A ROOT Tool for 3D Event Visualization in ATLAS Calorimeters

1
A ROOT Tool for 3D Event Visualization in ATLAS
Calorimeters

• Luciano Andrade
• José de Seixas

Federal University of Rio de Janeiro/COPPE
2
Outline

• 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.

3
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
4
ATLAS Calorimeter System
Electromagnetic - LArg
Inner detector
Electromagnetic Calorimeter

• Liquid argon as detection medium.
• Charged particles generate eletromagnetic
  showers.
• Electric field captures free electrons ? signal
  pulse.

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
5
Calorimeter Segmentation
Electromagnetic
Hadronic

• 64 Modules in f coordinate.
• Two readout channels by cell.
• 10,000 readout channels.
• Three layers.

• 100,000 readout channels.
• Four layers.

6
Trigger System
1 GHz
Level 1 Trigger
100 kHz
Region of Interest (RoI) (Region with signal
information)
Level 2 Trigger
RoI algorithm was checked with this visualization
tool (simulated data)
1 kHz
Event Filter
100 Hz
7
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
1
2
dicriminator
logic OR
trigger
Logic AND
dicriminator
logic OR
3
4
8
The Visualization Tool - Motivation

• 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
• Hadron Calorimeter specific.
• Combined Eletromagnetic/Hadron Calorimeters.
• Analysis examples
• Track visualization for cosmics real data.
• Level 2 Trigger RoI debug - simulated data.

9
TileCal Specific Tool - Overview

• ROOT macro (TileCosmicView.C).
• Input ? standard TileCal reconstruction nTuple.

To open the nTuple
Standard Root GL Viewer
Graphic User Interface (GUI)
some activated cells
cosmic track
TileCal
10
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.

11
Combined Calorimeter Tool - Overview

• ROOT macro (CaloGeoView.C).
• Input ? standard Athena reconstruction nTuple.

Standard Root GL Viewer
Graphic User Interface (GUI)
Example of a Level 2 Trigger RoI visualization
12
Features
Example of cosmic event reconstruction (real data)
log scale
green palette - Eletromagnetic
hot palette - Hadronic
13
Detecting Problems Cell Imbalance
TileCal cells have two readout channels
Cell
PMT right
PMT left
cell with asymmetric energy
14
Detecting Problems noisy modules
TileCal module LBA45 with high pedestals in most
of the cells
15
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)
16
Threshold by Cell Energy
Level 2 Trigger RoI seen from inside of the
detector
Threshold at 50 MeV (LArg detector)
17
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)
18
Identifying Problems Level 2 RoI
last cells (high eta) with wrong values
wrong cell information
after fix the problem
before fix the problem
19
Conclusion To do list

• 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.