Operation of the ATLAS trigger system in Run 2

Aad, G.; Abbott, B.; Abbott, D. C.; Abud, A. Abed; Abeling, K.; Aggarwal, A.; Bakos, E.; Caron, S.; Groot, N. De; Fabiani, V.; Filthaut, F.; Gottardo, C. A.; Igonkina, O.; Ilic, N.; König, A. C.; Moskvitina, Polina; Nellist, C.; Diaz, L. Pedraza; Schouwenberg, J. F. P.; Zou, R.; Zwalinski, L.

doi:10.1088/1748-0221/15/10/p10004

Cited by 68 publications

(26 citation statements)

References 49 publications

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“…Interesting collision events are selected using a two-level trigger system [17,18,32]. The L1 trigger processes events at a rate of 40 MHz, set by the LHC beam structure consisting of bunches separated by 25 ns.…”

Section: L1 Muon Barrel Triggermentioning

confidence: 99%

Performance of the ATLAS RPC detector and Level-1 muon barrel trigger at √(s)=13 TeV

Aad

Abbott

et al. 2021

J. Inst.

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Large Hadron Collider (LHC) employs a trigger system consisting of a first-level hardware trigger (L1) and a software-based high-level trigger. The L1 muon trigger system selects muon candidates, assigns them to the correct LHC bunch crossing and classifies them into one of six transverse-momentum threshold classes. The L1 muon trigger system uses resistive-plate chambers (RPCs) to generate the muon-induced trigger signals in the central (barrel) region of the ATLAS detector. The ATLAS RPCs are arranged in six concentric layers and operate in a toroidal magnetic field with a bending power of 1.5 to 5.5 Tm. The RPC detector consists of about 3700 gas volumes with a total surface area of more than 4000 m 2 . This paper reports on the performance of the RPC detector and L1 muon barrel trigger using 60.8 fb −1 of proton-proton collision data recorded by the ATLAS experiment in 2018 at a centre-of-mass energy of 13 TeV. Detector and trigger performance are studied using boson decays into a muon pair. Measurements of the RPC detector response, efficiency, and time resolution are reported. Measurements of the L1 muon barrel trigger efficiencies and rates are presented, along with measurements of the properties of the selected sample of muon candidates. Measurements of the RPC currents, counting rates and mean avalanche charge are performed using zero-bias collisions. Finally, RPC detector response and efficiency are studied at different high voltage and front-end discriminator threshold settings in order to extrapolate detector response to the higher luminosity expected for the High Luminosity LHC.

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Section: L1 Muon Barrel Triggermentioning

confidence: 99%

Performance of the ATLAS RPC detector and Level-1 muon barrel trigger at √(s)=13 TeV

Aad

Abbott

et al. 2021

J. Inst.

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“…Events are selected using a two-stage trigger system which is described in detail in Refs. [15,16]. The first-level (L1) trigger system uses coarse-granularity signals from the calorimeters and the muon system with a 2.5 μs fixed latency and accepts events from the 40 MHz bunch crossings at a rate below 100 kHz.…”

Section: Atlas Detector and Trigger Systemmentioning

confidence: 99%

“…The cause of this was found to be that the performance of the algorithm used to determine the hard-scatter primary-vertex position depended on the nominal online beamspot position (the centre of the region where the two proton bunches cross in the detector). The nominal beamspot position is estimated online by averaging the primary-vertex position over many events [19]. The track reconstruction in the trigger uses the nominal online beamspot position while the online primary-vertex position is defined relative to the detector origin, (x = 0, y = 0, z = 0).…”

Section: Datasets and Simulated Eventsmentioning

confidence: 99%

Configuration and performance of the ATLAS b-jet triggers in Run 2

Aad

Abbott

et al. 2021

Eur. Phys. J. C

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Several improvements to the ATLAS triggers used to identify jets containing b-hadrons (b-jets) were implemented for data-taking during Run 2 of the Large Hadron Collider from 2016 to 2018. These changes include reconfiguring the b-jet trigger software to improve primary-vertex finding and allow more stable running in conditions with high pile-up, and the implementation of the functionality needed to run sophisticated taggers used by the offline reconstruction in an online environment. These improvements yielded an order of magnitude better light-flavour jet rejection for the same b-jet identification efficiency compared to the performance in Run 1 (2011–2012). The efficiency to identify b-jets in the trigger, and the conditional efficiency for b-jets that satisfy offline b-tagging requirements to pass the trigger are also measured. Correction factors are derived to calibrate the b-tagging efficiency in simulation to match that observed in data. The associated systematic uncertainties are substantially smaller than in previous measurements. In addition, b-jet triggers were operated for the first time during heavy-ion data-taking, using dedicated triggers that were developed to identify semileptonic b-hadron decays by selecting events with geometrically overlapping muons and jets.

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“…Triggering in ATLAS in Run 2 and Run 3 Takuya Nobe and rate estimation framework described in Ref. [5]. In this framework, trigger rate, CPU usage and the data-flow over DAQ network can be estimated using pp data.…”

Section: Pos(lhcp2021)168mentioning

confidence: 99%

Triggering in ATLAS in Run 2 and Run 3

Nobe¹

2021

Proceedings of the Ninth Annual Conference on Large Hadron Collider Physics — PoS(LHCP2021)

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The ATLAS experiment at the LHC records about 1 kHz of physics collisions, out of the LHC design bunch crossing rate of 40 MHz. To achieve a high selection efficiency for physics events while reducing the significant background rate, a two-level trigger system is used. The event selection is based on physics signatures, such as the presence of energetic leptons, photons, jets or missing energy. In addition, the trigger system can exploit algorithms using topological information and multivariate methods to carry out the filtering for the many physics analyses pursued by the ATLAS collaboration. In Run 2, around 1 500 individual selection paths (trigger chains) were used, with specified rate and the output bandwidth assignments. The optimization of the trigger menus (the lists of the trigger chains enabled during data taking) was performed using a dedicated framework running over pp collisions data. The optimization of the Run-3 trigger menus is currently ongoing. For Run 3, the HLT software will be fully upgraded with a multithreading technique. Some improvements on the detector and electronics will be propagated to the trigger system. In this article, for example, the upgrade of the electron trigger project is presented briefly.

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Operation of the ATLAS trigger system in Run 2

Cited by 68 publications

References 49 publications

Performance of the ATLAS RPC detector and Level-1 muon barrel trigger at √(s)=13 TeV

Performance of the ATLAS RPC detector and Level-1 muon barrel trigger at √(s)=13 TeV

Configuration and performance of the ATLAS b-jet triggers in Run 2

Triggering in ATLAS in Run 2 and Run 3

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