Zuletzt publiziert

  • Zeitschriftenartikel

    Magnetisation switching of FePt nanoparticle recording medium by femtosecond laser pulses 

    John, R.; Berritta, M.; Hinzke, D.; Müller, C.; Santos, T.; Ulrichs, H.; Nieves, P.; Walowski, J.; Mondal, R.; Chubykalo-Fesenko, O.; et al.
    McCord, J.Oppeneer, P. M.Nowak, U.Münzenberg, M.
    Scientific Reports 2017; 7: Art. 4114
    Manipulation of magnetisation with ultrashort laser pulses is promising for information storage device applications. The dynamics of the magnetisation response depends on the energy transfer from the photons to the spins during the initial laser excitation. A material of special interest for magnetic storage are FePt nanoparticles, for which switching of the magnetisation with optical angular momentum was demonstrated recently. The mechanism remained unclear. Here we investigate experimentally and theoretically the all-optical switching of FePt nanoparticles. We show that the magnetisation switching is a stochastic process. We develop a complete multiscale model which allows us to optimize the number of laser shots needed to switch the magnetisation of high anisotropy FePt nanoparticles in our experiments. We conclude that only angular momentum induced optically by the inverse Faraday effect will provide switching with one single femtosecond laser pulse.
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    Relict high-Andean ecosystems challenge our concepts of naturalness and human impact 

    Sylvester, Steven P.; Heitkamp, Felix; Sylvester, Mitsy D. P. V.; Jungkunst, Hermann F.; Sipman, Harrie J. M.; Toivonen, Johanna M.; Gonzales Inca, Carlos A.; Ospina, Juan C.; Kessler, Michael
    Scientific Reports 2017; 7(1): Art. 3334
    What would current ecosystems be like without the impact of mankind? This question, which is critical for ecosystem management, has long remained unanswered due to a lack of present-day data from truly undisturbed ecosystems. Using mountaineering techniques, we accessed pristine relict ecosystems in the Peruvian Andes to provide this baseline data and compared it with the surrounding accessible and disturbed landscape. We show that natural ecosystems and human impact in the high Andes are radically different from preconceived ideas. Vegetation of these ‘lost worlds’ was dominated by plant species previously unknown to science that have become extinct in nearby human-affected ecosystems. Furthermore, natural vegetation had greater plant biomass with potentially as much as ten times more forest, but lower plant diversity. Contrary to our expectations, soils showed relatively little degradation when compared within a vegetation type, but differed mainly between forest and grassland ecosystems. At the landscape level, a presumed large-scale forest reduction resulted in a nowadays more acidic soilscape with higher carbon storage, partly ameliorating carbon loss through deforestation. Human impact in the high Andes, thus, had mixed effects on biodiversity, while soils and carbon stocks would have been mainly indirectly affected through a suggested large-scale vegetation change.
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    Iron L2,3-Edge X-ray Absorption and X-ray Magnetic Circular Dichroism Studies of Molecular Iron Complexes with Relevance to the FeMoco and FeVco Active Sites of Nitrogenase 

    Kowalska, Joanna K.; Nayyar, Brahamjot; Rees, Julian A.; Schiewer, Christine E.; Lee, Sonny C.; Kovacs, Julie A.; Meyer, Franc; Weyhermüller, Thomas; Otero, Edwige; DeBeer, Serena
    Inorganic Chemistry 2017; 56(14) p.8147-8158
    Herein, a systematic study of a series of molecular iron model complexes has been carried out using Fe L2,3-edge X-ray absorption (XAS) and X-ray magnetic circular dichroism (XMCD) spectroscopies. This series spans iron complexes of increasing complexity, starting from ferric and ferrous tetrachlorides ([FeCl4]−/2–), to ferric and ferrous tetrathiolates ([Fe(SR)4]−/2–), to diferric and mixed-valent iron–sulfur complexes [Fe2S2R4]2–/3–. This test set of compounds is used to evaluate the sensitivity of both Fe L2,3-edge XAS and XMCD spectroscopy to oxidation state and ligation changes. It is demonstrated that the energy shift and intensity of the L2,3-edge XAS spectra depends on both the oxidation state and covalency of the system; however, the quantitative information that can be extracted from these data is limited. On the other hand, analysis of the Fe XMCD shows distinct changes in the intensity at both L3 and L2 edges, depending on the oxidation state of the system. It is also demonstrated that the XMCD intensity is modulated by the covalency of the system. For mononuclear systems, the experimental data are correlated with atomic multiplet calculations in order to provide insights into the experimental observations. Finally, XMCD is applied to the tetranuclear heterometal–iron–sulfur clusters [MFe3S4]3+/2+ (M = Mo, V), which serve as structural analogues of the FeMoco and FeVco active sites of nitrogenase. It is demonstrated that the XMCD data can be utilized to obtain information on the oxidation state distribution in complex clusters that is not readily accessible for the Fe L2,3-edge XAS data alone. The advantages of XMCD relative to standard K-edge and L2,3-edge XAS are highlighted. This study provides an important foundation for future XMCD studies on complex (bio)inorganic systems.
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    An effective molecular approach for assessing cereal aphid-parasitoid-endosymbiont networks 

