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26. - 27 Sept. 2004 Weyer, Obersterreich Fast Simulation of the Trigger System of the ATLAS Detector at LHC B. Epp, V.M. Ghete, D. Kuhn, Y.J. Zhang Institute for Experimental Physics, University of Innsbruck, Austria 2004 2004

SLIDE 1

Fast Simulation of the Trigger System of the ATLAS Detector at LHC

B. Epp, V.M. Ghete, D. Kuhn, Y.J. Zhang

Institute for Experimental Physics, University of Innsbruck, Austria 2004 2004

26. - 27 Sept. 2004

Weyer, Oberösterreich

SLIDE 2

Introduction

Fast simulation:

use particle-level information only (i.e. generator output) no full detector simulation needed

Aims / objectives:

provide a tool for overall LVL1 + HLT optimization and strategy development provide fast trigger response for offline studies

compute approximate trigger rate and efficiencies
enable production of trigger-selected sample

Approach:

parametrized distributions, determined from full simulation possibly combined with simplified (averaged) detector description

Relation between full and fast simulation:

fast simulation integrated with full simulation (common interfaces) use full simulation framework for steering, configuration, etc.

SLIDE 3

ATLAS Trigger System

Trigger tasks:

reduce the total event rate to ~200 Hz, most dedicated to high-pT physics maximize coverage of discovery physics be open to new signatures use inclusive triggers as much as possible

Level-1 trigger (LVL1)

selection: based on reduced- granularity information from calorimeter and muon trigger chambers provides Region of Interest (η, φ of LVL1 signature, pT and energy sum of candidate objects) to LVL2

Level-2 trigger (LVL2)

has access to all event data, with full precision and granularity uses LVL1 RoIs to access selectively data, transfer minimum required data emphasis: fast rejection & algorithms

Event Filter (EF)

refines LVL2 selection, using LVL2 RoIs and sophisticated algorithms can access detailed alignment and calibration data

SLIDE 4

Full Simulation of LVL1 Trigger

Purpose: identify basic signatures of interesting physics

muons em/tau/jet calorimeter clusters missing/sum ET

LVL1 decision

based on multiplicities and thresholds thresholds are programmable

Full simulation of LVL1

package TrigT1, with algorithms for

calorimeter trigger: TrigT1Calo muon trigger: TrigT1TGC, TrigT1RPC

can be use to obtain parametrized distributions: e.g. for muons, provides efficiency and acceptance maps

SLIDE 5

HLT Event Selection Software

HLTSSW

Steering

Monitoring Service MetaData Service

ROB Data Collector Data Manager HLT Algorithms

Processing Task

Event Data Model L2PU Application

<<import>>

Event Data Model

Reconstr. Algorithms

<<import>>

StoreGate Athena/ Gaudi

<<import>> <<import>>

Interface Dependency Package

E vent Filter H LT C

re S
ftw

are O ffline C

re Softw

are O ffline R econstruction

HLT Algorithms

Level2

H LT D ata Flow Softw are

HLT Selection Software

Framework ATHENA/GAUDI Reuse offline components Common to Level-2 and EF

O ffline algorithms used in EF

SLIDE 6

LVL1 Muon Trigger: Input for Fast Simulation

Running full simulation to obtain:

trigger efficiency versus pT for various muon pT thresholds acceptance maps as a function of η and φ MuTruth → Fast Trigger Algorithm → Yes/No ↑ Look-up maps

SLIDE 7

Overview of Algorithms and Framework

LVL1 fast algorithms

run in a private AtlfastTrigT1Steer package

LVL2 fast algorithms

run in the general TrigSteer framework have the same interface as full simulation algorithms

AtlfastTrigT1Steer

“clone” of TrigSteer

SLIDE 8

Architecture of AtlfastTrigT1Steer

Class diagram of the HLT TrigSteer package Class diagram of the LVL1 AtlfastTrigT1Steer package

SLIDE 9

McConversion

Creates for every generated muon a pair {MuTruth object, trigger element (TE)} an example of the “separation of data and algorithms” using StoreGate mechanism

Diagram: simplified version

SLIDE 10

Sequence Diagram of a LVL1 Algorithm

SLIDE 11

Sequence Diagram of a LVL2 Algorithm

SLIDE 12

Final Remarks

Fast simulation of the trigger system: useful tool for

evaluation of feasibility for new physics studies trigger strategy and optimization

Development of the software: depends strongly on full simulation

to obtain the parametrizations for general framework (steering, configuration, etc.)

