TY - JOUR A1 - Winkler, Karol A1 - Fischer, Julian A1 - Schade, Anne A1 - Amthor, Matthias A1 - Dall, Robert A1 - Geßler, Jonas A1 - Emmerling, Monika A1 - Ostrovskaya, Elena A. A1 - Kamp, Martin A1 - Schneider, Christian A1 - Höfling, Sven T1 - A polariton condensate in a photonic crystal potential landscape JF - New Journal of Physics N2 - The possibility of investigating macroscopic coherent quantum states in polariton condensates and of engineering polariton landscapes in semiconductors has triggered interest in using polaritonic systems to simulate complex many-body phenomena. However, advanced experiments require superior trapping techniques that allow for the engineering of periodic and arbitrary potentials with strong on-site localization, clean condensate formation, and nearest-neighbor coupling. Here we establish a technology that meets these demands and enables strong, potentially tunable trapping without affecting the favorable polariton characteristics. The traps are based on a locally elongated microcavity which can be formed by standard lithography. We observe polariton condensation with non-resonant pumping in single traps and photonic crystal square lattice arrays. In the latter structures, we observe pronounced energy bands, complete band gaps, and spontaneous condensation at the M-point of the Brillouin zone. Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-125050 VL - 17 ER - TY - JOUR T1 - Centrality and rapidity dependence of inclusive jet production in \(\sqrt{^SNN}\)=5.02 TeV proton–lead collisions with the ATLAS detector JF - Physics Letters B N2 - Measurements of the centrality and rapidity dependence of inclusive jet production in \(\sqrt{^SNN}\)=5.02 TeV proton–lead (p+Pb) collisions and the jet cross-section in \(\sqrt{s}\)=2.76 TeV proton–proton collisions are presented. These quantities are measured in datasets corresponding to an integrated luminosity of 27.8 nb\(^{−1}\) and 4.0 pb\(^{−1}\), respectively, recorded with the ATLAS detector at the Large Hadron Collider in 2013. The p+Pb collision centrality was characterised using the total transverse energy measured in the pseudorapidity interval −4.9<η<−3.2 in the direction of the lead beam. Results are presented for the double-differential per-collision yields as a function of jet rapidity and transverse momentum (\(p_T\)) for minimum-bias and centrality-selected p+Pb collisions, and are compared to the jet rate from the geometric expectation. The total jet yield in minimum-bias events is slightly enhanced above the expectation in a \(p_T\)-dependent manner but is consistent with the expectation within uncertainties. The ratios of jet spectra from different centrality selections show a strong modification of jet production at all \(p_T\) at forward rapidities and for large \(p_T\) at mid-rapidity, which manifests as a suppression of the jet yield in central events and an enhancement in peripheral events. These effects imply that the factorisation between hard and soft processes is violated at an unexpected level in proton–nucleus collisions. Furthermore, the modifications at forward rapidities are found to be a function of the total jet energy only, implying that the violations may have a simple dependence on the hard parton–parton kinematics. KW - jet production KW - proton-lead collision Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-139857 VL - 748 ER - TY - JOUR T1 - Constraints on the off-shell Higgs boson signal strength in the high-mass ZZ and WW final states with the ATLAS detector JF - European Physical Journal C: Particles and Fields N2 - Measurements of the ZZ and WW final states in the mass range above the 2m\(_Z\) and 2m\(_W\) thresholds provide a unique opportunity to measure the off-shell coupling strength of the Higgs boson. This paper presents constraints on the off-shell Higgs boson event yields normalised to the Standard Model prediction (signal strength) in the ZZ→4ℓ, ZZ→2ℓ2ν and WW→eνμν final states. The result is based on pp collision data collected by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 20.3 fb\(^{-1}\) at a collision energy of \(\sqrt {s}\)=8 TeV. Using the CL\(_S\) method, the observed 95 % confidence level (CL) upper limit on the off-shell signal strength