    Ye, Zhengpei; Vollhardt, Ines M. G.; Girtler, Susanne; Wallinger, Corinna; Tomanovic, Zeljko; Traugott, Michael
    Scientific Reports 2017; 7(1): Art. 3138 (2017)
    Molecular approaches are increasingly being used to analyse host-parasitoid food webs as they overcome several hurdles inherent to conventional approaches. However, such studies have focused primarily on the detection and identification of aphids and their aphidiid primary parasitoids, largely ignoring primary parasitoid-hyperparasitoid interactions or limiting these to a few common species within a small geographical area. Furthermore, the detection of bacterial secondary endosymbionts has not been considered in such assays despite the fact that endosymbionts may alter aphid-parasitoid interactions, as they can confer protection against parasitoids. Here we present a novel two-step multiplex PCR (MP-PCR) protocol to assess cereal aphid-primary parasitoid-hyperparasitoid-endosymbiont interactions. The first step of the assay allows detection of parasitoid DNA at a general level (24 primary and 16 hyperparasitoid species) as well as the species-specific detection of endosymbionts (3 species) and cereal aphids (3 species). The second step of the MP-PCR assay targets seven primary and six hyperparasitoid species that commonly occur in Central Europe. Additional parasitoid species not covered by the second-step of the assay can be identified via sequencing 16S rRNA amplicons generated in the first step of the assay. The approach presented here provides an efficient, highly sensitive, and cost-effective (~consumable costs of 1.3 € per sample) tool for assessing cereal aphid-parasitoid-endosymbiont interactions.
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    Nanotip-based photoelectron microgun for ultrafast LEED 

    Storeck, Gero; Vogelgesang, Simon; Sivis, Murat; Schäfer, Sascha; Ropers, Claus
    Structural Dynamics 2017; 4(4): Art. 044024
    We present the design and fabrication of a micrometer-scale electron gun for the implementation of ultrafast low-energy electron diffraction from surfaces. A multi-step process involving photolithography and focused-ion-beam nanostructuring is used to assemble and electrically contact the photoelectron gun, which consists of a nanotip photocathode in a Schottky geometry and an einzel lens for beam collimation. We characterize the low-energy electron pulses by a transient electric field effect and achieve pulse durations of 1.3 ps at an electron energy of 80 eV. First diffraction images in a backscattering geometry (at 50 eV electron energy) are shown.
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    Soil nitrogen transformation responses to seasonal precipitation changes are regulated by changes in functional microbial abundance in a subtropical forest 

