Fast Simulation of the Dirc with Pravda

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Fast Simulation of the Dirc with Pravda

• Rolf Andreassen / B. Meadows
• University of Cincinnati

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Outline

• Dirc Photon Ring Dictionary
• Some performance Plots
• Adaptability
• Summary

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What Do We Simulate?

• The Dirc must provide PID information.
• This means (?, ?, N?) for each track.
• These quantities can be combined into a
  probability
• where
• lt?gt is expected Cherenkov angle (depends on
  particle hypothesis, of course) and
• ? is the expected number of photons.
• ? is the hardest quantity to simulate!

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Dirc Ring Dictionary

• This was invented to provide the efficiency for
  photons to be detected and reconstructed given
  (p,?,?) at entry to bar.

• Why is this important?
• Without this, the Dirc efficiency shows dips in
  efficiency just above the Cherenkov thresholds.
• Measurement of number of photons N? is important
  in these regions

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Value Added by Ring Dictionary?

• Full Geant4 simulation used
• Tracks swum out to Dirc
• Photons generated during swim through bar
  (multiple scattering)
• Photons tracked through bar and H2O stand-off box
  (SOB) to PMTs

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Value Added by Ring Dictionary?

• Event fully reconstructed using BaBar code
• Effect of event environment is included.
• ? of reconstructed photons

? cos?/sin2?
? (radians)
? (degrees)
Tabulated by azimuth ?, dip ? at bar and
Cherenkov ?.
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Performance First Look
10,000 B0 ? ??- and recoil
Momentum (GeV/c)
Cos ?
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Performance First Look
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Performance First Look
Average Photons
Cos ?
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Performance First Look
Average Photons
Cos ?
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Performance First Look
Photons
Azimuth ? (radians)
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Performance First Look
Cherenkov Angle (radians)
Momentum p (GeV/c)
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Performance

• Rolfs plots here

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Adapt to Different Dirc ?

• Change ? detector
• If no change in time resolution, can simply scale
  ? using new QE
• In general, event environment in new time window
  will differ significantly

Probably need to make ring dictionary using (NEW)
full Geant4.
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Summary

• We have a simulation that is fast and (with work)
  somewhat realistic.
• Experience in physics studies is still required
• A few questions in implementation remain.
• It works with the present Dirc (with H2O SOB and
  PMTs)
• Upgrade in Dirc readout will require a new, full
  Geant4 production of new ring dictionary.