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ATLAS Trigger Configuration System: Design and Commissioning

This article outlines the design, implementation, and commissioning status of the ATLAS Trigger Configuration System, which is responsible for configuring the trigger in the ATLAS experiment.

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ATLAS Trigger Configuration System: Design and Commissioning

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  1. The ATLAS TriggerConfiguration System Design and Commissioning A.dos Anjos, P.Bell, D.Berge, J.Haller, S.Head, T.Kohno, S.Li, T.McMahon, M.Nozicka, H.v.d. Schmitt, J.Stelzer, T.Wengler, W.Wiedenmann

  2. Outline • Trigger design • Configurable components • Configuration system requirements • Data taking, MC production, offline analysis • Design and implementation • Commissioning status • Conclusions The ATLAS Trigger Configuration System

  3. Trigger Design introduction to the ATLAS trigger in ATLAS HLTsteering by S. George (Mo 16:50 Online Computing) 40 MHz bunch crossing 100-200 Hz storage rate ~40ms ~3% of detector ~4sec Fast, highly selective, efficient The ATLAS Trigger Configuration System

  4. Level 1 Trigger CTP Trigger objects: Muons,EM and hadronic clusters, jets,total and missing ET Configurable information on CTP: • Mapping of 480 hardware signals onto 160 CTP internal signals • these signals encode the object multiplicities • Thresholds of trigger objects • multiple thresholds for different object types • Item definitions: logic, prescale and veto rates • maximum 256 trigger items • Random trigger rates, trigger on bunches or bunch groups Calorimeter Detectors Muon Detectors Pre-processor Barrel Muon Trigger (RPC) End-cap Muon Trigger (TGC) Cluster Processor Jet/Energy Processor Muon-CTP-Interface (MuCTPI) Common Merger Modules Central Trigger Processor (CTP) LTP LTP TTC Busy TTC Busy Detector Front-Ends/Read-out The ATLAS Trigger Configuration System

  5. High Level Trigger (HLT) more details in talks about ATLAS HLT steering by S. George (Mo 16:50 Online Computing) and about Trigger Reconstruction Algorithms by T. Fonseca Martin (Mo 17:55 Online Computing) HLT Chain • Concept of trigger lines (chains) • Chain: ordered list of trigger conditions (multiplicities of HLT trigger elements) to be evaluated in sequence) • Description how algorithms produce trigger elements (example: L1EM3  ClusterFinder&Hypo  L2_e5cl) • Collection of chains (with prescale and forced-accept rates)  HLT menu (see Teresa’s talk) • HLT algorithms configured through parameters • Set via python (used in ATLAS as high level scripting language) Lvl1 Trigger Item EMJET Steering, see Simon’s talk Chain (EJ-L2) input = “EMJET” signature (e j) sequence (e) [EM  “e-FEX, e-Hypo”  e] sequence (j) [JET  “j-FEX, j-Hypo”  j] y/n signature (e’ j’) y/n L2 EF Chain (EJ-EF) input = “EJ-L2” Configurable information: • Chain definitions: logic (trigger conditions, algorithms), prescale and forced-accept rates • maximum 8192 chains per menu • Algorithm parameters • Data streams, monitoring groups y/n y/n The ATLAS Trigger Configuration System

  6. Design Requirements for the Configuration System • Complete and consistent configuration of the ATLAS trigger • Online software and hardware for data taking • Trigger simulation software in Monte Carlo production jobs • Configuration information provided to the user to perform trigger aware analyses and trigger studies • Flexible and fast configuration changes during data-taking to react to different beam and detector conditions • History of configurations for the purpose of understanding and reproduction of the trigger behavior The ATLAS Trigger Configuration System

