triggering at atlas

Martin zur Nedden, HU Berlin 1Trigger bei Atlas

Triggering at ATLAS

Trigger Challenge at the LHC Technical Implementation Trigger Strategy, Trigger Menus,

Operational Model, Physics Analyses and all that

Vortrag von Johannes Haller, Uni HHAm ATLAS-D Meeting, September 2006


Physics Goals at the LHC

p pH

µ +

µ-

µ+

µ-

Z

Z

p p

e- e

q

q

q

q

1-

g~

~

20~

q~

10~

EW symmetry breaking ?- search for the Higgs Boson

Extensions of the Standard Model ?- search for SUSY or other BSM physics

p pH

“The” trigger question:

What events do we need to take?

“The” trigger question:

What events do we need to take?

What else? - top, EW, QCD, B-physics

- physics events: , , e, , jets, ET,miss-high pT objects (un-pre-scaled)-low pT objects (pre-scaled or in exclusive selection)

- monitor events- calibration events

- physics events: , , e, , jets, ET,miss-high pT objects (un-pre-scaled)-low pT objects (pre-scaled or in exclusive selection)

- monitor events- calibration events

simple answer?

simple answer?


With every bunch crossing23 Minimum Bias events

with ~1725 particles produced

With every bunch crossing23 Minimum Bias events

with ~1725 particles produced

Event Rates and Multiplicities

tot(14 TeV) ≈ 100 mbinel(14 TeV) ≈ 70 mb

R = event rate

= luminosity = 1034 cm-2 s-1

inel = inel. Cross section = 70 mbN = interactions / bunch crossingt = bunch crossing interval = 25 ns

R = event rate

= luminosity = 1034 cm-2 s-1

inel = inel. Cross section = 70 mbN = interactions / bunch crossingt = bunch crossing interval = 25 ns

R = x inel = 1034cm-2 s-1 x 70mb = 7·108 Hz

N = R /t= 7·108 s-1 x 25·10-9 s = 17.5 = 17.5 x 3564 / 2808 (not all bunches filled) = 23 interactions / bunch crossing (pileup)

R = x inel = 1034cm-2 s-1 x 70mb = 7·108 Hz

N = R /t= 7·108 s-1 x 25·10-9 s = 17.5 = 17.5 x 3564 / 2808 (not all bunches filled) = 23 interactions / bunch crossing (pileup)

nch = charged particles / interactionNch = charged particles / BCNtot = all particles / BC

nch = charged particles / interactionNch = charged particles / BCNtot = all particles / BC

nch ≈ 50Nch= nch x 23 = ~ 1150Nto= Nch x 1.5 = ~ 1725

nch ≈ 50Nch= nch x 23 = ~ 1150Nto= Nch x 1.5 = ~ 1725

cm energy (GeV)

cross section of p-p collisions

LHC


Looking for Interesting Events

Higgs → ZZ → 2e+2Higgs → ZZ → 2e+2 23 min bias events23 min bias events


another Constraint: ATLAS Event Size

Atlas event size: 1.5 MB (Atlas event size: 1.5 MB (140 million channels)140 million channels)

at 40 MHz: 1 PB/sec

affordable mass storage: 300 MB/sec

storage rate: < 200 Hz

3 PB/year for offline analysis

at 40 MHz: 1 PB/sec

affordable mass storage: 300 MB/sec

storage rate: < 200 Hz

3 PB/year for offline analysis

pile-up, adequate precision need small granularity detectors

Detector Channels Fragment size [KB]

Pixels 1.4*108 60

SCT 6.2*106 110

TRT 3.7*105 307

LAr 1.8*105 576

Tile 104 48

MDT 3.7*105 154

CSC 6.7*104 256

RPC 3.5*105 12

TGC 4.4*105 6

LVL1 28


ET

total interaction rate

The Trigger Challenge

IA rate:~ 1 GHz; BC rate: 40 MHz; storage:~ 200 Hz online rejection: 99.9995% (!) crucial for physics (!)