    Chen, Jie; Xiao, Guoliang; Kuzyakov, Yakov; Jenerette, G. Darrel; Ma, Ying; Liu, Wei; Wang, Zhengfeng; Shen, Weijun
    Biogeosciences 2017; 14(9) p.2513-2525
    The frequency of dry-season droughts and wet-season storms has been predicted to increase in subtropical areas in the coming decades. Since subtropical forest soils are significant sources of N2O and NO3−, it is important to understand the features and determinants of N transformation responses to the predicted precipitation changes. A precipitation manipulation field experiment was conducted in a subtropical forest to reduce dry-season precipitation and increase wet-season precipitation, with annual precipitation unchanged. Net N mineralization, net nitrification, N2O emission, nitrifying (bacterial and archaeal amoA) and denitrifying (nirK, nirS and nosZ) gene abundance, microbial biomass carbon (MBC), extractable organic carbon (EOC), NO3−, NH4+ and soil water content (SWC) were monitored to characterize and explain soil N transformation responses. Dry-season precipitation reduction decreased net nitrification and N mineralization rates by 13–20 %, while wet-season precipitation addition increased both rates by 50 %. More than 20 % of the total variation of net nitrification and N mineralization could be explained by microbial abundance and SWC. Notably, archaeal amoA abundance showed the strongest correlation with net N transformation rates (r  ≥  0.35), suggesting the critical role of archaeal amoA abundance in determining N transformations. Increased net nitrification in the wet season, together with large precipitation events, caused substantial NO3− losses via leaching. However, N2O emission decreased moderately in both dry and wet seasons due to changes in nosZ gene abundance, MBC, net nitrification and SWC (decreased by 10–21 %). We conclude that reducing dry-season precipitation and increasing wet-season precipitation affect soil N transformations through altering functional microbial abundance and MBC, which are further affected by changes in EOC and NH4+ availabilities.
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    ESTIMATION OF PARAMETERS IN A PLANAR SEGMENT PROCESS WITH A BIOLOGICAL APPLICATION 

    Beneš, Viktor; Večeřa, Jakub; Eltzner, Benjamin; Wollnik, Carina; Rehfeldt, Florian; Králová, Veronika; Huckemann, Stephan
    Image Analysis & Stereology 2017; 36(1) p.25-33
    The paper deals with modeling of segment systems in a bounded planar set (a cell) by means of random segment processes. Two models with a density with respect to the Poisson process are presented. In model I interactions are given by the number of intersections, model II includes the length distribution and takes into account distances from the centre of the cell. The estimation of parameters of the models is suggested based on Takacz-Fiksel method. The method is tested first using simulated data. Further the real data from fluorescence imaging of stress fibres in mesenchymal human stem cells are evaluated. We apply model II which is inhomogeneous. The degree-of-fit testing of the model using various characteristics yields quite satisfactory results.
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    Jitter-correction for IR/UV-XUV pump-probe experiments at the FLASH free-electron laser 

    Savelyev, Evgeny; Boll, Rebecca; Bomme, Cédric; Schirmel, Nora; Redlin, Harald; Erk, Benjamin; Düsterer, Stefan; Müller, Erland; Höppner, Hauke; Toleikis, Sven; et al.
    Müller, JostKristin Czwalinna, MarieTreusch, RolfKierspel, ThomasMullins, TerenceTrippel, SebastianWiese, JossKüpper, JochenBrauβe, FelixKrecinic, FarukRouzée, ArnaudRudawski, PiotrJohnsson, PerAmini, KasraLauer, AlexandraBurt, MichaelBrouard, MarkChristensen, LaugeThøgersen, JanStapelfeldt, HenrikBerrah, NoraMüller, MariaUlmer, AnatoliTechert, SimoneRudenko, ArtemRolles, Daniel
    New Journal of Physics 2017; 19(4) p.1-13: Art. 043009
    In pump-probe experiments employing a free-electron laser (FEL) in combination with a synchronized optical femtosecond laser, the arrival-time jitter between the FEL pulse and the optical laser pulse often severely limits the temporal resolution that can be achieved. Here, we present a pump-probe experiment on the UV-induced dissociation of 2,6-difluoroiodobenzene (C6H3F2I) molecules performed at the FLASH FEL that takes advantage of recent upgrades of the FLASH timing and synchronization system to obtain high-quality data that are not limited by the FEL arrival-time jitter. We discuss in detail the necessary data analysis steps and describe the origin of the time-dependent effects in the yields and kinetic energies of the fragment ions that we observe in the experiment.
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    What do consumers think about farm animal welfare in modern agriculture? Attitudes and shopping behaviour 

    Heise, Heinke; Theuvsen, Ludwig
    International Food and Agribusiness Management Review 2017; 20(3) p.379-399
    Several food crises damaged the image of the agricultural sector and consumers have lost trust, especially in animal production practices. Large parts of society believe that animal welfare standards in livestock production need to be improved. As a result, numerous animal welfare products have emerged on the market. This consumer paper identifies five clusters and, thus, strategic groups for the purchase of animal welfare products within the large group of consumers that differ significantly in their attitudes towards modern agriculture, their perception of animal welfare, their social acceptance of meat consumption and their shopping behaviour. Even personal differences are found between the clusters. Based on the results, we derived specific marketing implications for each cluster. These implications can help to develop a more differentiated market segment for animal welfare products in terms of animal welfare level and required price premium, enabling consumers to make product choices according to their preferences.
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    Problems related to the taxonomic placement of incompletely preserved amber fossils: transfer of the Paleogene liverwort Cylindrocolea dimorpha (Cephaloziellaceae) to the extant Odontoschisma sect. Iwatsukia (Cephaloziaceae) 

