A root tool for 3d event visualization in atlas calorimeters
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A ROOT Tool for 3D Event Visualization in ATLAS Calorimeters. Luciano Andrade José de Seixas. Federal University of Rio de Janeiro/COPPE. Outline. The LHC and ATLAS detector. ATLAS calorimeter system. Trigger system and Level 2 Trigger RoI. Commissioning phase with cosmics.

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A root tool for 3d event visualization in atlas calorimeters

A ROOT Tool for 3D Event Visualization in ATLAS Calorimeters

Luciano Andrade

José de Seixas

Federal University of Rio de Janeiro/COPPE


Outline
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.


The lhc and atlas detector
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


Atlas calorimeter system
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


Calorimeter segmentation
Calorimeter Segmentation

Hadronic

Electromagnetic

  • 64 Modules in φcoordinate.

  • Two readout channels by cell.

  • 10,000 readout channels.

  • Three layers.

  • 100,000 readout channels.

  • Four layers.


Trigger system
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


Commissioning with cosmic muons
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


The visualization tool motivation
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.


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


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.


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


Features

Example of cosmic event reconstruction (real data)

log scale

green palette - Eletromagnetic

hot palette - Hadronic


Detecting Problems – Cell Imbalance

TileCal cells have two readout channels

Cell

PMT left

PMT right

cell with asymmetric energy


Detecting Problems – noisy modules

TileCal module LBA45 with high pedestals in most of the cells


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)


Threshold by Cell Energy

Level 2 Trigger RoI seen from inside of the detector

Threshold at 50 MeV (LArg detector)


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)


Identifying Problems – Level 2 RoI

last cells (high eta) with wrong values

wrong cell information

after fix the problem

before fix the problem


Conclusion to do list
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.