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  • 51. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al
    Search for massive long-lived highly ionising particles with the ATLAS detector at the LHC2011Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 698, nr 5, s. 353-370Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search is made for massive highly ionising particles with lifetimes in excess of 100 ns, with the ATLAS experiment at the Large Hadron Collider, using 3.1 pb(-1) of pp collision data taken at root s = 7 TeV. The signature of energy loss in the ATLAS inner detector and electromagnetic calorimeter is used. No such particles are found and limits on the production cross section for electric charges 6e <= vertical bar q vertical bar <= 17e and masses 200 GeV <= m <= 1000 GeV are set in the range 1-12 pb for different hypotheses on the production mechanism.

  • 52. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al
    Search for neutral MSSM Higgs bosons decaying to tau(+)tau(-) pairs in proton-proton collisions root s=7 TeV with the ATLAS detector2011Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 705, nr 3, s. 174-192Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for neutral Higgs bosons decaying to pairs of tau leptons with the ATLAS detector at the LHC is presented. The analysis is based on proton-proton collisions at a center-of-mass energy of 7 TeV, recorded in 2010 and corresponding to an integrated luminosity of 36 pb(-1). After signal selection, 276 events are observed in this data sample. The observed number of events is consistent with the total expected background of 269 +/- 36 events. Exclusion limits at the 95% confidence level are derived for the production cross section of a generic Higgs boson phi as a function of the Higgs boson mass and for A/H/h production in the Minimal Supersymmetric Standard Model (MSSM) as a function of the parameters m(A) and tan beta.

  • 53. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al
    Search for pair production of first or second generation leptoquarks in proton-proton collisions at root s=7 TeV using the ATLAS detector at the LHC2011Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 83, nr 11, s. 112006-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper describes searches for the pair production of first or second generation scalar leptoquarks using 35 pb(-1) of proton-proton collision data recorded by the ATLAS detector at root s = 7 TeV. Leptoquarks are searched in events with two oppositely-charged muons or electrons and at least two jets, and in events with one muon or electron, missing transverse momentum and at least two jets. After event selection, the observed yields are consistent with the predicted backgrounds. Leptoquark production is excluded at the 95% CL for masses M-LQ < 376 (319) GeV and M-LQ < 422 (362) GeV for first and second generation scalar leptoquarks, respectively, when assuming the branching fraction of a leptoquark to a charged lepton is equal to 1.0 (0.5).

  • 54. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al
    Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in root s=7 TeV proton-proton collisions2011Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 701, nr 2, s. 186-203Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for squarks and gluinos in final states containing jets, missing transverse momentum and no electrons or muons 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 35 pb(-1) of analysed data. Gluino masses below 500 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. The exclusion increases to 870 GeV for equal mass squarks and gluinos. In MSUGRA/CMSSM models with tan beta = 3, A(0) = 0 and mu > 0, squarks and gluinos of equal mass are excluded below 775 GeV. These are the most stringent limits to date.

  • 55. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al
    Search for stable hadronising squarks and gluinos with the ATLAS experiment at the LHC2011Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 701, nr 1, s. 1-19Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hitherto unobserved long-lived massive particles with electric and/or colour charge are predicted by a range of theories which extend the Standard Model. In this Letter a search is performed at the ATLAS experiment for slow-moving charged particles produced in proton-proton collisions at 7 TeV centre-of-mass energy at the LHC, using a data-set corresponding to an integrated luminosity of 34 pb(-1). No deviations from Standard Model expectations are found. This result is interpreted in a framework of supersymmetry models in which coloured sparticles can hadronise into long-lived bound hadronic states, termed R-hadrons, and 95% CL limits are set on the production cross-sections of squarks and gluinos. The influence of R-hadron interactions in matter was studied using a number of different models, and lower mass limits for stable sbottoms and stops are found to be 294 and 309 GeV respectively. The lower mass limit for a stable gluino lies in the range from 562 to 586 GeV depending on the model assumed. Each of these constraints is the most stringent to date.

  • 56. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al
    Search for supersymmetric particles in events with lepton pairs and large missing transverse momentum in root s=7 TeV proton-proton collisions with the ATLAS experiment2011Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 71, nr 7, s. 1682-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Results are presented of searches for the production of supersymmetric particles decaying into final states with missing transverse momentum and exactly two isolated leptons in root s = 7 TeV proton-proton collisions at the Large Hadron Collider. Search strategies requiring lepton pairs with identical-sign or opposite-sign electric charges are described. In a data sample corresponding to an integrated luminosity of 35 pb(-1) collected with the ATLAS detector, no significant excesses are observed. Based on specific benchmark models, limits are placed on the squark mass between 450 and 690 GeV for squarks approximately degenerate in mass with gluinos, depending on the supersymmetric mass hierarchy considered.

  • 57. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al
    Search for supersymmetry in pp collisions at root s=7 TeV in final states with missing transverse momentum and b-jets2011Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 701, nr 4, s. 398-416Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Results are presented of a search for supersymmetric particles in events with large missing transverse momentum and at least one heavy flavour jet candidate in root s = 7 TeV proton proton collisions. In a data sample corresponding to an integrated luminosity of 35 pb(-1) recorded by the ATLAS experiment at the Large Hadron Collider, no significant excess is observed with respect to the prediction for Standard Model processes. For R-parity conserving models in which sbottoms (stops) are the only squarks to appear in the gluino decay cascade, gluino masses below 590 GeV (520 GeV) are excluded at the 95% C.L. The results are also interpreted in an MSUGRA/CMSSM supersymmetry breaking scenario with tan beta = 40 and in an SO(10) model framework.

