UTA GEM DHCAL SIM

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UTA GEM DHCAL SIM

• J. Yu
• Univ. of Texas at Arlington
• Nov. 7 - 9, 2002
• NIU/NICADD

• Introduction
• Digital Hadron Calorimeter Requirements
• GEM in the sensitive gap
• UTA GEM DHCAL Prototype Status
• Simulation Status
• Summary

(On behalf of the UTA team A. Brandt, K. De, S.
Habib, V. Kaushik, J. Li, M. Sosebee, A. White)
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Introduction

• LC physics topics
• Distinguish W from Z in two jet final states ?
  Good jet mass resolution
• Higher Jet energy resolution
• Excellent jet angular resolution
• Energy flow algorithm is one of the solutions
• Replace charged track energy with momentum
  measured in the tracking system
• Requires efficient removal of associated energy
  cluster ? Good position resolution
• Higher calorimeter granularity
• Use calorimeter only for neutral particle
  energies
• Best known method for jet energy resolution
  improvement
• Large number of readout channel will drive up the
  cost for analogue style energy measurement ?
  Digital HCAL
• Tracking calorimeter with high gain sensitive gap

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Goals for UTA DHCAL Development

• Develop digital hadron calorimetry for use with
  EFA
• Aim for cost effectiveness and high granularity
• Look for a good tracking device for the sensitive
  gap
• Develop GEM cell(s) and prototype
• Develop module/stack design for EFA optimization
• Simulate GEM behavior in calorimeter
• Implement GEM readout structure into simulation
• Develop EF and calorimeter tracking algorithms
• Cost effective, large scale GEM DHCAL

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Why GEM?

• GEM developed by F. Sauli (CERN) for use as
  pre-amplification stage for MSGCs
• Allow flexible and geometrical design, using
  printed circuit readout ? Can be as fine a
  readout as GEM tracking chamber!!
• High gains, above 104,with spark probabilities
  per incident ? less than 10-10
• Fast response
• 40ns drift time for 3mm gap with ArCO2
• Relatively low HV
• A few 100V per each GEM gap compared to 10-16kV
  for RPC
• Rather reasonable cost
• Foils are basically copper-clad kapton
• 400 for a specially prepared and framed
  10cmx10cm foil

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CERN-open-2000-344, A. Sharma
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GEM gains
CERN GDD group
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Double GEM DHCAL Design
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Double GEM test chamber

• Sufficient space for foil manipulation
• Readout feed-through, retaining large space for
  ease of connection
• Clear cover to allow easy monitoring
• Readout pads connection at the top

2cmx2cm pad design
J. Li, UTA
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UTA GEM Test Chamber HV layout
Drift gap
HV fed from one supply but individually adjusted
? Good to prevent HV damage on the foils
2.1kV
Transfer gap
Induction gap
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UTA GEM Prototype Status

• Readout circuit board (2cmx2cm pads) constructed
• HV Connection implemented
• Two GEM foils in the UTA Nano fabrication
  facility cleanroom
• Preamp in hand and characterization completed
  (LeCroy HQV800)

Amplification factor of 300 for 5xGEM size signal
(LeCroy HQV800 )
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Want to know how GEM Foils look like?
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Single GEM gain/discharge probability

• Simulation study in progress using single pions
  before multi-jets
• Determine Maximum total charge deposit in a cell
  of various sizes and gains
• Study fake signal from spiraling charged particle
  in the gap

A.Bressan et al, NIM A424, 321 (1998)
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UTA Simulation Status

• Two masters students have been working on this
  project
• Pandora-Phythia implementation and HEPEvt ASCII
  output in place
• Mokka successfully installed
• Mokka Geometry database downloaded and installed
  at UTA
• Completed single pion studies using default
  geometry
• Reproduced expected response
• Energy resolution seems to be reasonable also
• Preliminary mixture GEM geometry implemented
• Single pion study with mixture GEM begun
• Root macro and JAS based analysis packages
  developed
• Proceed with more detailed GEM geometry
  implementation

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Single Pion Studies w/ Default TESLA Geometry

• Single pion events using Mokka particle gun
  command.
• Incident energy range 5 200GeV
• kinematics information on primary particles in
  the files
• Developed an analysis program to read total
  energies deposited per pion for each incident
  energy.
• Mean Energy vs Incident pion energies
• Energy conversion from the slope of the straight
  line
• Conversion factor is 3.47 and agrees with the
  computed sampling fraction

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TESLA TDR Geometry

• Ecal Electromagnetic Calorimeter Material
  W/G10/Si/G10 plates (in yellow)
• 1mm W absorber plates
• 0.5 mm thick Si, embeded 2 G10 plates of 0.8 mm
  each

• Hcal Hadronic Calorimeter
• Material
• 18 mm of Fe
• 6.5 mm of Polystyrene scintillator (in green)

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TESLA TDR detector live energy deposit for single
pions
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TESLA TDR Elive vs Ep

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TESLA TDR CAL Single Pion Resolution
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GEM Simulation Status

• Mokka Geometry database downloaded and installed
  at UTA
• New Geometry driver written ? Mixture GEM
  geometry implemented ?Need to use ArCO2 only
• Single pion study begun for discharge probability
• Initial study shows that the number of electron,
  ion pair with gain of 104 will be on the order of
  107 for single 200GeV pions
• Getting pretty close to the 108 from other
  studies ? Might get worse for jets from W pairs,
  due to fluctuation
• Need more studies to compute the discharge
  probability.
• Cell energy deposit being investigated to
  determine optimal threshold based on cell energy
  ? Proceed to energy resolution studies
• Determine optimal gain using live energy deposit
  vs incident energy

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GEM Prototype Geometry
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GEM Geometry Implementation Mechanics in Mokka

• TDR / Hcal02 Model chosen for modification
• Fe-GEM sub-detector instead of the existing
  Fe-Scintillator
• New driver for the HCal02 sub-detector module
• Local database connectivity for HCal02 ? Database
  downloaded and implemented at UTA

Courtesy Paulo deFrietas
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Single Pion Cell Energy Deposit in GEM HCal
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Single pion Energy with GEM
50GeV p ELive
15GeV p EMeas
10.6MeV
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GEM Sampling Weight
Sampling 24x10-3
Statistics too low to produce reliable gaussian
fit ? This depends heavily on EM section without
proper GEM gain factor taken into account.
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Summary

• Hardware prototype making significant progress
• GEM foils delivered and are in the clean room for
  safe keeping
• Preamp and Discriminator in hands ? Preamp
  characterized
• HV System implemented
• Readout Pad implemented
• Almost ready to put GEM foils in the prototype
  box
• GEM foil mass production being looked into by 3M
  in Austin, Texas
• Simulation effort made a marked progress
• Single pion study of Mokka default TESLA TDR
  geometry complete
• Analysis tools in place and seem to work well
• The resolution seems to be reasonable
• Preliminary GEM Mixture geometry implemented
• Need to redo the response study with gain
  factored in
• Initial estimate of eIon pair seems to be at
  about 107 for 200GeV pions
• Local Geometry database implemented
• Optimal threshold for digitization and gain
  factor will come soon
• Will soon move onto realistic events, WW, ZZ, or
  tt ? jets
• Still ways to go before effective EFA and TRKA
  studies