The large rate of multiple simultaneous proton–proton interactions, or pile-up, generated by the Large Hadron Collider in Run 1 required the development of many new techniques to mitigate the adverse ...effects of these conditions. The methods employed to correct for the impact of pile-up on jet energy, shapes and multiplicity with the ATLAS detector are presented here. They include energy correction techniques based on estimates of the average pile-up energy density and jet-to-vertex association techniques. Extensions of these methods to reduce the impact of pile-up on jet shapes use both subtraction and grooming procedures. Prospects for pile-up suppression at the HL-LHC are also shown.
Single event upsets in the ATLAS IBL front end ASICs Rozanov, A.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2019, Letnik:
936
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During operation at instantaneous LHC luminosities of up to 2.1 ×1034 cm−2 s−1 front-end chips of the ATLAS innermost pixel layer (IBL) experienced single event upsets affecting their global ...registers as well as the settings for the individual pixels, causing, amongst other things, loss of occupancy, noisy pixels, and silent pixels. A quantitative analysis of the single event upsets as well as the operational issues and mitigation techniques are presented.
ATLAS LAr calorimeter performance in LHC Run-2 Morgenstern, S.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2019, Letnik:
936
Journal Article
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The Liquid-argon (LAr) sampling calorimeters are employed by ATLAS for all electromagnetic calorimetry in the pseudo-rapidity region |η|<3.2, and for hadronic and forward calorimetry in the region ...1.5<|η|<4.9. In the first LHC run a total luminosity of 27fb−1 has been collected at centre-of-mass energies of 7−8TeV. After detector consolidation during a long shutdown, Run-2 started in 2015 and 86.4fb−1 of data at a centre-of-mass energy of 13TeV have been recorded. In order to realise the level-1 acceptance rate of 100kHz in Run-2 data taking, the number of readout samples recorded and used for the energy and the time measurement has been modified from five to four while keeping the expected performance. The well calibrated and highly granular LAr calorimeter reached its design values both in energy measurement as well as in direction resolution. This contribution will give an overview of the detector operation, hardware improvements, changes in the monitoring and data quality procedures required to cope with increased pileup, as well as the achieved performance, including the calibration and stability of the electromagnetic scale, noise level, response uniformity and time resolution.
Upgrade of the ATLAS muon system for the HL-LHC Amelung, Ch
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2019, Letnik:
936
Journal Article
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The muon spectrometer of the ATLAS detector will be significantly upgraded during the Phase-II upgrade in Long Shutdown 3 in order to cope with the operational conditions at the High-Luminosity LHC ...in Run 4 and beyond. Most of the electronics for the Resistive Plate Chambers (RPC), Thin Gap Chambers (TGC), and Monitored Drift Tube (MDT) chambers will be replaced to make them compatible with the higher trigger rates and longer latencies necessary for the new level-0 trigger. The MDT chambers will be integrated into the level-0 trigger in order to sharpen the momentum threshold. Additional RPC chambers will be installed in the inner barrel layer to increase the acceptance and robustness of the trigger. Some of the MDT chambers in the inner barrel layer will be replaced with new small-diameter MDTs. New TGC triplet chambers in the barrel–endcap transition region will replace the current TGC doublets to suppress the high trigger rate from random coincidences in this region. The power system for the RPC, TGC, and MDT chambers and electronics will need to be replaced due to component obsolescence, aging, and radiation damage. A high-η tagger is under consideration to extend the angular acceptance for muon identification. The Phase-II upgrade concludes the process of adapting the muon spectrometer to the ever increasing performance of the LHC, which started with the Phase-I upgrade New Small Wheel project that will replace the Cathode Strip Chambers and the MDT chambers of the innermost endcap wheels by Micromegas and small-strip TGCs.
The Insertable B-Layer (IBL) is the innermost layer of the ATLAS tracking system. It consists of planar pixel modules in the central region and 3D pixel modules at the two extremities. We use the ...longitudinal cluster-size distributions in 3D modules of the IBL to determine the number of pixel clusters per bunch crossing produced by primary charged particles in randomly triggered collision events, and to suppress the associated backgrounds. This Pixel-Cluster-Counting algorithm can provide both bunch-integrated and bunch-by-bunch relative-luminosity measurements, and thereby contribute independent constraints to the understanding and the evaluation of the systematic uncertainties that dominate the luminosity determination at the ATLAS experiment.
