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Preparing for data analysis in ATLAS
Andrea Dell’Acqua - CERN PH/SFT
<Andrea.Dellacqua@cern.ch>
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
Preparing for data analysis in ATLAS 3
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
Preparing for data analysis in ATLAS 4
Building the detector…
Preparing for data analysis in ATLAS 5
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…
Preparing for data analysis in ATLAS 6
The Rome Physics Workshop
441 registered participantsSpeakers age distribution
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91 entries (out of about 100 talks),21 F plus 70 M(preliminary)
Preparing for data analysis in ATLAS 7
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
Preparing for data analysis in ATLAS 8
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
Preparing for data analysis in ATLAS 9
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
Preparing for data analysis in ATLAS 10
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…
Preparing for data analysis in ATLAS 11
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
Preparing for data analysis in ATLAS 12
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
Preparing for data analysis in ATLAS 13
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…
Preparing for data analysis in ATLAS 14
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!
Preparing for data analysis in ATLAS 15
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
Preparing for data analysis in ATLAS 16
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
Preparing for data analysis in ATLAS 17
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
Preparing for data analysis in ATLAS 18
Still, all of this is just simulation, right?
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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
Preparing for data analysis in ATLAS 20
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
Preparing for data analysis in ATLAS 21
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
Preparing for data analysis in ATLAS 22
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
Preparing for data analysis in ATLAS 23
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
Preparing for data analysis in ATLAS 24
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
Preparing for data analysis in ATLAS 25
ATLAS is taking data!
ATLAS Tile calorimeter already recording cosmics going through
More detectors to follow soon
Sub-detector commissioning starting
Preparing for data analysis in ATLAS 26
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
Preparing for data analysis in ATLAS 27
One track reconstructed in Muon chambers
Two tracks reconstructed in Inner Detector
Will happen every ~10 s
A “typical” event
Preparing for data analysis in ATLAS 28
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
Preparing for data analysis in ATLAS 29
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
Preparing for data analysis in ATLAS 30
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
Preparing for data analysis in ATLAS 31
Beam-gas collisions are essentially boosted minimum-bias events low-pT particles
Rate : ~ 2500 interactions/m/s
Preparing for data analysis in ATLAS 32
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 ….
Preparing for data analysis in ATLAS 33
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
Preparing for data analysis in ATLAS 34
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
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