Showing papers by "Werner Wiedenmann published in 2019"
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TL;DR: In this article, a search for high-mass dielectron and dimuon resonances in the mass range of 250 GeV to 6 TeV was performed at the Large Hadron Collider.
248 citations
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TL;DR: An exclusion limit on the H→invisible branching ratio of 0.26(0.17_{-0.05}^{+0.07}) at 95% confidence level is observed (expected) in combination with the results at sqrt[s]=7 and 8 TeV.
Abstract: Dark matter particles, if sufficiently light, may be produced in decays of the Higgs boson. This Letter presents a statistical combination of searches for H→invisible decays where H is produced according to the standard model via vector boson fusion, Z(ll)H, and W/Z(had)H, all performed with the ATLAS detector using 36.1 fb^{-1} of pp collisions at a center-of-mass energy of sqrt[s]=13 TeV at the LHC. In combination with the results at sqrt[s]=7 and 8 TeV, an exclusion limit on the H→invisible branching ratio of 0.26(0.17_{-0.05}^{+0.07}) at 95% confidence level is observed (expected).
234 citations
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TL;DR: In this article, an improved energy clustering algorithm is introduced, and its implications for the measurement and identification of prompt electrons and photons are discussed in detail, including corrections and calibrations that affect performance, including energy calibration, identification and isolation efficiencies.
Abstract: This paper describes the reconstruction of electrons and photons with the ATLAS detector, employed for measurements and searches exploiting the complete LHC Run 2 dataset. An improved energy clustering algorithm is introduced, and its implications for the measurement and identification of prompt electrons and photons are discussed in detail. Corrections and calibrations that affect performance, including energy calibration, identification and isolation efficiencies, and the measurement of the charge of reconstructed electron candidates are determined using up to 81 fb−1 of proton-proton collision data collected at √s=13 TeV between 2015 and 2017.
227 citations
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TL;DR: In this article, the ATLAS Collaboration during Run 2 of the Large Hadron Collider (LHC) was used to identify jets containing b-hadrons, and the performance of the algorithms was evaluated in the s...
Abstract: The algorithms used by the ATLAS Collaboration during Run 2 of the Large Hadron Collider to identify jets containing b-hadrons are presented. The performance of the algorithms is evaluated in the s ...
210 citations
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TL;DR: Algorithms used for the reconstruction and identification of electrons in the central region of the ATLAS detector at the Large Hadron Collider (LHC) are presented in this article, these algorithms a...
Abstract: Algorithms used for the reconstruction and identification of electrons in the central region of the ATLAS detector at the Large Hadron Collider (LHC) are presented in this paper; these algorithms a ...
140 citations
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TL;DR: In this article, the authors measured the yield and nuclear modification factor (R-AA) of the Pb+Pb data at root s(NN) = 5.02 TeV and 25 pb−Pb−1 data at r...
108 citations
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TL;DR: In this paper, a search for a heavy charged-boson resonance decaying into a charged lepton (electron or muon) and a neutrino is reported, where the observed transverse mass distribution computed from the lepton and missing transverse momenta is consistent with the distribution expected from the Standard Model.
Abstract: A search for a heavy charged-boson resonance decaying into a charged lepton (electron or muon) and a neutrino is reported. A data sample of 139 fb−1 of proton-proton collisions at √s=13 TeV collected with the ATLAS detector at the LHC during 2015–2018 is used in the search. The observed transverse mass distribution computed from the lepton and missing transverse momenta is consistent with the distribution expected from the Standard Model, and upper limits on the cross section for pp→W′→lν are extracted (l=e or μ). These vary between 1.3 pb and 0.05 fb depending on the resonance mass in the range between 0.15 and 7.0 TeV at 95% confidence level for the electron and muon channels combined. Gauge bosons with a mass below 6.0 and 5.1 TeV are excluded in the electron and muon channels, respectively, in a model with a resonance that has couplings to fermions identical to those of the Standard Model W boson. Cross-section limits are also provided for resonances with several fixed Γ/m values in the range between 1% and 15%. Model-independent limits are derived in single-bin signal regions defined by a varying minimum transverse mass threshold. The resulting visible cross-section upper limits range between 4.6 (15) pb and 22 (22) ab as the threshold increases from 130 (110) GeV to 5.1 (5.1) TeV in the electron (muon) channel.
