is observed over the Standard Model predictions for background. Exclusion limits are set within the context of gauge mediated supersymmetry breaking models, with the lightest neutralino being the next-to-lightest supersymmetric particle and decaying into a photon and gravitino with a lifetime in the range from 250 ps to about 100 ns.

  • 116. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for pair and single production of new heavy quarks that decay to a Z boson and a third-generation quark in pp collisions at root s=8 TeV with the ATLAS detector2014Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search is presented for the production of new heavy quarks that decay to a Z boson and a third-generation Standard Model quark. In the case of a new charge +2/3 quark (T), the decay targeted is T -> Zt, while the decay targeted for a new charge -1/3 quark (B) is B -> Zb. The search is performed with a dataset corresponding to 20.3 fb(-1) of p p collisions at root s = 8TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider. Selected events contain a high transverse momentum Z boson candidate reconstructed from a pair of oppositely charged same-flavor leptons (electrons or muons), and are analyzed in two channels defined by the absence or presence of a third lepton. Hadronic jets, in particular those with properties consistent with the decay of a b-hadron, are also required to be present in selected events. Different requirements are made on the jet activity in the event in order to enhance the sensitivity to either heavy quark pair production mediated by the strong interaction, or single production mediated by the electroweak interaction. No significant excess of events above the Standard Model expectation is observed, and lower limits are derived on the mass of vector-like T and B quarks under various branching ratio hypotheses, as well as upper limits on the magnitude of electroweak coupling parameters.

  • 117. Aad, G
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for production of WW/WZ resonances decaying to a lepton, neutrino and jets in pp collisions at root s = 8 TeV with the ATLAS detector (vol 75, pg 209, 2015)2015Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 75, nr 8, artikkel-id 370Artikkel i tidsskrift (Fagfellevurdert)
  • 118. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for production of WW/WZ resonances decaying to a lepton, neutrino and jets in pp collisions at root s=8 TeV with the ATLAS detector2015Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 75, nr 5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Studies of the spin and parity quantum numbers of the Higgs boson in the WW* -> ev mu v final state are presented, based on proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb(-1) at a centre-of-mass energy of root s = 8 TeV. The Standard Model spin-parity J(CP) = 0(++) hypothesis is compared with alternative hypotheses for both spin andCP. The case where the observed resonance is a mixture of the Standard-Model-like Higgs boson and CP-even (J(CP) = 0(++)) or CP-odd (J(CP) = 0(+-)) Higgs boson in scenarios beyond the Standard Model is also studied. The data are found to be consistent with the Standard Model prediction and limits are placed on alternative spin and CP hypotheses, including CP mixing in different scenarios.

  • 119. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for Quantum Black Hole Production in High-Invariant-Mass Lepton plus Jet Final States Using pp Collisions at root s=8 TeV and the ATLAS Detector2014Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 112, nr 9, s. 091804-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This Letter presents a search for quantum black-hole production using 20.3 fb(-1) of data collected with the ATLAS detector in pp collisions at the LHC at root s = 8 TeV. The quantum black holes are assumed to decay into a final state characterized by a lepton (electron or muon) and a jet. In either channel, no event with a lepton-jet invariant mass of 3.5 TeV or more is observed, consistent with the expected background. Limits are set on the product of cross sections and branching fractions for the lepton + jet final states of quantum black holes produced in a search region for invariant masses above 1 TeV. The combined 95% confidence level upper limit on this product for quantum black holes with threshold mass above 3.5 TeV is 0.18 fb. This limit constrains the threshold quantum black-hole mass to be above 5.3 TeV in the model considered.

  • 120. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for s-channel single top-quark production in proton-proton collisions at root s=8 TeV with the ATLAS detector2015Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 740, s. 118-136Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This Letter presents a search at the LHC for s-channel single top-quark production in proton-proton collisions at a centre-of-mass energy of 8 TeV. The analyzed data set was recorded by the ATLAS detector and corresponds to an integrated luminosity of 20.3 fb(-1). Selected events contain one charged lepton, large missing transverse momentum and exactly two b-tagged jets. A multivariate event classifier based on boosted decision trees is developed to discriminate s-channel single top-quark events from the main background contributions. The signal extraction is based on a binned maximum-likelihood fit of the output classifier distribution. The analysis leads to an upper limit on the s-channel single topquark production cross-section of 14.6 pb at the 95% confidence level. The fit gives a cross-section of sigma(s) = 5.0 +/- 4.3 pb, consistent with the Standard Model expectation.

