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Non-radiative Bhabha Calibration in the EMC


Calibration - find relation between detector signal and stimulus

Why Bhabhas ?

  • well known reaction
  • well known topology -> easy to select
  • high rate
algorithm:
  • do a full Emc reconstruction
  • select events
  • minimize the following:( BaBar note 363
  • This yields a linear matrix equation that can be solved numerically.

    The deposited Xtal energy needs to be extracted from MC.

    The result are single-Xtal calibration constants for all Xtals that convert the raw energy of a Xtal into the deposited energy of the Xtal. The sum over these Xtal energies of a cluster gives the deposited cluster energy of the particle. In addition corrections need to be made to take into account front, rear and side leakage. This will be done for the complete shower and is a function of the point, direction, type and energy of the incident particle. The final result will be the shower energy of the particle.

precision and frequency of calibration:
  • The statistical precsision reached by now is 0.35%.
  • To reach this goal we need about 200 direct hits per crystal what means about 12 hours of data taking.
selection: Results:
  • A list with links to plots of the calibration constants can be found here. It shows also the results on energy resolution.
Software:
  • algorithm is implemented (package EmcCalBhabha)
  • extraction of the MC deposited cluster energies is automated (with ROOT classes - package EmcCalRoot and macros)
  • will run in OPR
  • constants are saved in conditions database - classes - description
  • intermediate accumulated data (matrix) is saved using the spatial and temporal databases (spatial db - one db per node of the OEP farm, temporal db - collects all the data from the spatial databases and merges them)
  • Software documentation
MC results: papers, talks:


Heiko Jasper
Last modified: