Preparing for data analysis in ATLAS Andrea Dell’Acqua - CERN PH/SFT on behalf of the ATLAS...

Preparing for data analysis in ATLAS

Andrea Dell’Acqua - CERN PH/SFT

<[email protected]>

on behalf of the ATLAS collaboration

Preparing for data analysis in ATLAS 2

The ATLAS detector

Easily the most ambitious (and complex) ever

Diameter 25 mBarrel toroid length 26 mEnd-cap end-wall chamber span 46 mOverall weight 7000 Tons


The road to data taking

Two years from the first collisions Activity is becoming hectic…

building the detector… building the community… building the software (online and offline) tools…

ATLAS takes up the challenge


Building the detector…


Building a community

Only 2 years from data taking and so many things to do…

People becoming aware the experiment is coming up and willing to get going at analysis What? How??

Set up a full-scale exercise which looks at the experiment in its initial phase Still, a small-scale exercise when compared to real

life…


The Rome Physics Workshop

441 registered participantsSpeakers age distribution

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Age (years)

Ent

ries

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91 entries (out of about 100 talks),21 F plus 70 M(preliminary)


The Rome Workshop

Concentrate on the initial phases of the experiment Priority to e.g. SM physics rather than rare channels Initial layout of the detector

Use the latest SW tools First “exposure” (for many) to

Distributed production (Grid) Athena Geant4 “Event Data Model” New analysis style/tools

Physics results presented at this conference


The Rome aftermath The exercise was a terrific success from many

respects The “user” community was bootstrapped

They like what they used (constructive feedback) They ran the whole chain …and now ask for more and more….

basically all SW tools delivered in a timely fashion and in good shape The meeting set a checkpoint for the computing

community: we know now we are going in the right direction…

It set also a baseline for future activities


This is the first successful use of the grid by a largeuser community, which has however also revealed several shortcomings which need now to be fixed as LHC turn-on is onlytwo years ahead!

Very instructive comments from the user feedback have been presented at the Workshop (obviously this was one of the main themes and purposes of the meeting)

All this is available on the Web


What is next?

Continuous production and physics analysis Keep the momentum, improve on what we’ve got until now,

help the “users” become “experts” Commissioning of the offline computing

Aim at having a functional system by mid ‘06 Commissioning of the experiment

It’s already happening, now, as we speak Another large-scale physics exercise?

Last chance before… Show time…


Offline computing commissioning Major commissioning exercise of all aspects of the offline

computing during the first half of 2006 Formerly called “DC3” More a running-in of continuous operation than a stand-alone

challenge Main aim of Computing System Commissioning will be to

test the software and computing infrastructure that we will need at the beginning of 2007 Calibration and alignment procedures and conditions DB Full trigger chain Tier-0 reconstruction and data distribution Distributed access to the data for analysis

At the end (summer 2006) we will have a working and operational system, ready to take data with cosmic rays at increasing rates


The ATLAS Event Data Model RAW:

“ByteStream” format, ~1.6 MB/event ESD (Event Summary Data):

Full output of reconstruction in object (POOL/ROOT) format: Tracks (and their hits), Calo Clusters, Calo Cells, combined reconstruction objects etc.

Nominal size 500 kB/event currently 2.5 times larger: contents and technology under revision, following feedback

on the first prototype implementation AOD (Analysis Object Data):

Summary of event reconstruction with “physics” (POOL/ROOT) objects: electrons, muons, jets, etc.

Nominal size 100 kB/event currently 70% of that: contents and technology under revision, following feedback on

the first prototype implementation TAG:

Database used to quickly select events in AOD and/or ESD files


Offline SW: Architecture The architecture of the Athena framework is based on

Gaudi: Separation of data from algorithms Separation of transient (in-memory) from persistent (in-file)

data Extensive use of abstract interfaces to decouple the various

components

Backbone of the ATLAS computing system

Quite extensively used It scales, it works…


Offline SW: Detector description The GeoModel detector description system provides us with an application-

independent way to describe the geometry In this way Simulation, Reconstruction, Event Display etc. use by definition

the same geometry Geometry data are stored in a database with a Hierarchical Versioning

System Alignment corrections are applied with reference to a given baseline

geometry Time to be even more ambitious!


Offline SW: Simulation Event generator framework interfaces multiple packages

including the Genser distribution provided by LCG-AA Simulation with Geant4 since early 2004

automatic geometry build from GeoModel (~5M volumes) >25M events fully simulated up to now since mid-2004

Digitization tested and tuned with Test Beam

Fast simulation also used for preliminary large-statistics (physics) background level studies


Offline SW: Reconstruction Separation of data and algorithms:

Tracking code:

Calorimetry code:

Resource needs (memory and CPU) currently larger than target values Optimization and performance, rather than functionality, will be the

focus of developments until detector turn-on


Offline SW: Physics Analysis Tools The Physics Analysis Tools group develops common utilities for

analysis based on the Athena framework classes for selections, sorting, combinations etc. of data objects constituent navigation (e.g. jets to clusters) and back navigation

(e.g. AOD to ESD) UserAnalysis package in Athena interactive analysis in Athena analysis in Python interfaces to event displays testing the concept of “Event View”: a coherent list of physics

objects that are mutually exclusive any object appears only once in the list of reconstructed objects

available for analysis


Still, all of this is just simulation, right?