IA rate:~ 1 GHz; BC rate: 40 MHz; storage:~ 200 Hz online rejection: 99.9995% (!) crucial for physics (!)

storage rated

isco

veri

es

σ rate

powerful trigger needed:•enormous rate reduction •retaining the rare events in the very tough LHC environment

•remember: 0.000005 must be shared:•physics triggers

- high pT physics (un-pre-scaled)- low pT physics (pre-scaled, excl.)

•technical triggers:- monitor triggers- calibration triggers- …

powerful trigger needed:•enormous rate reduction •retaining the rare events in the very tough LHC environment

•remember: 0.000005 must be shared:•physics triggers

- high pT physics (un-pre-scaled)- low pT physics (pre-scaled, excl.)

•technical triggers:- monitor triggers- calibration triggers- …


Technical Implementation


~ 10 ms

ATLAS Trigger: Overviewsoft

war

eh

ard

wa

re

2.5 s

~ sec.

3-Level Trigger System:

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


LVL1 Trigger Overview

multiplicities of for 6 pT thresholdsCentral Trigger

Processor (CTP)

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

miss over 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)

…TTC TTC TTC TTCTTC

L1A signal

LV

L1 laten

cy: 2.5 s =

100 BC


LVL1 Calorimeter Trigger

electronic components (installed in counting room outside the cavern; heavily FPGA based):

electronic components (installed in counting room outside the cavern; heavily FPGA based):

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

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

available thresholds:

• EM (e/gamma): 8 - 16

• Tau/ hadron: 0 - 8

• Jets: 8

• fwd. Jets: 8

• ETsum, ET

sum(jets), ETmiss : 4 (each)

available thresholds:

• EM (e/gamma): 8 - 16

• Tau/ hadron: 0 - 8

• Jets: 8

• fwd. Jets: 8

• ETsum, ET

sum(jets), ETmiss : 4 (each)

PPM crate

7 JEMs 6 CPMs


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:

Available thresholds:

• Muon: 6

Available thresholds:

• Muon: 6


LVL1 Trigger Decision in CTP

CTP: (one 9U VME64x crate, FPGA based)central part of LVL1 trigger system

CTP: (one 9U VME64x crate, FPGA based)central part of LVL1 trigger system

signals from LVL1 systems:8-16 EM, 0-8 TAU8 JET, 8 FWDJET4 XE, 4 JE, 4 TE, 6 Muon

signals from LVL1 systems:8-16 EM, 0-8 TAU8 JET, 8 FWDJET4 XE, 4 JE, 4 TE, 6 Muon

internal signals:2 random rates2 pre-scaled clocks8 bunch groups

internal signals:2 random rates2 pre-scaled clocks8 bunch groups

other externalsignals e.g. MB scintillator, …

other externalsignals e.g. MB scintillator, …

calculation of trigger decision for up to 256 trigger items:e.g. “XE70+JET70” raw trigger bits

application of pre-scale factors actual trigger bits

application of veto/ dead time

all of these steps need to be taken into account in offline data analysis all of these steps need to be taken into account in offline data analysis

CTP in USA15:

note: 2 different dead-time settings: trigger groups with “high” and “low” priority will see different luminosities!

CTP

L1A


Interface to HLT: RoI Mechanism

LVL1

• triggers on (high) pT objects

• L1Calo and L1Muon send Regions of Interest (RoI) to LVL2 for e//-jet- candidates above thresholds

LVL1

• triggers on (high) pT objects

• L1Calo and L1Muon send Regions of Interest (RoI) to LVL2 for e//-jet- candidates above thresholds

LVL2

• uses Regions of Interest as “seed” for reconstruction (full granularity)

• only data in RoI are used• advantage: total amount of

transfered data is small• ~2% of the total event data• can be dealt with at 75 kHz

LVL2

• uses Regions of Interest as “seed” for reconstruction (full granularity)

• only data in RoI are used• advantage: total amount of

transfered data is small• ~2% of the total event data• can be dealt with at 75 kHz

EF runs after event building, full access to eventEF runs after event building, full access to event


ATLAS Trigger & DAQ Architecture

• LVL2 and EF run in large PC farms on the surface

• DAQ and HLT closely coupled• pre-series (corr. ~10% of HLT)

