12,307 research outputs found
An overview of the ATLAS High Level Trigger Dataflow and Supervision.
No full textThe ATLAS high-level trigger (HLT) system provides software-based event selection after the initial LVL1 hardware trigger. It is composed of two stages, the LVL2 trigger and the event filter (EF). The LVL2 trigger performs event selection with optimized algorithms using selected data guided by Region of Interest pointers provided by the LVL1 trigger. Those events selected by LVL2 are built into complete events, which are passed to the EF for a further stage of event selection and classification using off-line algorithms. Events surviving the EF selection are passed for off-line storage. The two stages of HLT are implemented on processor farms. The concept of distributing the selection process between LVL2 and EF is a key element in the architecture, which allows it to be flexible to changes (luminosity, detector knowledge, background conditions, etc.) Although there are some differences in the requirements between these subsystems there are many commonalities. An overview of the dataflow (event selection) and supervision (control, configuration, monitoring) activities in the HLT is given, highlighting where commonalities between the two subsystems can be exploited and indicating where requirements dictate that implementations differ. An HLT prototype system has been built at CERN. Functional testing is being carried out in order to validate the HLT architecture
Algorithms for the ATLAS High Level Trigger.
No full textFollowing rigorous software design and analysis methods, an object-based architecture has been developed to derive the second- and third-level trigger decisions for the future ATLAS detector at the LHC. The functional components within this system responsible for generating elements of the trigger decisions are algorithms running within the software architecture. Relevant aspects of the architecture are reviewed along with concrete examples of specific algorithms and their performance in "vertical" slices of various physics selection strategies
Second Level Trigger of the ATLAS Experiment at CERN's LHC.
No full textThe ATLAS trigger reduces the rate of interesting events to be recorded for off-line analysis in three successive levels from 40 MHz to ∼100 kHz, ∼2 kHz and ∼200 Hz. The high level triggers and data acquisition system are designed to profit from commodity computing and networking components to achieve the required performance. In this paper, we discuss data flow aspects of the design of the second level trigger (LVL2) and present results of performance measurements
Performance of the ATLAS trigger system in 2010
No full textProton–proton collisions at Ös=7s=7 TeV and heavy ion collisions at Ö{sNN}=2.76sNN=276 TeV were produced by the LHC and recorded using the ATLAS experiment’s trigger system in 2010. The LHC is designed with a maximum bunch crossing rate of 40 MHz and the ATLAS trigger system is designed to record approximately 200 of these per second. The trigger system selects events by rapidly identifying signatures of muon, electron, photon, tau lepton, jet, and B meson candidates, as well as using global event signatures, such as missing transverse energy. An overview of the ATLAS trigger system, the evolution of the system during 2010 and the performance of the trigger system components and selections based on the 2010 collision data are shown. A brief outline of plans for the trigger system in 2011 is presented
Performance of the ATLAS muon trigger in pp collisions at [Formula: see text] TeV
No full textThe performance of the ATLAS muon trigger system is evaluated with proton-proton collision data collected in 2012 at the Large Hadron Collider at a centre-of-mass energy of 8 TeV. It is primarily evaluated using events containing a pair of muons from the decay of [Formula: see text] bosons. The efficiency of the single-muon trigger is measured for muons with transverse momentum [Formula: see text] GeV, with a statistical uncertainty of less than 0.01 % and a systematic uncertainty of 0.6 %. The [Formula: see text] range for efficiency determination is extended by using muons from decays of [Formula: see text] mesons, [Formula: see text] bosons, and top quarks. The muon trigger shows highly uniform and stable performance. The performance is compared to the prediction of a detailed simulation
Hydro-meteorological trigger conditions of debris flows in Austria
No full textDifferent factors influence the disposition of a watershed for initiation of debris flows, including meteorological trigger conditions as well as the hydrologic and geomorphic disposition. The latter includes slowly changing factors like relief energy or sediment availability, whereas the hydrologic state of a watershed may vary over short time scales. This contribution summarizes the outcomes of a long term project to quantify meteorological and hydrological trigger conditions leading to debris flows at different temporal and spatial scales in the Austrian Alps. The analysis employs a database of more than 4,500 debris flows over the last 100+ years, which is the period for which systematic rainfall data is available. A Bayesian analysis was carried out for determining occurrence probabilities for all Austria. For selected regions, hydrological trigger conditions were assessed using a semi-distributed, conceptual rainfall-runoff model, which was calibrated to measured runoff data. As expected we find increasing trigger probabilities with increasing rainfall amounts and intensities. However, the additional information of regional hydrological parameters as well as their temporal evolution over days prior to a debris-flow event, enables to capture different trigger conditions, including short duration rainstorms, long lasting rainfall events, and snow melt. We also find that a trigger-type resolved prediction of debris-flow susceptibility based on the hydro-meteorological catchment information is superior to simple rainfall-only approaches. The results of this analysis shall improve our understanding of long-term trigger conditions and trends of extreme mass wasting processes in the Alps and aim to become a valuable tool in engineering hazard assessment.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Water Resource