  • 121. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using root s=8 TeV proton-proton collision data2014Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 9, s. 176-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for squarks and gluinos in final states containing high-pT jets, missing transverse momentum and no electrons or muons is presented. The data were recorded in 2012 by the ATLAS experiment in root s = 8 TeV proton-proton collisions at the Large Hadron Collider, with a total integrated luminosity of 20.3 fb(-1). Results are interpreted in a variety of simplified and specific supersymmetry-breaking models assuming that R-parity is conserved and that the lightest neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 1330 GeV for a simplified model incorporating only a gluino and the lightest neutralino. For a simplified model involving the strong production of first- and second-generation squarks, squark masses below 850 GeV (440 GeV) are excluded for a massless lightest neutralino, assuming mass degenerate ( single light-flavour) squarks. In mSUGRA/CMSSM models with tan beta = 30, A(0) = -2m(0) and mu > 0, squarks and gluinos of equal mass are excluded for masses below 1700 GeV. Additional limits are set for non-universal Higgs mass models with gaugino mediation and for simplified models involving the pair production of gluinos, each decaying to a top squark and a top quark, with the top squark decaying to a charm quark and a neutralino. These limits extend the region of supersymmetric parameter space excluded by previous searches with the ATLAS detector.

  • 122. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for supersymmetry at root 8=8 TeV in final states with jets and two same-sign leptons or three leptons with the ATLAS detector2014Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 6, s. 035-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for strongly produced supersymmetric particles is conducted using signatures involving multiple energetic jets and either two isolated leptons (e or mu) with the same electric charge, or at least three isolated leptons. The search also utilises jets originating from b-quarks, missing transverse momentum and other observables to extend its sensitivity. The analysis uses a data sample corresponding to a total integrated luminosity of 20.3 fb(-1) of = 8 TeV proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider in 2012. No deviation from the Standard Model expectation is observed. New or significantly improved exclusion limits are set on a wide variety of supersymmetric models in which the lightest squark can be of the first, second or third generations, and in which R-parity can be conserved or violated.

  • 123. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for supersymmetry in events with four or more leptons in root s=8 TeV pp collisions with the ATLAS detector2014Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 90, nr 5, s. 052001-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Results from a search for supersymmetry in events with four or more leptons including electrons, muons and taus are presented. The analysis uses a data sample corresponding to 20.3 fb(-1) of proton proton collisions delivered by the Large Hadron Collider at root s = 8 TeV and recorded by the ATLAS detector. Signal regions are designed to target supersymmetric scenarios that can be either enriched in or depleted of events involving the production of a Z boson. No significant deviations are observed in data from standard model predictions and results are used to set upper limits on the event yields from processes beyond the standard model. Exclusion limits at the 95% confidence level on the masses of relevant supersymmetric particles are obtained. In R-parity-violating simplified models with decays of the lightest supersymmetric particle to electrons and muons, limits of 1350 and 750 GeV are placed on gluino and chargino masses, respectively. In R-parity-conserving simplified models with heavy neutralinos decaying to a massless lightest supersymmetric particle, heavy neutralino masses up to 620 GeV are excluded. Limits are also placed on other supersymmetric scenarios.

  • 124. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for supersymmetry in events with large missing transverse momentum, jets, and at least one tau lepton in 20 fb(-1) of root s=8 TeV proton-proton collision data with the ATLAS detector2014Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 9Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for supersymmetry (SUSY) in events with large missing transverse momentum, jets, at least one hadronically decaying tau lepton and zero or one additional light leptons (electron/muon), has been performed using 20.3 fb(-1) of proton-proton collision data at root s = 8 TeV recorded with the ATLAS detector at the Large Hadron Collider. No excess above the Standard Model background expectation is observed in the various signal regions and 95% confidence level upper limits on the visible cross section for new phenomena are set. The results of the analysis are interpreted in several SUSY scenarios, significantly extending previous limits obtained in the same final states. In the framework of minimal gauge-mediated SUSY breaking models, values of the SUSY breaking scale Lambda below 63 TeV are excluded, independently of tan beta. Exclusion limits are also derived for an mSUGRA/CMSSM model, in both the R-parity-conserving and R-parity-violating case. A further interpretation is presented in a framework of natural gauge mediation, in which the gluino is assumed to be the only light coloured sparticle and gluino masses below 1090 GeV are excluded.

