Showing papers by "Malik Aliev published in 2017"
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TL;DR: This paper presents a short overview of the changes to the trigger and data acquisition systems during the first long shutdown of the LHC and shows the performance of the trigger system and its components based on the 2015 proton–proton collision data.
Abstract: During 2015 the ATLAS experiment recorded 3.8 fb(-1) of proton-proton collision data at a centre-of-mass energy of 13 TeV. The ATLAS trigger system is a crucial component of the experiment, respons ...
488 citations
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TL;DR: In this article, a search for new resonant and non-resonant high-mass phenomena in dielectron and dimuon fi nal states was conducted using 36 : 1 fb(-1) of proton-proton collision data.
Abstract: A search is conducted for new resonant and non-resonant high-mass phenomena in dielectron and dimuon fi nal states. The search uses 36 : 1 fb(-1) of proton-proton collision data, collected at root ...
329 citations
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Aix-Marseille University1, University of Oklahoma2, University of Iowa3, Azerbaijan National Academy of Sciences4, Université Paris-Saclay5, University of Amsterdam6, Michigan State University7, University of California, Santa Cruz8, University of Sussex9, Tel Aviv University10, Technion – Israel Institute of Technology11, University of Oregon12, Stockholm University13, International Centre for Theoretical Physics14, AGH University of Science and Technology15, Brookhaven National Laboratory16, Northern Illinois University17, Ludwig Maximilian University of Munich18, Rutherford Appleton Laboratory19, University of Liverpool20, University of Belgrade21, University of Göttingen22, University of Granada23, Boston University24, Joint Institute for Nuclear Research25, University of Rome Tor Vergata26, Lund University27, Russian Academy of Sciences28, University of Bologna29, University of Victoria30, University of Grenoble31, National University of La Plata32, CERN33, National Technical University of Athens34, University of Chicago35, Columbia University36, University of Birmingham37, University of Copenhagen38, University of Washington39, Spanish National Research Council40, Lawrence Berkeley National Laboratory41, KEK42, Federal University of Rio de Janeiro43, Brandeis University44, University of Michigan45, University of Coimbra46, University of Lisbon47, University of Sheffield48, University of Geneva49, University of Texas at Austin50, Heidelberg University51, University of Milan52, National and Kapodistrian University of Athens53, Dresden University of Technology54, Budker Institute of Nuclear Physics55, IFAE56, University of Pisa57, National Research Nuclear University MEPhI58, Slovak Academy of Sciences59
TL;DR: In this paper, a direct search for lepton flavour violation in decays of the Higgs and Z bosons with the ATLAS detector at the LHC is presented, and upper limits on the lepton-flavour-violating branching ratios are set at the 95[Formula: see text] confidence level.
Abstract: Direct searches for lepton flavour violation in decays of the Higgs and Z bosons with the ATLAS detector at the LHC are presented. The following three decays are considered: [Formula: see text], [Formula: see text], and [Formula: see text]. The searches are based on the data sample of proton-proton collisions collected by the ATLAS detector corresponding to an integrated luminosity of 20.3 [Formula: see text] at a centre-of-mass energy of [Formula: see text] TeV. No significant excess is observed, and upper limits on the lepton-flavour-violating branching ratios are set at the 95[Formula: see text] confidence level: Br[Formula: see text], Br[Formula: see text], and Br[Formula: see text].
132 citations
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TL;DR: 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, which improves the accuracy of the charged-hadron measurement, while retaining the calorimeters' measurements of neutral-particle energies.
Abstract: 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 remo ...
125 citations
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TL;DR: 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, with model-independent limits set on the fiducial cross section.
Abstract: 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 rep ...
115 citations
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TL;DR: In this article, a search for the decay of the Standard Model Higgs boson into a b (b) over bar pair when produced in association with a W or Z boson is performed with the ATLAS detector.