• LVL2 and EF run in large PC farms on the surface

• DAQ and HLT closely coupled• pre-series (corr. ~10% of HLT)

HLT HW:DESY, Humboldt


Staging of HLT Components

2006 2007 2008 2009

L2P – LVL2 PC 30 270 510 510

SFI – EventBuilder 32 48 96 128

EFP – EventFilter PC 93 837 1581 1922

SFO – Storage element 3 10 10 10

deferred due to

financial constraints

max LVL1 rate per L2P: 150 Hz

EventBuilder rate per SFI: 40 Hz

max EB rate per EFP: 2 Hz

physics storage rate per EFP: 0.1 Hz

storage rate per storage element: 60 MB/s

40 Hz for 1.5 MB

SFOs non-deferred; allow b/w for calib., debug, etc

max LVL1 rate per L2P: 150 Hz

EventBuilder rate per SFI: 40 Hz

max EB rate per EFP: 2 Hz

physics storage rate per EFP: 0.1 Hz

storage rate per storage element: 60 MB/s

40 Hz for 1.5 MB

SFOs non-deferred; allow b/w for calib., debug, etc

consequences for physics:e.g. in 2007/2008: • LVL1 rate: ~40 KHz (cf. design:75/100 KHz)

• physics storage: ~80 Hz(cf. design: 200 Hz)

consequences for physics:e.g. in 2007/2008: • LVL1 rate: ~40 KHz (cf. design:75/100 KHz)

• physics storage: ~80 Hz(cf. design: 200 Hz)


Trigger Strategy


HLT Selection Strategy

2) seeded reconstruction• algorithms use results from previous steps

• initial seeds for LVL2 are LVL1 RoIs

2) seeded reconstruction• algorithms use results from previous steps

• initial seeds for LVL2 are LVL1 RoIs

1) step-wise processing and decision• inexpensive (data, time) algorithms first,

complicated algorithms last.

1) step-wise processing and decision• inexpensive (data, time) algorithms first,

complicated algorithms last.

Example: Dielectron Trigger

ATLAS trigger terminology: Trigger chain Trigger signature (called item in LVL1) Trigger element

fundamental principles:

LVL2 confirms & refines LVL1 EF confirms & refines LVL2

note: EF tags accepted events according to physics selection ( streams, offline analysis!)

LVL2 confirms & refines LVL1 EF confirms & refines LVL2

note: EF tags accepted events according to physics selection ( streams, offline analysis!)


in parallel: Trigger Chains

in principle: N-Level trigger systembut: Only one pre-scale per chain per level.(to be discussed if used in HLT)

in principle: N-Level trigger systembut: Only one pre-scale per chain per level.(to be discussed if used in HLT)

ATLAS follows “early reject” principle:

- Look at signatures one by one

i.e. do not try to reconstruct full event upfront

if no signatures left, reject event

- Save resources

minimize data transfer and required CPU power

ATLAS follows “early reject” principle:

- Look at signatures one by one

i.e. do not try to reconstruct full event upfront

if no signatures left, reject event

- Save resources

minimize data transfer and required CPU power

HLT Steering enables running of Trigger Chains in parallel w/o interferenceHLT Steering enables running of Trigger Chains in parallel w/o interference

Trigger Chains are independent:

“easy” to calculate trigger efficiencies

“easy” to operate the trigger (finding problems, pre-dictable behavior)

scalable system

Trigger Chains are independent:

“easy” to calculate trigger efficiencies

“easy” to operate the trigger (finding problems, pre-dictable behavior)

scalable system


Physics Analysis: the Trigger Part

Every physics analysis needs dedicated thoughts about the trigger:

• trigger rejects 0.999995 more or less hard cuts (in the signal region)

• (each) trigger has an inefficiency that needs to be corrected (turn-on curve)– Similar to offline reconstruction efficiency, but important difference: no retrospective

optimization: “The events are lost forever.”

• trigger optimization (as early as possible)

• trigger data quality during data-taking is crucial

Every physics analysis needs dedicated thoughts about the trigger:

• trigger rejects 0.999995 more or less hard cuts (in the signal region)

• (each) trigger has an inefficiency that needs to be corrected (turn-on curve)– Similar to offline reconstruction efficiency, but important difference: no retrospective

optimization: “The events are lost forever.”