  • 58. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al
    Search for Supersymmetry Using Final States with One Lepton, Jets, and Missing Transverse Momentum with the ATLAS Detector in root s=7 TeV pp Collisions2011Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 106, nr 13, s. 131802-1-131802-19Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This Letter presents the first search for supersymmetry in final states containing one isolated electron or muon, jets, and missing transverse momentum from root s = 7 TeV proton-proton collisions at the LHC. The data were recorded by the ATLAS experiment during 2010 and correspond to a total integrated luminosity of 35 pb(-1). No excess above the standard model background expectation is observed. Limits are set on the parameters of the minimal supergravity framework, extending previous limits. Within this framework, for A(0) = 0 GeV, tan beta = 3, and mu > 0 and for equal squark and gluino masses, gluino masses below 700 GeV are excluded at 95% confidence level.

  • 59. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al
    Search for the Standard Model Higgs boson in the decay channel H -> ZZ(()*()) -> 4l with the ATLAS detector2011Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 705, nr 5, s. 435-451Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for the Standard Model Higgs boson in the decay channel H -> ZZ(()*()) l(+)l(-)l'l'(-), where l = e, mu, is presented. Proton-proton collision data at root s = 7 TeV recorded with the ATLAS detector and corresponding to an average integrated luminosity of 2.1 fb(-1) are compared to the Standard Model expectations. Upper limits on the production cross section of a Standard Model Higgs boson with a mass between 110 and 600 GeV are derived. The observed (expected) 95% confidence level upper limit on the production cross section for a Higgs boson with a mass of 194 GeV, the region with the best expected sensitivity for this search, is 0.99 (1.01) times the Standard Model prediction. The Standard Model Higgs boson is excluded at 95% confidence level in the mass ranges 191-197, 199-200 and 214-224 GeV.

  • 60. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al
    Study of jet shapes in inclusive jet production in pp collisions at root s=7 TeV using the ATLAS detector2011Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 83, nr 5, s. 052003-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Jet shapes have been measured in inclusive jet production in proton-proton collisions at root s = 7 TeV using 3 pb(-1) of data recorded by the ATLAS experiment at the LHC. Jets are reconstructed using the anti-k(t) algorithm with transverse momentum 30 GeV < p(T) < 600 GeV and rapidity in the region vertical bar y vertical bar < 2.8. The data are corrected for detector effects and compared to several leading-order QCD matrix elements plus parton shower Monte Carlo predictions, including different sets of parameters tuned to model fragmentation processes and underlying event contributions in the final state. The measured jets become narrower with increasing jet transverse momentum and the jet shapes present a moderate jet rapidity dependence. Within QCD, the data test a variety of perturbative and nonperturbative effects. In particular, the data show sensitivity to the details of the parton shower, fragmentation, and underlying event models in the Monte Carlo generators. For an appropriate choice of the parameters used in these models, the data are well described.

  • 61. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    University of Chicago.
    Zychacek, V.
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    et, al
    The ATLAS Experiment at the CERN Large Hadron Collider2008Inngår i: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 3, s. S08003-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ATLAS detector as installed in its experimental cavern at point 1 at CERN is described in this paper. A brief overview of the expected performance of the detector when the Large Hadron Collider begins operation is also presented.

  • 62. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    zur Nedden, M.
    et al.,
    The ATLAS Collaboration2009Inngår i: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 830, nr 1-4, s. 925c-940cArtikkel i tidsskrift (Fagfellevurdert)
  • 63. Aad, Georges
    et al.
    Grahn, Karl Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L
    et, al
    Measurement of the inclusive isolated prompt photon cross section in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector2011Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 83, nr 5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A measurement of the cross section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy root s = 7 TeV is presented. The measurement covers the pseudorapidity ranges vertical bar eta(gamma)vertical bar < 1: 37 and 1: 52 <= vertical bar eta(gamma)vertical bar < 1: 81 in the transverse energy range 15 <= E(T)(gamma) < 100 GeV. The results are based on an integrated luminosity of 880 nb(-1), collected with the ATLAS detector at the Large Hadron Collider. Photon candidates are identified by combining information from the calorimeters and from the inner tracker. Residual background in the selected sample is estimated from data based on the observed distribution of the transverse isolation energy in a narrow cone around the photon candidate. The results are compared to predictions from next-to-leading-order perturbative QCD calculations.

