Cherenkov light detection by PPDs
In order to improve hadron energy measurement, we are investigating to utilize active absorber in the sampling hadron calorimeter. The active absorber consists of heavy transparent material such as Lead Glass and thin photo-sensors attached to form sampling calorimeter. The detection of Cherenkov lights needs to overcome the low light yield and to have enough sensitivity for short wave length region. We discuss our current study and further improvements at the conference.