• trigger optimization (as early as possible)

• trigger data quality during data-taking is crucial

typical turn-on curve: Example: trigger optimisation:

L2Calo


Physics Analysis: the Trigger Part

analysis preparation:

• setup/ optimize a trigger for your physics signal– define a trigger strategy (based on the available resources)

– convert to trigger chain (already existing?)

– determine rates and efficiencies from MC

• define a monitoring strategy– define trigger chain to be used for monitoring of your physics

trigger (efficiency from data)

– rates of the monitoring trigger (pre-scales?)

• integrate this in the overall trigger menu (done by Trigger Coordination for online running)

analysis preparation:

• setup/ optimize a trigger for your physics signal– define a trigger strategy (based on the available resources)

– convert to trigger chain (already existing?)

– determine rates and efficiencies from MC

• define a monitoring strategy– define trigger chain to be used for monitoring of your physics

trigger (efficiency from data)

– rates of the monitoring trigger (pre-scales?)

• integrate this in the overall trigger menu (done by Trigger Coordination for online running)

OKnot OK use the trigger online (take data)

monitor trigger qualitydetermine trigger eff. (from

data)correct your measurement

use the trigger online (take data)

monitor trigger qualitydetermine trigger eff. (from

data)correct your measurement

threshold?more

exclusive?pre-scaling ?

threshold?more

exclusive?pre-scaling ?


Trigger Efficiency from Data

studies of this kind are important and are just starting in ATLAS

studies of this kind are important and are just starting in ATLAS

other methods:- di-object samples (J/ Z0,

Z0+jets)- minimum bias and pre-scaled

low-threshold triggers (“bootstrap”)

- orthogonal selections in HLT (ID, muon, calo)

- …

note:- selection bias to be carefully

checked !- trigger efficiency may depend on

physics sample (e.g. electrons in W e and top) investigate in physics groups

other methods:- di-object samples (J/ Z0,

Z0+jets)- minimum bias and pre-scaled

low-threshold triggers (“bootstrap”)

- orthogonal selections in HLT (ID, muon, calo)

- …

note:- selection bias to be carefully

checked !- trigger efficiency may depend on

physics sample (e.g. electrons in W e and top) investigate in physics groups

rec. Z0-peak

trigger effi.

eta

example: possible monitoring of inclusive lepton triggers:

• reconstruct good Z0 candidates offline (triggered by at least one electron trigger)

• Count second electrons fulfilling trigger

example: possible monitoring of inclusive lepton triggers:

• reconstruct good Z0 candidates offline (triggered by at least one electron trigger)

• Count second electrons fulfilling trigger

time-evolution of accuracy

number of events

total efficiency for muons

electronpositron


LVL1 Menu (as of today, TDR)

general trigger problem: cover as much as possible of the kinematic phase space for

physics low trigger thresholds

keep the trigger rate low high trigger thresholds

trigger menu is a compromise

general trigger problem: cover as much as possible of the kinematic phase space for

physics low trigger thresholds

keep the trigger rate low high trigger thresholds

trigger menu is a compromise LVL1 rate is dominated by electromagnetic clusters: 78% of physics triggers

LVL1 rate is dominated by electromagnetic clusters: 78% of physics triggers

Note:

• large uncertainties on predicted rates

• study of the global aspects needed: load balancing (e.g. jet triggers)

Note:

• large uncertainties on predicted rates

• study of the global aspects needed: load balancing (e.g. jet triggers)


HLT Menu (as of today, TDR)

e/ rate reduced mainly in LVL2 (full granularity in RoI)

e/ rate reduced mainly in LVL2 (full granularity in RoI)

Note:

• large uncertainties on predicted rates (no data!)

• these menu give an rough impression of what we will select.

• details of the menu are not yet worked out (pre-scales, monitoring, …)

• but first examples of realistic trigger menus needed soon

Note:

• large uncertainties on predicted rates (no data!)

• these menu give an rough impression of what we will select.

