Refine
Has Fulltext
- yes (740) (remove)
Year of publication
- 2017 (740) (remove)
Document Type
- Journal article (394)
- Doctoral Thesis (241)
- Complete part of issue (52)
- Preprint (12)
- Review (12)
- Book (8)
- Conference Proceeding (7)
- Jahresbericht (4)
- Book article / Book chapter (4)
- Master Thesis (2)
Language
- English (503)
- German (232)
- French (3)
- Multiple languages (2)
Keywords
- Würzburg (51)
- Wuerzburg (50)
- Wurzburg (50)
- Universität (48)
- University (45)
- Hadron-Hadron scattering (experiments) (28)
- High energy physics (26)
- medicine (14)
- physics (12)
- Medicine (11)
Institute
- Theodor-Boveri-Institut für Biowissenschaften (78)
- Universität - Fakultätsübergreifend (47)
- Physikalisches Institut (46)
- Graduate School of Life Sciences (34)
- Medizinische Klinik und Poliklinik I (25)
- Institut für Psychologie (24)
- Institut für Theoretische Physik und Astrophysik (24)
- Neurologische Klinik und Poliklinik (24)
- Medizinische Klinik und Poliklinik II (21)
- Fakultät für Physik und Astronomie (20)
Schriftenreihe
Sonstige beteiligte Institutionen
- Johns Hopkins School of Medicine, Baltimore, MD, U.S. (4)
- Institut für Optik und Atomare Physik, Technische Universität Berlin, 10623 Berlin, Germany (2)
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan (2)
- CERN (Geneva, Switzerland) (1)
- Deutsches Zentrum für Herzinsuffizienz (1)
- Didaktik der Chemie (1)
- Endokrinologie (1)
- Fraunhofer Institut für Silicatforschung ISC (1)
- Fraunhofer-Institut für Silicatforschung (1)
- Fraunhofer-Institut für Silicatforschung ISC (1)
ResearcherID
- D-3057-2014 (1)
- M-1240-2017 (1)
- N-8985-2015 (1)
This article presents searches for the \({Zγ}\) decay of the Higgs boson and for narrow high-mass resonances decaying to \(Z\)γ, exploiting \(Z\) boson decays to pairs of electrons or muons. The data analysis uses 36.1 fb\(^{−1}\) of \({pp}\) collisions at \(\sqrt{s}=13\) recorded by the ATLAS detector at the CERN Large Hadron Collider. The data are found to be consistent with the expected Standard Model background. The observed (expected — assuming Standard Model \({pp} → H → {Z}γ\) production and decay) upper limit on the production cross section times the branching ratio for \({pp} → H → {Z}γ\) is 6.6. (5.2) times the Standard Model prediction at the 95% confidence level for a Higgs boson mass of 125.09 GeV. In addition, upper limits are set on the production cross section times the branching ratio as a function of the mass of a narrow resonance between 250 GeV and 2.4 TeV, assuming spin-0 resonances produced via gluon-gluon fusion, and spin-2 resonances produced via gluon-gluon or quark-antiquark initial states. For high-mass spin-0 resonances, the observed (expected) limits vary between 88 fb (61 fb) and 2.8 fb (2.7 fb) for the mass range from 250 GeV to 2.4 TeV at the 95% confidence level.
A search for strongly produced supersymmetric particles using signatures involving multiple energetic jets and either two isolated same-sign leptons (\(e\) or \(µ\)), or at least three isolated leptons, is presented. The analysis relies on the identification of \(b\)-jets and high missing transverse momentum to achieve good sensitivity. A data sample of proton-proton collisions at \(\sqrt{s} = 13\) TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015 and 2016, corresponding to a total integrated luminosity of 36.1 fb\(^{−1}\), is used for the search. No significant excess over the Standard Model prediction is observed. The results are interpreted in several simplified supersymmetric models featuring \(R\)-parity conservation or \(R\)-parity violation, extending the exclusion limits from previous searches. In models considering gluino pair production, gluino masses are excluded up to 1.87 TeV at 95% confidence level. When bottom squarks are pair-produced and decay to a chargino and a top quark, models with bottom squark masses below 700 GeV and light neutralinos are excluded at 95% confidence level. In addition, model-independent limits are set on a possible contribution of new phenomena to the signal region yields.
