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Measurements sensitive to the Higgs boson production and decay performed at the Large Hadron Collider by the ATLAS experiment are reviewed. They are based on the analyses of 13 TeV proton-proton collision data collected between 2015 and 2017, corresponding to integrated luminosities ranging from 36 to 80 fb−1. Different analyses are discussed and the combined constraints on the Higgs boson couplings are also summarised.

Effective distributed user analysis requires a system which meets the demands of running arbitrary user applications on sites with varied configurations and availabilities. The challenge of tracking such a system requires a tool to monitor not only the functional statuses of each grid site, but also to perform large-scale analysis challenges on the ATLAS grids. This work presents one such tool, the ATLAS GangaRobot, and the results of its use in tests and challenges. For functional testing, the GangaRobot performs daily tests of all sites; specifically, a set of exemplary applications are submitted to all sites and then monitored for success and failure conditions. These results are fed back into Ganga to improve job placements by avoiding currently problematic sites. For analysis challenges, a cloud is first prepared by replicating a number of desired DQ2 datasets across all the sites. Next, the GangaRobot is used to submit and manage a large number of jobs targeting these datasets. The high-loads resulting from multiple parallel instances of the GangaRobot exposes shortcomings in storage and network configurations. The results from a series of cloud-by-cloud analysis challenges starting in fall 2008 are presented.

This paper presents a measurement of ZZ production with the ATLAS detector at the Large Hadron Collider. The measurement is carried out in the final state with two charged leptons and two neutrinos, using data collected during 2015 and 2016 in pp collisions at $\\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 36.1 fb-1. The integrated cross-sections in the total and fiducial phase spaces are measured with an uncertainty of 7% and compared with Standard Model predictions, and differential measurements in the fiducial phase space are reported. No significant deviations from the Standard Model predictions are observed, and stringent constraints are placed on anomalous couplings corresponding to neutral triple gauge-boson interactions.

A search for a narrow scalar resonance decaying into an opposite-sign muon pair produced in events with and without b-tagged jets is presented in this paper. The search uses 36.1 fb-1 of $ \\sqrt{s}=13 $ TeV proton-proton collision data recorded by the ATLAS experiment at the LHC. No significant excess of events above the expected Standard Model background is observed in the investigated mass range of 0.2 to 1.0 TeV. The observed upper limits at 95% confidence level on the cross section times branching ratio for b-quark associated production and gluon-gluon fusion are between 1.9 and 41 fb and 1.6 and 44 fb respectively, which is consistent with expectations. [Figure not available: see fulltext.].

During 2006 and the first half of 2007, the installation, integration and commissioning of trigger and data acquisition (TDAQ) equipment in the ATLAS experimental area have progressed. There have been a series of technical runs using the final components of the system already installed in the experimental area. Various tests have been run including ones where level 1 preselected simulated proton-proton events have been processed in a loop mode through the trigger and dataflow chains. The system included the readout buffers containing the events, event building, level 2 and event filter trigger algorithms. The scalability of the system with respect to the number of event building nodes used has been studied and quantities critical for the final system, such as trigger rates and event processing times, have been measured using different trigger algorithms as well as different TDAQ components. This paper presents the TDAQ architecture, the current status of the installation and commissioning and highlights the main test results that validate the system.

The mass and the total decay width of the W boson are measured with the L3 detector at the LEP e+e– collider using W-boson pairs produced in 0.7 fb–1 of data collected at centre-of-mass energies between 161 and 209 GeV. Combining semi-leptonic and fully-hadronic final states, the mass and the width of the W boson are determined to be where the first uncertainty is statistical and the second systematic.

The aim of the presented work is the development of single-stage amplification resistive Micro Pattern Gas Detectors (MPGD) based on Micromegas technology with the following characteristics: ability to efficiently operate up to 10 MHz/cm\\(^2\\) counting rate; scalability to large areas; fine granularity readout with small pads of the order of mm\\(^2\\); good spatial and time resolutions (below 100 \\(\\mu\\)m and 10 ns, respectively). The miniaturization of the readout elements and the optimization of the spark protection system, as well as the stability and robustness under operation, are the primary challenges of the project. Two families of resistive patterns were realized using different techniques: pad-patterned embedded resistors and double-layer of Diamond Like Carbon (DLC) structures foils. Their main difference is that for the embedded resistors the charge is evacuated through independent pads, for double-layer DLC the resistive layers are continuous and uniform and the charge is evacuated through a network of dot-connections, several millimetres apart. Using the DLC technique, a medium-size detector with an active area of 400 cm\\(^2\\) was recently built and tested, with the main results reported in this paper. Additionally, a large module (50x40 cm\\(^2\\) active area), suitable for tiling large systems in future experiments, has been successfully realised and is currently undergoing testing and performance studies. The characterization and performance studies of the detectors were conducted using radioactive sources and an X-rays generator, with the detectors operated with various gas mixtures. A comparison of the results obtained with different resistive layouts and configurations is provided, with a particular focus on the response under high-rate exposure. Key results on tracking and timing performance from test-beam data for the latest constructed medium-size detector are also presented.

Data collected at LEP at centre-of-mass energies \\(\\sqrt{s} = 189-209\\) GeV are used to study correlations of the spin of W bosons using \\(\\mathrm{e}^ + \\mathrm{e}^-\\to \\mathrm{W}^ + \\mathrm{W}^-\\to {\\ensuremath{\\ell\\nu\\mathrm{q\\bar{q}}}\\) events. Spin correlations are favoured by data, and found to agree with the Standard Model predictions. In addition, correlations between the W-boson decay planes are studied in \\(\\mathrm{e}^ + \\mathrm{e}^-{}\\to{}\\mathrm{W}^ + \\mathrm{W}^- \\to{}{\\ensuremath{\\ell\\nu\\mathrm{q\\bar{q}}}\\) and \\(\\mathrm{e}^ + \\mathrm{e}^-{}\\to{}\\mathrm{W}^ + \\mathrm{W}^-{}\\to{}{\\ensuremath{\\text{q}\\bar{\\text{q}}\\text{q}\\bar{\\text{q}}}{}\\) events. Decay-plane correlations are measured to be consistent with the Standard Model predictions.

The ATLAS detector at CERN's LHC will be exposed to proton-proton collisions from beams crossing at 40 MHz. At the design luminosity there are roughly 23 collisions per bunch crossing. ATLAS has designed a three-level trigger system to select potentially interesting events. The first-level trigger, implemented in custom-built electronics, reduces the incoming rate to less than 100 kHz with a total latency of less than 2.5μs. The next two trigger levels run in software on commercial PC farms. They reduce the output rate to 100-200 Hz. In preparation for collision data-taking which is scheduled to commence in May 2008, several cosmic-ray commissioning runs have been performed. Among the first sub-detectors available for commissioning runs are parts of the barrel muon detector including the RPC detectors that are used in the first-level trigger. Data have been taken with a full slice of the muon trigger and readout chain, from the detectors in one sector of the RPC system, to the second-level trigger algorithms and the data-acquisition system. The system is being prepared to include the inner-tracking detector in the readout and second-level trigger. We will present the status and results of these cosmic-ray based commissioning activities. This work will prove to be invaluable not only during the commissioning phase but also for cosmic-ray data-taking during the normal running for detector performance studies.