  • 64. Abat, E.
    et al.
    Abdallah, J. M.
    Addy, T. N.
    Adragna, P.
    Aharrouche, M.
    Ahmad, A.
    Akesson, T. P. A.
    Aleksa, M.
    Alexa, C.
    Anderson, K.
    Andreazza, A.
    Anghinolfi, F.
    Antonaki, A.
    Arabidze, G.
    Arik, E.
    Atkinson, T.
    Baines, J.
    Baker, O. K.
    Banfi, D.
    Baron, S.
    Barr, A. J.
    Beccherle, R.
    Beck, H. P.
    Belhorma, B.
    Bell, P. J.
    Benchekroun, D.
    Benjamin, D. P.
    Benslama, K.
    Kuutmann, E. Bergeaas
    Bernabeu, J.
    Bertelsen, H.
    Binet, S.
    Biscarat, C.
    Boldea, V.
    Bondarenko, V. G.
    Boonekamp, M.
    Bosman, M.
    Bourdarios, C.
    Broklova, Z.
    Chromek, D. Burckhart
    Bychkov, V.
    Callahan, J.
    Calvet, D.
    Canneri, M.
    Garrido, M. Capeans
    Caprini, M.
    Sas, L. Cardiel
    Carli, T.
    Carminati, L.
    Carvalho, J.
    Cascella, M.
    Castillo, M. V.
    Catinaccio, A.
    Cauz, D.
    Cavalli, D.
    Cavalli Sforza, M.
    Cavasinni, V.
    Cetin, S. A.
    Chen, H.
    Cherkaoui, R.
    Chevalier, L.
    Chevallier, F.
    Chouridou, S.
    Ciobotaru, M.
    Citterio, M.
    Clark, A.
    Cleland, B.
    Cobal, M.
    Cogneras, E.
    Conde Muino, P.
    Consonni, M.
    Constantinescu, S.
    Cornelissen, T.
    Correard, S.
    Radu, A. Corso
    Costa, G.
    Costa, M. J.
    Costanzo, D.
    Cuneo, S.
    Cwetanski, P.
    Da Silva, D.
    Dam, M.
    Dameri, M.
    Danielsson, H. O.
    Dannheim, D.
    Darbo, G.
    Davidek, T.
    De, K.
    Defay, P. O.
    Dekhissi, B.
    Del Peso, J.
    Del Prete, T.
    Delmastro, M.
    Derue, F.
    Di Ciaccio, L.
    Di Girolamo, B.
    Dita, S.
    Dittus, F.
    Djama, F.
    Djobava, T.
    Dobos, D.
    Dobson, M.
    Dolgoshein, B. A.
    Dotti, A.
    Drake, G.
    Drasal, Z.
    Dressnandt, N.
    Driouchi, C.
    Drohan, J.
    Ebenstein, W. L.
    Eerola, P.
    Efthymiopoulos, I.
    Egorov, K.
    Eifert, T. F.
    Einsweiler, K.
    El Kacimi, M.
    Elsing, M.
    Emelyanov, D.
    Escobar, C.
    Etienvre, A. I.
    Fabich, A.
    Facius, K.
    Fakhr-Edine, A. I.
    Fanti, M.
    Farbin, A.
    Farthouat, P.
    Fassouliotis, D.
    Fayard, L.
    Febbraro, R.
    Fedin, O. L.
    Fenyuk, A.
    Fergusson, D.
    Ferrari, P.
    Ferrari, R.
    Ferreira, B. C.
    Ferrer, A.
    Ferrere, D.
    Filippini, G.
    Flick, T.
    Fournier, D.
    Francavilla, P.
    Francis, D.
    Froeschl, R.
    Froidevaux, D.
    Fullana, E.
    Gadomski, S.
    Gagliardi, G.
    Gagnon, P.
    Gallas, M.
    Gallop, B. J.
    Gameiro, S.
    Gan, K. K.
    Garcia, R.
    Garcia, C.
    Gavrilenko, I. L.
    Gemme, C.
    Gerlach, P.
    Ghodbane, N.
    Giakoumopoulou, V.
    Giangiobbe, V.
    Giokaris, N.
    Glonti, G.
    Goettfert, T.
    Golling, T.
    Gollub, N.
    Gomes, A.
    Gomez, M. D.
    Gonzalez-Sevilla, S.
    Goodrick, M. J.
    Gorfine, G.
    Gorini, B.
    Goujdami, D.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Grenier, P.
    Grigalashvili, N.
    Grishkevich, Y.
    Grosse-Knetter, J.
    Gruwe, M.
    Guicheney, C.
    Gupta, A.
    Haeberli, C.
    Haertel, R.
    Hajduk, Z.
    Hakobyan, H.
    Hance, M.
    Hansen, J. D.
    Hansen, P. H.
    Hara, K.
    Harvey, A., Jr.
    Hawkings, R. J.
    Heinemann, F. E. W.
    Correia, A. Henriques
    Henss, T.
    Hervas, L.
    Higon, E.
    Hill, J. C.
    Hoffman, J.
    Hostachy, J. Y.
    Hruska, I.
    Hubaut, F.
    Huegging, F.
    Hulsbergen, W.
    Hurwitz, M.
    Iconomidou-Fayard, L.
    Jansen, E.
    Plante, I. Jen-La
    Johansson, P. D. C.
    Jon-And, K.
    Joos, M.
    Jorgensen, S.
    Joseph, J.
    Kaczmarska, A.
    Kado, M.
    Karyukhin, A.
    Kataoka, M.
    Kayumov, F.
    Kazarov, A.
    Keener, P. T.
    Kekelidze, G. D.
    Kerschen, N.
    Kersten, S.
    Khomich, A.
    Khoriauli, G.
    Khramov, E.
    Khristachev, A.
    Khubua, J.
    Kittelmann, T. H.
    Klingenberg, R.
    Klinkby, E. B.
    Kodys, P.
    Koffas, T.
    Kolos, S.
    Konovalov, S. P.
    Konstantinidis, N.
    Kopikov, S.
    Korolkov, I.
    Kostyukhin, V.
    Kovalenko, S.
    Kowalski, T. Z.
    Krueger, K.
    Kramarenko, V.
    Kudin, L. G.
    Kulchitsky, Y.
    Lacasta, C.
    Lafaye, R.
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    Laforge, B.
    Lampl, W.
    Lanni, F.
    Laplace, S.
    Lari, T.
    Le Bihan, A-C
    Lechowski, M.
    Ledroit-Guillon, F.
    Lehmann, G.
    Leitner, R.
    Lelas, D.
    Lester, C. G.
    Liang, Z.
    Lichard, P.
    Liebig, W.
    Lipniacka, A.
    Lokajicek, M.
    Louchard, L.
    Lourerio, K. F.
    Lucotte, A.
    Luehring, F.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lundberg, B.
    Ma, H.
