Development of Digital Hadron Calorimeter Using GEM

1. Development of Digital Hadron Calorimeter Using GEM Simulation of GEM using available software

2. Computer Simulation • My M Sc thesis is the discharge characteristics of GEM hadronic calorimeter. UTA is currently in the process of designing and building a GEM calorimeter. It is going to take sometime before the design process is over and the detector is built for testing but before we go to the stage of firing the interesting events in the detector we need to do computer simulation of the detector to make interesting predictions about the actual detector.

3. Introduction of GEM • The gas electron multiplier (GEM) consists of a thin, metal-clad polymer foil, chemically pierced by a high density of holes. • On application of a difference of potential between the two electrodes, electrons released by radiation in the gas on one side of the structure drift into the holes, multiply and transfer to a collection regions. • The multiplier can be used as detector on its own , or as a preamplifier in a multiple structure; in this case, it permits to reach large overall gains (104 with spark probabilities per incident pion less than 10-10) in harsh radiation environment. • Fast response (40ns drift time for 3mm gap with ArCO2) • Relatively low voltage (A few 100V compared to 10-16KV for Resistive Plate Chamber) • Reasonable cost (Foils are basically copper-clad kapton - $400 for a specially prepared framed 10cm by 10cm)

5. Computer Simulation • Before I can start work on GEM I needed to learn how to run the software used for Linear Collider Physics. • For that I had to start first with the default geometry and then learn how to incorporate the GEM geometry and material information. • Before I start with complicated events I need to understand events of a single particle. • So I started with 1000 events using pions.

6. Software used in the simulation • Detector simulation involve • Event generation • Detector simulation of the event • Reconstruction • Analysis • Software used for event generation is Pandora_Pythia version 3.2. PANDORA_PYTHIA interfaces the PANDORA Monte Carlo to the Pythia version 6.1 program. Pythia is used to simulate gluon showering and fragmentation of final-state quarks. To decay tau leptons, TAUOLA is used with including the polarization effects. Events are output in STDHEP format. • Software used for Detector simulation is Mokka and the default detector is TDR TESLA Design Report. ….. • For Analysis I am using ROOT, a program developed by CERN.

7. Mokka Detector Simulation • Mokka is Geant4 full simulation for the TESLA detector calorimeter. • Mokka has been used extensively for the TESLA T.D.R calorimeter energy flow studies. • Advantage of Mokka is that we can add sub detector of our design and replace Mokka’s default Hcal and that is going to be our next stage. This is the stage on which my colleague Venkat is working.

8. TESLA TDR

9. 1000 Events generated • I generated 1000 events using Mokka particle gun command. Mokka produced 1000 hits file for ecal and 1000 hits files for Mokka. I also got kinematics information on primary particles. • Incident particle had 5,10,20,50 and 100 GeV energies. I developed a program to read total energies deposited per event so for each incident energy I got 1000 entries and then I plotted 5 graphs for ecal section of the detector and 5 for Hcal. • Then I plotted the Mean Energy I got from each graph against the incident energy and got a straight line, the slope of which gives me resolution of the detector.