  • 125. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for the b(b)over-bar decay of the Standard Model Higgs boson in associated (W/Z)H production with the ATLAS detector2015Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 1, artikkel-id 069Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for the b (b) over bar decay of the Standard Model Higgs boson is performed with the ATLAS experiment using the full dataset recorded at the LHC in Run 1. The integrated luminosities used are 4.7 and 20.3 fb(-1) from pp collisions at root s = 7 and 8 TeV, respectively. The processes considered are associated (WIZ)H production, where W -> e nu/mu nu, Z -> ee/mu mu, and Z -> nu nu. The observed (expected) deviation from the backgroundonly hypothesis corresponds to a significance of 1.4 (2.6) standard deviations and the ratio of the measured signal yield to the Standard Model expectation is found to be mu = 0.52 +/- 0.32 (stat.) +/- 0.24 (syst.) for a Higgs boson mass of 125.36 GeV. The analysis procedure is validated by a measurement of the yield of (W/Z)Z production with Z -> b (b) over bar in the same final states as for the Higgs boson search, from which the ratio of the observed signal yield to the Standard Model expectation is found to be 0.74 +/- 0.09 (stat.) +/- 0.14 (syst.).

  • 126. Aad, G
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for the direct production of charginos, neutralinos and staus in final states with at least two hadronically decaying taus and missing transverse momentum in pp collisions at root s=8 TeVwith the ATLAS detecto2014Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 10, s. 096-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Results of a search for the electroweak associated production of charginos and next-to-lightest neutralinos, pairs of charginos or pairs of tau sleptons are presented. These processes are characterised by final states with at least two hadronically decaying tau leptons, missing transverse momentum and low jet activity. The analysis is based on an integrated luminosity of 20.3 fb(-1) of proton-proton collisions at root s = 8 TeV recorded with the ATLAS experiment at the Large Hadron Collider. No significant excess is observed with respect to the predictions from Standard Model processes. Limits are set at 95% confidence level on the masses of the lighter chargino and next-to-lightest neutralino for various hypotheses for the lightest neutralino mass in simplified models. In the scenario of direct production of chargino pairs, with each chargino decaying into the lightest neutralino via an intermediate tau slepton, chargino masses up to 345 GeV are excluded for a massless lightest neutralino. For associated production of mass-degenerate charginos and next-to-lightest neutralinos, both decaying into the lightest neutralino via an intermediate tau slepton, masses up to 410 GeV are excluded for a massless lightest neutralino.

  • 127. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for the lepton flavor violating decay Z -> e mu in pp collisions at root s=8 TeV with the ATLAS detector2014Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 90, nr 7, s. 072010-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ATLAS detector at the Large Hadron Collider is used to search for the lepton flavor violating process Z -> e mu in pp collisions using 20.3 fb(-1) of data collected at root s = 8 TeV. An enhancement in the e mu invariant mass spectrum is searched for at the Z-boson mass. The number of Z bosons produced in the data sample is estimated using events of similar topology, Z -> ee and mu mu, significantly reducing the systematic uncertainty in the measurement. There is no evidence of an enhancement at the Z-boson mass, resulting in an upper limit on the branching fraction, B(Z -> e mu) < 7.5 x 10(-7) at the 95% confidence level.

  • 128. Aad, G
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for the Standard Model Higgs boson decay to mu(+)mu(-) with the ATLAS detector2014Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 738, s. 68-86Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search is reported for Higgs boson decay to mu(+)mu(-) using data with an integrated luminosity of 24.8 fb(-1) collected with the ATLAS detector in pp collisions at root s = 7 and 8 TeV at the CERN Large Hadron Collider. The observed dimuon invariant mass distribution is consistent with the Standard Model background-only hypothesis in the 120-150 GeV search range. For a Higgs boson with a mass of 125.5 GeV, the observed (expected) upper limit at the 95% confidence level is 7.0 (7.2) times the Standard Model expectation. This corresponds to an upper limit on the branching ratio BR(H -> mu(+)mu(-)) of 1.5 x10(-3).

