1. EXAMINATION OF CORRUPTED DATA IN THE TILE CALORIMETER Stephanie Hamilton Michigan State University The ATLAS Collaboration Supervisor: Irene Vichou (U of IL at Urbana-Champaign)

2. Overview Introduction and Project Overview Summer Progress Plots Conclusions Future Work Thanks 9 August 2012 2

3. ATLAS – A Toroidal LHC ApparatuS One of two “general search” detectors at CERN Antimatter, Higgs boson, Extra Dimensions, SUSY…many more Composed of the inner detector, electromagnetic calorimeter, hadronic calorimeter, muon system Hadronic calorimeter a.k.a. “Tile Calorimeter” 9 August 2012 3

4. Tile Calorimeter (I) 9 August 2012 4 Total length ~12m, weight 2900 tons Hadronic sampling calorimeter made of steel plates (absorber) and plastic scintillator (active material) Divided in 4 read-out partitions (1 long barrel, 2x extended barrel), joint coverage |eta|<1.7

5. Tile Calorimeter (II) Structure & principles: Each partition consists of 64 module wedges Scintillator light from tiles collected by WLS fibers and delivered to PMTs Cells defined by grouping the fibers onto 1 PMT 9 August 2012 5 Readout cell granularity: Three radial layers (A, BC, D) Δφ x Δη = 0.1x0.1, each cell readout by 2 PMTs (except of special cells)

6. Reconstruction of Events in TileCal Digital readout path: Pulse shaping -> sampled every 25 ns -> to local memory (2.5 ms latency) Two gains to cover the required dynamic range High Gain (HG): up to ~12GeV Low Gain (LG): ~12GeV – 800GeV Energy is reconstructed in RODs 9 August 2012 6 Scintillator Tiles PMT LG ADC Digitizer HG ADC Digitizer Readout Driver (ROD) Local Memory FE Electronics BE Electronics 3-in-1 card: Shaper, integrator, divider

7. Project Overview Dividing pulses into 3 basic categories: Goal: Test in standard data integrity filters and new tests for cell energy, time reconstruction Find discriminating factors to detect failure of front end (FE) electronics – currently pass through all standard data quality tests Effects Prevent corrupted data leaks into good quality data = less headaches for everyone! 9 August 2012 7 Normal Failure of Front End Electronics Out-of-time Pileup.....................

8. Summer Progress Developed macro for plotting histograms with one test ntuple Created several plots for basic variables Time v. Energy, χ 2 χ 2 v. Energy ADC Counts with cuts on various energies Several plots when one sample is exactly zero Created several plots for possible discriminating factors Ediff v. eta, phi, quality factor, energy Timediff v. eta, phi, quality factor, time Beginning investigation for high v. low gain 9 August 2012 8

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12. Conclusions Preliminary work – creating plots to see relationships between different variables Creating a starting point Most plots seem normal There are a few suspicious spots This work will carry through this year 9 August 2012 12

13. Future Work? Find a way to detect FE electronics failures Implement discriminating factors in all data sets to identify failures If we know the cause of the corruption, we can remove the events from consideration Next Steps: Investigate the “suspicious” areas in the plots Continue search for further discriminating factors Investigate further the fit quality of signal reconstruction Modify code to yield energy/time by channel, implement cuts on energy 9 August 2012 13

14. What I Learned How to more efficiently use ROOT How to more efficiently use C++ The process behind reconstructing events in the detector and with electronics How the data-taking process works 9 August 2012 14

15. Thanks First, thank you to the coordinators of the University of Michigan REU at CERN (Dr. Steven Goldfarb, Dr. Homer Neal, Dr. Jean Krisch, and Dr. Junjie Zhu) and to the NSF for giving me such an incredible opportunity. Second, thank you to Irene Vichou and Giorgi Arabidze for giving me the instruction and guidance needed to complete my project and for assisting me when I was stuck. Third, thank you to Ana Henriquez and the TileCal group for allowing me to work with the performance data taken by the Tile Calorimeter. Thank you to Sanya Solodkov for allowing me to use the ROOT files he produced. Lastly, thank you to CERN and the ATLAS Collaboration for allowing me to come to this laboratory and use the data taken by ATLAS, provided by the LHC. 9 August 2012 15

16. Paris Zermatt Bern Travels! 9 August 2012 16 Rome Barcelona Hiking in the Jura Geneva At CERN