is in the range 5.1–8.6, with an expected range of 6.7–11.0. In each case the range is determined by varying the unknown gg→ZZ and gg→WW background K-factor from higher-order quantum chromodynamics corrections between half and twice the value of the known signal K-factor. Assuming the relevant Higgs boson couplings are independent of the energy scale of the Higgs boson production, a combination with the on-shell measurements yields an observed (expected) 95 % CL upper limit on Γ\(_H\)/Γ\(^{SM}_{H}\) in the range 4.5–7.5 (6.5–11.2) using the same variations of the background K-factor. Assuming that the unknown gg→VV background K-factor is equal to the signal K-factor, this translates into an observed (expected) 95 % CL upper limit on the Higgs boson total width of 22.7 (33.0) MeV. KW - Higgs boson KW - coupling strength Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-149615 VL - 75 IS - 7 ER - TY - JOUR T1 - Determination of spin and parity of the Higgs boson in the WW\(^{*}\)→eνμν decay channel with the ATLAS detector JF - European Physical Journal C: Particles and Fields N2 - Studies of the spin and parity quantum numbers of the Higgs boson in the WW\(^{*}\)→eνμν 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 \(\sqrt {s}\)=8 TeV. The Standard Model spin-parity J\(^{CP}\)=0\(^{++}\) hypothesis is compared with alternative hypotheses for both spin and CP. 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. KW - Higgs boson KW - spin KW - parity Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-149632 VL - 75 IS - 5 ER - TY - JOUR A1 - Sessi, Paolo A1 - Silkin, Vyacheslav M. A1 - Nechaev, Ilya A. A1 - Bathon, Thomas A1 - El-Kareh, Lydia A1 - Chulkov, Evgueni V. A1 - Echenique, Pedro M. A1 - Bode, Matthias T1 - Direct observation of many-body charge density oscillations in a two-dimensional electron gas JF - Nature Communications N2 - Quantum interference is a striking manifestation of one of the basic concepts of quantum mechanics: the particle-wave duality. A spectacular visualization of this effect is the standing wave pattern produced by elastic scattering of surface electrons around defects, which corresponds to a modulation of the electronic local density of states and can be imaged using a scanning tunnelling microscope. To date, quantum-interference measurements were mainly interpreted in terms of interfering electrons or holes of the underlying band-structure description. Here, by imaging energy-dependent standing-wave patterns at noble metal surfaces, we reveal, in addition to the conventional surface-state band, the existence of an 'anomalous' energy band with a well-defined dispersion. Its origin is explained by the presence of a satellite in the structure of the many-body spectral function, which is related to the acoustic surface plasmon. Visualizing the corresponding charge oscillations provides thus direct access to many-body interactions at the atomic scale. KW - scanning tunneling spectroscopy KW - acoustic surface plasmon KW - metal surfaces KW - Cu(111) KW - excitations KW - microscopy KW - local density KW - standing wave formation KW - states KW - steps Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-145246 VL - 6 IS - 8691 ER - TY - JOUR A1 - Lee, Chang-Min A1 - Lim, Hee-Jin A1 - Schneider, Christian A1 - Maier, Sebastian A1 - Höfling, Sven A1 - Kamp, Martin A1 - Lee, Yong-Hee T1 - Efficient single photon source based on \(\mu\)-fibre-coupled tunable microcavity JF - Scientific Reports N2 - Efficient and fast on-demand single photon sources have been sought after as critical components of quantum information science. We report an efficient and tunable single photon source based on an InAs quantum dot (QD) embedded in a photonic crystal cavity coupled with a highly curved \(\mu\)-fibre. Exploiting evanescent coupling between the \(\mu\)-fibre and the cavity, a high collection efficiency of 23% and Purcell-enhanced spontaneous emissions are observed. In our scheme, the spectral position of a resonance can be tuned by as much as 1.5 nm by adjusting the contact position of the \(\mu\)-fibre, which increases the spectral coupling probability between the QD and the cavity mode. Taking advantage of the high photon count rate and the tunability, the