TY - THES A1 - Hartmann, Fabian T1 - Elektrooptische Transporteigenschaften und stochastisch aktivierte Prozesse Resonanter Tunneldioden T1 - Electro-optical and transport properties and stochastically activated processes of resonant tunneling diodes N2 - Im Rahmen der vorliegenden Arbeit wurden elektrooptische Transporteigenschaften und stochastisch aktivierte Prozesse Resonanter Tunneldioden (RTDs) bei Raumtemperatur untersucht. Die RTDs wurden auf dem III-V Halbleitermaterialsystem AlGaAs/GaAs durch Molekularstrahlepitaxie, Elektronenstrahllithographie und trockenchemischen Ätztechniken hergestellt. Im Bereich des negativen differentiellen Leitwerts konnte bistabi-les Schalten und hierbei stochastisch aktivierte Dynamik nichtlinearer Systeme untersucht werden. Die Flächenabhängigkeit der Ätzrate konnte ausgenutzt werden, um RTDs mit einem Stamm und zwei Transportästen zu realisieren, welche hinsichtlich ihrer optischen und elektrischen Eigenschaften untersucht wurden. Im ersten experimentellen Abschnitt 3.1 werden die elektrischen Transporteigenschaften Resonanter Tunneldioden bei Raum-temperatur und die Flächenabhängigkeit des kohärenten und nicht-kohärenten Elektronen-transports analysiert. Die Realisierung universeller logischer Gatter (NOR und NAND) und deren Rekonfigurierbarkeit durch einen externen Kontrollparameter wird in Abschnitt 3.2 gezeigt. In Abschnitt 3.3 wird die Lichtsensitivität Resonanter Tunneldioden als Photode-tektoren für den sichtbaren Wellenlängenbereich und in Abschnitt 3.4 für die Telekommu-nikationswellenlänge bei λ = 1,3 µm demonstriert. N2 - In this thesis, electro-optical transport properties and stochastically-activated processes of resonant tunneling diodes (RTDs) were investigated at room temperature. The RTDs were prepared on the basis of AlGaAs/GaAs heterostructures by molecular beam epitaxy, elec-tron beam lithography and dry chemical etching techniques. In the region of negative dif-ferential conductance (NDC) bistable RTD switching was achieved by exploiting the load line effect in combination with stochastically-activated dynamics of nonlinear systems. The surface dependence of the etching rate was exploited in order to realize RTDs with a stem and two transport branches, which were studied with respect to their optical and electrical properties. In the first section of the experimental part, electrical transport properties of resonant tunneling diodes at room temperature and the area dependence of the coherent and non-coherent electron transport properties are described. The realization of universal logic gates (NAND and NOR) and their reconfigurability by external control parameters is then demonstrated in Section 3.2. The light sensitivity of resonant tunneling diode photo-detectors was studied for the visible wavelength range and for the telecommunication wavelength at λ = 1.3 µm, in Section 3.3, and 3.4, respectively. KW - Resonanz-Tunneldiode KW - resonant tunneling diode KW - Resonanztunneldiode KW - noise KW - stochastic resonance KW - photo detector KW - Rauschen KW - Stochastische Resonanz KW - Lichtsensor KW - Elektrooptische Eigenschaft KW - Tunneldiode Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-90876 ER - TY - JOUR A1 - Aad, G. A1 - Abbott, B. A1 - Abdallah, J. A1 - Abdelalim, A. A. A1 - Abdesselam, A. T1 - Performance of the ATLAS Trigger System in 2010 JF - The European Physical Journal C N2 - Proton–proton collisions at √s=7 TeV and heavy ion collisions at \(\sqrt{sNN}\)=2.76 TeV were produced by the LHC and recorded using the ATLAS experiment’s trigger system in 2010. The LHC is designed with a maximum bunch crossing rate of 40 MHz and the ATLAS trigger system is designed to record approximately 200 of these per second. The trigger system selects events by rapidly identifying signatures of muon, electron, photon, tau lepton, jet, and B meson candidates, as well as using global event signatures, such as missing transverse energy. An overview of the ATLAS trigger system, the evolution of the system during 2010 and the performance of the trigger system components and selections based on the 2010 collision data are shown. A brief outline of plans for the trigger system in 2011 is presented. KW - ATLAS KW - Trigger System Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-127321 VL - 72 IS - 1849 ER - TY - JOUR A1 - Aad, G. A1 - Abbott, B. A1 - Abdallah, J. A1 - Abdelalim, A. A. A1 - Abdesselam, A. T1 - Forward-backward correlations and charged-particle azimuthal distributions in pp interactions using the ATLAS detector JF - Journal of High Energy Physics N2 - Using inelastic proton-proton interactions at s√=900 GeV and 7 TeV, recorded by the ATLAS detector at the LHC, measurements have been made of the correlations between forward and backward charged-particle multiplicities and, for the first time, between forward and backward charged-particle summed transverse momentum. In addition, jet-like structure in the events is studied by means of azimuthal distributions of charged particles relative to the charged particle with highest transverse momentum in a selected kinematic region of the event. The results are compared with predictions from tunes of the pythia and herwig++ Monte Carlo generators, which in most cases are found to provide a reasonable description of the data. KW - Hadron-Hadron Scattering Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-127336 VL - 7 IS - 19 ER - TY - JOUR T1 - Measurement of the W boson polarization in top quark decays with the ATLAS detector JF - Journal of High Energy Physics N2 - This paper presents measurements of the polarization of W bosons in top quark decays, derived from \(t\overline{t}\) events with missing transverse momentum, one charged lepton and at least four jets, or two charged leptons and at least two jets. Data from pp collisions at a centre-of-mass energy of 7 TeV were collected with the ATLAS experiment at the LHC and correspond to an integrated luminosity of 1.04 fb\(^{−1}\). The measured fractions of longitudinally, left- and right-handed polarization are F\(_0\) = 0.67 ± 0.07, F\(_L\) = 0.32 ± 0.04 and F\(_R\) = 0.01 ± 0.05, in agreement with the Standard Model predictions. As the polarization of the W bosons in top quark decays is sensitive to the Wtb vertex Lorentz structure and couplings, the measurements were used to set limits on anomalous contributions to the Wtb couplings. KW - hadron-hadron scattering Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-127417 VL - 06 IS - 88 ER - TY - JOUR T1 - Search for a fermiophobic Higgs boson in the diphoton decay channel with the ATLAS detector JF - The European Physical Journal C N2 - A search for a fermiophobic Higgs boson using diphoton events produced in proton-proton collisions at a centre-of-mass energy of √s=7 TeV is performed using data corresponding to an integrated luminosity of 4.9 fb\(^{−1}\) collected by the ATLAS experiment at the Large Hadron Collider. A specific benchmark model is considered where all the fermion couplings to the Higgs boson are set to zero and the bosonic couplings are kept at the Standard Model values (fermiophobic Higgs model). The largest excess with respect to the background-only hypothesis is found at 125.5 GeV, with a local significance of 2.9 standard deviations, which reduces to 1.6 standard deviations when taking into account the look-elsewhere effect. The data exclude the fermiophobic Higgs model in the ranges 110.0–118.0 GeV and 119.5–121.0 GeV at 95 % confidence level. KW - unconverted photon KW - Higgs boson signal KW - photon energy scale KW - invariant mass resolution KW - diphoton invariant mass Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-127427 VL - 72 IS - 2157 ER - TY - JOUR T1 - Search for a heavy top-quark partner in final states with two leptons with the ATLAS detector at the LHC JF - Journal of High Energy Physics N2 - The results of a search for direct pair production of heavy top-quark partners in 4.7 fb\(^{−1}\) of integrated luminosity from pp collisions at √s=7 TeV collected by the ATLAS detector at the LHC are reported. Heavy top-quark partners decaying into a top quark and a neutral non-interacting particle are searched for in events with two leptons in the final state. No excess above the Standard Model expectation is observed. Limits are placed on the mass of a supersymmetric scalar top and of a spin-1/2 top-quark partner. A spin-1/2 top-quark partner with a mass between 300 GeV and 480 GeV, decaying to a top quark and a neutral non-interacting particle lighter than 100 GeV, is excluded at 95% confidence level. KW - hadron-hadron scattering Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-127511 VL - 11 IS - 094 ER - TY - JOUR T1 - Search for top and bottom