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• We can use the model of CsI scintillation to predict the light yield for particles of different mass and charge and thus account for antiquenching effect for electromagnetic showers
  • Recently Eric Grove found a paper published in 2001, which confirms and explains the difference in light yield produced in CsI crystals by electrons and alphas similar to the "antiquenching" effect seen in our test in GSI (2003 & 2006) and on-orbit:
    • Dependence of Scintillation Characteristics in the CsI(Tl) Crystal on Tl Concentrations Under Electron and Alpha Particles Excitations
  •  This paper gives rather comprehensive model of CsI scintillation mechanism, which could be used to predict the light yield for particles of different charge, mass and energy
  • We plan to implement this model and try to tune the parameters (mainly doppant concentration and scintillation time constants for different mechanisms) to fit simultaineously GSI 2003 data at 1.0 and 1.7 GeV/nucleon, GANIL data at low energies and on-orbit data (> 4 GeV/nucleon with known spectrum)
  • Once model parameters are defined, it can be used to predict the "antiquenching" effect for electromagnetic showers and see if  it could explain the data/MC discrepancy seen in 2006 Beam Test. 
  • In the NIM paper presenting the results of  2003 GSI beam test the conclusion was made that there are no signs of quenching/antiquenching effect for showers
  • but this conclusion was based on the results of 2002-2003 CERN beam test, where energy depositions per crystal were mostly above 1 GeV, while the non-linear behaviour of data/MC ratio in 2006 Beam Test was noticed mainly in the energy range 100-1000 MeV per crystal
  • the energy calibration in 2002-2003 beam tests was based on 50 GeV muons from the beam lines, which could be affected by antiquenching effect because of relativistic rise in ionization density. 
    • that could explain that while both muons and showers are affected by antiquenching effect, their ratio is unchanged
    Another effect which can contribut to light yield of CsI crystals to the relativistic particles is Cherenkov light emitted by the nock-on electrons.
    • unchanged 
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    • in our geometry (especially for beam test at zero incident angle) the relatively low energy (but still relativistic) nock-on electrons are moving mainly perpendicular to the initial particle trajectory i.e. along the crystal, the cherenkov light direction is within the cone of full internal reflection of the crystals and light collection efficiency is high.
    • we could expect additional 2-3% increase of light depending on angle and energy.