  7. Components of the Configuration System offline user shift crew expert TriggerTool TriggerDB Relational Access Layer datataking simulation production conditions database TriggerDB Schema Level 1 Menu + Prescales HLT Menu + Prescales Algorithm parameters Release version • Relational database stores trigger configuration (TriggerDB) • Trigger configuration via a single key • Offline reproducibility • Trigger history • Schema reflects trigger design • Tool for database browsing and manipulation (TriggerTool) • Flexible and fast changes of the trigger during data taking • Trigger experts, shift crew, offline analyst • Software clients to directly access the TriggerDB for • Data taking, simulation, and distribution of configuration data (conditions database) The ATLAS Trigger Configuration System

  8. Operation of the Configuration System – Preparation ATLAS Trigger community responsible for the development and testing of the trigger algorithms to achieve the ATLAS physics goals Level 1 Trigger • Menu: stable in time, small changes to thresholds and trigger items by hand using TriggerTool • Trigger-Menu-Compiler creates image for Level 1 hardware • Prescales: adjusted by shifter to match the luminosity  optimize bandwidth usage High Level Trigger • Prepare and validate trigger menu for data taking • Populate the TriggerDB with the HLT configuration information • Menu, algorithm parameters, prescale rates • Check consistency with Level 1 configuration Configuration alias for shifter • Logical names (‘PHYSICS’, ‘COSMICS’, ‘CALIBRATION’) pointing to current valid configurations The ATLAS Trigger Configuration System

  9. TriggerDB during Data Taking see talk about ATLAS Online Configuration Database by I. Soloviev (Wed 15:05 Online Computing) • Shifter to chose trigger configuration alias before CONFIG transition • Configuration key written to online configuration database to be picked up by Level 1 CTP controller and HLT processes • At CONFIG: • CTP controller loads image from TriggerDB into the CTP hardware • HLT processes load configuration from TriggerDB into memory and initialize themselves • At START run: • partial configuration information is written into the ATLAS conditions database (COOL) as run-wise trigger configuration data • While RUNNING: • Level 1 prescales can change written to COOL Trigger Panel in the ATLAS Run Control interface The ATLAS Trigger Configuration System

  10. Trigger Result Event wise trigger decision encoded in the bytestream • Level 1 trigger: Acceptance flags for the up to 256 active trigger items beforeand afterthe application of prescale and veto 3 x 256 bits • High level trigger: Acceptance flags for each chain beforeand afterthe application of prescale and forced-accept • Chains are identified by a short integer (chain counter) • Index of last successfully processed step for each chain • Trigger objects e.g. hadronic clusters, muon tracks • Information to link these HLT trigger objects to the Level 1 trigger objects (trigger studies) Run-wise configuration data to interpret trigger decision (conditions database) • Maps: trigger names to bit position and chain counter • Allows for access to the trigger decision using trigger names • Information about trigger definition at each step of chain-processing • To rebuild the HLT menu and access the trigger objects by name • Prescale, LVL1 veto and HLT forced accept rates and trigger chains The ATLAS Trigger Configuration System

  11. Flow of Configuration Data More details in talk about ATLAS Databases by A. Vaniachine (Wed 14:40 Distributed data analysis) and about ATLAS Tag DBby F. Viegas (Wed 14:40 Software Components) ConditionsDatabase to Tier0 TriggerDB Front-end Tier 0 RODs LVL1/CTP express calib LVL2 DbProxy Express Reconstruction, calibration LVL2 Result Trigger Menus into Conditions DB Prompt Reconstruction Event Builder ESD ESD 100MB/s Subfarm Input AOD 20MB/s Tier 1 transfer AOD Tier 1 Reprocessing ConditionsDatabase EF EF EF EF Tier 2MC production EFResult Subfarm Output TAG files/DB Trigger Result Trigger Objects TriggerDB Replication • TriggerDB to configure trigger for data taking • Configuration data to COOL • Trigger result in each event • Shipped to reconstruct-ion sites • ESD, AOD, TAG for trigger aware analysis L1Result The ATLAS Trigger Configuration System