Abstract: A search for the decay of the Standard Model Higgs boson into a b (b) over bar pair when produced in association with a W or Z boson is performed with the ATLAS detector. The analysed data, corresp ...
99 citations
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TL;DR: The results of a search for vector-like top quarks using events with exactly one lepton, at least four jets, and large missing transverse momentum are reported in this paper.
Abstract: The results of a search for vector-like top quarks using events with exactly one lepton, at least four jets, and large missing transverse momentum are reported The search is optimised for pair pro
76 citations
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TL;DR: In this article, a search for the pair production of heavy vector-like T quarks was presented, targeting the T quark decays to a W boson and a b-quark.
Abstract: A search is presented for the pair production of heavy vector-like T quarks, primarily targeting the T quark decays to a W boson and a b-quark. The search is based on 36: 1 fb(-1) of pp collisions ...
63 citations
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TL;DR: In this article, the production cross section of a Z boson in association with jets in proton-proton collisions at root s = 13TeV was measured using data corresponding to an integrated luminosity.
Abstract: Measurements of the production cross section of a Z boson in association with jets in proton-proton collisions at root s = 13TeV are presented, using data corresponding to an integrated luminosity
60 citations
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TL;DR: In this article, the authors present searches for the Zγ decay of the Higgs boson and for narrow high-mass resonances decaying to Zγ, exploiting Z boson decays to pairs of electrons or muons.
Abstract: This article presents searches for the Zγ decay of the Higgs boson and for narrow high-mass resonances decaying to Zγ, exploiting Z boson decays to pairs of electrons or muons. The data analysis uses 36.1 fb−1 of pp collisions at √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 → Zγ production and decay) upper limit on the production cross section times the branching ratio for pp → H → Zγ 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.
59 citations
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TL;DR: In this article, a search for heavy resonances decaying to a W or Z boson and a Higgs boson in the qq¯(′)bb¯ final state is described.
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TL;DR: In this article, the authors presented a search for new resonances with mass larger than 250 GeV, decaying to a Z boson and a photon, and the data were found to be consistent with the expected background in the whole mass range investigated and upper limits were set on the production cross section times decay branching ratio to Z\gamma.
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TL;DR: In this paper, the triple-differential cross section for the Drell-Yan process was measured for invariant masses of the lepton pairs, m$_{ll}$, between 46 and 200 GeV using a sample of 20.2 fb$−1}$ of pp collisions data at a centre-of-mass energy of $ \sqrt{s}=8 $ TeV collected by the ATLAS detector at the LHC in 2012.
Abstract: This paper presents a measurement of the triple-differential cross section for the Drell-Yan process Z/γ$^{*}$ → l$^{+}$ l$^{−}$ where l is an electron or a muon. The measurement is performed for invariant masses of the lepton pairs, m$_{ll}$ , between 46 and 200 GeV using a sample of 20.2 fb$^{−1}$ of pp collisions data at a centre-of-mass energy of $ \sqrt{s}=8 $ TeV collected by the ATLAS detector at the LHC in 2012. The data are presented in bins of invariant mass, absolute dilepton rapidity, |y$_{ll}$|, and the angular variable cos θ$^{*}$ between the outgoing lepton and the incoming quark in the Collins-Soper frame. The measurements are performed in the range |y$_{ll}$ | < 2.4 in the muon channel, and extended to |y$_{ll}$ | < 3.6 in the electron channel. The cross sections are used to determine the Z boson forward-backward asymmetry as a function of |y$_{ll}$ | and m$_{ll}$ . The measurements achieve high-precision, below the percent level in the pole region, excluding the uncertainty in the integrated luminosity, and are in agreement with predictions. These precision data are sensitive to the parton distribution functions and the effective weak mixing angle.
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TL;DR: The results of a search for squarks and gluinos in final states with an isolated electron or muon, multiple jets and large missing transverse momentum using proton-proton collision data at a center-of-mass energy of s=13 TeV are presented in this article.
