Commissioning of the ATLAS High Level Trigger with Single Beam and Cosmic Rays Alessandro Di Mattia...

Commissioning of the ATLAS High Level Trigger with Single

Beam and Cosmic Rays

Alessandro Di MattiaMichigan State University

On behalf of the Atlas Collaboration

CHEP ’09, March 21-27, 2009

Prague - March 24, 2009 A. Di Mattia, MSU2

OutlineOutline

• Introduction to the LHC and the ATLAS Trigger/DAQ

• The Event Selection Software

• The Trigger Configuration

• Online and Offline Monitoring

• Experience with beam and cosmic

• Main HLT achievements


The LHC challenge to ATLAS Trigger/DAQThe LHC challenge to ATLAS Trigger/DAQ

LHC: proton-proton collisions @ ECM = 14 TeV

L = 1034 cm-2 s-1 23 collisions per bunch crossing @ 25 ns interval 1 year at L = 1034 cm-2 s-1 ∫Ldt ≈ 100 fb -1

Challenge to the ATLAS Trigger/DAQ interaction rate 109 Hz, offline computing can handle O(102 Hz).

cross section of physics processes vary over many order of magnitude:

Inelastic: 109 Hz W → l : 102 Hz tt production: 10 Hz Higgs (100 GeV): 0.1 Hz Higgs (600 GeV):10-2 Hz

ATLAS has O(108) read-out channels → average event size ~1.6 MByte

Muon System Barrel:Trigger Chamber: RPCPrecision chamber: MDT

Inner Detector: Transition Radiation Tracker (TRT) Silicon Detector (SCT) Pixel

Muon System Endcap:Trigger Chamber: TGCPrecision chamber: MDT,CSC


~3 KHz

75 KHz

Level-1(hardware FPGA/ASIC)

– analyzes coarse granularity data from CALO and MUON detector;

– identifies the Region of Interest (RoI), seeds Level-2.

Level-2 (software based)– accesses full granularity data

within the RoI (2% total event size);

– uses algorithms optimized for fast rejection.

Event Filter (software based)– uses offline algorithms;– potential full event access;– exploits the seed from Level-

2.

Read Out System

ROB ROB

SFO

EFN

Event Builder ~100 farm nodes

SFI

DFM

ROB

ATLAS: the Trigger/DAQ systemATLAS: the Trigger/DAQ systemOther detectors

ROD ROD ROD

High LevelTrigger

L2 ~ 40 ms

L2P500 farm nodes

L2SVROIB

EF ~ 4sEFP

~1600 farm nodes

DCN

CALO

CTP

MUON

L1 2.5 s

L1 accept, 75 KHz

RoI request,data (~2%)

L2 accept, ~3KHz

RoI

Dataflow

40 MHz

~200 HzTypical event size ~1.6 MBytes,up to 14 MBytes for CALO calibration

EF accept, ~ 200 Hz

Calo +Muon tr. ch.

Details given by T. Pauly - The ATLAS Level-1 Central Trigger System in Operation

320 MB/s

1 PB/s

120 GB/s

3 GB/s


ATLAS Trigger/DAQ: the resourcesATLAS Trigger/DAQ: the resources

DAQ (ROS, EB, SFO): 100% of the final system available– delivered x2 design rate of event throughput with 5 SFO.

Trigger farms (L2P, EFP): 35% of the final system available– ~850 nodes on 27 racks;– 8 cores per node (2 x Harpertown quad-core @ 2.5GHz), 2 GBytes memory per core;– sufficient for the early data taking period.

Homemade resource monitoring based on nagios

Flexible resources assignment to DAQ/HLT:configuration allows for changing within a day the workload amongLevel-2 / Dataflow / Event Filter to cope with unexpected increase ofdata throughput (calo calibration runs, bad detector conditions

etc..);

Reconfiguration successfully exercised in the 2008 runs!