collection efficiencies and the decay rates are systematically investigated as a function of the QD-cavity detuning. KW - tapers KW - semiconductor quantum dots KW - crystal KW - nanowire KW - generation KW - nanoactivity KW - mode KW - emission Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-145835 VL - 5 IS - 14309 ER - TY - JOUR A1 - Fuchs, F. A1 - Stender, B. A1 - Trupke, M. A1 - Simin, D. A1 - Pflaum, J. A1 - Dyakonov, V. A1 - Astakhov, G.V. T1 - Engineering near-infrared single-photon emitters with optically active spins in ultrapure silicon carbide JF - Nature Communications N2 - Vacancy-related centres in silicon carbide are attracting growing attention because of their appealing optical and spin properties. These atomic-scale defects can be created using electron or neutron irradiation; however, their precise engineering has not been demonstrated yet. Here, silicon vacancies are generated in a nuclear reactor and their density is controlled over eight orders of magnitude within an accuracy down to a single vacancy level. An isolated silicon vacancy serves as a near-infrared photostable single-photon emitter, operating even at room temperature. The vacancy spins can be manipulated using an optically detected magnetic resonance technique, and we determine the transition rates and absorption cross-section, describing the intensity-dependent photophysics of these emitters. The on-demand engineering of optically active spins in technologically friendly materials is a crucial step toward implementation of both maser amplifiers, requiring high-density spin ensembles, and qubits based on single spins. KW - nuclear magnetic resonance KW - coherent control KW - 4H KW - phosphorus KW - qubits KW - defects KW - entanglement KW - room temperature KW - vacancy Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-148502 VL - 6 IS - 7578 ER - TY - JOUR T1 - Identification and energy calibration of hadronically decaying tau leptons with the ATLAS experiment in pp collisions at \(\sqrt {s}\)=8 TeV JF - European Physical Journal C: Particles and Fields N2 - This paper describes the trigger and offline reconstruction, identification and energy calibration algorithms for hadronic decays of tau leptons employed for the data collected from pp collisions in 2012 with the ATLAS detector at the LHC center-of-mass energy \(\sqrt {s}\)=8 TeV. The performance of these algorithms is measured in most cases with Z decays to tau leptons using the full 2012 dataset, corresponding to an integrated luminosity of 20.3 fb\(^{-1}\). An uncertainty on the offline reconstructed tau energy scale of 2–4 %, depending on transverse energy and pseudorapidity, is achieved using two independent methods. The offline tau identification efficiency is measured with a precision of 2.5 % for hadronically decaying tau leptons with one associated track, and of 4 % for the case of three associated tracks, inclusive in pseudorapidity and for a visible transverse energy greater than 20 GeV. For hadronic tau lepton decays selected by offline algorithms, the tau trigger identification efficiency is measured with a precision of 2–8 %, depending on the transverse energy. The performance of the tau algorithms, both offline and at the trigger level, is found to be stable with respect to the number of concurrent proton–proton interactions and has supported a variety of physics results using hadronically decaying tau leptons at ATLAS. KW - tau leptons KW - hadronic decays Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-149829 VL - 75 IS - 7 ER - TY - JOUR A1 - Charnukha, A. A1 - Thirupathaiah, S. A1 - Zabolotnyy, V. B. A1 - Büchner, B. A1 - Zhigadlo, N. D. A1 - Batlogg, B. A1 - Yaresko, A. N. A1 - Borisenko, S. V. T1 - Interaction-induced singular Fermi surface in a high-temperature oxypnictide superconductor JF - Scientific Reports N2 - In the family of iron-based superconductors, LaFeAsO-type materials possess the simplest electronic structure due to their pronounced two-dimensionality. And yet they host superconductivity with the highest transition temperature T\(_{c}\)\(\approx\)55K. Early theoretical predictions of their electronic structure revealed multiple large circular portions of the Fermi surface with a very good geometrical