• details of the menu are not yet worked out (pre-scales, monitoring, …)

• but first examples of realistic trigger menus needed soon


towards a more complete Menu

• study slice-wise:- optimization of cuts- need distributions of rates, rate vs. eff- more realism to algorithms- detailed studies of threshold behaviour, noise- consequences on physics reach

• study of the global aspects: - load balancing (e.g. jet triggers balancing)- overlap between selections, optimization

• the important details of the menu- monitoring strategy- pre-scaling strategy (dynamic, static) triggers- concurrent data-taking (pre-scales) or

sequentially (i.e. dedicated runs)?- time evolution (luminosity, background, etc.)

pre-scale changes ala H1/CDF?- technical triggers (bunch-groups, etc.)

- …

• study slice-wise:- optimization of cuts- need distributions of rates, rate vs. eff- more realism to algorithms- detailed studies of threshold behaviour, noise- consequences on physics reach

• study of the global aspects: - load balancing (e.g. jet triggers balancing)- overlap between selections, optimization

• the important details of the menu- monitoring strategy- pre-scaling strategy (dynamic, static) triggers- concurrent data-taking (pre-scales) or

sequentially (i.e. dedicated runs)?- time evolution (luminosity, background, etc.)

pre-scale changes ala H1/CDF?- technical triggers (bunch-groups, etc.)

- …

-…

aim: get concrete examples of more complete and realistic trigger menus for discussion at the next trigger and physics weeks.

aim: get concrete examples of more complete and realistic trigger menus for discussion at the next trigger and physics weeks.

ad-hoc-group: • started rethinking about the

trigger menus• invites input from physics,

combined performance and detector groups

ad-hoc-group: • started rethinking about the

trigger menus• invites input from physics,

combined performance and detector groups

priorities:• consolidate work on menu

for 14 TeV and 1031.• in parallel: limited study for

0.9 TeV and 1029

• later look at 1032 and above

priorities:• consolidate work on menu

for 14 TeV and 1031.• in parallel: limited study for

0.9 TeV and 1029

• later look at 1032 and above


Ideas for early Data Taking

conditions of early data-taking:initial luminosity: 1031(1029), bunch spacing 75ns (~500ns) BCID not critical, can relax the trigger timing windows

conditions of early data-taking:initial luminosity: 1031(1029), bunch spacing 75ns (~500ns) BCID not critical, can relax the trigger timing windows

trigger commissioningunderstanding of LVL1 is crucial at startup

first phase: • rates are low • DAQ can stand 400 MB/s• LVL1 only, HLT “transparent” • some pre-scaling needed only for very low thresholds.

• HLT selections studied offlinesecond phase:

• insert HLT • start with very simple and basic algorithms

trigger commissioningunderstanding of LVL1 is crucial at startup

first phase: • rates are low • DAQ can stand 400 MB/s• LVL1 only, HLT “transparent” • some pre-scaling needed only for very low thresholds.

• HLT selections studied offlinesecond phase:

• insert HLT • start with very simple and basic algorithms

minimum bias events:• important esp. at the beginning:

- crucial for timing-in of the experiment - for commissioning of detectors/ trigger/ offline

selection- physics: as bkg. (important for 14 TeV), per se

• possible implementation:• BC LVL1 trigger + selection on LVL2/EF

• bias free at LVL1

• MBTS trigger at LVL1 + selection in HLT• some bias at LVL1 (η range; efficiency for MIPS;

multiplicity requirements; etc.)• needed where interactions per BC << 1

minimum bias events:• important esp. at the beginning:

- crucial for timing-in of the experiment - for commissioning of detectors/ trigger/ offline

selection- physics: as bkg. (important for 14 TeV), per se

• possible implementation:• BC LVL1 trigger + selection on LVL2/EF

• bias free at LVL1

• MBTS trigger at LVL1 + selection in HLT• some bias at LVL1 (η range; efficiency for MIPS;

multiplicity requirements; etc.)• needed where interactions per BC << 1


The technical Side: Trigger Configuration

LVL1 HLT

Unique key

•TrigConf system under development•real data-taking: trigger menu can change between runs

optimization,falling luminosity during a fill (pre-scales, cuts)…

•book-keeping of all settings crucial

•TrigConf system under development•real data-taking: trigger menu can change between runs

optimization,falling luminosity during a fill (pre-scales, cuts)…

•book-keeping of all settings crucial

Offline data analyzer users will have to look up the TriggerDB to interpret the trigger result in the events, e.g. to find the settings for their triggers and the corresponding run ranges.