The ATLAS Combined Test BeamFull “vertical slice” of ATLAS tested on CERN H8 beam line May-November 2004

x

z

y

Geant4 simulated layout of the test-beam set-up

For first time, all ATLAS sub-detectors integrated and run together with common DAQ, “final” electronics, slow-control, etc. Gained lot of global operation experience during ~ 6 month run. Common ATLAS software used to analyze the data


TRT LAr

Tilecal

MDT-RPC BOS

End-cap Muon chambers

~ 90 million events collected ~ 4.5 TB of data:e, 1 250 GeV , , p up to 350 GeV ~ 30 GeV B-field = 0 1.4 T


150 GeV , =1.2

Z-position: Muon system vs Inner Detector

ECAL vs HCAL energy

A few very preliminary

results

LVL1 trigger vs ECAL energy25 ns beam structure

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

(B=1.4 T) 9 GeV pion track in Pixels, SCT, TRT

ATLAS


Validating detector simulation at the CTB

E = 100 GeV = 16 m

Simulated data, = 17 m

Simulated data, = 23 m

E = 180 GeV= 22 m

Pixels

SCT

ATLAS preliminary


Validating detector simulation at the CTB

E [MeV]

Due to different reconstruction

between G4 and data_ G4

Data

LAr

_ G4

Data

TileCal

_ G4

Data

Total

_ G4

Data

LAr

_ G4

Data

TileCal

_ G4

Data

Total

Too few energy in data or too much in G4 ?

E = 350 GeVE = 20 GeV

ATLAS preliminary


Next stop: detector commissioningPhase ASystem commissioning to ROD level.System commissioning for LVL1 and DAQCheck cable connections.Infrastructure commissioning(refrigerators, water cooling, etc.)

Phase CSystem/Trigger/DAQ combined commissioning

Phase DGlobal commissioning cosmic ray runs, planning for initial physics runs; initial off-line analysis software available, first collisions.

Phase BROD – Local DAQ connections established.Calibration runs on local systems.Skeleton TTC system needs to be available.

1/03 03/04 08/06 11/06

Commissioning with “physics data”

starts here


ATLAS is taking data!

ATLAS Tile calorimeter already recording cosmics going through

More detectors to follow soon

Sub-detector commissioning starting


Cosmic muons in ATLAS pit in 0.01 s ….

From full simulation of ATLAS (including cavern, overburden, surface buildings) + measurementswith scintillators in the cavern:

~ 106 events in ~ 3 months of data taking enough for initial detector shake-down (catalog problems, gain operation experience, some alignment/calibration, detector synchronization, …)

Through-going muons ~ 25 Hz(hits in ID + top and bottom muon chambers)

Pass by origin ~ 0.5 Hz(|z| < 60 cm, R < 20 cm, hits in ID)

Useful for ECAL calibration ~ 0.5 Hz (|z| < 30 cm, E cell > 100 MeV, ~ 900 )

Check detector operation with cosmic muons


One track reconstructed in Muon chambers

Two tracks reconstructed in Inner Detector

Will happen every ~10 s

A “typical” event


Beam-haloSimulation of machine background performed by LHC crew (V. Talanov):

-- based on MARS; recent machine optics V 6.4

-- scoring plane at the cavern entrance before ATLAS shielding (z = 23 m from IP)

then particles are transported by ATLAS full simulation

Beam-gasBeam-halo

Scoring plane

Single beam period: beam-halo muons and beam-gas events


Examples of beam-halo muons in ATLAS

A typical snake …

Total rate 105 kHz E > 10 GeV 16 kHzE > 100 GeV 1 kHzE > 1 TeV 10 Hz

L=1034

Muons at cavern entrance


Beam-gasBeam-halo

Scoring plane

Beam-gas:-- p(7 TeV) on p(rest)-- vertices uniformly distributed over 23 m -- (pH, pC, pO, …) (pp)×A0.7 (inelastic only)-- vacuum estimate: ~3.10-8 Torr (~1015 mol/m3)

Single beam period: beam-halo muons and beam-gas events


Beam-gas collisions are essentially boosted minimum-bias events low-pT particles

Rate : ~ 2500 interactions/m/s


What more?

Detector “as-built” Reproduce the situation as in the pit

Calorimeters are “pear-shaped” The LAr barrel in not centered on the beam line A barrel coil is not at its nominal position …

Good reproduction of “inert” material Pipes, rails, gangways, elevators, cables and what not…

Alignment Field ….


Are we done now?

Not quite, yet… EDM evolution (ESD/AOD as per user feedback) Analysis model Distributed production Distributed analysis Tier-0 operations Condition DBs …

…but the tunnel is past


Summary

The ATLAS detector is coming up, steadily and on schedule. It will be there for the first collisions

The ATLAS collaboration is getting prepared for data analysis. All major bits & pieces are falling in place

There is still a looong road in front of us, and time is getting tight, but we now believe we can make it

Quite an interesting list of things to do even before the first collisions

Preparing for data analysis in ATLAS Andrea Dell’Acqua - CERN PH/SFT on behalf of the ATLAS...

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