The First-Level Trigger of ATLAS Johannes Haller (CERN) on behalf of the ATLAS First-Level Trigger...

The First-Level Trigger of ATLAS

Johannes Haller (CERN)

on behalf of the ATLAS First-Level Trigger Groups

International Europhysics Conference on High Energy Physics,July 21st-27th 2005, Lisbon, Portugal

Johannes Haller The First Level Trigger of ATLAS 2

ET

total interaction rate

e.g.: Higgs → ZZ → 2e+2

e.g.: Higgs → ZZ → 2e+2

Triggering at the LHC

23 min. bias events: ~ 1725 particles/BC

23 min. bias events: ~ 1725 particles/BC

bunch crossing rate: 40 MHztotal interaction rate:~ 1 GHzevent size: ~ 1.5 MB

bunch crossing rate: 40 MHztotal interaction rate:~ 1 GHzevent size: ~ 1.5 MB

storage rated

isco

veri

es

σ rate

affordable: ~ 300 MB/sstorage rate: ~ 200 Hz→ online rejection: 99.9995%

powerful trigger needed• enormous rate reduction • retaining the rare events in the very

tough LHC environment

powerful trigger needed• enormous rate reduction • retaining the rare events in the very

tough LHC environment


~ 10 ms

ATLAS Trigger Systemsoft

war

eh

ard

war

e

2.5 s

~ sec.

3-Level Trigger System:

this talk:

LVL1: Calorimeter Trigger Muon Trigger Central Trigger

1) LVL1 decision based on data from calorimeters and muon trigger chambers; synchronous at 40 MHz; bunch crossing identification

2) LVL2 uses Regions of Interest (identified by LVL1) data (ca. 2%) with full granularity from all detectors

3) Event Filter has access to full event and can perform more refined event reconstruction

1) LVL1 decision based on data from calorimeters and muon trigger chambers; synchronous at 40 MHz; bunch crossing identification

2) LVL2 uses Regions of Interest (identified by LVL1) data (ca. 2%) with full granularity from all detectors

3) Event Filter has access to full event and can perform more refined event reconstruction


Analoguetower sums0.1 x 0.1(~7200)

LVL1 Calorimeter Trigger

to LVL2

4 CP crates

electronic components (installed in counting room heavily FPGA based flexibility):

• PPr: digitisation of analogue signals from calorimeters and bunch crossing ID

• JEP: jet finding and energy sums• CP: e/ and had. cluster finding

electronic components (installed in counting room heavily FPGA based flexibility):

• PPr: digitisation of analogue signals from calorimeters and bunch crossing ID

• JEP: jet finding and energy sums• CP: e/ and had. cluster finding

output:• at 40 MHz: multiplicities for e/, jets, /had and

flags for energy sums to Central Trigger (CTP)• accepted events: position of objects (RoIs) to

LVL2 and additional information to DAQ

output:• at 40 MHz: multiplicities for e/, jets, /had and

flags for energy sums to Central Trigger (CTP)• accepted events: position of objects (RoIs) to

LVL2 and additional information to DAQ

featuretypes/positions

DAQ

RODsInput/output data

to DAQ

e/, /hadClusters

(CP)

0.2 x 0.2Jet / ET

(JEP)

0.1 x 0.1

Pre-Processor(PPr)

RoIRODs

to CTP

8 PPr crates

2 JEP crates

2 ROD crates

to CTP

example: e/ algorithm:

• goal: good discrimination e/ ↔ jets

• identify 2x2 RoI with local ET maximum

• cluster/ isolation cuts on various ET sums

example: e/ algorithm:

• goal: good discrimination e/ ↔ jets

• identify 2x2 RoI with local ET maximum

• cluster/ isolation cuts on various ET sums


LVL1 Muon Trigger

dedicated muon chambers with good timing resolution for trigger:• Barrel |η|<1.0 : Resistive Plate

Chambers (RPCs)• End-caps 1.0<|η|<2.4 : Thin Gap

Chambers (TGCs)• local track finding for LVL1 done on-

detector (ASICs)

dedicated muon chambers with good timing resolution for trigger:• Barrel |η|<1.0 : Resistive Plate

Chambers (RPCs)• End-caps 1.0<|η|<2.4 : Thin Gap

Chambers (TGCs)• local track finding for LVL1 done on-

detector (ASICs)

• looking for coincidences in chamber layers • programmable widths of 6 coincidence windows determines pT threshold

• looking for coincidences in chamber layers • programmable widths of 6 coincidence windows determines pT threshold

algorithm:


LVL1 Central Trigger

Central Trigger Processor (CTP)

multiplicities of e/, /h, jet for 8 pT thresholds each; flags for ET, ET j, ET

miss over thresholds

multiplicities of for 6 pT thresholds

Calorimeter trigger Muon trigger

Cluster Processor (e/, /h)

Pre-Processor (analogue ET)

Jet / Energy-sum Processor

Muon-CTP Interface (MuCTPI)

Muon Barrel Trigger (RPC)

Muon End-cap Trigger (TGC)

CTP: (one 9U VME64x crate, FPGA based)CTP: (one 9U VME64x crate, FPGA based)

• central part of LVL1 trigger system• combination of up to 160 input bits (plus internal bits) to

256 triggers (with prescale factors)• calculation of trigger decision based on inputs from

L1Calo and L1Muon according to trigger menu

ATLAS LVL1 trigger strategy is as inclusive as possible to

reduce bias and be open for new physics

LVL1 Menu 2x1033cm-2s-1

MU20 0.8

2MU6 0.2

EM25i 12.0

2EM15i 4.0

J200 0.2

3J90 0.2

4J65 0.2

J60+xE60 0.4

TAU25+xE30 2.0

MU10+EM15i 0.1

Others 5.0

Total rate (kHz) ~ 25

big uncertainties on predicted rates

example trigger menu:


ATLAS Combined Test Beamsetup at CERN’s SPS H8 beam-line: (2004)

beam (π, μ, e, p,

Ebeam = (1 to 360) GeV

• full scale ATLAS slice, all sub-detectors

• test of prototypes and final modules • periods of 25ns structured beam

(like LHC) • aim to establish full trigger and data

acquisition chain

• full scale ATLAS slice, all sub-detectors

• test of prototypes and final modules • periods of 25ns structured beam

(like LHC) • aim to establish full trigger and data

acquisition chain

L1Muon setup

end-cap chambers barrel chambers


LVL1 Trigger at the Test-Beam

all trigger, timing, control and readout paths successfully established:all trigger, timing, control and readout paths successfully established:

full LVL1 trigger chain established for the first timeATLASrun control

LVL1 latency projected to ATLAS: 2.13 μs

LVL1 triggered the readout of all sub-detectors

CTP latency: 95 nsat test-beam ~125 ns (not optimized)

signal distribution at test-beam:

Muon Trigger

Calo Trigger allsub-detec-tors


Test-Beam Results: Muon Trigger

position in precision muon chambers vs. position in RPCs

Triggered Bunch Next Bunch Previous Bunch

total efficiency pT threshold 6

nice correlation between RPC and MDT position

measurement trigger efficiency at test-beam

(3/4, phi): 99.4% efficiency for correct identification of bunch crossing: 99.5%

nice correlation between RPC and MDT position

measurement trigger efficiency at test-beam

(3/4, phi): 99.4% efficiency for correct identification of bunch crossing: 99.5%

barrel (RPCs): end-caps (TGCs):

efficiency and BCIDthreshold efficiency after

chamber shifting

pT threshold 5 pT threshold 4

chamber was shifted to emulate the effect of deflection in magnetic field

coincidence algorithm works

big timing margin where (correct bunch) high and (bunches before and after) tiny

chamber was shifted to emulate the effect of deflection in magnetic field

coincidence algorithm works

big timing margin where (correct bunch) high and (bunches before and after) tiny


Test-Beam Results: Calorimeter Trigger

Correlation of energy in LAr calo. and CPM

ROD

PreProcessor

Receivers

CPMs/JEMs

L1Calo setup

a full slice of the calorimeter trigger system was installed: ~1% of final capacity

checks of data consistency very successful

a full slice of the calorimeter trigger system was installed: ~1% of final capacity

checks of data consistency very successful

counting room reality:

good correlation of energy values measured in calorimeter and received in CP module

no event below e.m. trigger threshold of 20 GeV calorimeter trigger did work

good correlation of energy values measured in calorimeter and received in CP module

no event below e.m. trigger threshold of 20 GeV calorimeter trigger did work


Summary

• The trigger and its performance are of paramount importance at the LHC

• The First Level Trigger of ATLAS is based on calorimeters and dedicated muon chambers and reduces the event rate to ~75 kHz

• Successful test of the First Level Trigger system at the ATLAS Combined Test Beam

• Status: Prototypes of all types of modules and all ASICs validated; mass production started

• Road to data-taking at the LHC: muon trigger chamber integration already started CTP installation: September 2005 calorimeter trigger installation starts in September 2005 first cosmic ray runs with a subset of detectors early 2006 ATLAS expects to be ready for first pp collisions in 2007

• The trigger and its performance are of paramount importance at the LHC

• The First Level Trigger of ATLAS is based on calorimeters and dedicated muon chambers and reduces the event rate to ~75 kHz

• Successful test of the First Level Trigger system at the ATLAS Combined Test Beam

• Status: Prototypes of all types of modules and all ASICs validated; mass production started

• Road to data-taking at the LHC: muon trigger chamber integration already started CTP installation: September 2005 calorimeter trigger installation starts in September 2005 first cosmic ray runs with a subset of detectors early 2006 ATLAS expects to be ready for first pp collisions in 2007

The First-Level Trigger of ATLAS Johannes Haller (CERN) on behalf of the ATLAS First-Level Trigger...

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