98 citations
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TL;DR: In this paper, a search for heavy charged long-lived particles was performed using a data sample of 36.1 fb−1 of proton-proton collisions at s=13µTeV collected by the ATLAS experiment at the Large Hadron Collider.
Abstract: A search for heavy charged long-lived particles is performed using a data sample of 36.1 fb−1 of proton-proton collisions at s=13 TeV collected by the ATLAS experiment at the Large Hadron Collider. The search is based on observables related to ionization energy loss and time of flight, which are sensitive to the velocity of heavy charged particles traveling significantly slower than the speed of light. Multiple search strategies for a wide range of lifetimes, corresponding to path lengths of a few meters, are defined as model independently as possible, by referencing several representative physics cases that yield long-lived particles within supersymmetric models, such as gluinos/squarks (R-hadrons), charginos and staus. No significant deviations from the expected Standard Model background are observed. Upper limits at 95% confidence level are provided on the production cross sections of long-lived R-hadrons as well as directly pair-produced staus and charginos. These results translate into lower limits on the masses of long-lived gluino, sbottom and stop R-hadrons, as well as staus and charginos of 2000, 1250, 1340, 430, and 1090 GeV, respectively.
98 citations
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TL;DR: In this paper, a search for the decay of neutral, weakly interacting, long-lived particles using data collected by the ATLAS detector at the LHC is presented, using 36.1 fb(-1) of proton...
Abstract: A search for the decay of neutral, weakly interacting, long-lived particles using data collected by the ATLAS detector at the LHC is presented. The analysis in this paper uses 36.1 fb(-1) of proton ...
83 citations
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TL;DR: In this article, the Higgs boson production cross-sections in proton-proton collisions are measured in the H -> WW*-> e nu mu nu decay channel, and the collision data were produced at the Large Hadron C
83 citations
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TL;DR: In this paper, a search for new light resonances decaying to pairs of quarks and produced in association with a high- pT photon or jet is presented, but no evidence of new resonance is observed in the data, which are used to exclude the production of a lepto-phobic axial-vector Z′ boson.
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TL;DR: In this article, the efficiency of the photon identification criteria in the ATLAS detector was measured using 36.1 fb1 to 36.7 fb 1 collision data at v s = 13 TeV collected in 2015 and 2016.
Abstract: The efficiency of the photon identification criteria in the ATLAS detector is measured using 36.1 fb1 to 36.7 fb1 of pp collision data at v s = 13 TeV collected in 2015 and 2016. The efficiencies a ...
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TL;DR: In this paper, the authors performed searches for scalar leptoquarks pair-produced in proton-proton collisions at the Large Hadron Collider (LHC) at the ATLAS experiment.
Abstract: Searches for scalar leptoquarks pair-produced in proton–proton collisions at $\sqrt{s}=13$ TeV at the Large Hadron Collider are performed by the ATLAS experiment. A data set corresponding to an integrated luminosity of 36.1 fb$^{-1}$ is used. Final states containing two electrons or two muons and two or more jets are studied, as are states with one electron or muon, missing transverse momentum and two or more jets. No statistically significant excess above the Standard Model expectation is observed. The observed and expected lower limits on the leptoquark mass at 95% confidence level extend up to 1.29 TeV and 1.23 TeV for first- and second-generation leptoquarks, respectively, as postulated in the minimal Buchmuller–Ruckl–Wyler model, assuming a branching ratio into a charged lepton and a quark of 50%. In addition, measurements of particle-level fiducial and differential cross sections are presented for the $Z\rightarrow ee$ , $Z\rightarrow \mu \mu $ and $t\bar{t}$ processes in several regions related to the search control regions. Predictions from a range of generators are compared with the measurements, and good agreement is seen for many of the observables. However, the predictions for the $Z\rightarrow \ell \ell $ measurements in observables sensitive to jet energies disagree with the data.
