Hycal Calibration with p0

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Hycal Calibration with p0

• Gives gains for the same runs and same intensity
  rate as for production measurements
• All parts of Hycal are exposed by p0
• Calibration on gammas
• It doesnt feel effect of Hycal misalignment or
  coordinate reconstruction systematics
• But it gives average gains for large data sample
• (at least half million of p0 are required,
  i.e. 50 good production runs on Carbon). Lead
  target runs have more forward p0s and less
  accidental and inelastic p0 s. Thus lead
  exposition needs more runs for successful p0
  calibration.
• Good LMS monitoring in conjunction with
  additional p0 calibration will give the maximum
  of resolution

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Runs which were taken first for p0 calibration
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Calibration procedure

• We used iterational calibration procedure
• (matrix inversion will give very rough results,
  since there is a background in our two gamma
  invariant mass distributions).

• 3-4 iterations gave reasonable results
• Final results (no more further improvement)
  appeared after 10 iterations
• PWO-only mass and elasticity distributions in
  conjunction gives Z of the target with the best
  fit of both distributions mean values (mass
  distribution to 0.134977 GeV and elasticity to
  1.0). The same result is given by the mass
  distribution after the elasticity fit.
• Z of target which gives the best fit is 731.3cm
  for PWO only part. Lead glass part of Hycal
  pointing to greater (cm) values of this
  parameter.

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p0 mass before/after calibration (PWO part of
Hycal)
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p0 mass before/after calibration (PWO Lead
Glass)
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p0 mass before/after calibration (Lead Glass
part of Hycal)
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p0 mass after calibration (elasticity fit is
applied)
PWO only
PWO Lead Glass
Lead Glass only
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Obtained results for resolutionusing double
gaussian fit of mass distributions
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Summary

• Calibration gives Hycal energy resolution
  improvement by factor of 1.2 Significant
  systematic p0 mass shift for LG part is fixed.
  Both these factors must reduce systematics of p0
  Signal / Background separation in analysis.
• Mass resolution after elasticity fit is mostly
  defined by Hycal coordinate resolution and it is
  twice more narrow. Thus original mass resolution
  is mostly defined by the energy reconstruction
  fluctuations.
• This work is in progress not all run regions are
  covered yet need reliable LMS gains to finalize
  this work may be needs additional database entry
  (like Compton gains already have)