Performance of alternative scintillator tile geometry for AHCAL

Abstract: The CALICE Analogue Hadron CALorimeter (AHCAL) at the International Linear Collider (ILC) is a high-granularity hadron calorimeter based on scintillator tiles readout by MPPCs. Toward the construction of ILC, the optimization of the AHCAL granularity is revisited, and we are studying mixed granularity with larger scintillator tile. We first measured the performance of $60\times60~\mathrm{mm^2}$ tile, which is larger than the standard $30\times30~\mathrm{mm^2}$ tile. The light yield of $60\times60~\mathrm{mm^2}$ tile was measured to be about a half of that of $30\times30~\mathrm{mm^2}$ tile, while the uniformity of the tile response turned out to be very good. Then, a detection layer composed of 144 tiles of $60\times60~\mathrm{mm^2}$ was constructed. The detection layer was added to the large technological prototype of AHCAL composed of 38 detection layers with $30\times30~\mathrm{mm^2}$ tiles. The detection layer was successfully tested in test beam experiments at CERN SPS.