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 Inner Detector Muon Chambers Eletromagnetic Calorimeter Hadronic Calorimeter 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.

4 ATLAS Calorimeter System Inner detector Electromagnetic Calorimeter Hadronic Calorimeter Electromagnetic - LArg  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.

5 Calorimeter Segmentation  100,000 readout channels.  Four layers. Electromagnetic Hadronic  64 Modules in φ coordinate.  Two readout channels by cell.  10,000 readout channels.  Three layers.

6 Trigger System Level 1 Trigger Level 2 Trigger Event Filter 1 GHz 100 kHz 1 kHz 100 Hz Region of Interest (RoI) (Region with signal information) RoI algorithm was checked with this visualization tool (simulated data)

7 Commissioning with cosmic muons dicriminatorlogic OR dicriminatorlogic OR Logic AND coincidence board  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. trigger Trigger tower

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

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 ViewerGraphic User Interface (GUI) Example of a Level 2 Trigger RoI visualization

12 Features green palette - Eletromagnetichot palette - Hadronic log scale Example of cosmic event reconstruction (real data)

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 Low threshold in the Eletromagnetic Calorimeter (all cells are showed) buttom to force same threshold activated cells

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 Threshold at 2 GeV (only activated cells are showed) energy of some activated cells

18 Identifying Problems – Level 2 RoI wrong cell information before fix the problem after fix the problem last cells (high eta) with wrong values

19 Conclusion & To do list Easy way to go through the events and check for problems. Needs only Root (v ). 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.