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TL;DR: A measurement of the associated production of a top-quark pair (tt) with a vector boson (W, Z) in proton-proton collisions at a center-of-mass energy of 13 TeV is presented, using 36.1 fb-1 of integrated luminosity collected by the ATLAS detector at the Large Hadron Collider as mentioned in this paper.
Abstract: A measurement of the associated production of a top-quark pair (tt) with a vector boson (W, Z) in proton-proton collisions at a center-of-mass energy of 13 TeV is presented, using 36.1 fb-1 of integrated luminosity collected by the ATLAS detector at the Large Hadron Collider. Events are selected in channels with two same- or opposite-sign leptons (electrons or muons), three leptons or four leptons, and each channel is further divided into multiple regions to maximize the sensitivity of the measurement. The ttZ and ttW production cross sections are simultaneously measured using a combined fit to all regions. The best-fit values of the production cross sections are σttZ=0.95±0.08stat±0.10syst pb and σttW=0.87±0.13stat±0.14syst pb in agreement with the Standard Model predictions. The measurement of the ttZ cross section is used to set constraints on effective field theory operators which modify the ttZ vertex.
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TL;DR: A search for new particles decaying into a pair of top quarks is performed using proton-proton collision data recorded with the ATLAS detector at the Large Hadron Collider at a center-of-mass energ...
Abstract: A search for new particles decaying into a pair of top quarks is performed using proton-proton collision data recorded with the ATLAS detector at the Large Hadron Collider at a center-of-mass energ ...
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TL;DR: Jets created in association with a photon can be used as a calibrated probe to study energy loss in the medium created in nuclear collisions Measurements of the transverse momentum balance between.
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TL;DR: In this article, a search for a right-handed gauge boson decaying into a boosted right-hand heavy neutrino N-R in the framework of Left-Right Symmetric Models is presented.
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TL;DR: In this paper, a search for four-top-quark production, tttt, is presented based on proton-proton collision data with a center-of-mass energy s=13 TeV collected by the ATLAS detector at the Large Hadron Collider during the years 2015 and 2016, corresponding to an integrated luminosity of 36.1 fb-1.
Abstract: A search for four-top-quark production, tttt, is presented. It is based on proton-proton collision data with a center-of-mass energy s=13 TeV collected by the ATLAS detector at the Large Hadron Collider during the years 2015 and 2016, corresponding to an integrated luminosity of 36.1 fb-1. Data are analyzed in both the single-lepton and opposite-sign dilepton channels, characterized by the presence of one or two isolated electrons or muons with high-transverse momentum and multiple jets. A data-driven method is used to estimate the dominant background from top-quark pair production in association with jets. No significant excess above the Standard Model expectation is observed. The result is combined with the previous same-sign dilepton and multilepton searches carried out by the ATLAS Collaboration and an observed (expected) upper limit of 5.3 (2.1) times the four-top-quark Standard Model cross section is obtained at 95% confidence level. Additionally, an upper limit on the anomalous four-top-quark production cross section is set in the context of an effective field theory model. © 2019 CERN.
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TL;DR: In this article, a search for singly produced vector-like quarks, where Q can be either a T quark with charge +2/3 or a Y quark having charge −4/3, is performed in proton-proton collision data at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 36.1 fb−1, recorded with the ATLAS detector at the LHC in 2015 and 2016.
Abstract: A search for singly produced vector-like quarks Q, where Q can be either a T quark with charge +2/3 or a Y quark with charge −4/3, is performed in proton–proton collision data at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 36.1 fb−1, recorded with the ATLAS detector at the LHC in 2015 and 2016. The analysis targets Q → Wb decays where the W boson decays leptonically. No significant deviation from the expected Standard Model background is observed. Upper limits are set on the QWb coupling strength and the mixing between the Standard Model sector and a singlet T quark or a Y quark from a (B, Y) doublet or a (T, B, Y) triplet, taking into account the interference effects with the Standard Model background. The upper limits set on the mixing angle are as small as |sin θL| = 0.18 for a singlet T quark of mass 800 GeV, |sin θR| = 0.17 for a Y quark of mass 800 GeV in a (B, Y) doublet model and |sin θL| = 0.16 for a Y quark of mass 800 GeV in a (T, B, Y) triplet model. Within a (B, Y) doublet model, the limits set on the mixing parameter |sin θR| are comparable with the exclusion limits from electroweak precision observables in the mass range between about 900 GeV and 1250 GeV.