    Mackeprang, R.
    Maio, A.
    Maleev, V. P.
    Malek, F.
    Mandelli, L.
    Maneira, J.
    Mangin-Brinet, M.
    Manousakis, A.
    Mapelli, L.
    Marques, C.
    Marti i Garcia, S.
    Martin, F.
    Mathes, M.
    Mazzanti, M.
    McFarlane, K. W.
    McPherson, R.
    Mchedlidze, G.
    Mehlhase, S.
    Meirosu, C.
    Meng, Z.
    Meroni, C.
    Mialkovski, V.
    Mikulec, B.
    Milstead, D.
    Minashvili, I.
    Mindur, B.
    Mitsou, V. A.
    Moed, S.
    Monnier, E.
    Moorhead, G.
    Morettini, P.
    Morozov, S. V.
    Mosidze, M.
    Mouraviev, S. V.
    Moyse, E. W. J.
    Munar, A.
    Myagkov, A.
    Nadtochi, A. V.
    Nakamura, K.
    Nechaeva, P.
    Negri, A.
    Nemecek, S.
    Nessi, M.
    Nesterov, S. Y.
    Newcomer, F. M.
    Nikitine, I.
    Nikolaev, K.
    Nikolic-Audit, I.
    Ogren, H.
    Oh, S. H.
    Oleshko, S. B.
    Olszowska, J.
    Onofre, A.
    Aranda, C. Padilla
    Paganis, S.
    Pallin, D.
    Pantea, D.
    Paolone, V.
    Parodi, F.
    Parsons, J.
    Parzhitskiy, S.
    Pasqualucci, E.
    Passmored, S. M.
    Pater, J.
    Patrichev, S.
    Peez, M.
    Reale, V. Perez
    Perini, L.
    Peshekhonov, V. D.
    Petersen, J.
    Petersen, T. C.
    Petti, R.
    Phillips, P. W.
    Pina, J.
    Pinto, B.
    Podlyski, F.
    Poggioli, L.
    Poppleton, A.
    Poveda, J.
    Pralavorio, P.
    Pribyl, L.
    Price, M. J.
    Prieur, D.
    Puigdengoles, C.
    Puzo, P.
    Rohne, O.
    Ragusa, F.
    Rajagopalan, S.
    Reeves, K.
    Reisinger, I.
    Rembser, C.
    de Renstrom, P. A. Bruckman
    Reznicek, P.
    Ridel, M.
    Risso, P.
    Riu, I.
    Robinson, D.
    Roda, C.
    Roe, S.
    Romaniouk, A.
    Rousseau, D.
    Rozanov, A.
    Ruiz, A.
    Rusakovich, N.
    Rust, D.
    Ryabov, Y. F.
    Ryjov, V.
    Salto, O.
    Salvachua, B.
    Salzburger, A.
    Sandaker, H.
    Rios, C. Santamarina
    Santi, L.
    Santoni, C.
    Saraiva, J. G.
    Sarri, F.
    Sauvage, G.
    Says, L. P.
    Schaefer, M.
    Schegelsky, V. A.
    Schiavi, C.
    Schieck, J.
    Schlager, G.
    Schlereth, J.
    Schmitt, C.
    Schultes, J.
    Schwemling, P.
    Schwindling, J.
    Seixas, J. M.
    Seliverstov, D. M.
    Serin, L.
    Sfyrla, A.
    Shalanda, N.
    Shaw, C.
    Shin, T.
    Shmeleva, A.
    Silva, J.
    Simion, S.
    Simonyan, M.
    Sloper, J. E.
    Smirnov, S. Yu.
    Smirnova, L.
    Solans, C.
    Solodkov, A.
    Solovianov, O.
    Soloviev, I.
    Sosnovtsev, V. V.
    Spano, F.
    Speckmayer, P.
    Stancu, S.
    Stanek, R.
    Starchenko, E.
    Straessner, A.
    Suchkov, S. I.
    Suk, M.
    Szczygiel, R.
    Tarrade, F.
    Tartarelli, F.
    Tas, P.
    Tayalati, Y.
    Tegenfeldt, F.
    Teuscher, R.
    Thioye, M.
    Tikhomirov, V. O.
    Timmermans, C. J. W. P.
    Tisserant, S.
    Toczek, B.
    Tremblet, L.
    Troncon, C.
    Tsiareshka, P.
    Tyndel, M.
    Unel, M. Karagoez
    Unal, G.
    Unel, G.
    Usai, G.
    Van Berg, R.
    Valero, A.
    Valkar, S.
    Valls, J. A.
    Vandelli, W.
    Vannucci, F.
    Vartapetian, A.
    Vassilakopoulos, V. I.
    Vasilyeva, L.
    Vazeille, F.
    Vernocchi, F.
    Vetter-Cole, Y.
    Vichou, I.
    Vinogradov, V.
    Virzi, J.
    Vivarelli, I.
    de Vivie, J. B.
    Volpi, M.
    Anh, T. Vu
    Wang, C.
    Warren, M.
    Weber, J.
    Weber, M.
    Weidberg, A. R.
    Weingarten, J.
    Wells, P. S.
    Werner, P.
    Wheeler, S.
    Wiessmann, M.
    Wilkens, H.
    Williams, H. H.
    Wingerter-Seez, I.
    Yasu, Y.
    Zaitsev, A.
    Zenin, A.
    Zenis, T.
    Zenonos, Z.
    Zhang, H.
    Zhelezko, A.
    Zhou, N.
    Combined performance studies for electrons at the 2004 ATLAS combined test-beam2010Inngår i: Journal of Instrumentation, ISSN 1748-0221, Vol. 5, s. P11006-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In 2004 at the ATLAS (A Toroidal LHC ApparatuS) combined test beam, one slice of the ATLAS barrel detector (including an Inner Detector set-up and the Liquid Argon calorimeter) was exposed to particles from the H8 SPS beam line at CERN. It was the first occasion to test the combined electron performance of ATLAS. This paper presents results obtained for the momentum measurement p with the Inner Detector and for the performance of the electron measurement with the LAr calorimeter (energy E linearity and resolution) in the presence of a magnetic field in the Inner Detector for momenta ranging from 20 GeV/c to 100 GeV/c. Furthermore the particle identification capabilities of the Transition Radiation Tracker, Bremsstrahlungs-recovery algorithms relying on the LAr calorimeter and results obtained for the E/p ratio and a way how to extract scale parameters will be discussed.

