A ROOT Tool for 3D Event Visualization in
ATLAS Calorimeters
Luciano Andrade
José de Seixas
Federal University of Rio de Janeiro/COPPE
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Outline
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The LHC and ATLAS detector.
ATLAS calorimeter system.
Trigger system and Level 2 Trigger RoI.
Commissioning phase with cosmics.
The visualization tool.
Some problems found by this tool.
Conclusion and To-Do list.
The LHC and ATLAS Detector
 LHC - it is being finished at CERN.
 ATLAS - high granularity, TBytes/sec of data.
 Trigger system – to save only relevant events.
Eletromagnetic Calorimeter
Hadronic Calorimeter
Muon Chambers
Inner Detector
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ATLAS Calorimeter System
Electromagnetic - LArg
 Liquid argon as detection
medium.
 Charged particles generate
eletromagnetic showers.
 Electric field captures free
electrons → signal pulse.
Inner detector
Electromagnetic Calorimeter
Hadronic - TileCal
 Scintillating tiles.
 Iron to absorv the energy.
 Energetic hadrons interact with
the tiles → light generation.
 Photomultipliers transform the
light in a electrical signal.
Hadronic Calorimeter
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Calorimeter Segmentation
Hadronic
Electromagnetic
 64 Modules in φ coordinate.
 Two readout channels by cell.
 10,000 readout channels.
 Three layers.
 100,000 readout channels.
 Four layers.
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Trigger System
1 GHz
Level 1 Trigger
100 kHz
Region of Interest (RoI)
(Region with signal information)
Level 2 Trigger
1 kHz
RoI algorithm was checked
with this visualization tool
(simulated data)
Event Filter
100 Hz
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Commissioning with cosmic muons
Trigger tower
 Use of a standalone coincidence board.
 Bypass the Trigger System.
 Back-to-back coincidence – projective events.
 Use TileCal Trigger Towers.
 Commissioning of the calorimeters with real data.
coincidence board
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2
dicriminator
logic OR
Logic
AND
dicriminator
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trigger
logic OR
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The Visualization Tool - Motivation
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Three-dimensional event visualization of the Calorimeter
cells.
Tool used in the commissioning phase.
Simple and intuitive way to look for potential problems.
Easy connection with reconstructed data (ROOT).
Two versions:
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Analysis examples:
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Hadron Calorimeter specific.
Combined Eletromagnetic/Hadron Calorimeters.
Track visualization for cosmics – real data.
Level 2 Trigger RoI debug - simulated data.
TileCal Specific Tool - Overview
• ROOT macro (TileCosmicView.C).
• Input → standard TileCal reconstruction nTuple.
Standard Root GL Viewer
To open the nTuple
Graphic User Interface (GUI)
some activated cells
cosmic track
TileCal
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Features
 Fast response.
 Color palette adjustment.
 Threshold by cell energy.
 Show individual PMTs.
 Cell selection with mouse.
 Projective views.
 Show ADC counts.
 Rotate and zoom.
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Combined Calorimeter Tool - Overview
• ROOT macro (CaloGeoView.C).
• Input → standard Athena reconstruction nTuple.
Standard Root GL Viewer
Example of a Level 2 Trigger RoI visualization
Graphic User Interface (GUI)
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Features
Example of cosmic event reconstruction (real data)
log scale
green palette - Eletromagnetic
hot palette - Hadronic
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Detecting Problems – Cell Imbalance
TileCal cells have two readout channels
Cell
PMT left
PMT right
cell with asymmetric energy
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Detecting Problems – noisy modules
TileCal module LBA45 with high pedestals in most of the cells
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Threshold by Cell Energy
Level 2 Trigger RoI seen from inside of the detector
buttom to force same threshold
activated cells
Low threshold in the Eletromagnetic Calorimeter (all cells are showed)
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Threshold by Cell Energy
Level 2 Trigger RoI seen from inside of the detector
Threshold at 50 MeV (LArg detector)
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Threshold by Cell Energy
Level 2 Trigger RoI seen from inside of the detector
energy of some activated cells
Threshold at 2 GeV (only activated cells are showed)
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Identifying Problems – Level 2 RoI
last cells (high eta) with wrong values
wrong cell information
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after fix the problem
before fix the problem
Conclusion & To do list
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Easy way to go through the events and check for
problems.
Needs only Root (v5.14.00).
Easy to run and to modify.
No need to recompile.
It has helped commissioning phase with cosmic.
Some bugs in the L2 Trigger algorithms has been
found with this tool.
Next steps: Include LArg EndCap and Inner Detector.