Abstract: The results of a search for squarks and gluinos in final states with an isolated electron or muon, multiple jets and large missing transverse momentum using proton-proton collision data at a center-of-mass energy of s=13 TeV are presented. The data set used was recorded during 2015 and 2016 by the ATLAS experiment at the Large Hadron Collider and corresponds to an integrated luminosity of 36.1 fb-1. No significant excess beyond the expected background is found. Exclusion limits at 95% confidence level are set in a number of supersymmetric scenarios, reaching masses up to 2.1 TeV for gluino pair production and up to 1.25 TeV for squark pair production.
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TL;DR: In this article, a search for the supersymmetric partners of the Standard Model bottom and top quarks is presented using 36.1 fb$^{−1}$ of pp collision data at 13 $ TeV collected by the ATLAS experiment at the Large Hadron Collider.
Abstract: A search for the supersymmetric partners of the Standard Model bottom and top quarks is presented. The search uses 36.1 fb$^{−1}$ of pp collision data at $ \sqrt{s}=13 $ TeV collected by the ATLAS experiment at the Large Hadron Collider. Direct production of pairs of bottom and top squarks ( $ {\overline{b}}_1 $ and $ {\overline{t}}_1 $ ) is searched for in final states with b-tagged jets and missing transverse momentum. Distinctive selections are defined with either no charged leptons (electrons or muons) in the final state, or one charged lepton. The zero-lepton selection targets models in which the $ {\overline{b}}_1 $ is the lightest squark and decays via $ {\overline{b}}_1\to b{\overline{\chi}}_1^0 $ , where $ {\overline{\chi}}_1^0 $ is the lightest neutralino. The one-lepton final state targets models where bottom or top squarks are produced and can decay into multiple channels, $ {\overline{b}}_1\to b{\overline{\chi}}_1^0 $ and $ {\overline{b}}_1\to t{\overline{\chi}}_1^{\pm } $ , or $ {\overline{t}}_1\to t{\overline{\chi}}_1^0 $ and $ {\overline{t}}_1\to b{\overline{\chi}}_1^{\pm } $ , where $ {\overline{\chi}}_1^{\pm } $ is the lightest chargino and the mass difference $ {m}_{{\overline{\chi}}_1^{\pm }}-{m}_{{\overline{\chi}}_1^0} $ is set to 1 GeV. No excess above the expected Standard Model background is observed. Exclusion limits at 95% confidence level on the mass of third-generation squarks are derived in various supersymmetry-inspired simplified models.
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TL;DR: In this article, the electroweak production of a W boson in association with two jets at high dijet invariant mass was performed using root s = 7 and 8 TeV proton-proton collision data.
Abstract: Measurements of the electroweak production of a W boson in association with two jets at high dijet invariant mass are performed using root s = 7 and 8 TeV proton-proton collision data produced by t ...
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TL;DR: A measurement of the production cross section for two isolated photons in proton-proton collisions at a center-of-mass energy of root s = 8 TeV is presented in this paper.
Abstract: A measurement of the production cross section for two isolated photons in proton-proton collisions at a center-of-mass energy of root s = 8 TeV is presented. The results are based on an integrated ...
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TL;DR: The top-quark mass was measured in the all-hadronic top-antitop quark decay channel using proton-proton collisions at a centre-of-mass energy of s=8.
Abstract: The top-quark mass is measured in the all-hadronic top-antitop quark decay channel using proton-proton collisions at a centre-of-mass energy of s=8" role="presentation">s√=8 TeV with the ATLAS d ...
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TL;DR: In this article, measurements of differential cross-sections of top-quark pair production in fiducial phase-spaces are presented as a function of topquark and tt¯ system kinematic observables in proton-proton collisions at a centre-of-mass energy of √s=13 TeV.
