Artemis SchoolOn Calibration and Performance of ATLAS DetectorsJörg Stelzer / David Berge

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 node19. Sep 2008Trigger Tutorial Introduction 2

The Level 1 Trigger

Pre-processor

ClusterProcessor

Jet/EnergyProcessor

End-cap MuonTrigger (TGC)

Barrel MuonTrigger (RPC)

Muon-CTP-Interface (MuCTPI)

Central Trigger Processor (CTP)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 ET

CTP

Available in AOD:

19. Sep 2008 3Trigger Tutorial Introduction

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 4Trigger Tutorial Introduction

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

y/n

y/n

y/n

L2

EF

HLT Chain

19. Sep 2008 5Trigger Tutorial Introduction

TriggerDB

Easy trigger configuration via 3 integer keys

Easy reproducibility Configuration history

19. Sep 2008Trigger Tutorial Introduction 6

Level 1 Menu + PrescalesHLT Menu + PrescalesAlgorithm parametersRelease version

ConditionsDatabase

(COOL)

TriggerDB Schemareflects trigger design

Configuration data becomes conditions data when used for data taking

Relational database stores trigger configuration – TriggerDB

Trigger Features and TriggerElements Sequence: description how algorithms produce

TriggerElements, example (in xml): <SEQENCE inputTEs=“EM3”

algorithms=“T2CaloCluster T2CaloHypo_5” outputTE=“L2_Photon_5”/>

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 7Trigger Tutorial Introduction

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 8Trigger Tutorial Introduction

The Flow of Trigger Data1.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

ES

D 1

00

MB

/s

AO

D 2

0M

B/s

ESDAOD

TAG files/DB

L1Result

to

Tier0

express calib

Tie

r 1

tr

an

sfer

Tier 0

Prompt Reconstruction

Express Reconstruction,calibration

Tier 1 ReprocessingTier 2MC production

ConditionsDatabase

Tri

gger

Menus

into

Condit

ions

DB

ConditionsDatabase

TriggerDB

DbProxy

LVL2 Result

EFResult

RODs

Front-end

LVL2

Subfarm Input

EF EF EF

Event Builder

LVL1/CTP

Subfarm Output

EF

Trigger Result

Trigger ObjectsTriggerDBReplication

DPD

Trigger Data for Analysis

19. Sep 2008Trigger Tutorial Introduction 10

TriggerDBAll configuration

data

OnlineConditionsDatabase

COOL

ESD

AOD

TAG

Configure

s Store

s

decod

e

d

Trig

ger

Men

u

DPD

With

decre

asin

gam

ou

nt o

f deta

il

The TrigDecisionTool InterfaceAccess 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,

ChainGroups19. Sep 2008 11Trigger Tutorial Introduction

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 pT and

η

Homework: Look at overlap of different triggers 19. Sep 2008 12Trigger Tutorial Introduction