overlap (nesting), believed to enhance the pairing interaction and thus superconductivity. The prevalence of such large circular features in the Fermi surface has since been associated with many other iron-based compounds and has grown to be generally accepted in the field. In this work we show that a prototypical compound of the 1111-type, SmFe\(_{0.92}\)Co\(_{0.08}\)AsO, is at odds with this description and possesses a distinctly different Fermi surface, which consists of two singular constructs formed by the edges of several bands, pulled to the Fermi level from the depths of the theoretically predicted band structure by strong electronic interactions. Such singularities dramatically affect the low-energy electronic properties of the material, including superconductivity. We further argue that occurrence of these singularities correlates with the maximum superconducting transition temperature attainable in each material class over the entire family of iron-based superconductors. KW - electronic structure KW - photoemission spectroscopy KW - iron pnictides KW - chalcogenides KW - ARPES Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-151987 VL - 5 IS - 10392 ER - TY - JOUR A1 - Motyka, Marcin A1 - Sęk, Grzegorz A1 - Ryczko, Krzysztof A1 - Dyksik, Mateusz A1 - Weih, Robert A1 - Patriarche, Gilles A1 - Misiewicz, Jan A1 - Kamp, Martin A1 - Höfling, Sven T1 - Interface Intermixing in Type II InAs/GaInAsSb Quantum Wells Designed for Active Regions of Mid-Infrared-Emitting Interband Cascade Lasers JF - Nanoscale Research Letters N2 - The effect of interface intermixing in W-design GaSb/AlSb/InAs/Ga\(_{0.665}\)In\(_{0.335}\)As\(_x\)Sb\(_{1-x}\)/InAs/AlSb/GaSb quantum wells (QWs) has been investigated by means of optical spectroscopy supported by structural data and by band structure calculations. The fundamental optical transition has been detected at room temperature through photoluminescence and photoreflectance measurements and appeared to be blueshifted with increasing As content of the GaInAsSb layer, in contrast to the energy-gap-driven shifts calculated for an ideally rectangular QW profile. The arsenic incorporation into the hole-confining layer affects the material and optical structure also altering the InAs/GaInAsSb interfaces and their degree of intermixing. Based on the analysis of cross-sectional transmission electron microscopy images and energy-dispersive X-ray spectroscopy, we could deduce the composition distribution across the QW layers and hence simulate more realistic confinement potential profiles. For such smoothed interfaces that indicate As-enhanced intermixing, the energy level calculations have been able to reproduce the experimentally obtained trend. KW - FTIR spectroscopy KW - type II GaIn(As)Sb/GaSb KW - QW interface profile KW - intermixing KW - interband cascade lasers KW - EDX spectra Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-136386 VL - 10 IS - 471 ER - TY - JOUR T1 - Jet energy measurement and its systematic uncertainty in proton-proton collisions at \(\sqrt {s}\)=7 TeV with the ATLAS detector JF - European Physical Journal C: Particles and Fields N2 - The jet energy scale (JES) and its systematic uncertainty are determined for jets measured with the ATLAS detector using proton–proton collision data with a centre-of-mass energy of \(\sqrt {s}\)=7 TeV corresponding to an integrated luminosity of 4.7 fb\(^{-1}\). Jets are reconstructed from energy deposits forming topological clusters of calorimeter cells using the anti-k\(_t\) algorithm with distance parameters R=0.4 or R=0.6, and are calibrated using MC simulations. A residual JES correction is applied to account for differences between data and MC simulations. This correction and its systematic uncertainty are estimated using a combination of in situ techniques exploiting the transverse momentum balance between a jet and a reference object such as a photon or a Z boson, for 20≤p\(^{jet}_{T}\)<1000 GeV and pseudorapidities |η|<4.5. The effect of multiple proton–proton interactions is corrected for, and an uncertainty is evaluated using in situ techniques. The smallest JES uncertainty of less than 1 % is found in the central calorimeter region (|η|<1.2) for jets with 55≤p\(^{jet}_{T}\)<500 