Optimization of layer composition for ILD ECAL

International Large Detector (ILD) adopts Particle Flow Algorithm (PFA) for precise measurement of multiple jets. The electromagnetic calorimeter (ECAL) of ILD has two candidates sensor technologies for PFA, which are pixelized silicon sensors and scintillator-strips with silicon photomultipliers. Pixelized silicon sensors have higher granularity for PFA, however they have an issue of cost reduction. In contrast, scintillator-strips have an advantage of relatively low cost and a disadvantage of degradation of position resolution by ghost hits, which are generated by orthogonal arrangement. Hybrid ECAL using both candidates is proposed to supplement these disadvantages. In this paper, we report an optimization study of the hybrid ECAL using detector simulation.