Details given by A. Zaytsev - System Administration of ATLAS TDAQ Computing Environment and by R. Sjoen - Monitoring Individual Traffic Flows in the ATLAS TDAQ Network

Details of the Dataflow given by W. Vandelli – ATLAS DataFlow Infrastructure: recent results from ATLAS cosmic and first-beam data-taking


The HLT Selection SoftwareThe HLT Selection Software

Performance and functionalities tested in technical runs and combined detector runs Details given by W. Wiedenmann - The ATLAS Online High Level Trigger Framework: Experience reusing

Offline Software Components in the ATLAS Trigger

HLTSSW

Steering Monitoring Service

1..*

MetaData Service

1..*ROB DataCollector

DataManager

HLTAlgorithms

Processing Task

Event DataModel

L2PU Application

<<import>>

Event DataModel

Reconstr. Algorithms

<<import>>

StoreGateAthena/Gaudi

<<import>><<import>>

Interface

Dependency

Package

Event Filter

HLT Core Software

Offline Core Software Offline Reconstruction

HLT Algorithms

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

Offline algorithms used in EF

HLT Data Flow Software


The HLT SteeringThe HLT Steering

HLT steering manages the execution of the selection code– algorithms configurable by parameters; – applies early rejection: abort full chain as soon as a selection steps fails;– applies prescales and passthrough factors;– caches full history of TE and FEX and writes them into the HLT result:

• allows navigation through the steps of the trigger decision;• avoids multiple execution of the same feature extraction; • allows offline re-run of trigger selection with different Hypo cuts;

Collection of Chains implements the trigger menu– in python or xml, recorded in the Trigger Configuration Database

Steering used to select events in the 2008 cosmic data taking.

From LVL1

Chain for Level-2 muon

To EF selection

L2_MU20Track ?Muon

TrackingMuon

Feature

MuonRoI

Trigger Element

Algorithms for extracting features of physics object from dataResults (FEX) from feature extractionTrigger Elements (TE), marking the atomic selection steps (Sequences)Algorithms applying selection on FEX, thus confirming the TE

Inn. Det.tracking

combinedtrack

CombinedFeature

L2TrigInDetTrack

Comb. ?


Trigger ConfigurationTrigger Configuration• Trigger configuration:

– active trigger Chains, algorithm parameters, prescale factors, passthrough fractions.

• Relational Database (TriggerDB) with no duplication of objects

– four Database keys: LVL1 & HLT menu, L1 prescales, HLT prescales, bunch number;

– user interface (TriggerTool); – read and write menu into XML format– menu consistency checks

• 2-month cosmic commissioning:over 3k chains, 6k components (algorithms, tools, services), 5k parameters. [Counting all versions of all objects]

• After run, Trigger Configuration becomes conditions data

• Run control can change complete menu at any run stop/start, prescales/passthroughs at any lumi block boundary

• Database proxy mechanism in place to avoid direct connection from every application Database exploited in the 2008 data taking for both online and offline


The Online monitoringThe Online monitoring

Trigger Presenter (TriP)– Provide rate information and farm status accessing the online Information System;– displays instantaneous trigger rate per selection chain / level and history plots;– allows for fast reaction against unexpected beam/detector conditions;

Algorithms online monitor– algorithms produce histograms for shifter and experts;– statistic from Processing Units is collected by the Online Histogram Presenter (OHP); – automatic checks are performed on a subset of histos for data quality assessment:

Exercised by the shifter crews. Provided also feedback to detector people during the early phases of the 2008 data taking.

Distance between the track from LVL1 and the Distance between the track from LVL1 and the muon hits in the precision chambers selected in muon hits in the precision chambers selected in

Level-2Level-2. Allows for checking the time . Allows for checking the time sinchronization among muon trigger and muon sinchronization among muon trigger and muon

precision detectors.precision detectors.

OHP ToolTrigger

presenter

Details given by A. Corso Radu, Y. Ilchenko, P. Renkel, A. Dotti


The Offline monitoringThe Offline monitoring

Tier0 [1600 cores, 2GB/core, CERN batch workers] Designed to reconstruct all events (~200Hz) from ATLAS within 1 day. Allows review of saved trigger quantities (used extensively) and comparison with offline (some tools yet in development).