GeV. For central jets at lower p\(_{T}\), the uncertainty is about 3 %. A consistent JES estimate is found using measurements of the calorimeter response of single hadrons in proton–proton collisions and test-beam data, which also provide the estimate for p\(^{jet}_{T}\)>1 TeV. The calibration of forward jets is derived from dijet p\(_{T}\) balance measurements. The resulting uncertainty reaches its largest value of 6 % for low-p\(_{T}\) jets at |η|=4.5. Additional JES uncertainties due to specific event topologies, such as close-by jets or selections of event samples with an enhanced content of jets originating from light quarks or gluons, are also discussed. The magnitude of these uncertainties depends on the event sample used in a given physics analysis, but typically amounts to 0.5–3 %. KW - jet energy scale KW - proton-proton-collision Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-149854 VL - 75 IS - 1 ER - TY - JOUR T1 - Measurement of colour flow with the jet pull angle in t\(\overline{t}\) events using the ATLAS detector at \(\sqrt {s}\)=8 TeV JF - Physics Letters B N2 - The distribution and orientation of energy inside jets is predicted to be an experimental handle on colour connections between the hard-scatter quarks and gluons initiating the jets. This Letter presents a measurement of the distribution of one such variable, the jet pull angle. The pull angle is measured for jets produced in t\(\overline{t}\) events with one W boson decaying leptonically and the other decaying to jets using 20.3 fb\(^{−1}\) of data recorded with the ATLAS detector at a centre-of-mass energy of \(\sqrt {s}\)=8 TeV at the LHC. The jet pull angle distribution is corrected for detector resolution and acceptance effects and is compared to various models. KW - physics KW - colour flow Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-144229 VL - 750 ER - TY - JOUR T1 - Measurement of exclusive γγ→ℓ\(^{+}\)ℓ\(^{−}\) production in proton–proton collisions at \(\sqrt {s}\)=7 TeV with the ATLAS detector JF - Physics Letters B N2 - This Letter reports a measurement of the exclusive γγ→ℓ\(^{+}\)ℓ\(^{−}\) (ℓ=e, μℓ=e, μ) cross-section in proton–proton collisions at a centre-of-mass energy of 7 TeV by the ATLAS experiment at the LHC, based on an integrated luminosity of 4.6 fb\(^{−1}\). For the electron or muon pairs satisfying exclusive selection criteria, a fit to the dilepton acoplanarity distribution is used to extract the fiducial cross-sections. The cross-section in the electron channel is determined to be \(^{excl.}_{γγ→e^{+}e^{-}}\)=0.428 ± 0.035 (stat.) ± 0.018 (syst.) pb for a phase–space region with invariant mass of the electron pairs greater than 24 GeV, in which both electrons have transverse momentum p\(_{T}\)>12 GeV and pseudorapidity |η|<2.4. For muon pairs with invariant mass greater than 20 GeV, muon transverse momentum p\(_{T}\)>10 GeV and pseudorapidity |η|<2.4, the cross-section is determined to be \(^{excl.}_{γγ→μ^{+}μ^{-}}\) =0.628 ± 0.032 (stat.) ± 0.021 (syst.) pb. When proton absorptive effects due to the finite size of the proton are taken into account in the theory calculation, the measured cross-sections are found to be consistent with the theory prediction. KW - physics Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-144247 VL - 749 ER - TY - JOUR T1 - Measurement of the branching ratio Γ(Λ\(^0_b\)→ψ(2S)Λ\(^0\))/Γ(Λ\(^0_b\)→J/ψΛ\(^0\)) with the ATLAS detector JF - Physics Letters B N2 - An observation of the View the Λ\(^0_b\)→ψ(2S)Λ\(^0\) decay and a comparison of its branching fraction with that of the Λ\(^0_b\)→J/ψΛ\(^0\) decay has been made with the ATLAS detector in proton–proton collisions at \(\sqrt {s}\)=8 TeV at the LHC using an integrated luminosity of 20.6 fb\(^{-1}\). The J/ψJ/ψ and ψ(2S) mesons are reconstructed in their decays to a muon pair, while the Λ\(^0\)→pπ\(^-\) decay is exploited for the Λ\(^0\) baryon reconstruction. The Λ\(^0_b\) baryons are reconstructed with transverse momentum p\(_T\)>10 GeV pT>10 GeV and pseudorapidity |η|<2.1. The measured branching ratio of the Λ\(^0_b\)→ψ(2S)Λ\(^0\) and Λ\(^0_b\)→J/ψΛ\(^0\) decays is Γ(Λ\(^0_b\)→ψ(2S)Λ\(^0\))/Γ(Λ\(^0_b\)→J/ψΛ\(^0\))=0.501±0.033(stat)±0.019(syst), lower than the expectation from the covariant