  • 129. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for the X-b and other hidden-beauty states in the pi(+)pi(-)gamma(1S) channel at ATLAS2015Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 740, s. 199-217Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This Letter presents a search for a hidden-beauty counterpart of the X(3872) in the mass ranges of 10.05-10.31 GeV and 10.40-11.00 GeV, in the channel X-b -> pi(+)pi(-)gamma(1S)(-> mu(+)mu(-)), using 16.2 fb(-1) of root s = 8 TeV pp collision data collected by the ATLAS detector at the LHC. No evidence for new narrow states is found, and upper limits are set on the product of the Xb cross section and branching fraction, relative to those of the gamma(25), at the 95% confidence level using the CLs approach. These limits range from 0.8% to 4.0%, depending on mass. For masses above 10.1 GeV, the expected upper limits from this analysis are the most restrictive to date. Searches for production of the gamma(1(3)D(J)), gamma(10860), and gamma(11 020) states also reveal no significant signals.

  • 130. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for W ' -> t(b)over-bar in the lepton plus jets final state in proton-proton collisions at a centre-of-mass energy of root s=8 TeV with the ATLAS detector2015Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 743, s. 235-255Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for new charged massive gauge bosons, called W', is performed with the ATLAS detector at the LHC, in proton-proton collisions at a centre-of-mass energy of root s = 8 TeV, using a dataset corresponding to an integrated luminosity of 20.3 fb(-1). This analysis searches for W' bosons in the W' -> t (b) over tilde decay channel in final states with electrons or muons, using a multivariate method based on boosted decision trees. The search covers masses between 0.5 and 3.0 TeV, for right-handed or left-handed W' bosons. No significant deviation from the Standard Model expectation is observed and limits are set on the W' -> t (b) over bar cross-section times branching ratio and on the W'-boson effective couplings as a function of the W'-boson mass using the CLs procedure. For a left-handed (right-handed) W' boson, masses below 1.70 (1.92) TeV are excluded at 95% confidence level.

  • 131. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for W’→tb→qqbb decays in collisions at (Formula presented.) = 8 TeV with the ATLAS detector2015Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 75, nr 4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for a massive W′ gauge boson decaying to a top quark and a bottom quark is performed with the ATLAS detector in pp collisions at the LHC. The datasetwas taken at a centre-of-mass energy of √s = 8 TeV and corresponds to 20.3 fb−1 of integrated luminosity. This analysis is done in the hadronic decay mode of the top quark, where novel jet substructure techniques are used to identify jets from high-momentum top quarks. This allows for a search for high-mass W′ bosons in the range 1.5-3.0 TeV. b-tagging is used to identify jets originating from b-quarks. The data are consistent with Standard Model background-only expectations, and upper limits at 95%confidence level are set on the W′ → tb cross section times branching ratio ranging from 0.16 pb to 0.33 pb for left-handed W′ bosons, and ranging from 0.10 pb to 0.21 pb for W′ bosons with purely righthanded couplings. Upper limits at 95% confidence level are set on the W′-boson coupling to tb as a function of the W′ mass using an effective field theory approach, which is independent of details of particular models predicting a W′ boson.

  • 132. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for WZ resonances in the fully leptonic channel using pp collisions at root s=8 TeV with the ATLAS detector2014Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 737, s. 223-243Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for resonant WZ production in the l nu l'l' (l, l' = e, mu) decay channel using 20.3 fb(-1) of root s = 8 TeV pp collision data collected by the ATLAS experiment at LHC is presented. No significant deviation from the Standard Model prediction is observed and upper limits on the production cross sections of WZ resonances from an extended gauge model W' and from a simplified model of heavy vector triplets are derived. A corresponding observed (expected) lower mass limit of 1.52 (1.49) TeV is derived for the W' at the 95% confidence level.