  • 65. Abat, E.
    et al.
    Abdallah, J. M.
    Egorov, K.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zhou, N.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    et, al
    Study of the response of the ATLAS central calorimeter to pions of energies from 3 to 9 GeV2009Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 607, nr 2, s. 372-386Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A fully instrumented slice of the ATLAS central detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. in this paper, the response of the central calorimeters to pions with energies in the range between 3 and 9 GeV is presented. The linearity and the resolution of the combined calorimetry (electromagnetic and hadronic calorimeters) was measured and compared to the prediction of a detector simulation program using the toolkit Geant 4.

  • 66. Abat, E.
    et al.
    Grahan, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zhou, N.
    et, al
    Photon reconstruction in the ATLAS Inner Detector and Liquid Argon Barrel Calorimeter at the 2004 Combined Test Beam2011Inngår i: Journal of Instrumentation, ISSN 1748-0221, Vol. 6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The reconstruction of photons in the ATLAS detector is studied with data taken during the 2004 Combined Test Beam, where a full slice of the ATLAS detector was exposed to beams of particles of known energy at the CERN SPS. The results presented show significant differences in the longitudinal development of the electromagnetic shower between converted and unconverted photons as well as in the total measured energy. The potential to use the reconstructed converted photons as a means to precisely map the material of the tracker in front of the electromagnetic calorimeter is also considered. All results obtained are compared with a detailed Monte-Carlo simulation of the test-beam setup which is based on the same simulation and reconstruction tools as those used for the ATLAS detector itself.

