ALICE Off-line Computing: Status and Plans

P.Hristov for the ALICE Collaboration

14/09/2007

NEC’2007, Varna

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History

NEC’2001 AliRoot for simulation NEC’2003 Reconstruction with AliRoot NEC’2005 AliRoot for analysis NEC’2007 Still no LHC data => Status and

plans of the ALICE offline software

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Outline

ALICE Experiment Simulation Reconstruction Analysis First physics Conclusions

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ALICE detectors

L3 magnet B<0.5 T HMPID TRD Dipole magnet

MUON spectrometer

Absorber

TPCPHOS

ITS

PMD

TOF

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Offline framework AliRoot in development since 1998

Directly based on ROOT Used since the detector TDR’s for all ALICE studies

Few packages to install: ROOT, AliRoot, G3/G4/FLUKA, AliEn client Ported on most common architectures/OS

Linux i686, ia64 and x86_64, Mac OS X, Digital True64, Solaris x86,… Distributed development

Over 50 developers and a single CVS repository 2/3 of the code developed outside CERN

Integration with DAQ (data recorder) and HLT (same code-base) Abstract interfaces and “restricted” subset of C++ used for maximum

portability

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Software management Regular release schedule

Major release every two months, minor release (tag) every month Nightly produced UML diagrams, code listing, coding rule violations,

build and tests , single repository with all the code No version management software (we have very few packages!)

Advanced code tools under development (with IRST/Trento) “Smell” detection Aspect oriented programming tools Automated genetic testing

Documentation for AliRoot and AliEn produced Intensive training ongoing

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The Simulation

User Code

VMC

Geometrical Modeller

G3 G3 transport

G4 transportG4

FLUKA transportFLUKA

Reconstruction

Visualisation

Generators

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Event Generation:Kinematics

Particle Transport:Hits (energy

deposition at givenPoint, MC label)

Detector Response:Summable Digits

(low ADC threshold,no noise, MC label)

Detector Response:Digits

(noise + normal Threshold, MC label)

Raw data formats:DDL files, DATE file,

“rootified” raw

Event Merging (MC + MC): Summable Digits Signal+Summable Digits BackgroundNeeded to reduce the simulation time

Event embedding (MC + Raw): Summable Digits Signal+Raw converted to SDigitsStudies of reconstruction efficiency

Event mixing: tracks or clusters fromone event are combined with tracksor clusters from another (but “similar”)event.

SIMULATION

Reconstruction

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Visualisation

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QuickTime™ and aTIFF (Uncompressed) decompressor

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QuickTime™ and aTIFF (Uncompressed) decompressor

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Plans - AliRoot Framework

Improvements in the CPU and the memory consumption Ongoing redesign of the ESDs classes Finalize common AOD classes Data size reduction: ESD, AOD Optimize access to OCDB & metadata selection Simplification of the IO management RAW data: take into account the latest modifications in the hardware

Simulation Urgent – document & implement ALICE geometry as built Material in tracking region & fwd direction (services, cables) Getting TFluka & G4 production ready

Visualization Preparation for event scanning and visual quality assurance

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Local DetectorReconstruction:

Clusterization, vertex

Seeding:2 clusters in TPC+ primary vertex

Kalman Filter:Forward propagation

TPCITS

Kalman Filter:Backward propagationITSTPCTRDTOF

Kalman Filter:Refit inward

TRDTPCITS

RECONSTRUCTION

BARREL

TRACKING

TPC seeding,Forward tracking

ITS forward tracking,Combinatorial Kalman

filter

ITS forward tracking

TPC V0 and kinkfinder

ITS V0 finder

ITS tracking

TPC tracking

TRD tracking, seeding

Update ofV0s and kinks

TRD tracking, PID

TPC tracking, PID

ITS tracking, PID

Update ofV0s and kinks

Update ofV0s

TOF PID

Propagation to PHOS,EM,HMPID

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Tracking efficiency

TPC

all detectors

For realistic particle densitiesdN/dy = 2000 – 4000

combined efficiency well above 90%and fake track probability below 5%

Challenge in high-particle density environment

Efficiency normalized to number of

“reconstructable” track

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Combined efficiencyEfficiency normalized to number of

generated particles at primary vertex

within the central acceptance |η|<0.9 protons – absorption kaons and pions – decays

central Pb – Pb TPC

At lower pt : TRD inclusion dropsthe efficiency due to unavoidable material between TRD sectors

pp

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Plans – Reconstruction Alignment-aware reconstruction