Status:

not yet collaboration-wide available good progress for the muon trigger slow development of the calorimeter trigger (external dependencies, major re-write of offline software – now close to usability)

Fast Simulation of the Trigger System of the ATLAS Detector at LHC

Institute for Experimental Physics, University of Innsbruck, Austria 2004 2004

Introduction

Fast simulation:

use particle-level information only (i.e. generator output) no full detector simulation needed

Aims / objectives:

provide a tool for overall LVL1 + HLT optimization and strategy development provide fast trigger response for offline studies

Approach:

parametrized distributions, determined from full simulation possibly combined with simplified (averaged) detector description

Relation between full and fast simulation:

fast simulation integrated with full simulation (common interfaces) use full simulation framework for steering, configuration, etc.

ATLAS Trigger System

Trigger tasks:

reduce the total event rate to ~200 Hz, most dedicated to high-pT physics maximize coverage of discovery physics be open to new signatures use inclusive triggers as much as possible

Level-1 trigger (LVL1)

selection: based on reduced- granularity information from calorimeter and muon trigger chambers provides Region of Interest (η, φ of LVL1 signature, pT and energy sum of candidate objects) to LVL2

Level-2 trigger (LVL2)

has access to all event data, with full precision and granularity uses LVL1 RoIs to access selectively data, transfer minimum required data emphasis: fast rejection & algorithms

Event Filter (EF)

refines LVL2 selection, using LVL2 RoIs and sophisticated algorithms can access detailed alignment and calibration data

Full Simulation of LVL1 Trigger

Purpose: identify basic signatures of interesting physics

muons em/tau/jet calorimeter clusters missing/sum ET

LVL1 decision

based on multiplicities and thresholds thresholds are programmable

Full simulation of LVL1

package TrigT1, with algorithms for

calorimeter trigger: TrigT1Calo muon trigger: TrigT1TGC, TrigT1RPC

can be use to obtain parametrized distributions: e.g. for muons, provides efficiency and acceptance maps

HLT Event Selection Software

HLT Selection Software

LVL1 Muon Trigger: Input for Fast Simulation

Running full simulation to obtain:

trigger efficiency versus pT for various muon pT thresholds acceptance maps as a function of η and φ MuTruth → Fast Trigger Algorithm → Yes/No ↑ Look-up maps

Overview of Algorithms and Framework

LVL1 fast algorithms

run in a private AtlfastTrigT1Steer package

LVL2 fast algorithms

run in the general TrigSteer framework have the same interface as full simulation algorithms

AtlfastTrigT1Steer

“clone” of TrigSteer

Architecture of AtlfastTrigT1Steer

Class diagram of the HLT TrigSteer package Class diagram of the LVL1 AtlfastTrigT1Steer package

McConversion

McConversion

Creates for every generated muon a pair {MuTruth object, trigger element (TE)} an example of the “separation of data and algorithms” using StoreGate mechanism

Diagram: simplified version

Sequence Diagram of a LVL1 Algorithm

Sequence Diagram of a LVL2 Algorithm

Final Remarks

Fast simulation of the trigger system: useful tool for

evaluation of feasibility for new physics studies trigger strategy and optimization

Development of the software: depends strongly on full simulation

to obtain the parametrizations for general framework (steering, configuration, etc.)

Status:

not yet collaboration-wide available good progress for the muon trigger slow development of the calorimeter trigger (external dependencies, major re-write of offline software – now close to usability)

Target for (partial) implementation:

ATLAS Physics Workshop (Rome, June 2005)