  • 67. Abata, E.
    et al.
    Abdallah, J. M.
    Addy, T. N.
    Adragna, P.
    Aharrouche, M.
    Ahmad, A.
    Akesson, T. P. A.
    Aleksa, M.
    Alexa, C.
    Anderson, K.
    Anghinolfi, F.
    Antonaki, A.
    Arabidze, G.
    Arik, E.
    Baker, O. K.
    Banfi, D.
    Baron, S.
    Beck, H. P.
    Belhorma, B.
    Benchekroun, D.
    Benjamin, D. P.
    Benslama, K.
    Kuutmann, E. Bergeaas
    Bertelsen, H.
    Binet, S.
    Biscarat, C.
    Boldea, V.
    Bondarenko, V. G.
    Boonekamp, M.
    Bosman, M.
    Bourdarios, C.
    Chromek, D. Burckhart
    Bychkov, V.
    Callahan, J.
    Calvet, D.
    Canneri, M.
    Garrido, M. Capeans
    Caprini, M.
    Sas, L. Cardiel
    Carli, T.
    Carminati, L.
    Carvalho, J.
    Cascella, M.
    Castillo, M. V.
    Catinaccio, A.
    Sforza, M. Cavalli
    Cavalli, D.
    Cavasinni, V.
    Cetin, S. A.
    Chen, H.
    Cherkaoui, R.
    Chevallier, F.
    Ciobotaru, M.
    Citterio, M.
    Cleland, B.
    Cogneras, E.
    Muino, P. Conde
    Consonni, M.
    Constantinescu, S.
    Cornelissen, T.
    Radu, A. Corso
    Costa, G.
    Cwetanski, P.
    Da Silva, D.
    DAM, M.
    Danielsson, H. O.
    Dannheim, D.
    Davidek, T.
    De, K.
    Defay, P. O.
    Dekhissi, B.
    Del Peso, J.
    Delmastro, M.
    Del Prete, T.
    Derue, F.
    Di Ciaccio, L.
    Di Girolamo, B.
    Dita, S.
    Dittus, F.
    Djama, F.
    Djobava, T.
    Dobson, M.
    Dolgoshein, B. A.
    Dotti, A.
    Drake, G.
    Dressnandt, N.
    Driouchi, C.
    Ebenstein, W. L.
    Eerola, P.
    Efthymiopoulos, I.
    Egorov, K.
    Eifert, T. F.
    El Kacimi, M.
    Etienvre, A. I.
    Fabich, A.
    Fakhr-Edine, A. I.
    Fanti, M.
    Farbin, A.
    Farthouat, P.
    Fassouliotis, D.
    Fayard, L.
    Febbraro, R.
    Fedin, O. L.
    Fenyuk, A.
    Ferrari, R.
    Ferreira, B. C.
    Ferrer, A.
    Filippini, G.
    Fournier, D.
    Francavilla, P.
    Francis, D.
    Froeschl, R.
    Froidevaux, D.
    Fullana, E.
    Gadomski, S.
    Gagnon, P.
    Gameiro, S.
    Garcia, R.
    Ghodbane, N.
    Giakoumopoulou, V.
    Giangiobbe, V.
    Giokaris, N.
    Glonti, G.
    Gollub, N.
    Comes, A.
    Gomez, M. D.
    Gonzalez, V.
    Gorini, B.
    Goujdamiav, D.
    Grahn, K. J.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Grenier, P.
    Grigalashvili, N.
    Grishkevich, Y.
    Gruwe, M.
    Guicheney, C.
    Gupta, A.
    Haeberli, C.
    Hajduk, Z.
    Hakobyan, H.
    Hance, M.
    Hansen, P. H.
    Harvey, A., Jr.
    Correia, A. Henriques
    Hervas, L.
    Higon, E.
    Hoffman, J.
    Hostachy, J. Y.
    Hruska, I.
    Hubaut, F.
    Hulsbergen, W.
    Hurwitz, M.
    Iconomidou-Fayard, L.
    Jen-La Plante, I.
    Johansson, P. D. C.
    Jon-And, K.
    Joos, M.
    Jorgensen, S.
    Kaczmarska, A.
    Kado, M.
    Karyukhin, A.
    Kataoka, M.
    Kayumov, F.
    Kazarov, A.
    Keener, P. T.
    Kekelidze, G. D.
    Kerschen, N.
    Khoriauli, G.
    Khramov, E.
    Khristachev, A.
    Khubua, J.
    Kittelmann, T. H.
    Klinkby, E.
    Koffas, T.
    Kolos, S.
    Konovalov, S. P.
    Kopikov, S.
    Korolkov, I.
    Kovalenko, S.
    Kowalski, T. Z.
    Kruger, K.
    Kramarenko, V.
    Kudin, L. G.
    Kulchitsky, Y.
    Lafaye, R.
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    Laforge, B.
    Lampl, W.
    Lanni, F.
    Laplace, S.
    Le Bihan, A. C.
    Lechowski, M.
    Ledroit-Guillon, F.
    Lehmann, G.
    Leitner, R.
    Lelas, D.
    Liang, Z.
    Lichard, P.
    Lokajicek, M.
    Louchard, L.
    Loureiro, K.
    Lucotte, A.
    Luehring, F.
    Lundberg, B.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Ma, H.
    Mackeprang, R.
    Maio, A.
    Maleev, V. P.
    Malek, F.
    Maneira, J.
    Mandelli, L.
    Mazzanti, M.
    Manousakis, A.
    Mapelli, L.
    Marques, C.
    Martin, F.
    McFarlane, K. W.
    Mchedlidze, G.
    McPherson, R.
    Meirosu, C.
    Meng, Z.
    Miagkov, A.
    Mialkovski, V.
    Milstead, D.
    Minashvili, I.
    Mindur, B.
    Mitsou, V. A.
    Monnier, E.
    Morozov, S. V.
    Mosidze, M.
    Mouraviev, S. V.
    Munar, A.
    Nadtochi, A. V.
    Negri, A.
    Nemecek, S.
    Nessi, M.
    Nesterov, S. Y.
    Newcomer, F. M.
    Nikitine, I.
    Nikolic-Audit, I.
    Ogren, H.
    Oh, S. H.
    Oleshko, S. B.
    Olszowska, J.
    Onofre, A.
    Aranda, C. Padilla
    Paganis, S.
    Pallin, D.
    Pantea, D.
    Paolone, V.
    Parsons, J.
    Pasqualucci, E.
    Passmore, M. S.
    Patrichev, S.
    Peez, M.
    Reale, V. Perez
    Perini, L.
    Peshekhonov, V. D.
    Petersen, J.
    Petersen, T. C.
    Petti, R.
    Pilcher, J.
    Pina, J.
    Pinto, B.
    Podlyski, F.
    Poggioli, L.
    Poveda, J.
    Pralavorio, P.
    Pribyl, L.
    Price, M. J.
    Prieur, D.
    Puigdengoles, C.
    Puzo, P.
    Rajagopalan, S.
    Rembser, C.
    Ridel, M.
    Riu, I.
    Roda, C.
    Rohne, O.
    Romaniouk, A.
    Rousseau, D.
    Ruiz, A.
    Rusakovich, N.
    Rust, D.
    Ryabov, Y. F.
    Ryjov, V.
    Salto, O.
    Salvachua, B.
    Sanchis, E.
    Rios, C. Santamarina
    Santoni, C.
    Saraiva, J. G.
    Sarri, F.
    Sauvage, G.
    Says, L. P.
    Schaefer, M.
    Schegelsky, V. A.
    Schlager, G.
    Schlereth, J.
    Schmitt, C.
    Schwemling, P.
    Schwindling, J.
    Seixas, J. M.
    Seliverstov, D. M.
    Serin, L.
    Shalanda, N.
    Shin, T.
    Shmeleva, A.
    Silva, J.
    Simion, S.
    Simonyan, M.
    Sloper, J. E.
    Smirnov, S. Yu.
    Smirnova, L.
    Solans, C.
    Solodkov, A.
    Solovianov, O.
    Soloviev, I.
    Sosnovtsev, V. V.
    Spano, F.
    Speckmeyer, P.
    Stancu, S.
    Stanek, R.
    Starchenko, E.
    Straessner, A.
    Suchkov, S. I.
    Suk, M.
    Szczygiel, R. R.
    Tarrade, F.
    Tartarelli, F.
    Tas, P.
    Tayalati, Y.
    Teuscher, R.
    Thioye, M.
    Tikhomirov, V. O.
    Tisserant, S.
    Torres, J.
    Tremblet, L.
    Tsiareshka, P.
    Tsiskaridze, V.
    Unal, G.
    Unel, G.
    Usai, G.
    Valero, A.
    Valkar, S.
    Valls, J. A.
    Van Berg, R.
    Vandelli, W.
    Vannucci, F.
    Vartapetian, A.
    Vassilakopoulos, V. I.
    Vassilieva, L.
    Vazeille, F.
    Vetter-Cole, Y.
    Vichou, I.
    Vinogradov, V.
    Vivarelli, I.
    Volpi, M.
    Wang, C.
    Werner, P.
    Wheeler, S.
    Wiesmann, M.
    Wilkens, H.
    Williams, H. H.
    Wingerter-Seez, I.
    Yasu, Y.
    Zaitsev, A.
    Zenin, A.
    Zenis, T.
    Zenonos, Z.
    Zhang, H.
    Zhou, N.
    Study of energy response and resolution of the ATLAS barrel calorimeter to hadrons of energies from 20 to 350 GeV2010Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 621, nr 1-3, s. 134-150Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A fully instrumented slice of the ATLAS detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. In this paper, the results of the measurements of the response of the barrel calorimeter to hadrons with energies in the range 20-350 GeV and beam impact points and angles corresponding to pseudo-rapidity values in the range 0.2-0.65 are reported. The results are compared to the predictions of a simulation program using the Geant 4 toolkit. (C) 2010 Published by Elsevier B.V.