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TL;DR: In this paper, a search for supersymmetry in events with large missing transverse momentum, jets, and at least one hadronically decaying τ-lepton is presented, and the analysis is based on proton-proton collisions at s=13 TeV corresponding to an integrated luminosity of 36.1 fb-1 delivered by the Large Hadron Collider and recorded by the ATLAS detector in 2015 and 2016.
Abstract: A search for supersymmetry in events with large missing transverse momentum, jets, and at least one hadronically decaying τ-lepton is presented. Two exclusive final states with either exactly one or at least two τ-leptons are considered. The analysis is based on proton-proton collisions at s=13 TeV corresponding to an integrated luminosity of 36.1 fb-1 delivered by the Large Hadron Collider and recorded by the ATLAS detector in 2015 and 2016. No significant excess is observed over the Standard Model expectation. At 95% confidence level, model-independent upper limits on the cross section are set and exclusion limits are provided for two signal scenarios: a simplified model of gluino pair production with τ-rich cascade decays, and a model with gauge-mediated supersymmetry breaking (GMSB). In the simplified model, gluino masses up to 2000 GeV are excluded for low values of the mass of the lightest supersymmetric particle (LSP), while LSP masses up to 1000 GeV are excluded for gluino masses around 1400 GeV. In the GMSB model, values of the supersymmetry-breaking scale are excluded below 110 TeV for all values of tanβ in the range 2≤tanβ≤60, and below 120 TeV for tanβ>30. © 2019 CERN, for the ATLAS Collaboration. Published by the American Physical Society under the terms of the »https://creativecommons.org/licenses/by/4.0/» Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.
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TL;DR: In this paper, a search for flavour-changing neutral current decays of a top quark into an up-type quark and the Standard Model Higgs boson, t Hq, is presented.
Abstract: A search for flavour-changing neutral current decays of a top quark into an up-type quark (q = u, c) and the Standard Model Higgs boson, t Hq, is presented. The search is based on a dataset of pp c ...
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TL;DR: In this paper, the inclusion of four isolated charged leptons in pp collisions is analyzed for the presence of hard double-parton scattering, using 20.2 fb(-1) of data recorded in the ATLAS detector.
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TL;DR: In this paper, a measurement of quantities related to the formation of jets from high-energy quarks and gluons (fragmentation) is presented, with transverse momentum 100 GeV 500 MeV.
Abstract: This paper presents a measurement of quantities related to the formation of jets from high-energy quarks and gluons (fragmentation). Jets with transverse momentum 100 GeV 500 MeV and vertical bar ...
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TL;DR: In this paper, a search for heavy long-lived multicharged particles is performed using the ATLAS detector at the LHC using data with an integrated luminosity of 36.1 fb(-1) collected in 2015 and 2016 from proton-proto...
Abstract: A search for heavy long-lived multicharged particles is performed using the ATLAS detector at the LHC. Data with an integrated luminosity of 36.1 fb(-1) collected in 2015 and 2016 from proton-proto ...
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TL;DR: A search for the production of three massive vector bosons in proton-proton collisions was performed using data at root s = 13 TeV recorded with the ATLAS detector at the Large Hadron Collider in this article.
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TL;DR: In this paper, a measurement of forward-forward and forward-central dijet azimuthal angular correlations and conditional yields in proton-proton (pp) and proton lead (p + Pb) collisions as a p + pb collision is presented.
Abstract: This paper presents a measurement of forward-forward and forward-central dijet azimuthal angular correlations and conditional yields in proton-proton (pp) and proton-lead (p + Pb) collisions as a p ...
