Summary of ECAL discussions:
- In previous discussions it has been agreed that the inner radius of the ECAL should be ~1500mm. This fact alone results a significant cost reduction with respect to the ILD ECAL which starts at ~1800mm.
- The ILC detector concepts assume 30 ECAL layers, where the Silicon Tungsten option is considered the baseline. The optimal cell size was found to be 5x5 mm^2.
- Reducing the number of ECAL layers results in a moderate increase of the sampling term in the photon energy resolution. The photon energy resolution is not a major physics driver. Similarly the electron energy resolution is purely based on the track momentum resolution for low energy electrons, while high energy electron reconstruction is not driven by the sampling term of the energy resolution. It has been decided that the penalty for reducing the baseline design to 25 layers is acceptable. The number of layers for the two ECAL sections should be scaled accordingly.
- The jet energy resolution is not driven by the lateral segmentation of the ECAL. The impact needs be studied in hadronic Tau decays. The baseline remains 5x5 mm^2 cell sizes.
- Using thin scintillators as active layers remains an option but more the cost implications need to be better understood.