Survey data usage Development and tests of the alignment algorithms

Calibration-aware reconstruction Ongoing review detector by detector Development of detector algorithms

Reconstruction parameters in separate classes Factorization of reconstruction features

Magnetic Field Ongoing analysis of the measurements, close to completion

PID: consistent treatment of the mismatch between detectors

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AlignmentSimulation

Ideal Geometry

Misalignment

Reconstruction

Raw data

File from survey

Ideal Geometry

Alignment procedure

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OCDBGrid File Catalog

DIMtriggerECS

RunLogbook

DAQ

FXS DB

FXS

DCSarch. DB

DCS

FXS DB

FXS

HLTFXS DB

FXS

SHUTTLE

TR

D

MP

H

SP

D

TP

C

...Calibration: The Shuttle

No alternative system to extract data (especially online calibration results) between data-taking and first reconstruction pass!

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High-level dataflow

CAF

WN{se’s}guid lfn

{se’s}guid lfn

{se’s}guid lfn

{se’s}guid lfn

guid {se’s}lfn

ALICE File Catalogue

Publishagent xrootd

Castorcache

CASTOR

LDC

DAQNetwork

GDC

Conditionfiles

Data files

Data fileFTS

SRM

SRM

T1’s

OfflineOnline

HLT

DDL

240TB

DCS Shuttle

Publish in AliEn

Monit.Calib.

DAQFXSDAQ

Logbook DB

Condition files

HLTFXSDCS

FXS

Run info

DCSDB

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p

ALICE Analysis Basic Concepts Analysis Models

Prompt data processing (calib, align, reco, analysis) @CERN with PROOF

Batch Analysis using GRID infrastructure Local analysis Interactive analysis PROOF+GRID

User Interface Access GRID via AliEn or ROOT UIs

PROOF/ROOT Enabling technology for CAF GRID API class TAliEn

Analysis Object Data contain only data needed for a particular analysis

Analysis à la PAW ROOT + at most a small library

Work on the distributed infrastructure has been done by the ARDA project

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CAFlfn guid {se’s}

lfn guid {se’s}

lfn guid {se’s}

lfn guid {se’s}

lfn guid {se’s}

xrootdCASTOR

WNPROOFXROOTD

WNPROOFXROOTD

WNPROOFXROOTD

WNPROOFXROOTD

WNPROOFXROOTD

WNPROOFXROOTD

PROOF master

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The whole CAF becomes a xrootd cluster

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QuickTime™ and aTIFF (LZW) decompressor

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For prompt and pilot analysis, calibration and alignment, fast simulation and reconstruction

Working with the PROOF team on optimisation S/W versions handling now in PROOF Disk quotas are already partly implemented and

under test Data distribution at the moment “by hand" Fairshare algorithm under development

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First Physics Studies:Measuring the Pseudorapidity Density of Primary Charged Particles using the TPC (ALICE-INT-2007-005)

Event and track quality selection. E.g. Events with reconstructed

vertex Require track origin in

proximity to the primary vertex Corrections

Track-to-particle (track level):f(, z vtx, pT) Geometrical acceptance, reconstruction efficiency, decay, feed-down

Vertex reconstruction efficiency (event level) f(z vtx, multiplicity)

Trigger efficiency (event level) Corrects to INEL, NSD f(z vtx, multiplicity)

Studies of systematics Track selection Influence of secondaries Particle composition Pt cutoff Relative frequency of processes Beam-gas and pileup events Misalignment Bias from the vertex reconstruction

PDC06 data:400K events (corrections)100K events (analysis)Different event sample for corrections and analysis!

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Conclusions The ALICE offline software is making steady

progress towards readiness Well prepared for real data and first physics studies Optimization of the code performance (CPU, memory,

file size) Last chance to add missing functionality Extensive tests during the detector commissioning

The area between online and offline is the most demanding at the moment Contingency is small but positive