squarks from gluino pair production in final states with missing transverse energy and at least three b-jets with the ATLAS detector JF - The European Physical Journal C N2 - This letter reports the results of a search for top and bottom squarks from gluino pair production in 4.7 fb\(^{−1}\) of pp collisions at √s=7 TeV using the ATLAS detector at the LHC. The search is performed in events with large missing transverse momentum and at least three jets identified as originating from a b-quark. Exclusion limits are presented for a variety of gluino-mediated models with gluino masses up to 1 TeV excluded. KW - SM Background KW - jet response KW - direct pair production KW - visible cross section KW - jet energy scale KW - Anti-k Jet KW - PDF set KW - validation region Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-127523 VL - 72 IS - 2174 ER - TY - JOUR T1 - Performance of missing transverse momentum reconstruction in proton-proton collisions at √s=7 TeV with ATLAS JF - The European Physical Journal C N2 - The measurement of missing transverse momentum in the ATLAS detector, described in this paper, makes use of the full event reconstruction and a calibration based on reconstructed physics objects. The performance of the missing transverse momentum reconstruction is evaluated using data collected in pp collisions at a centre-of-mass energy of 7 TeV in 2010. Minimum bias events and events with jets of hadrons are used from data samples corresponding to an integrated luminosity of about 0.3 nb\(^{−1}\) and 600 nb\(^{−1}\) respectively, together with events containing a Z boson decaying to two leptons (electrons or muons) or a W boson decaying to a lepton (electron or muon) and a neutrino, from a data sample corresponding to an integrated luminosity of about 36 pb\(^{−1}\). An estimate of the systematic uncertainty on the missing transverse momentum scale is presented KW - momentum scale KW - Atlas detector KW - pp collision KW - systematic uncertainty KW - transverse momentum Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-127530 VL - 72 IS - 1844 ER - TY - JOUR T1 - Measurement of inclusive two-particle angular correlations in pp collisions with the ATLAS detector at the LHC JF - Journal of High Energy Physics N2 - We present a measurement of two-particle angular correlations in proton- proton collisions at √s=900 GeV and 7 TeV. The collision events were collected during 2009 and 2010 with the ATLAS detector at the Large Hadron Collider using a single-arm minimum bias trigger. Correlations are measured for charged particles produced in the kinematic range of transverse momentum p\(_T\)  > 100 MeV and pseudorapidity |η| < 2.5. A complex structure in pseudorapidity and azimuth is observed at both collision energies. Results are compared to PYTHIA 8 and HERWIG++ as well as to the AMBT2B, DW and Perugia 2011 tunes of PYTHIA 6. The data are not satisfactorily described by any of these models. KW - hadron-hadron scattering Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-127350 VL - 05 IS - 157 ER - TY - JOUR T1 - Search for heavy neutrinos and right-handed W bosons in events with two leptons and jets in pp collisions at \(\sqrt{s}\)=7TeV with the ATLAS detector JF - The European Physical Journal C N2 - This letter reports on a search for hypothetical heavy neutrinos, N, and right-handed gauge bosons, W R, in events with high transverse momentum objects which include two reconstructed leptons and at least one hadronic jet. The results were obtained from data corresponding to an integrated luminosity of 2.1 fb\(^{−1}\) collected in proton–proton collisions at √s=7 TeV with the ATLAS detector at the CERN Large Hadron Collider. No excess above the Standard Model background expectation is observed. Excluded mass regions for Majorana and Dirac neutrinos are presented using two approaches for interactions that violate lepton and lepton-flavor numbers. One approach uses an effective operator framework, the other approach is guided by the Left–Right Symmetric Model. The results described in this letter represent the most stringent limits to date on the masses of heavy neutrinos and W\(_R\) bosons obtained in direct searches. KW - dilepton invariant mass, KW - heavy neutrino KW - non-prompt lepton KW - Anti-k Jet KW - fake lepton Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-127796 VL - 72 IS - 2056 ER -