CAF (CERN Analysis Facility) [ 400 cores, 64 for trigger] Designed to rerun ~10% of collected events for calibration and

commissioning.• Deployment of new code to HLT farm: separate patch branch of trigger

code with its own nightlies, tests with real data at CAF• Check the HLT decision: run on minimum bias stream and on events

taken in passthrough mode, deep monitoring of the algorithm functionalities

• Handles debug stream: events with HLT, errors and timeouts. (~2.5% of total events collected in Sept-Oct run, but really less than 0.1% from Oct onwards. Expected to be much lower for real collisions.)


First experience with LHC beamFirst experience with LHC beam

• Stability and reliability priority for the first beam.

• Simple trigger configuration (LVL1 decision only).

• Crucial to have the LVL1 triggers ( BPTX & MBTS) well timed-in.

• HLT used only for tagging events and routing them to data streams.

• Re-run the HLT offline on those events having Muon and Calo RoIs in time with BPTX or MBTS:

– few statistic available (less than 1k event), due to short operation and non pointing tracks.

Minbias Trigger Scintillator: 32 sectors on LAr cryostat

BPTX, 175 m

Tertiary collimators, 140 mbeam splash events when closed

Operation conditions– Pixel off;– Muon Sytem and Silicon

Detector at reduced HV;– Other detectors on;

LHC beamLoss monitor

Details given by C. OhmThe ATLAS beam pick-up based timing system

Details given by T. Pauly - The ATLAS Level-1 Central Trigger System in Operation


Cosmic running and events Cosmic running and events collectedcollected

• HLT provided streaming and event selection for detectors• Track selection for ID and Muon needed for alignment and calibration• Fast turn around exercised to accommodate detector requirements

Few cosmic runsbefore Sept. 2008

First time we hadthe Pixel Detectorin a global run

Mostly selected bythe LVL1 Muon

trigger


LVL1 Muon LVL1 Muon algorithmalgorithm

BARREL ENDCAP

Searches for TGC or RPC hit patternscompatible with tracks coming fromInteraction Point. Uses coincidence windows.

RPC

MDT

TGC

MDT

TGC 2


Issues on cosmic event dataIssues on cosmic event data

No beam clock: timing provided by trigger Muon Trigger Chambers– Phase issues in read-out/calibration of trigger and precision muon chambers

(MDT), transition radition tracker (TRT), etc.

The r-z view could not be fully reconstructed @ L2 because algorithms are designed for pointing tracks and data access happens in trigger towers heading to Interaction Point.

Pivot plane

Confirm plane high pt

Confirm plane low pt

Muon Spectrometer:RPC trigger setup

Muon Algorithms

Possible to relax pointing requirement to study efficiency / rejection.

Inner Detector TrackingSignificant modification to get tracks needed for Inner Detector alignment.

No tracks from Interaction Point : selected tracks distributed over d0, z0– track selection unbiased in the r-z view for most of the runs


Cosmic run: use of Physics MenuCosmic run: use of Physics Menu

• Despite low expected statics, a full physics menu run in parallel to cosmic chains.• eγ, jets/missing ET, , μ,

minimum bias…

• ROIs with eγ, , etc. signatures not very common with cosmics, rarer to get events until the end of the chains.

• A few thousand of events

• Both L2 and EF algorithms exercised successfully

Example plot from eγ FEX algorithms comparing L2 and EF: Shower shape in 2nd EM sampling Rη=E(3×7)/E(7×7).

Details on Tau trigger given by M. Dam - The ATLAS Tau Trigger

Prague - March 24, 2009 A. Di Mattia, MSU

• Hot cells in the eta region around 0.475 are seen by the HLT monitoring and by the detector monitoring. Plots normalized wrt the counting of the bin 0.475.

• Cross checking possible. Calo Trigger functional and may help identifying hot detector regions.