    Feldberg, Kathrin; Váňa, Jiří; Schäfer-Verwimp, Alfons; Krings, Michael; Gröhn, Carsten; Schmidt, Alexander R.; Heinrichs, Jochen
    Fossil Record 2017; 20(2) p.147-157
    A revision of the Baltic and Bitterfeld amber fossils assigned to Cylindrocolea dimorpha (Cephaloziellaceae) has yielded evidence of the presence of multicellular, bifid underleaves, which have not previously been reported for this species and conflict with the current circumscription of the family. We transfer the fossil species to Odontoschisma (sect. Iwatsukia) and propose the new combination O. dimorpha of the Cephaloziaceae. Characteristics of the fossil include an overall small size of the plant, entire-margined, bifid leaves and underleaves, more or less equally thickened leaf cell walls, ventral branching that includes stoloniform branches with reduced leaves, and the lack of a stem hyalodermis and gemmae. Placement of the fossil in Cephaloziaceae profoundly affects divergence time estimates for liverworts based on DNA sequence variation with integrated information from the fossil record. Our reclassification concurs with hypotheses on the divergence times of Cephaloziaceae derived from DNA sequence data that provide evidence of a late Early Cretaceous to early Eocene age of the Odontoschisma crown group and an origin of O. sect. Iwatsukia in the Late Cretaceous to Oligocene.
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    Measurement of WW/WZ → νqq production with the hadronically decaying boson reconstructed as one or two jets in pp collisions at √ s = 8 TeV with ATLAS, and constraints on anomalous gauge couplings 

    Aaboud, M. et al. (ATLAS COllaboration)
    The European Physical Journal C 2017; 77: Art. 563
    This paper presents a study of the production of WW orWZ boson pairs, with oneW boson decaying to eν or μν and one W or Z boson decaying hadronically. The analysis uses 20.2 fb−1 of √ s = 8TeV pp collision data, collected by the ATLAS detector at the Large Hadron Collider. Crosssections for WW/WZ production are measured in high-pT fiducial regions defined close to the experimental event selection. The cross-section is measured for the case where the hadronically decaying boson is reconstructed as two resolved jets, and the case where it is reconstructed as a single jet. The transverse momentum distribution of the hadronically decaying boson is used to search for new physics. Observations are consistent with the Standard Model predictions, and 95% confidence intervals are calculated for parameters describing anomalous triple gauge-boson couplings.
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    Fiducial, total and differential cross-section measurements of t-channel single top-quark production in pp collisions at 8TeV using data collected by the ATLAS detector 

    Aaboud, M. et al. (ATLAS Collaboration)
    The European Physical Journal C 2017; 77: Art. 531
    Detailed measurements of t-channel single topquark production are presented. They use 20.2 fb−1 of data collected by the ATLAS experiment in proton–proton collisions at a centre-of-mass energy of 8TeV at the LHC. Total, fiducial and differential cross-sections are measured for both top-quark and top-antiquark production. The fiducial crosssection is measured with a precision of 5.8% (top quark) and 7.8% (top antiquark), respectively. The total cross-sections are measured to be σtot(tq) = 56.7+4.3 −3.8 pb for top-quark production and σtot(¯tq) = 32.9+3.0 −2.7 pb for top-antiquark production, in agreement with the Standard Model prediction. In addition, the ratio of top-quark to top-antiquark production cross-sections is determined to be Rt = 1.72 ± 0.09. The differential cross-sections as a function of the transverse momentum and rapidity of both the top quark and the top antiquark are measured at both the parton and particle levels. The transverse momentum and rapidity differential crosssections of the accompanying jet from the t-channel scattering are measured at particle level. All measurements are compared to various Monte Carlo predictions as well as to fixed-order QCD calculations where available.
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    Measurements of electroweak W j j production and constraints on anomalous gauge couplings with the ATLAS detector 