Offline data analyzer users will have to look up the TriggerDB to interpret the trigger result in the events, e.g. to find the settings for their triggers and the corresponding run ranges.

•TriggerDB is central part:stores all information for the online selectionstores all versions of trigger settings.identified with a unique key to be stored in

CondDB.

•TriggerDB is central part:stores all information for the online selectionstores all versions of trigger settings.identified with a unique key to be stored in

CondDB.


The technical side: Trigger Configuration

Java front-end for the TriggerDB under development: TriggerTool

• three modes are foreseen:1) experts: construct consistent menus in

TriggerDB2) shift-crew: choice of predefined options

(menus, pre-scale sets)

3) offline user: extract menus in text file for development, or simulation etc, browse DB to find settings of triggers and run ranges

Java front-end for the TriggerDB under development: TriggerTool

• three modes are foreseen:1) experts: construct consistent menus in

TriggerDB2) shift-crew: choice of predefined options

(menus, pre-scale sets)

3) offline user: extract menus in text file for development, or simulation etc, browse DB to find settings of triggers and run ranges


German Contributions

Contributions:• Hardware:

• L1Calo Preprocessor Heidelberg• L1Calo Jet-Energy Module Mainz• HLT computing racks DESY, Humboldt

• Technical software around trigger:• Trigger Configuration DESY/HH• Trigger Monitoring DESY/Humboldt

• Simulation, algorithms, performance:• CTP Simulation DESY/HH• MB Trigger DESY/Humboldt • Jets, ETmiss Mainz• B-physics Siegen (planned), • B-tagging on LVL2 Wuppertal (finished)• Muons MPI (planned for SLHC)

• Trigger strategy:• Operation, HLT Steering Mainz, DESY/HH• Combined Trigger Menu DESY/HH• Pre-scaling Heidelberg, Mainz,

DESY/HH

Contributions:• Hardware:

• L1Calo Preprocessor Heidelberg• L1Calo Jet-Energy Module Mainz• HLT computing racks DESY, Humboldt

• Technical software around trigger:• Trigger Configuration DESY/HH• Trigger Monitoring DESY/Humboldt

• Simulation, algorithms, performance:• CTP Simulation DESY/HH• MB Trigger DESY/Humboldt • Jets, ETmiss Mainz• B-physics Siegen (planned), • B-tagging on LVL2 Wuppertal (finished)• Muons MPI (planned for SLHC)

• Trigger strategy:• Operation, HLT Steering Mainz, DESY/HH• Combined Trigger Menu DESY/HH• Pre-scaling Heidelberg, Mainz,

DESY/HH

Institutes:• Heidelberg• Mainz• DESY/Hum-

boldt/HH• (Siegen)• (Wuppertal)• (MPI)

Institutes:• Heidelberg• Mainz• DESY/Hum-

boldt/HH• (Siegen)• (Wuppertal)• (MPI)


Summary

triggering at the LHC is crucial for physics• only 0.000005 of the events selected• cuts and efficiencies affect the results

each data analyzer must understand the trigger• choice of trigger, trigger optimization• trigger (in-)efficiency

- how to measure it (from data)? - how to correct for it?

need to develop more complete and realistic trigger menus for (early) data taking

German contributions in many areas (HW+SW)• very good collaboration !

triggering at the LHC is crucial for physics• only 0.000005 of the events selected• cuts and efficiencies affect the results

each data analyzer must understand the trigger• choice of trigger, trigger optimization• trigger (in-)efficiency

- how to measure it (from data)? - how to correct for it?

need to develop more complete and realistic trigger menus for (early) data taking

German contributions in many areas (HW+SW)• very good collaboration !

triggering at atlas

Documents