  • 68. Aharrouche, M.
    et al.
    Adam-Bourdarios, C.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zhang, H.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    Measurement of the response of the ATLAS liquid argon barrel calorimeter to electrons at the 2004 combined test-beam2010Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 614, nr 3, s. 400-432Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    During summer and fall 2004, the response of a full slice of the ATLAS barrel detector to different particles was studied in controlled beam. One module of the ATLAS liquid argon barrel calorimeter identical to the production modules and read out by the final front-end and back-end electronics was used for electromagnetic calorimetry. This paper presents and discusses the electron performance of the LAr barrel calorimeter, including linearity, uniformity, and resolution with different amounts of material upstream the calorimeter and energies ranging from 1 to 250 GeV.

  • 69. Dannheim, Dominik
    et al.
    Voigt, Alexander
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Speckmayer, Peter
    Carli, Tancredi
    PDE-Foam-A probability density estimation method using self-adapting phase-space binning2009Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 606, nr 3, s. 717-727Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Probability density estimation (PDE) is a multi-variate discrimination technique based on sampling signal and background densities defined by event samples from data or Monte-Carlo (MC) simulations in a multi-dimensional phase space. In this paper, we present a modification of the PDE method that uses a self-adapting binning method to divide the multi-dimensional phase space in a finite number of hyper-rectangles (cells). The binning algorithm adjusts the size and position of a predefined number of cells inside the multi-dimensional phase space, minimising the variance of the signal and background densities inside the cells. The implementation of the binning algorithm (PDE-Foam) is based on the MC event-generation package Foam. We present performance results for representative examples (toy models) and discuss the dependence of the obtained results on the choice of parameters. The new PDE-Foam shows improved classification capability for small training samples and reduced classification time compared to the original PDE method based on range searching.

  • 70.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    A Layer Correlation Technique for Pion Energy Calibration at the 2004 ATLAS Combined Beam Test2009Inngår i: 2009 IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD, VOLS 1-5  / [ed] Yu B, 2009, s. 751-757Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A new method for calibrating the hadron response of a segmented calorimeter is developed. It is based on a principal component analysis of the calorimeter layer energy deposits, exploiting longitudinal shower development information to improve the measured energy resolution. Corrections for invisible hadronic energy and energy lost in dead material in front of and between the ATLAS calorimeters were calculated with simulated Geant4 Monte Carlo events and used to reconstruct the energy of pions impinging on the calorimeters during the 2004 Barrel Combined Beam Test at the CERN H8 area. For pion beams with energies between 20 and 180 GeV, the particle energy is reconstructed within 3% and the energy resolution is improved by about 20% compared to the electromagnetic scale.