Abstract: Measurements of differential cross-sections of top-quark pair production in fiducial phase-spaces are presented as a function of top-quark and tt¯ system kinematic observables in proton-proton collisions at a centre-of-mass energy of √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 tt¯ final state. The measured spectra are corrected for detector effects and are compared to several Monte Carlo simulations by means of calculated χ2 and p-values.
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TL;DR: In this paper, the authors presented a study of the production of WW or WZ boson pairs, with one W boson decaying to ev or mu v and one W or Z bosons decaying hadronically.
Abstract: This paper presents a study of the production of WW or WZ boson pairs, with one W boson decaying to ev or mu v and one W or Z boson decaying hadronically. The analysis uses 20.2 fb(-1) of root s = ...
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TL;DR: In this paper, a search for triboson production in two decay channels was carried out in the Large Hadron Collider with an expected upper bound of 730 fb with the expected limit of 560 fb in the absence of SM.
Abstract: This paper reports a search for triboson $W^{\pm}W^{\pm}W^{\mp}$ production in two decay channels ($W^{\pm}W^{\pm}W^{\mp}\rightarrow \ell^{\pm}
u\ell^{\pm}
u\ell^{\mp}
u$ and $W^{\pm}W^{\pm}W^{\mp}\rightarrow \ell^{\pm}
u\ell^{\pm}
u{}jj$ with $\ell=e, \mu$) 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.
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TL;DR: The dynamics of isolated-photon plus one-, two-and three-jet production in pp collisions at a centre-of-mass energy of 8 TeV were studied with the ATLAS detector at the LHC using a data set with an...
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TL;DR: In this article, 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 √s=8 TeV with the ATLAS detector at the LHC.
Abstract: 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 √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 Pythia8, Herwig++, MadGraph5_aMC@NLO+Pythia8 and Sherpa event generators, providing new constraints on heavy flavour production.
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TL;DR: In this paper, 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 the Standard Model (SM) Higgs boson (h) is presented.
Abstract: 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 root s = 13 TeV collected with the ATLAS detector at the LHC in 20152016, 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) over tilde (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) over tilde (2)) decaying via (t) over tilde (2) -> Z (t) over tilde (1) or (t) over tilde (2) -> h (t) over tilde (1). The results exclude at 95% confidence level (t) over tilde (2) and (t) over tilde (1) masses up to about 800 GeV, extending the exclusion region of supersymmetric parameter space covered by previous LHC searches.
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TL;DR: In this article, an observable ratio of cross sections is defined for events containing jets and large missing transverse momentum in the plane transverse to the proton beams at the Large Hadron Collider, which can be used to constrain new physics models beyond those shown in this paper.
Abstract: Observables sensitive to the anomalous production of events containing hadronic jets and missing momentum in the plane transverse to the proton beams at the Large Hadron Collider are presented. The observables are defined as a ratio of cross sections, for events containing jets and large missing transverse momentum to events containing jets and a pair of charged leptons from the decay of a $Z/\gamma ^*$ boson. This definition minimises experimental and theoretical systematic uncertainties in the measurements. This ratio is measured differentially with respect to a number of kinematic properties of the hadronic system in two phase-space regions, one inclusive single-jet region and one region sensitive to vector-boson-fusion topologies. The data are found to be in agreement with the Standard Model predictions and used to constrain a variety of theoretical models for dark-matter production, including simplified models, effective field theory models, and invisible decays of the Higgs boson. The measurements use 3.2 fb$^{-1}$ of proton–proton collision data recorded by the ATLAS experiment at a centre-of-mass energy of 13 $\text {TeV}$ and are fully corrected for detector effects, meaning that the data can be used to constrain new-physics models beyond those shown in this paper.
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TL;DR: In this article, the cross section of a top-quark pair produced in association with a photon is measured in proton-proton collisions at a center-of-mass energy of root s = 8 TeV with 20.2 fb(-1) of data collected b...
Abstract: 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 root s = 8 TeV with 20.2 fb(-1) of data collected b ...
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