  • 133. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Searches for heavy long-lived charged particles with the ATLAS detector in proton-proton collisions at root s=8 TeV2015Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 1, artikkel-id 068Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Searches for heavy long-lived charged particles are performed using a data sample of 19.1 fb(-1) from proton-proton collisions at a centre-of-mass energy of root s = 8 TeV collected by the ATLAS detector at the Large Hadron Collider. No excess is observed above the estimated background and limits are placed on the mass of long-lived particles in various supersymmetric models. Long-lived tau sleptons in models with gauge-mediated symmetry breaking are excluded up to masses between 440 and 385 GeV for tan,3 between 10 and 50, with a 290 GeV limit in the case where only direct tau slepton production is considered. In the context of simplified LeptoSUSY models, where sleptons are stable and have a mass of 300 GeV, squark and gluino masses are excluded up to a mass of 1500 and 1360 GeV, respectively. Directly produced charginos, in simplified models where they are nearly degenerate to the lightest neutralino, are excluded up to a mass of 620 GeV. R-hadrons, composites containing a gluino, bottom squark or top squark, are excluded up to a mass of 1270, 845 and 900 GeV, respectively, using the full detector; and up to a mass of 1260, 835 and 870 GeV using an approach disregarding information from the muon spectrometer.

  • 134. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Standalone vertex finding in the ATLAS muon spectrometer2014Inngår i: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 9, nr 2, s. P02001-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to b (b) over bar final states, and pp collision data at root s = 7 TeV collected with the ATLAS detector at the LHC during 2011.

  • 135. Aad, G
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Two-particle Bose-Einstein correlations in pp collisions at root s=0.9 and 7 TeV measured with the ATLAS detector2015Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 75, nr 10, artikkel-id 466Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The paper presents studies of Bose-EinsteinCorrelations (BEC) for pairs of like-sign charged particles measured in the kinematic range p(T) > 100 MeV and |eta| < 2.5 in proton-proton collisions at centre-of-mass energies of 0.9 and 7 TeV with the ATLAS detector at the CERN Large Hadron Collider. The integrated luminosities are approximately 7 mu b(-1), 190 mu b(-1) and 12.4 nb(-1) for 0.9 TeV, 7 TeV minimum-bias and 7 TeV high-multiplicity data samples, respectively. The multiplicity dependence of the BEC parameters characterizing the correlation strength and the correlation source size are investigated for charged-particle multiplicities of up to 240. A saturation effect in the multiplicity dependence of the correlation source size parameter is observed using the high-multiplicity 7 TeV data sample. The dependence of the BEC parameters on the average transverse momentum of the particle pair is also investigated.

  • 136. Aad, G
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    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 TeV2014Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 113, nr 17Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 137. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma S.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Evidence for the spin-0 nature of the Higgs boson using ATLAS data2013Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 726, nr 1-3, s. 120-144Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 138. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma S.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony K.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    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 detector2015Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 91, nr 1, artikkel-id 012006Artikkel i tidsskrift (Fagfellevurdert)
    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).

  • 139. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma S.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony K.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Monitoring and data quality assessment of the ATLAS liquid argon calorimeter2014Inngår i: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 9, nr 7Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 140. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma S.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony K.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for high-mass dilepton resonances in pp collisions at root s = 8 TeV with the ATLAS detector2014Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 90, nr 5, s. 052005-Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 141. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma S.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony K.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    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 detector2015Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 91, nr 1, artikkel-id 012008Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 142. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma S.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony K.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    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 TeV2015Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 743, s. 15-34Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 143. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma S.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony K.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    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 detector2014Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 90, nr 5Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 144. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma S.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony K.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    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 detector2015Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 75, nr 2, artikkel-id 69Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 145. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma S.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony K.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for Scalar Charm Quark Pair Production in pp Collisions at root s=8 TeV with the ATLAS Detector2015Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 114, nr 16, artikkel-id UNSP 161801Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 146. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma S.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony K.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    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 detector2015Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 4, artikkel-id UNSP 116Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 147. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma S.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony K.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    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 detector2014Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 10, s. UNSP 024-Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 148. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma S.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony K.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    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 detector2014Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 11, artikkel-id UNSP 118Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 149. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Kuwertz, Emma S.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Morley, Anthony K.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Zwalinski, Lukasz
    et al,
    Search for long-lived neutral particles decaying into lepton jets in proton-proton collisions at √s= 8TeV with the ATLAS detector2014Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2014, nr 11, s. 48p-Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 150. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma S.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC2013Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 726, nr 1-3, s. 88-119Artikkel i tidsskrift (Fagfellevurdert)
    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.

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