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  • Energy resolution: stability of energy(-related) deposition in ECAL
    • Intrinsic resolution proportional to $1/\sqrt{E}$
      • Requires enough length of passive material (e.g. tungsten)
    • Leakage contribution
    • Energy-independent contribution
  • Position resolution: Based on position reconstruction from 
    • Position-related energy resolution: 

The energy resolution based on all 20 layers is about 19.5%.

The following are the fits from which the resolution is derived (the parameter named 'a'):

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The energy resolution based on 15 layers and a reconstruction of the other 5 is about 22%.

The resolution is of course derived in the same way:

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The total energy deposited in the missing layers was estimated to be the average of the energy in the following layer and in the preceding layer.

Missing Energy

To decide between several reconstruction options, the fraction of the missing energy in the calorimeter is presented below.

It shows the percentage of energy missing when we use 15 layers alone.

The two options shown are for 15 continuous layers (0-14) or for 10 continuous layers and another 5 every other layer (0-9, 11, 13, 15, 19).

Note that for the continuous layers we do not make up for the missing layers but simply ignore them.

For the (10 * 1X_0 + 5 * 2X_0) method we multiply the energy in a layer after a missing one by factor 2.

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