    Aaboud, M. et al. (ATLAS Collaboration)
    The European Physical Journal C 2017; 77(474)
    Measurements of the electroweak production of a W boson in association with two jets at high dijet invariant mass are performed using √ s = 7 and 8 TeV proton–proton collision data produced by the Large Hadron Collider, corresponding respectively to 4.7 and 20.2 fb−1 of integrated luminosity collected by the ATLAS detector. The measurements are sensitive to the production of a W boson via a triple-gauge-boson vertex and include both the fiducial and differential cross sections of the electroweak process.
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    Jet reconstruction and performance using particle flow with the ATLAS Detector 

    Aaboud, M. et al. (ATLAS Collaboration)
    The European Physical Journal C 2017; 77: Art. 466
    This paper describes the implementation and performance of a particle flow algorithm applied to 20.2 fb−1 of ATLAS data from 8 TeV proton–proton collisions in Run 1 of the LHC. The algorithm removes calorimeter energy deposits due to charged hadrons from consideration during jet reconstruction, instead using measurements of their momenta from the inner tracker. This improves the accuracy of the charged-hadron measurement, while retaining the calorimeter measurements of neutral-particle energies. The paper places emphasis on how this is achieved, while minimising double-counting of charged-hadron signals between the inner tracker and calorimeter. The performance of particle flow jets, formed from the ensemble of signals from the calorimeter and the inner tracker, is compared to that of jets reconstructed from calorimeter energy deposits alone, demonstrating improvements in resolution and pile-up stability.
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    Search for dark matter at √ s = 13 TeV in final states containing an energetic photon and large missing transverse momentum with the ATLAS detector 

    Aaboud, M. et al. (ATLAS Collaboration)
    The European Physical Journal C 2017; 77: Art. 393
    Results of a search for physics beyond the Standard Model in events containing an energetic photon and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. As the number of events observed in data, corresponding to an integrated luminosity of 36.1 fb−1 of proton–proton collisions at a centre-of-mass energy of 13 TeV, is in agreement with the Standard Model expectations, model-independent limits are set on the fiducial cross section for the production of events in this final state. Exclusion limits are also placed in models where dark-matter candidates are pair-produced. For darkmatter production via an axial-vector or a vector mediator in the s-channel, this search excludes mediator masses below 750–1200 GeV for dark-matter candidate masses below230– 480 GeV at 95% confidence level, depending on the couplings. In an effective theory of dark-matter production, the limits restrict the value of the suppression scale M∗ to be above 790 GeV at 95% confidence level. A limit is also reported on the production of a high-mass scalar resonance by processes beyond the Standard Model, in which the resonance decays to Zγ and the Z boson subsequently decays into neutrinos.
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    Measurement of multi-particle azimuthal correlations in pp, p + Pb and low-multiplicity Pb + Pb collisions with the ATLAS detector 

    Aaboud, M. et al. (ATLAS Collaboration)
    The European Physical Journal C 2017; 77: Art. 428
    Multi-particle cumulants and corresponding Fourier harmonics are measured for azimuthal angle distributions of charged particles in pp collisions at √ s = 5.02 and 13 TeVand in p + Pb collisions at √ sNN = 5.02 TeV, and compared to the results obtained for low-multiplicity Pb + Pb collisions at √ sNN = 2.76 TeV. These measurements aim to assess the collective nature of particle production. The measurements of multi-particle cumulants confirm the evidence for collective phenomena in p + Pb and low-multiplicity Pb + Pb collisions. On the other hand, the pp results for fourparticle cumulants do not demonstrate collective behaviour, indicating that they may be biased by contributions from nonflow correlations. A comparison of multi-particle cumulants and derived Fourier harmonics across different collision systems is presented as a function of the charged-particle multiplicity. For a given multiplicity, the measured Fourier harmonics are largest in Pb + Pb, smaller in p + Pb and smallest in pp collisions. The pp results show no dependence on the collision energy, nor on the multiplicity.
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    Measurements of the production cross section of a Z boson in association with jets in pp collisions at √ s = 13 TeV with the ATLAS detector 