Measurements of differential cross-sections of top-quark pair production in fiducial phase-spaces are presented as a function of top-quark and \(t\overline{t}\) system kinematic observables in proton-proton collisions at a centre-of-mass energy of \(\sqrt{s}\) = 13 TeV. The data set corresponds to an integrated luminosity of 3.2 fb\(^{−1}\), recorded in 2015 with the ATLAS detector at the CERN Large Hadron Collider. Events with exactly one electron or muon and at least two jets in the final state are used for the measurement. Two separate selections are applied that each focus on different top-quark momentum regions, referred to as resolved and boosted topologies of the \(t\overline{t}\) final state. The measured spectra are corrected for detector effects and are compared to several Monte Carlo simulations by means of calculated \(χ^2\) and \(p\)-values.
A measurement of the calorimeter response to isolated charged hadrons in the ATLAS detector at the LHC is presented. This measurement is performed with 3.2 nb\(^{−1}\) of proton–proton collision data at \(\sqrt{s}\) = 7 TeV from 2010 and 0.1 nb\(^{−1}\) of data at \(\sqrt{s}\) = 8 TeV from 2012. A number of aspects of the calorimeter response to isolated hadrons are explored. After accounting for energy deposited by neutral particles, there is a 5% discrepancy in the modelling, using various sets of GEANT4 hadronic physics models, of the calorimeter response to isolated charged hadrons in the central calorimeter region. The description of the response to anti-protons at low momenta is found to be improved with respect to previous analyses. The electromagnetic and hadronic calorimeters are also examined separately, and the detector simulation is found to describe the response in the hadronic calorimeter well. The jet energy scale uncertainty and correlations in scale between jets of different momenta and pseudorapidity are derived based on these studies. The uncertainty is 2–5% for jets with transverse momenta above 2 TeV, where this method provides the jet energy scale uncertainty for ATLAS.
This paper reports a search for triboson \({W^\pm}{W^\pm}{W^\mp}\) production in two decay channels (\({W^\pm}{W^\pm}{W^\mp}\) → \({ℓ^\pm}{νℓ^\pm}{νℓ^\mp}{ν}\) and \({W^\pm}{W^\pm}{W^\mp}\) → \({ℓ^\pm}{νℓ^\pm}{νjj}\) with \(ℓ=e,μ\)) in proton-proton collision data corresponding to an integrated luminosity of 20.3 fb\(^{−1}\) at a centre-of-mass energy of 8 TeV with the ATLAS detector at the Large Hadron Collider. Events with exactly three charged leptons, or two leptons with the same electric charge in association with two jets, are selected. The total number of events observed in data is consistent with the Standard Model (SM) predictions. The observed 95% confidence level upper limit on the SM \({W^\pm}{W^\pm}{W^\mp}\) production cross section is found to be 730 fb with an expected limit of 560 fb in the absence of SM \({W^\pm}{W^\pm}{W^\mp}\) production. Limits are also set on \(WWWW\) anomalous quartic gauge couplings.
Same- and opposite-sign charge asymmetries are measured in lepton+jets \({t\overline{t}}\) events in which a \(b\)-hadron decays semileptonically to a soft muon, using data corresponding to an integrated luminosity of 20.3 fb\(^{−1}\) from proton-proton collisions at a centre-of-mass energy of \(\sqrt{s}\) = 8 TeV collected with the ATLAS detector at the Large Hadron Collider at CERN. The charge asymmetries are based on the charge of the lepton from the top-quark decay and the charge of the soft muon from the semileptonic decay of a \(b\)-hadron and are measured in a fiducial region corresponding to the experimental acceptance. Four CP asymmetries (one mixing and three direct) are measured and are found to be compatible with zero and consistent with the Standard Model.
A measurement of \(b\)-hadron pair production is presented, based on a data set corresponding to an integrated luminosity of 11.4 fb\(^{−1}\) of proton-proton collisions recorded at \(\sqrt{s}=8\) TeV with the ATLAS detector at the LHC. Events are selected in which a \(b\)-hadron is reconstructed in a decay channel containing \(J/ψ → μμ\), and a second \(b\)-hadron is reconstructed in a decay channel containing a muon. Results are presented in a fiducial volume defined by kinematic requirements on three muons based on those used in the analysis. The fiducial cross section is measured to be 17.7 ± 0.1(stat.) ± 2.0(syst.) nb. A number of normalised differential cross sections are also measured, and compared to predictions from the PHYTHIA8, HERWIG++, MADGRAPH5_AMC@NLO+PYTHIA8 and SHERPA event generators, providing new constraints on heavy flavour production.