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TL;DR: In this paper, the cross-section for jet production in association with a Z boson decaying into an electronpositron pair is measured as a function of the transverse momentum and the absolute rapidity of the decay.
Abstract: The inclusive cross-section for jet production in association with a Z boson decaying into an electronpositron pair is measured as a function of the transverse momentum and the absolute rapidity of ...
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TL;DR: In this article, the results of a search for the pair production of photon-jets in the ATLAS detector at the Large Hadron Collider are reported, and the results are interpreted in the context of a model containing a new, high-mass scalar particle with narrow width, X, that decays into pairs of photonjets via new, light particles, a upper limits are placed on the cross section times the product of branching ratios σ×B(X→aa)×B (a→γγ)2 for 200 GeV.
Abstract: Results of a search for the pair production of photon-jets - collimated groupings of photons - in the ATLAS detector at the Large Hadron Collider are reported Highly collimated photon-jets can arise from the decay of new, highly boosted particles that can decay to multiple photons collimated enough to be identified in the electromagnetic calorimeter as a single, photonlike energy cluster Data from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 367 fb-1, were collected in 2015 and 2016 Candidate photon-jet pair production events are selected from those containing two reconstructed photons using a set of identification criteria much less stringent than that typically used for the selection of photons, with additional criteria applied to provide improved sensitivity to photon-jets Narrow excesses in the reconstructed diphoton mass spectra are searched for The observed mass spectra are consistent with the Standard Model background expectation The results are interpreted in the context of a model containing a new, high-mass scalar particle with narrow width, X, that decays into pairs of photon-jets via new, light particles, a Upper limits are placed on the cross section times the product of branching ratios σ×B(X→aa)×B(a→γγ)2 for 200 GeV
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TL;DR: In this paper, the production cross-sections for W and Z bosons are measured using ATLAS data corresponding to an integrated luminosity of 4.76$-TeV, where the decay channels can be an electron or a muon.
Abstract: The production cross-sections for $W^{\pm }$ and Z bosons are measured using ATLAS data corresponding to an integrated luminosity of 4.0 pb$^{-1}$ collected at a centre-of-mass energy $\sqrt{s}=2.76$ TeV. The decay channels $W \rightarrow \ell
u $ and $Z \rightarrow \ell \ell $ are used, where $\ell $ can be an electron or a muon. The cross-sections are presented for a fiducial region defined by the detector acceptance and are also extrapolated to the full phase space for the total inclusive production cross-section. The combined (average) total inclusive cross-sections for the electron and muon channels are: $\begin{aligned} \sigma ^{\text {tot}}_{W^{+}\rightarrow \ell
u }= & {} 2312 \pm 26\ (\text {stat.})\\&\pm 27\ (\text {syst.}) \pm 72\ (\text {lumi.}) \pm 30\ (\text {extr.})~\text {pb} , \\ \sigma ^{\text {tot}}_{W^{-}\rightarrow \ell
u }= & {} 1399 \pm 21\ (\text {stat.})\ \pm 17\ (\text {syst.}) \\&\pm 43\ (\text {lumi.}) \pm 21\ (\text {extr.})~\text {pb} , \\ \sigma ^{\text {tot}}_{Z \rightarrow \ell \ell }= & {} 323.4 \pm 9.8\ (\text {stat.}) \pm 5.0\ (\text {syst.})\\&\pm 10.0\ (\text {lumi.}) \pm 5.5 (\text {extr.}) ~\text {pb} . \end{aligned}$Measured ratios and asymmetries constructed using these cross-sections are also presented. These observables benefit from full or partial cancellation of many systematic uncertainties that are correlated between the different measurements.
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TL;DR: The momentum measurement capability of the ATLAS muon spectrometer relies fundamentally on the intrinsic single-hit spatial resolution of the monitored drift tube precision tracking chambers as mentioned in this paper, which is the same as that of the single-shot spatial resolution used in the LSTM.
Abstract: The momentum measurement capability of the ATLAS muon spectrometer relies fundamentally on the intrinsic single-hit spatial resolution of the monitored drift tube precision tracking chambers. Optim ...