Performance of the COMPASS II shashlyk calorimeter ECAL0 read out by SiPMs

Abstract The matrix of 3  ×  3 modules of the EM calorimeter ECAL0 (COMPASS II) read out by MPPC S12572-010P SiPMs with the pixel density of 10 4  mm −2 and an area of 3  ×  3 mm 2 is studied in the range of electron energies 1–30 GeV. It is observed that the MPPC has additional response nonlinearity and a significantly smaller dynamic range of output signals than expected. The influence of parasitic capacitance between pixels on the pixel gain is discussed and proposed as explanation. The energy resolution of the calorimeter is measured to be σ E ∕ E = 7 . 1 % ( 1 + 0 . 06 ∕ E ) ∕ E ⨁ 1 . 4 % E 0 . 25 , where electron energy E is given in GeV.