The cross section of a top-quark pair produced in association with a photon is measured in proton-proton collisions at a centre-of-mass energy of \(\sqrt{s} = 8\) TeV with 20.2 fb\(^{−1}\) of data collected by the ATLAS detector at the Large Hadron Collider in 2012. The measurement is performed by selecting events that contain a photon with transverse momentum \(p_T\) > 15 GeV, an isolated lepton with large transverse momentum, large missing transverse momentum, and at least four jets, where at least one is identified as originating from a \(b\)-quark. The production cross section is measured in a fiducial region close to the selection requirements. It is found to be 139 ± 7 (stat.) ± 17 (syst.) fb, in good agreement with the theoretical prediction at next-to-leading order of 151 ± 24 fb. In addition, differential cross sections in the fiducial region are measured as a function of the transverse momentum and pseudorapidity of the photon.
A search for the decay of the Standard Model Higgs boson into a \({b\overline{b}}\) pair when produced in association with a \(W\) or \(Z\) boson is performed with the ATLAS detector. The analysed data, corresponding to an integrated luminosity of 36.1 fb\(^{−1}\), were collected in proton-proton collisions in Run 2 of the Large Hadron Collider at a centre-of-mass energy of 13 TeV. Final states containing zero, one and two charged leptons (electrons or muons) are considered, targeting the decays \(Z\) → \({νν}\), \(W\) → \({ℓν}\) and \(Z\) → \({ℓℓ}\). For a Higgs boson mass of 125 GeV, an excess of events over the expected background from other Standard Model processes is found with an observed significance of 3.5 standard deviations, compared to an expectation of 3.0 standard deviations. This excess provides evidence for the Higgs boson decay into b-quarks and for its production in association with a vector boson. The combination of this result with that of the Run 1 analysis yields a ratio of the measured signal events to the Standard Model expectation equal to 0.90 ± 0.18(stat.)\(^{+0.21}_{−0.19}\)(syst.). Assuming the Standard Model production cross-section, the results are consistent with the value of the Yukawa coupling to \(b\)-quarks in the Standard Model.
The electroweak production and subsequent decay of single top quarks in the \(t\)-channel is determined by the properties of the \({Wtb}\) vertex, which can be described by the complex parameters of an effective Lagrangian. An analysis of a triple-differential decay rate in \(t\)-channel production is used to simultaneously determine five generalised helicity fractions and phases, as well as the polarisation of the produced top quark. The complex parameters are then constrained. This analysis is based on 20.2 fb\(^{−1}\) of proton-proton collision data at a centre-of-mass energy of 8 TeV collected with the ATLAS detector at the LHC. The fraction of decays containing transversely polarised \(W\) bosons is measured to be \(f_1\) = 0.30 ± 0.05. The phase between amplitudes for transversely and longitudinally polarised \(W\) bosons recoiling against left-handed \(b\)-quarks is measured to be \(\delta\)_ = 0.002\(\pi^{+0.016\pi}_{+0.017\pi}\), giving no indication of CP violation. The fractions of longitudinal or transverse \(W\) bosons accompanied by right-handed \(b\)-quarks are also constrained. Based on these measurements, limits are placed at 95% CL on the ratio of the complex coupling parameters Re [\({g_R/V_L}\) \(\in\) [−0.12, 0.17] and Im [\({g_R/V_L}\) \(\in\) [−0.07, 0.06]. Constraints are also placed on the ratios |\({V_R}/{V_L}\)| and |\({g_L}/{V_L}\)|. In addition, the polarisation of single top quarks in the \(t\)-channel is constrained to be \(P\) > 0.72 (95% CL). None of the above measurements make assumptions about the value of any of the other parameters or couplings and all of them are in agreement with the Standard Model.
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 \(g_R\) are also set from model independent measurements.
A measurement of the splitting scales occuring in the \(k_t\) jet-clustering algorithm is presented for final states containing a \(Z\) boson. The measurement is done using 20.2 fb\(^{−1}\) of proton-proton collision data collected at a centre-of-mass energy of \(\sqrt{s} = 8\) TeV by the ATLAS experiment at the LHC in 2012. The measurement is based on charged-particle track information, which is measured with excellent precision in the \(p_T\) region relevant for the transition between the perturbative and the non-perturbative regimes. The data distributions are corrected for detector effects, and are found to deviate from state-of-the-art predictions in various regions of the observables.