Detector monitoring per partition (½ EM eta space)

Hardware issues addressed during shutdown


ATLAS preliminary


MeV

Detector Online monitoring

LVL2 Calo: HLT feedback to the DetectorLVL2 Calo: HLT feedback to the Detector

Details given by D. Damazio – Atlas High Level Calorimeter Trigger Software Performance for Cosmic Ray Events


High statistic availableexercised some algorithms

• at L2:– Fast;– Iso;– TileRODMu;

• at EF:– TrigMuonEF;

Fast operated since the very beginning, being serving

data for the Muon Spectrometer Calibration and onlineData Quality.(for details on remote MDT calibration see A. De Salvo

ATLAS MDT remote calibration centers)

Re-run on data for cross checking:

• basic distributions (track position, calo noise / m.i.p. signal) against montecarlo prediction;

• track finding efficiency studies at L2;• studies on muon systems alignment at L2;

HLT muon: commissioning with HLT muon: commissioning with cosmiccosmic

Display of a cosmic event, run 90272

Description of muon trigger algorithmsgiven by A. Ventura: The Muon High Level

Trigger of the ATLAS experiment


Drift space from time

Bad conversion(unphysical)

Inefficiency position

EMS5A14 missing

LVL2 muon: LVL2 muon: Fast MDT cluster Fast MDT cluster findingfinding

MDT cluster residual (w.r.t. TGC seed)vs

nr. of TGC hits used as seed

• Cluster finding efficiency: 93%– design goal 99%– 4.7% inefficiency due to missing MDT data– 2% inefficiency due to bad MDT calibration

noisy chamber


L2 muon: calorimeter algorithmL2 muon: calorimeter algorithm

• Algorithm implemented into the CALO ROD DSP

• Poor efficiency (<< 1%) due to lack of pointing

• Back-to back distribution seen

• Energy deposition agrees with that for a m.i.p.

Run 91060energy deposition and distributions of muon tracks in Tile Calorimeter

ATLAS PreliminaryCosmic Monte Carlo


Muon Event FilterMuon Event Filter

TrigMuonEF algorithm exercised on cosmic data

angular resolutions (,):=0.007, =17mrad

• Solenoidal and toroidal field on• Resolutions with respect to Offline

resolution resolution


L2 ID TrackingL2 ID Tracking

• Three L2 tracking algorithms:– Si Track: Combinatoric search for

track seeds in innermost Si layers and their extension into tracks in outer Si layers. Si algo with TRT extension.

– IDSCAN: use histogramming techniques to find z-position of the IP and identify tracks originating from there. Si algo with TRT extension.

– TRTSegFinder: TRT-only algorithm looking for segments in the TRT.

Goal: Record as many ID tracks as possible, do not introduce biases in selection, keep rate at acceptable levels.

Secondary goal: to the extend possible, try to use machinery, setup, algorithms, etc. that are used for collisions.

Earliest tracking possible at L2(TRT can be read at LVL1 for cosmic)


L2 ID Tracking: performanceL2 ID Tracking: performance

• Trigger chain starting with all L1 accepted events and involving an OR of any L2 tracking algorithm finding tracks.

• Allowed collection of a good fraction of cosmic muons passing through the inner detector, with no significant biases

Performance:– Uniform event efficiency of >99%

for “golden Si” tracks.– Fake rates 0.01%-1%.– Algorithms complementary.

Rerun 1 month later: HLT trackingworks out of the box, despite somechanges in the detector

configuration!

Details on ID tracking given by M. Sutton - Commissioning the ATLAS Inner Detector TriggerDetails on data stream given by B. Pinto - Alignment data streams for the ATLAS Inner Detector


ConclusionsConclusions

HLT system fully exercisedAll the HLT infrastructure (steering, monitoring, data streaming, L2 &

EF algorithms) tested to work under actual data taking conditions.

Physicsmenu run in parallel to the cosmic slice.

HLT performed event selectionL2 ID tracking provided the data for detector alignment, L2 muon

serveddata for online detector Data Quality and Monitoring.

HLT operation was robustHLT commissioning performed while serving the subsystems. Provided

agood balance between stability and responsiveness to detector

condition /request.

Lot of understanding driving further the commissioning work


Backup(i.e. not to be shown on

Chep)


HLT TimingHLT Timing

• Timing studies done in “technical runs”, where MC events are injected to the HLT.

10^31 menu

L2 EF


First beam !!!First beam !!!