Graphical processors for HEP trigger systems
No full textGeneral-purpose computing on GPUs is emerging as a new paradigm in several fields of science, although so far applications have been tailored to employ GPUs as accelerators in offline computations. With the steady decrease of GPU latencies and the increase in link and memory throughputs, time is ripe for real-time applications using GPUs in high-energy physics data acquisition and trigger systems. We will discuss the use of online parallel computing on GPUs for synchronous low level trigger systems, focusing on tests performed on the trigger of the CERN NA62 experiment. Latencies of all components need analysing, networking being the most critical. To keep it under control, we envisioned NaNet, an FPGA-based PCIe Network Interface Card (NIC) enabling GPUDirect connection. Moreover, we discuss how specific trigger algorithms can be parallelised and thus benefit from a GPU implementation, in terms of increased execution speed. Such improvements are particularly relevant for the foreseen LHC luminosity upgrade where highly selective algorithms will be crucial to maintain sustainable trigger rates with very high pileup
Enforcing International Trade Agreements with Imperfect Private Monitoring: Private Trigger Strategies and the Possible Role of the WTO
No full textInternational trade disputes often involve the WTO as a third party that generates impartial opinions on potential violations when countries receive imperfect and private signals of violations. To identify the role that the WTO plays in enforcing trade agreements, this paper first explores what countries can achieve without the WTO by characterizing optimal private trigger strategies (PTS) under which each country triggers a punishment phase by imposing an explicit tariff based on privately-observed imperfect signals of the other country's concealed trade barriers. It identifies the condition under which countries can restrain the use of concealed barriers based on PTS and establishes that countries will not reduce the cooperative protection level to its minimum attainable level under the optimal PTS. This paper then considers third-party trigger strategies (TTS) under which the WTO allows each country to initiate a punishment phase based on the WTO's judgment (i.e., its signals) about potential violations. The WTO thus changes the nature of punishment-triggering signals from private into public, enabling countries to use punishment phases of any length under TTS, which in turn facilitates a better cooperative equilibrium. The optimal TTS will involve an asymmetric and minimum punishment if the probability of a punishment phase being triggered is lower than a critical level, but it will entail punishments involving a permanent Nash tariff war if the probability of a punishment phase is higher than a certain level. A numerical comparison of the optimal TTS and optimal PTS indicates that the contribution of the WTO is likely to be significant when the signals of potential violations are relatively accurate, as this enables countries to use a more efficient punishment, such as an asymmetric and minimum punishment.Concealed Trade Barriers, Imperfect Private Monitoring, International Trade Agreements, Repeated Game, Trade Disputes, Trigger Strategies, WTO
Experimental validation of FEA modelling of touch trigger probes
No full textThe authors have previously proposed the use of finite element method (FEM) for the modeling of coordinate measuring machine probes. Whilst the modeling results have been published previously, this paper presents the detailed experimental validation to compare the FEM and experimental results. The comparison shows that the agreement is generally good with probing contacts at lower latitudes near the equator of the reference sphere. The differences between the modeling and experimental results become large at higher latitudes. This is believed to be mainly caused by the sliding effects which occur during probing contact in the experiments
The CMS trigger system
No full textThis paper describes the CMS trigger system and its performance during Run 1 of the LHC. The trigger system consists of two levels designed to select events of potential physics interest from a GHz (MHz) interaction rate of proton-proton (heavy ion) collisions. The first level of the trigger is implemented in hardware, and selects events containing detector signals consistent with an electron, photon, muon, tau lepton, jet, or missing transverse energy. A programmable menu of up to 128 object-based algorithms is used to select events for subsequent processing. The trigger thresholds are adjusted to the LHC instantaneous luminosity during data taking in order to restrict the output rate to 100 kHz, the upper limit imposed by the CMS readout electronics. The second level, implemented in software, further refines the purity of the output stream, selecting an average rate of 400 Hz for offline event storage. The objectives, strategy and performance of the trigger system during the LHC Run 1 are described
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