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High Level Trigger Studies for the ATLAS Detector Efstathios (Stathis) Stefanidis

High Level Trigger Studies for the ATLAS Detector Efstathios (Stathis) Stefanidis University College London. OUTLINE. The ATLAS Detector : Overview. The Trigger System. Overview. High Level Trigger. Performance Studies. IDScan. e/ γ vertical slice. RoI size. Future Plans.

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High Level Trigger Studies for the ATLAS Detector Efstathios (Stathis) Stefanidis

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  1. High Level Trigger Studies for the ATLAS Detector Efstathios (Stathis) Stefanidis University College London Efstathios (Stathis) Stefanidis sstef@hep.ucl.ac.uk http://www.hep.ucl.ac.uk/~sstef

  2. OUTLINE • The ATLAS Detector : Overview. • The Trigger System. • Overview. • High Level Trigger. • Performance Studies. • IDScan. • e/γ vertical slice. • RoI size. • Future Plans. Efstathios (Stathis) Stefanidis sstef@hep.ucl.ac.uk http://www.hep.ucl.ac.uk/~sstef

  3. The ATLAS Detector: Overview. • pp colliding beams 14 TeV c.m. energy. • Design Luminosity: L=1034 cm-2s-1. • Three Parts: • Inner Detector • Calorimeter (EM – HAD) • Muon Spectrometer • Magnet System: • Solenoid: 2 T • Toroid: 0.4 T Efstathios (Stathis) Stefanidis sstef@hep.ucl.ac.uk http://www.hep.ucl.ac.uk/~sstef

  4. High Level Trigger (HLT) The Trigger System: Overview. • LVL1: • 40 MHz  75 kHz • < 2.5 μs • Hardware trigger • Reduced granularity information • LVL2: • 75 kHz  2 kHz • 10 ms • Full granularity information from both ID and Calorimeter • RoI mechanism • Event Filter (EF): • 2 kHz  100 Hz •  2s • Sophisticated algorithms • Alignment data available Efstathios (Stathis) Stefanidis sstef@hep.ucl.ac.uk http://www.hep.ucl.ac.uk/~sstef

  5. The Trigger System: HLT. • Event Selection Strategy: • Signature validation • Checks for signatures coming from interesting physics events • REJECT UNINTERESTING EVENTS VERY EARLY • RoI mechanism • (i) Defines the area where HLT • will start from. • (ii) Seeded by LVL1 • (iii) Only the data needed are • transferred •  MINIMISE THE PROCESSING TIME AND NETWORK TRAFFIC Efstathios (Stathis) Stefanidis sstef@hep.ucl.ac.uk http://www.hep.ucl.ac.uk/~sstef

  6. The Trigger System: HLT. • Event Selection Software: • ATHENA • Written using GAUDI architecture • Provides common services (Transient Data Store, Histograms, Auditing etc) • Well-defined interface not only to developers but also to the end-users • IMPROVE COHERENCY OF THE DIFFERENT SOFTWARE DOMAINS • IDScan • LVL2 track reconstruction algorithm • SPACE POINTS as input – Track parameters as output • Runs several times per event and once per RoI Efstathios (Stathis) Stefanidis sstef@hep.ucl.ac.uk http://www.hep.ucl.ac.uk/~sstef

  7. Performance Studies: IDScan. Pattern Recognition • |pTgen – pTrec|<15 GeV • |ηgen – ηrec|<0.01 • |φgen – φrec|<0.01 rads Efstathios (Stathis) Stefanidis sstef@hep.ucl.ac.uk http://www.hep.ucl.ac.uk/~sstef

  8. Electron selection • Weνe sample 22.5 GeV Performance Studies: e/γ slice. • Determine selection efficiencies and rates at each Trigger Level. • Apply isolation, energy, tracking matching etc cuts. Efstathios (Stathis) Stefanidis sstef@hep.ucl.ac.uk http://www.hep.ucl.ac.uk/~sstef

  9. Performance Studies: RoI size. • How is the RoI constructed? • Take the information from LVL1 Calo : (η,φ) of the active region. The η coordinate is calculated w.r.t to z=0 • Construct the shape of the RoI: • z=0 ± 168 mm (3 of the beam spread) • η ± 0.1 • φ ± 0.1 rad • Motivation? • Optimize the size of the RoI. • Less Space Points. • Less Combinatories. • Quicker Algorithms. • Improve efficiency. Implementation? Use the shower position at the 1st and 2nd EM sampling. Efstathios (Stathis) Stefanidis sstef@hep.ucl.ac.uk http://www.hep.ucl.ac.uk/~sstef

  10. Z vertex resolution Phi vertex resolution Theta vertex resolution σ_low = 3.626 cm σ_high = 3.593 cm σ_low = 1.719 mrad σ_high = 1.692 mrad σ_low = 14.26 mrad σ_high = 14.11 mrad Performance Studies: RoI size. Efstathios (Stathis) Stefanidis sstef@hep.ucl.ac.uk http://www.hep.ucl.ac.uk/~sstef

  11. Physics Studies • Low Mass Higgs (mH<150 GeV) • Hγγ • Hbb • Study the full production/simulation/reconstruction chain. Future Plans. • Performance Studies • IDScan : Optimize the size the RoI • e/γ analysis : Improve, validate, optimize the cuts Efstathios (Stathis) Stefanidis sstef@hep.ucl.ac.uk http://www.hep.ucl.ac.uk/~sstef

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