May 29, 2007 Calorimetry

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May 29, 2007, Calorimetry meeting, 1:00 PM EDT

Low Energy ReSAM

'Low Energy MC SF Resolution'
'Low Energy MC SF Resolution vs Theta'

Time Difference Resolution

'7 only'
'8 only'
'9 only'
'7 and 8'
'7,8,9 and 10'

Time Average Resolution

'w/ tagger reference'
'w/ t7 reference'

  • AOB

Dial-In Information


Present: Simon, David, Eugene, Elke, Elton, Richard, Alex, Zisis, Blake, George

  • Alex began by presenting results from his analysis of shower depth in the BCAL.
    • He showed fractional energy deposited in a layer as a function of incident beam energy as described in BCAL_res_cal.pdf above. He then took the integrated parametrization for longitudinal energy deposition in the PDG and adjusted the BCAL calibration to match. It should be noted that the PDG parametrization is derived from data > 1 GeV. The gross features match, but there are clear discrepancies for incident photons below 300 MeV.
    • He then compared similar data for the beam incident at a 40 degree angle with what one might expect from lengthening the layer thickness by 1 / sin 40. Agreement here is not so good, but it was noted that the transverse development of the shower now becomes relevant.
    • Action Item: Have Blake produce MC predicted energy depositions as a function of layer. These will likely be much better than the PDG expression and can then be used to calibrate the data in the same fashion.
    • Action Item: Analyze lower level data to look for possible electronics issues, non-linearity, pedestal problems, etc., that may lead to problems at low energy. (Note that Alex circulated some raw ADC spectra -- the plots can be found here.)
  • Blake presented plots of both the sampling fraction and sampling fraction error as a a function of energy for photons normal to the BCAL (shown above). Interesting variations of the sampling fraction as a function of incident photon energy are observed. Blake also showed variation of sampling fraction as a function of angle.
    • Action Item: In order to better understand what fraction of shower leaks out of the module it was suggested that Blake generate plots with both E_fiber / E_incident and E_fiber / E_BCAL, where E_fiber(BCAL) is the energy deposited in the fibers (BCAL).
    • Action Item: Examine the shape of the sampling fraction distribution for low energy events. Is a Gaussian parametrization sufficient?
    • Action Item: Examine how the sampling fraction varies between layers or readout cells for showers of a fixed incident energy.
  • Blake's results on sampling fraction and sampling fraction error can already start to be incorporated into the GEANT simulation. Zisis, Richard, et al will work offline to start to make these changes.
  • Matt reminded people to try to send messages to the halld-cal list so that there is at least searchable archive generated of calorimetry related messages.
  • Alex also noted the need for a "report card" to evaluate progress towards the July goals. Matt will set this up on the Wiki.