The Trigger ToolThe Trigger Tool

One tool for the shifters, experts and

offline users

Offline user can easily get read-only access using java webstart.

Trigger shifter can modify prescales and passthroughs.

Experts can modify all aspects of trigger configuration.


• Angle of muon track defined as follows

IP

IP

w.r.t. pointing direction w.r.t. =0 direction

x-y view

r-z viewr-z view

x-y view

DefinitionsDefinitions


LVL2 muon:LVL2 muon:Fast cross check on Fast cross check on alignment alignment

with only Middle fit:• poor match due to noise and bad MDT calibration;

with Middle+Outer fit:• good match, performance limited by alignment

MOOM

TGC

Cross check of alignment: match angle measurement from TGC and MDT


Algorithm assumes tracks are pointing

to the IP

2 out of 3 segments:• high efficiency on non

pointing tracks;• poor performance on the

Sagitta reconstruction.

3 out of 3 segments:• low efficiency on non

pointing tracks;• good Sagitta

reconstruction, performance limited by the alignment.

No magnetic field: straight tracks, cross check pattern recognition and reconstructionMDT angle: angle of MDT fit (in Middle Station) slope w.r.t. pointing direction

LVL2 muon: LVL2 muon: Fast track Fast track reconstructionreconstruction


ID Tracking: offline reconstructed ID Tracking: offline reconstructed trackstracks

• d0 ~ 18 mm

• would be rejected by the standard cut of the LVL2 ID tracking (efficiency up to d0=1 mm).


L2 ID tracking: adjustments for CosmicsL2 ID tracking: adjustments for Cosmics

• A simple independent pattern recognition for Si

• Start with hits in outermost layers, define a cigar-shaped road, if road contains enough hits, compute impact parameter for the road and apply a shift in x-y plane to all Si hits in detector.


The MDTThe MDT


Assembling MDT+TGC for the Assembling MDT+TGC for the EndcapEndcap


The HLT Event Selection SoftwareThe HLT Event Selection Software

Integration into online proceeds through stepsassess the same offline physics performance in

– run single-node online emulator (check RoI-based data access)– run multi-node partition (full check of online infrastructure)

Performance and functionalities tested in technical runs and combined detector runs

HLTSSW

Steering Monitoring Service

1..*

MetaData Service

1..*ROB DataCollector

DataManager

HLTAlgorithms

Processing Task

Event DataModel

L2PU Application

<<import>>

Event DataModel

Reconstr. Algorithms

<<import>>

StoreGateAthena/Gaudi

<<import>><<import>>

Interface

Dependency

Package

Event Filter

HLT Core Software

Offline Core Software Offline Reconstruction

HLT Algorithms

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


The HLT SteeringThe HLT Steering

HLT steering manages the execution of the selection code– algorithms configurable by parameters; – applies early rejection: abort full chain as soon as a selection steps fails;– applies prescales and passthrough factors;– caches full history of TE and FEX and writes them into the HLT result:

• allows navigation through the steps of the trigger decision;• avoids multiple execution of the same feature extraction; • allows offline re-run of trigger selection with different Hypo cuts;

Collection of Chains implements the trigger menu– in python or xml, recorded in the Trigger Configuration Database

Steering used to select events in the 2008 cosmic data taking.

From LVL1Example of a Level-2

Chain for muon

To EF selection

L2_MU20

Isol.Feature

IsoHypo

Isoisolatio

n

FastHypo

FastMS reco

MuonFeature

IDSCANID reco

CombCB reco

CombinedFeature

L2TrigInDetTrack

CombHypo

MuonRoI

Trigger Element A

Trigger Element B

Algorithms for extracting features of physics object from dataResults (FEX) from feature extractionTrigger Elements (TE), marking the atomic selection steps (Sequences)Algorithms applying selection on FEX, thus confirming the TE


Cosmic event recordedCosmic event recorded

• Cosmic event recorded as a function of the run number. Plots shows also the status of the magnetic field

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Commissioning of the ATLAS High Level Trigger with Single Beam and Cosmic Rays Alessandro Di Mattia...

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