New g2 Calorimeters

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New g-2 Calorimeters

• GEANT4 Simulations

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Calorimeter Segmentation
4cm
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Structure of BlocksDecisions

• Depth of block
• W/SciFi ratio
• Number of layers
• Close packing
• Harder to construct
• Better resolution

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Energy Resolution and Statistical Error

• Simulated data
• Inserted energy resolution
• 2 GeV cut
• Fit 5 parameter function
• 10 in resolution means 20 more run time

Error on vs Energy Resolution
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GEANT 4 Calorimeter

• Recently completed
• Layers of Tungsten and SciFi (and glue)
• Input electrons from old g2GEANT
• Parameters
• Number of Layers
• Fiber Diameter
• Depth of Block
• 10000 events/hr

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Output Data

• Initial Position
• Initial Momentum/Energy
• Total energy deposited in calorimeter
• Energy deposited in the fibers of each block
• Output as text file, converted to ROOT ntuple

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Determining Energy Resolution

• Calibrate to convert fiber energy to total
• Plot Energy (MeasuredActual)/Actual

• Use hits in detector center
• Mean of is offset in calibration
• RMS is fractional energy resolution

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Resolution vs Energy
20 Layers 0.8mm Fibers 1.2mm Tungsten
Expected
GeV
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More Layers, Same W/SciFi
40 Layers 0.4mm Fibers 0.6mm Tungsten Same W/SciFi
Better resolution but still wrong energy
dependence
GeV
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Larger Proportion of Fiber
20 Layers 1.2mm Fibers 0.8mm Tungsten
Again Better resolution, wrong energy dependence
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Whats the Problem?

• Depth of Calorimeter 15cm (Artificially high)
• Fiber geometry
• GEANT shower parameters

Variation in resolution vs angle for 2GeV Beam
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Number of Blocks Hit
of Hits gt 200 MeV
of Hits gt 20 MeV
Hit
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Number Hit vs Electron Energy
of Hits gt 200 MeV
of Hits gt 20 MeV
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To Do

• Get GEANT4 running on more machines
• Make parameters adjustable, not hard coded.
• Questions
• Why does the resolution have the wrong energy
  dependence?
• Is the close packing scheme significantly better
  than fiber strips?
• What block depth and W/SciFi ratio should we use?
• At what level can we separate pileup events?
• What is the best layout of blocks?