  • 71.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    ATLAS Calorimetry: Hadronic Calibration Studies2008Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    The ATLAS experiment -- situated at the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) in Geneva -- is on schedule to take its first collision data in 2009. Physics topics include finding the Higgs boson, heavy quark physics, and looking for extensions of the standard model such as supersymmetry. Upon acceptance of an event by the level 1 trigger, data is read out from the liquid argon calorimeters using multi-mode optical fibers. In total, 58 cables were installed, corresponding to 232 12-fiber ribbons or 2784 individual fibers. The cables, about one hundred meters in length, were installed between the main ATLAS cavern and the counting room in the USA15 cavern. Patch cables were spliced onto the ribbons and the fiber attenuation was measured. For 1296 fiber pairs in 54 cables, the average attenuation was 0.69 dB. Only five fibers were found to have losses exceeding 4 dB, resulting in a failure rate of less than 2 per mil. In the ATLAS liquid argon barrel presampler, short circuits consisting of small pieces of dust, metal, etc. can be burned away in situ by discharging a capacitor over the high voltage lines. In a burning campaign in November 2006, seventeen existing short circuits were successfully removed. An investigation on how to implement saturation effects in liquid argon due to high ionization densities resulted into the implementation of the effect in the ATLAS Monte Carlo code, improving agreement with beam test data. The timing structure of hadronic showers was investigated using a Geant4 Monte Carlo. The expected behavior as described in the literature was reproduced, with the exception that some sets of physics models gave unphysical gamma energies from nuclear neutron capture. An ATLAS Combined Beam Test was conducted in the summer/fall of 2004 in the CERN H8 area, containing a whole slice of the ATLAS detectors in the central barrel region. The controlled single-particle environment allows the validation of Monte Carlo code and calibration. A method for calibrating the response of a segmented calorimeter to hadrons was developed. The ansatz is that information on longitudinal shower fluctuations gained from a principal component analysis of the layer energy depositions can improve energy resolution by correcting for hadronic invisible energy and dead material losses: projections along the eigenvectors of the correlation matrix are used as input for the calibration. The technique was used to reconstruct the energy of pions impinging on the ATLAS calorimeters during the 2004 Combined Beam Test. Simulated Monte Carlo events were used to derive corrections for invisible energy lost in nuclear reactions and in dead material in front and in between the calorimeters.  For pion beams with energies between 20 and 180 GeV, the particle energy was reconstructed within 3% and the resolution was improved by about 20%. As a comparison, a simple iterative scheme with a single e/π factor and dead material corrections was devised, giving similar performance.

  • 72.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Measurement of Multi-Jet Production in Proton-Proton Collisions at 7 TeV Center-of-Mass Energy and Hadronic Calibration Studies with the ATLAS Detector at CERN2011Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    The ATLAS experiment – situated at the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) in Geneva – took its first collsion data in 2010. Physics topics include finding the Higgs boson, heavy quark physics, and looking for extensions of the Standard Model of Particle Physics such as supersymmetry.

    In this thesis, inclusive multi-jet production has been studied with the ATLAS detector in proton-proton collisions at a center-of-mass energy of 7 TeV, using an integrated luminosity of 17 nb−1. The anti-kt algorithm with distance parameter ℝ = 0.6 is used to identify jets. The inclusive multi-jet cross section is measured, as well as the ratio ofcross sections for inclusive production of n − 1 and n jets for n ≤ 6. The differential cross sections of the first, second, third and fourth leading jets as a function of transverse momentum, and the differential cross section as a function of the scalar sum of the pT of selected jets, HT, for different jet multiplicities are presented. The ratio of the differential cross section as a function of HT for 3-jet and 2-jet events is also measured. The results are compared to expectations based on leading order QCD, which agree with the data.

    In addition, a new method for calibrating the hadron response of a segmented calorim-ter is developed and successfully applied to 2004 ATLAS combined beam test data. It is based on a principal component analysis of the calorimeter layer energy deposits, exploiting longitudinal shower development information to improve the measured energyresolution. For pion beams with energies between 20 and 180 GeV, the particle energy is reconstructed within 3% and the energy resolution is improved by 11% to 25% comparedto the response at the electromagnetic scale.

    Multi-mode optical readout cables for the ATLAS liquid argon calorimeters, about one hundred meters in length, were installed between the main ATLAS cavern and the counting room in the USA15 cavern. Patch cables were spliced onto the ribbons and the fiber attenuation was measured. For 1296 fiber pairs in 54 cables, the average attenuation was 0.69 dB. Only five fibers were found to have losses exceeding 4 dB, resulting in a failure rate of less than 2 per mill.

    In the ATLAS liquid argon barrel presampler, short circuits consisting of small pieces of dust, metal, etc. can be burned away in situ by discharging a capacitor over the high voltage lines. In a burning campaign in November 2006, seventeen existing short circuits were successfully removed.

    An investigation on how to implement saturation effects in liquid argon due to high ionization densities resulted in the implementation of the effect in the ATLAS Monte Carlo code, improving agreement with beam test data.

    The timing structure of hadronic showers was investigated using a Geant4 Monte Carlo. The expected behavior as described in the literature was reproduced, with the exception that some sets of physics models gave unphysical gamma energies from nuclear neutron capture.

  • 73.
    Grahn, Karl-Johan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kiryunin, Andrey
    Pospelov, Guennadi
    Tests of Local Hadron Calibration Approaches in ATLAS Combined Beam Tests2011Inngår i: XIV INTERNATIONAL CONFERENCE ON CALORIMETRY IN HIGH ENERGY PHYSICS (CALOR 2010) / [ed] Wang, YF; Hu, T, 2011, Vol. 293Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Three ATLAS calorimeters in the region of the forward crack at vertical bar eta vertical bar = 3.2 in the nominal ATLAS setup and a typical section of the two barrel calorimeters at vertical bar eta vertical bar = 0.45 of ATLAS have been exposed to combined beam tests with single electrons and pions. Detailed shower shape studies of electrons and pions with comparisons to various Geant4 based simulations utilizing different physics lists are presented for the endcap beam test. The local hadron calibration approach as used in the full Atlas setup has been applied to the endcap beam test data. An extension of it using layer correlations has been tested with the barrel test beam data. Both methods utilize modular correction steps based on shower shape variables to correct for invisible energy inside the reconstructed clusters in the calorimeters (compensation) and for lost energy deposits outside of the reconstructed clusters (dead material and out-of-cluster deposits). Results for both methods and comparisons to Monte Carlo simulations are presented.

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