The expected factor four increase in peak luminosity of the high-luminosity LHC (HL-LHC) compared to the current LHC system will force the ATLAS experiment to increase early stage trigger selection ...power. The agreed strategy is to implement precise hardware track reconstruction, through which sharper trigger turn-on curves can be achieved for primary single-lepton selections, while contributing to b-tagging and tau-tagging techniques as well as pileup mitigation for hadronic signatures, such as multijet and missing transverse momentum.
This work discusses the requirements, architecture and projected performance of the system in terms of tracking capability, and trigger selection, based on detailed simulations.
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•Hardware-based system for precise particle track reconstruction.•It uses a combination of Associative Memory ASICs and FPGAs.•It allows for reduced lepton transverse momentum trigger thresholds.•Factor 5 background rejection for 95% signal efficiency for electrons.•It also contributes to pile-up mitigation, essential for hadronic signatures.
The High Luminosity-Large Hadron Collider is expected to start data-taking in 2026 and to provide an integrated luminosity of 3000 fb−1, giving a factor 10 more data than that will be collected by ...2023. This high statistics will make it possible to perform precise measurements in the Higgs sector and improve searches of new physics at the TeV scale. The peak luminosity is expected to be 7.5 × 1034 cm−2 s−1, corresponding to about 200 proton–proton interactions per event (pile-up), which will increase the rates at each level of the trigger and degrade the reconstruction performance. To cope with such a harsh environment many sub-detectors of the ATLAS experiment will be upgraded and some completely substituted. The Trigger-DAQ system will be upgraded. In this talk an overview of two new sub-detectors enabling powerful pile-up suppression, a new Inner Tracker and a High Granularity Timing Detector, will be given, describing the two technologies, their performance, and their interplay. Emphasis will also be given to the possibility of using tracking and timing information at the earliest, hardware based, ATLAS trigger stage.
•Pileup suppression techniques for jets reconstruction at HL-LHC.•Tracking and Timing detectors of ATLAS detector at HL-LHC.•Tracking for Trigger at HL-LHC.
Silicon pixel sensors are at the core of the current ATLAS detector at the Large Hadron Collider (LHC), and as the detector component closest to the interaction point, they are exposed to a ...significant amount of radiation during operation. This paper presents a digitization model incorporating radiation damage effects to the pixel sensors. Predictions for basic pixel cluster properties such as the charge collection efficiency are also presented alongside validation studies with Run 2 collision data in ATLAS Pixel Detector.
The operational experience and requirements to ensure optimum data quality and data taking efficiency with the 4-layer ATLAS Pixel Detector are discussed. The detector has undergone significant ...hardware and software upgrades to meet the challenges imposed by the Large Hadron Collider (LHC). The LHC is exceeding expectations for instantaneous luminosity by more than a factor of two (to more than 2×1034 cm−2 s−1). Emphasizing radiation damage effects, the key status and performance metrics are described.
The High-Luminosity LHC will provide the unique opportunity to explore the nature of physics beyond the Standard Model. Highly selective first level triggers are essential for the physics programme ...of the ATLAS experiment at the HL-LHC, where the instantaneous luminosity will exceed the LHC design luminosity by almost an order of magnitude. The ATLAS first level muon trigger rate is dominated by low momentum muons, selected due to the moderate momentum resolution of the current system. This first level trigger limitation can be overcome by including data from the precision muon drift tube (MDT) chambers. This requires the fast continuous transfer of the MDT hits to the o -detector trigger logic and a fast track reconstruction algorithm performed in the trigger logic. The feasibility of this approach was studied with LHC collision data and simulated data. Two main options for the hardware implementation will be studied with demonstrators: an FPGA based option with an embedded ARM microprocessor and an associate memory chip base option. In this note the basic MDT trigger concept and the design of a demonstrator for the two hardware options are presented.
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