55 research outputs found
Resource utilization by the ATLAS High Level Trigger during 2010 and 2011 LHC running
No full textIn 2010 and 2011, the ATLAS experiment successfully recorded data from LHC collisions with high efficiency and excellent data quality. ATLAS employs a three-level trigger system to select events of interest for physics analyses and detector commissioning. The trigger system consists of a custom-designed hardware trigger at level-1 and software algorithms at the two higher levels. The trigger selection is defined by a trigger menu which consists of more than 300 individual trigger signatures, such as electrons, muons, particle jets, etc. An execution of a trigger signature incurs computing and data storage costs. Th composition of the deployed trigger menu depends on the instantaneous LHC luminosity, the experiment's goals for the recorded data, and the limits imposed by the available computing power, network bandwidth and storage space. This paper describes a trigger monitoring framework for assigning computing costs for individual trigger signatures and trigger menus as a whole. These costs can be extrapolated to higher luminosity allowing development of trigger menus for a higher LHC collision rate than currently achievable
Tests of the electroweak sector with diboson final states at the ATLAS experiment
No full textMeasurements of the cross sections of the production of pairs of electroweak gauge bosons at he LHC constitute stringent tests of the electroweak sector and provide model independent means to search for new physics at the TeV scale. Similarly, the electroweak production of vector bosons in proton-proton collisions tests the gauge structure of the Standard Model. The ATLAS collaboration has performed detailed measurements of integrated and differential cross sections of the production of ZZ di-boson pairs as well as WZ and WW di-boson pairs at 8 and 13 TeV. The results will be presented and compared to predictions at NLO (and NNLO) in pQCD. Constraints on new physics are provided by setting limits on anomalous triple gauge couplings. If available, a measurement of the unfolded 4-lepton mass at 13 TeV will be presented
New results on ttW and 4-top production with the ATLAS experiment
No full textNew results on ttW and 4-top production with the ATLAS experimen
Performance of the ATLAS RPC detector and L1 Muon Barrel trigger at = 13 TeV
No full textThe ATLAS experiment at the Large Hadron Collider utilizes a trigger system consisting of a first level hardware trigger and a higher level software trigger. The Level-1 muon trigger system selects muon candidates with six transverse momentum thresholds and associate them with a correct LHC bunch crossing. The Level-1 Muon Barrel Trigger uses Resistive Plate Chambers (RPC) detectors to generate trigger signals for selecting muon candidates within the pseudorapidity range of up to 1.05. The RPC detectors are arranged in three concentric double layers and consist of about 3600 gas volumes, with a total surface of more than 4000 square meters, that operate in a toroidal magnetic field. This contribution will discuss the performance of the RPC detector system and of the Level-1 Muon Barrel trigger during the 2018 data taking period. Measurements of RPC detector response obtained using muon candidates produced in LHC collisions will be presented. Trigger performance and efficiency measurements that are obtained using Z boson decays to a muon pair will be also discussed. Finally, studies of the RPC detector response at different high voltage and threshold settings will be discussed, in the context of expected detector response after the High Luminosity LHC upgrades
Performance of muon identification with the ATLAS detector at ~TeV
No full textMuon reconstruction and identification play a fundamental role in many analyses of central importance in the LHC run-2 Physics pro-gramme. The algorithms and the criteria used in ATLAS for the re-construction and identification of muons with transverse momentum from a few GeV to the TeV scale will be presented. Their performance is measured in data based on the decays of Z and J/ψto pair of muons,that provide a large statistics calibration sample. Reconstruction and identification efficiencies are evaluated, and the results are used to de-rive precise MC simulation corrections. Isolation selection criteria and their performance in presence of high pileup will also be presented
Top-quark production in association with
No full textSummary of ATLAS and CMS results for measuring top-quark production in association with
25th International Conference on Computing in High Energy & Nuclear Physics
No full textEffective selection of muon candidates is the cornerstone of the LHC physics programme. The ATLAS experiment uses the two-level trigger system for real-time selections of interesting events. The first-level hardware trigger system uses the Resistive Plate Chamber detector (RPC) for selecting muon candidates in the central (barrel) region of the detector. With the planned upgrades, the entirely new FPGA-based muon trigger system will be installed in 2025-2026. In this paper, neural network regression models are studied for potential applications in the new RPC trigger system. A simple simulation model of the current detector is developed for training and testing neural network regression models. Effects from additional cluster hits and noise hits are evaluated. Efficiency of selecting muon candidates is estimated as a function of the transverse muon momentum. Several models are evaluated and their performance is compared to that of the current detector, showing promising potential to improve on current algorithms for the ATLAS Phase-II barrel muon trigger upgrade
Searching for Higgs boson production in association with a top quark pair with the ATLAS detector
No full textThis contribution will report on most recent searches for Higgs boson production in association with a top quark pair (ttH) performed by the ATLAS experiment at the LHC. The ttH process is interesting because it can measure directly the Higgs boson coupling to the top quark, which otherwise is known only via virtual top quark loop contributions to the inclusive Higgs boson production at the LHC. The ttH production process has not been observed yet and it is a subject of extensive experimental studies by the ATLAS and CMS collaborations. This presentation will discuss most recent ATLAS searches for the ttH production, focusing on Higgs boson decays to a pair of W or Z bosons, or to a pair of tau leptons. These decay modes result in final states with multiple leptons and jets, thus allowing significant suppression of background processes. This presentation will discuss new experimental techniques for suppressing these background processes and present latest results in different multi-lepton channels. The presentation will also briefly review results from other Higgs boson decay modes and will include results for a combination of all the ttH channels studied by ATLAS
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