  12. Configuration Data in Offline Analysis Decoded Trigger Menu Configures for Data taking online DB (COOL) TriggerDBAll configuration data • Trigger Information for trigger studies and physics analysis Decoded trigger menu Trigger Information (transient) Encoded trigger decision • Configuration: Lvl1 items and HLT chains (name, version), prescale-, Lvl1 veto- and HLT pass-through rates • Trigger result: pass or fail? reason: prescaled, vetoed, pass-through? last successful step in each chain? • Navigation: which trigger object caused the trigger decision ? • Trigger Event Data: rerun the trigger selection offline with tightened criteria ESD Event Summary Data AOD Analysis Object Data Persistence Transient The ATLAS Trigger Configuration System

  13. Analysis and Trigger Studies Most trigger analyses possible on AOD data! • Common: check if event passed a desired trigger • Trigger efficiency, luminosity calculations (on TAG DB) • Navigate to trigger object that caused trigger-accept • Zee trigger + single electron trigger to study electron trigger efficiency • Rerunning the trigger without reconstruction of trigger objects • Run trigger as during data taking, but switch off trigger feature extraction (FEX) algorithms (see Simon’s talk) • Perform selection with tighter requirements (HYPO algorithms) • Turn on curves, … The ATLAS Trigger Configuration System

  14. Interaction with the TriggerDB – TriggerTool Intuitive JAVA based GUI to browse andmanipulate trigger configurations Simple and advanced search capabilities Search results Integrated consistency checking Tree view for trigger menus (and subsets) Edit pane (e.g. for chains) Table view for plain data User Mode Browse: trigger menus, detailed information like algorithm parameters Shifter Mode Change prescale factors or trigger menu to react on changing detector or beam conditions Expert mode Upload new and manipulate existing configurations The ATLAS Trigger Configuration System

  15. Commissioning LVL1 Configuration See also Commissioning the ATLAS triggerby J. Boyd (Wed 17:30 Online Computing) • ATLAS Central Trigger Processor (CTP) tested for over a 1 year on cosmic data using input from various detector sub-systems ATLAS access shafts • Complete muon cosmic ray slice LVL1 + LVL2 in February 2007 • Muon trigger  LVL1 provides trigger and seed for LVL2  LVL2 algorithm requests detector data to reconstruct muon candidates • Configuration of CTP from the TriggerDB is default • August commissioning week: • Writing of LVL1 trigger configuration to conditions database for each run Cosmic-ray RPC impact points, extrapolated to ground level The ATLAS Trigger Configuration System

  16. Commissioning HLT Configuration • Large Scale Tests in December 2006 • Simple trigger setup, large computing farm: 600 dual core processors • TriggerDB access via the ATLAS DbProxy – service that caches database requests and replies to reduce load on primary database • Two following technical runs in March and May 2007 on simulated and cosmic data • Small computing farm (part of the final ATLAS trigger farm) • Test of complex trigger menus • Exercising the TriggerTool in a shift-like environment • August commissioning week: • Tested writing of HLT configuration to conditions database for each run ATLAS Run Control interface during LST The ATLAS Trigger Configuration System

  17. Trigger Configuration for Simulation Production TriggerDB holds complete trigger configuration  can be used to simulate the trigger in the exact same way as it is configured for data taking Advantages • Consistency between online trigger and simulation • Configurations created and used during data taking can easily be used in MC production • More flexible propagation of configuration changes to MC production sites • Currently a new MC production cycle requires a new software release • Can be replaced by software release + configuration key  faster turn around if only trigger menus or algorithm parameters need adjustment • System under construction The ATLAS Trigger Configuration System

  18. Summary • System designed and implemented to provide consistent configuration of all three trigger levels • Access to trigger configuration consistently for data taking, Monte Carlo production, and trigger studies / trigger aware analysis • Fast and flexible response to changing detector or beam conditions during data taking • System provides a trigger history over the ATLAS lifetime, easily accessible by the analyst using the TriggerTool • Commissioning of the system for Level 1 and HLT separately and combined during cosmic test runs and large scale farm tests The ATLAS Trigger Configuration System

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