    Aaboud, M. et al. (ATLAS Collaboration)
    The European Physical Journal C 2017; 77: Art. 361
    Measurements of the production cross section of a Z boson in association with jets in proton–proton collisions at s√=13 TeV are presented, using data corresponding to an integrated luminosity of 3.16 fb−1 collected by the ATLAS experiment at the CERN Large Hadron Collider in 2015. Inclusive and differential cross sections are measured for events containing a Z boson decaying to electrons or muons and produced in association with up to seven jets with pT>30 GeV and |y|<2.5. Predictions from different Monte Carlo generators based on leading-order and next-to-leading-order matrix elements for up to two additional partons interfaced with parton shower and fixed-order predictions at next-to-leading order and next-to-next-to-leading order are compared with the measured cross sections. Good agreement within the uncertainties is observed for most of the modelled quantities, in particular with the generators which use next-to-leading-order matrix elements and the more recent next-to-next-to-leading-order fixed-order predictions.
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    Measurement of jet fragmentation in Pb+Pb and pp collisions at √ sNN = 2.76 TeV with the ATLAS detector at the LHC 

    Aaboud, M. et al. (ATLAS Collaboration)
    The European Physical Journal C 2017; 77: Art. 379
    The distributions of transverse momentum and longitudinal momentum fraction of charged particles in jets are measured in Pb+Pb and pp collisions with the ATLAS detector at the LHC. The distributions are measured as a function of jet transverse momentum and rapidity. The analysis utilises an integrated luminosity of 0.14 nb−1 of Pb+Pb data and 4.0 pb−1 of pp data collected in 2011 and 2013, respectively, at the same centre-of-mass energy of 2.76 TeV per colliding nucleon pair. The distributions measured in pp collisions are used as a reference for those measured in Pb+Pb collisions in order to evaluate the impact on the internal structure of jets from the jet energy loss of fast partons propagating through the hot, dense medium created in heavy-ion collisions. Modest but significant centrality-dependent modifications of fragmentation functions in Pb+Pb collisions with respect to those in pp collisions are seen. No significant dependence of modifications on jet pT and rapidity selections is observed except for the fragments with the highest transverse momenta for which some reduction of yields is observed for more forward jets.
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    Search for direct top squark pair production in events with a Higgs or Z boson, and missing transverse momentum in s√=13 TeV pp collisions with the ATLAS detector 

    Aaboud, M. et al. (ATLAS Collaboration)
    Journal of High Energy Physics 2017; 8: Art. 6
    A search for direct top squark pair production resulting in events with either a same-flavour opposite-sign dilepton pair with invariant mass compatible with a Z boson or a pair of jets compatible with a Standard Model (SM) Higgs boson (h) is presented. Requirements on the missing transverse momentum, together with additional selections on leptons, jets, jets identified as originating from b-quarks are imposed to target the other decay products of the top squark pair. The analysis is performed using proton-proton collision data at s√=13 TeV collected with the ATLAS detector at the LHC in 2015–2016, corresponding to an integrated luminosity of 36.1 fb−1. No excess is observed in the data with respect to the SM predictions. The results are interpreted in two sets of models. In the first set, direct production of pairs of lighter top squarks (t~1) with long decay chains involving Z or Higgs bosons is considered. The second set includes direct pair production of the heavier top squark pairs (t~2) decaying via t~2→Zt~1 or t~2→ht~1. The results exclude at 95% confidence level t~2 and t~1 masses up to about 800 GeV, extending the exclusion region of supersymmetric parameter space covered by previous LHC searches.
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    Probing the W tb vertex structure in t-channel single-top-quark production and decay in pp collisions at s√=8 TeV with the ATLAS detector 

    Aaboud, M. et al. (ATLAS Collaboration)
    Journal of High Energy Physics 2017; 4: Art. 124
    To probe the W tb vertex structure, top-quark and W -boson polarisation observables are measured from t-channel single-top-quark events produced in proton-proton collisions at a centre-of-mass energy of 8 TeV. The dataset corresponds to an integrated luminosity of 20.2 fb−1, recorded with the ATLAS detector at the LHC. Selected events contain one isolated electron or muon, large missing transverse momentum and exactly two jets, with one of them identified as likely to contain a b-hadron. Stringent selection requirements are applied to discriminate t-channel single-top-quark events from background. The polarisation observables are extracted from asymmetries in angular distributions measured with respect to spin quantisation axes appropriately chosen for the top quark and the W boson. The asymmetry measurements are performed at parton level by correcting the observed angular distributions for detector effects and hadronisation after subtracting the background contributions. The measured top-quark and W -boson polarisation values are in agreement with the Standard Model predictions. Limits on the imaginary part of the anomalous coupling gR are also set from model-independent measurements.
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