quark model. KW - physics KW - proton–proton collisions KW - Large Hadron Collider KW - decay Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-143375 VL - 751 ER - TY - JOUR T1 - Measurement of the production and lepton charge asymmetry of bosons in Pb+Pb collisions at \(\sqrt {^{S}NN}\) with the ATLAS detector JF - European Physical Journal C: Particles and Fields N2 - A measurement of W boson production in lead-lead collisions at \(\sqrt {^{S}NN}\)=2.76 TeV is presented. It is based on the analysis of data collected with the ATLAS detector at the LHC in 2011 corresponding to an integrated luminosity of 0.14 nb\(^{-1}\) and 0.15 nb\(^{-1}\) in the muon and electron decay channels, respectively. The differential production yields and lepton charge asymmetry are each measured as a function of the average number of participating nucleons ⟨N\(_{part}\)⟩ and absolute pseudorapidity of the charged lepton. The results are compared to predictions based on next-to-leading-order QCD calculations. These measurements are, in principle, sensitive to possible nuclear modifications to the parton distribution functions and also provide information on scaling of W boson production in multi-nucleon systems. KW - Higgs boson KW - lead-lead collision Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-149889 VL - 75 IS - 1 ER - TY - JOUR T1 - Measurement of the top quark mass in the t\(\overline{t}\)→ lepton+jets and t\(\overline{t}\)→ dilepton channels using \(\sqrt {s}\)=7 TeV ATLAS data JF - European Physical Journal C: Particles and Fields N2 - The top quark mass was measured in the channels t\(\overline{t}\) → lepton+jets and t\(\overline{t}\) → dilepton (lepton = e,μ) based on ATLAS data recorded in 2011. The data were taken at the LHC with a proton–proton centre-of-mass energy of \(\sqrt {s}\) = 7 TeV and correspond to an integrated luminosity of 4.6 fb\(^{-1}\). The t\(\overline{t}\) → lepton+jets analysis uses a three-dimensional template technique which determines the top quark mass together with a global jet energy scale factor (JSF), and a relative b-to-light-jet energy scale factor(bJSF), where the terms b-jets and light-jets refer to jets originating from b-quarks and u, d, c, s-quarks or gluons, respectively. The analysis of the t\(\overline{t}\) → dilepton channel exploits a one-dimensional template method using the m\(_{lb}\) observable, defined as the average invariant mass of the two lepton+b-jet pairs in each event. The top quark mass is measured to be 172.33±0.75(stat + JSF + bJSF)±1.02(syst) GeV, and 173.79 ± 0.54(stat) ± 1.30(syst) GeV in the t\(\overline{t}\) → lepton+jets and t\(\overline{t}\) → dilepton channels, respectively. The combination of the two results yields m\(_{top}\) =172.99 ± 0.48(stat) ± 0.78(syst) GeV, with a total uncertainty of 0.91 GeV. KW - top quark mass Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-149890 VL - 75 IS - 7 ER - TY - JOUR T1 - Measurement of the top-quark mass in the fully hadronic decay channel from ATLAS data at \(\sqrt {s}\)=7TeV JF - European Physical Journal C: Particles and Fields N2 - The mass of the top quark is measured in a data set corresponding to 4.6  fb\(^{-1}\) of proton–proton collisions with centre-of-mass energy \(\sqrt {s}\)=7 TeV collected by the ATLAS detector at the LHC. Events consistent with hadronic decays of top–antitop quark pairs with at least six jets in the final state are selected. The substantial background from multijet production is modelled with data-driven methods that utilise the number of identified b-quark jets and the transverse momentum of the sixth leading jet, which have minimal correlation. The top-quark mass is obtained from template fits to the ratio of three-jet to dijet mass. The three-jet mass is calculated from the three jets produced in a top-quark decay. Using these three jets the dijet mass is obtained from the two jets produced in the W boson decay. The top-quark mass obtained from this fit is thus less sensitive to the uncertainty in the energy measurement of the jets. A binned likelihood fit yields a top-quark mass of m\(_{t}\)= 175.1 ± 1.4 (stat.) ± 1.2 (syst.) GeV. KW - ATLAS KW - proton–proton collisions KW - top-quark mass KW - fully hadronic KW - LHC Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-149905 VL - 75 IS - 4 ER - TY - JOUR T1 - Measurement of three-jet production cross-sections in pp collisions at 7 TeV centre-of-mass energy using the ATLAS detector JF - European Physical Journal C: Particles and Fields N2 - Double-differential three-jet production cross-sections are measured in proton–proton collisions at a centre-of-mass energy of \(\sqrt {s}\) = 7 TeV using the ATLAS detector at the large hadron collider. The measurements are presented as a function of the three-jet mass (m\(_{jjj}\)), in bins of the sum of the absolute rapidity separations between the three leading jets (|Y\(^{*}\)|). Invariant masses extending up to 5 TeV are reached for 8 < |Y\(^{*}\)| < 10. These measurements use a sample of data recorded using the ATLAS detector in 2011, which corresponds to an integrated luminosity of 4.51 fb\(^{-1}\). Jets are identified using the anti-k\(_{t}\) algorithm with two different jet radius parameters, R = 0.4 and R = 0.6. The dominant uncertainty in these measurements comes from the jet energy scale. Next-to-leading-order QCD calculations corrected to account for non-perturbative effects are compared to the measurements. Good agreement is found between the data and the theoretical predictions based on most of the available sets of parton distribution functions, over the full kinematic range, covering almost seven orders of magnitude in the measured cross-section values. KW - proton-proton-collisions KW - ATLAS detector Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-149918 VL - 75 IS - 5 ER - TY - JOUR T1 - Measurement of transverse energy–energy correlations in multi-jet events in pp collisions at \(\sqrt {s}\)=7 TeV using the ATLAS detector and determination of the strong coupling constant αs(m\(_{Z}\)) JF - Physics Letters B N2 - High transverse momentum jets produced in pp collisions at a centre of mass energy of 7 TeV are used to measure the transverse energy–energy correlation function and its associated azimuthal asymmetry. The data were recorded with the ATLAS detector at the LHC in the year 2011 and correspond to an integrated luminosity of 158 pb\(^{-1}\). The selection criteria demand the average transverse momentum of the two leading jets in an event to be larger than 250 GeV. The data at detector level are well described by Monte Carlo event generators. They are unfolded to the particle level and compared with theoretical calculations at next-to-leading-order accuracy. The agreement between data and theory is good and provides a precision test of perturbative Quantum Chromodynamics at large momentum transfers. From this comparison, the strong coupling constant given at the Z   boson mass is determined to be αs(m\(_{Z}\))=0.1173±0.0010 (exp.) \(^{+0.0065}_{−0.0026}\) (theo.). KW - physics KW - high transverse momentum jets KW - transverse energy–energy correlation function Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-143398 VL - 750 ER - TY - JOUR T1 - Measurements of the W production cross sections in association with jets with the ATLAS detector JF - European Physical Journal C: Particles and Fields N2 - This paper presents cross sections for the production of a W boson in association with jets, measured in proton–proton collisions at \(\sqrt {s}\) = 7 TeV with the ATLAS experiment at the large hadron collider. With an integrated luminosity of 4.6 fb\(^{−1}\), this data set allows for an exploration of a large kinematic range, including jet production up to a transverse momentum of 1 TeV and multiplicities up to seven associated jets. The production cross sections for W bosons are measured in both the electron and muon decay channels. Differential cross sections for many observables are also presented including measurements of the jet observables such as the rapidities and the transverse momenta as well as measurements of event observables such as the scalar sums of the transverse momenta of the jets. The measurements are compared to numerous QCD predictions including next-to-leading-order perturbative calculations, resummation calculations and Monte Carlo generators. KW - ATLAS detector KW - W boson KW - proton-prton-collision Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-149925 VL - 75 IS - 2 ER -