1. Artemis School On Calibration and Performance of ATLAS Detectors Jörg Stelzer / David Berge

2. 3 Level Trigger System  Level 1:  Hardware based  Coarse granularity detector data  Calorimeter and muons only  Latency 2.2  s  Output rate up to ~75 kHz  Level 2: ~500 farm nodes(*)  Seeded by level 1  Only detector ”Regions of Interest” (RoI) processed  Full detector granularity in RoIs  Fast reconstruction  Average execution time ~40 ms  Output rate up to ~2 kHz  Event Builder: ~100 farm nodes(*)  Event Filter (EF):~1600 farm nodes(*)  Seeded by level 2  Full detector granularity  Potential full event access  Offline algorithms  Average execution time ~4s  Output rate up to ~200 Hz (*) four dual-CPU cores at ~2GHz per farm node 19. Sep 2008Trigger Tutorial Introduction 2

3. The Level 1 Trigger Pre-processor Cluster Processor Jet/Energy Processor End-cap Muon Trigger (TGC) Barrel Muon Trigger (RPC) Muon-CTP-Interface (MuCTPI) Central Trigger Processor (CTP) LTP BusyTTC Detector Front-Ends/Read-out LTP BusyTTC Muon DetectorsCalorimeter Detectors Common Merger Modules Trigger objects: Muons, EM and hadronic clusters, jets, total and missing E T CTP Available in AOD: 19. Sep 2008 3 Trigger Tutorial Introduction

4. The High Level Trigger  HLT configuration described by the trigger menu  Trigger chains: signatures (1 electron and some missing ET)  Description how electrons and missing ET are calculated and what selection criteria are applied: sequence of algorithms  Algorithm properties are also part of trigger configuration  Information not available for analysis 19. Sep 2008 4 Trigger Tutorial Introduction

5. HLT Configuration  Concept of Chains (trigger lines)  Chain: list of trigger conditions (multiplicities of HLT TriggerElements) to be evaluated in order  Sequence: Description how algorithms produce TriggerElements  example: EM3  ClusterFinder & Hypo  L2_e5cl  Collection of Chains (each with prescale and path-through rates) is called HLT Menu  Available in AOD:  chains, trigger conditions, TriggerElements, prescales, pass-through  Not available: algorithm names signature (2e j) sequence (e) [EM  “e-FEX, e-Hypo”  e] sequence (j) [JET  “j-FEX, j-Hypo”  j] signature (e’ j’) Chain (2EJ-L2) input = “2EMJET” Chain (2EJ-EF) input = “2EJ-L2” Lvl1 Trigger Item 2EMJET y/n L2 EF HLT Chain 19. Sep 2008 5 Trigger Tutorial Introduction

6. TriggerDB  Easy trigger configuration via 3 integer keys  Easy reproducibility  Configuration history 19. Sep 2008Trigger Tutorial Introduction 6 Level 1 Menu + Prescales HLT Menu + Prescales Algorithm parameters Release version Conditions Database (COOL) TriggerDB Schema reflects trigger design Configuration data becomes conditions data when used for data taking  Relational database stores trigger configuration – TriggerDB

7. Trigger Features and TriggerElements  Sequence: description how algorithms produce TriggerElements, example (in xml):   At least two algorithms in sequence  First is a FEX_algo which calculates a “trigger feature” e.g. a TopoCluster  This feature is attached to the TriggerElement “L2_Photon_5”  More features can be calculated and attached to this TE  Last is a Hypo_alg which checks the feature (e.g. “energy of TopoCluster>5?”) and enables/disables TriggerElement  Trigger features are ‘physics objects’. TriggerElements are logical objects (feature based selection decision) 19. Sep 2008 7 Trigger Tutorial Introduction

8. Two More Terms HLT Steering (during trigger running):  Framework that executes chains of a menu (after application of prescales/pass-throughs)  Stops chain execution if condition is failed  Caches results of algorithms that are called multiple times HLT Navigation (during AOD analysis):  Framework that enables access to trigger features through chains or trigger elements 19. Sep 2008 8 Trigger Tutorial Introduction

9. The Flow of Trigger Data 1. TriggerDB to configure trigger for data taking 2. Configuration data to COOL 3. Trigger result in each event 4. Shipped to reconstruct- ion sites 5. ESD, AOD, TAG for trigger aware analysis 19. Sep 2008Trigger Tutorial Introduction 9 ESD 100MB/s AOD 20MB/s ESD AOD TAG files/DB L1Result to Tier0 express calib Tier 1 transfer Tier 0 Prompt Reconstruction Express Reconstruction, calibration Tier 1 Reprocessing Tier 2 MC production Conditions Database Trigger Menus into Conditions DB Conditions Database TriggerDB DbProxy LVL2 Result EF Result RODs Front-end LVL2 Subfarm Input EF Event Builder LVL1/ CTP Subfarm Output EF Trigger Result Trigger Objects TriggerDB Replication DPD

10. Trigger Data for Analysis 19. Sep 2008Trigger Tutorial Introduction 10 TriggerDB All configuration data Online Conditions Database COOL ESD AOD TAG Configures Stores decoded Trigger Menu DPD With decreasing amount of detail

11. The TrigDecisionTool Interface Access to  Trigger result (L1 items passed, prescaled, vetoed; HLT chains passed, prescaled, pass-through)  HLT::CTPItem, HLT::Chain  Trigger features through TrigNavigation  Trigger configuration  TrigConf::TriggerItem, TrigConf::HLTChain  Not mentioned yet: access to Streams, ChainGroups 19. Sep 2008 11 Trigger Tutorial Introduction

12. Goal of the Tutorial 1. Check out and run standard UserAnalysis 2. Simple printout of trigger menu 3. Print full chain L1 – L2 – EF 4. Print simple trigger statistics of a few triggers 5. Determine trigger efficiencies with respect to an offline selection 6. Plot trigger efficiencies as function of p T and η Homework: Look at overlap of different triggers 19. Sep 2008 12 Trigger Tutorial Introduction