
Nonradiative 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 singleXtal 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:

