  Ahigh-granularity scintillator calorimeter readout with silicon
photomultipliers (SiPMs) is an electromagnetic calorimeter (ECAL) candidate for
experiments at the Circular Electron Positron Collider (CEPC). A critical
design parameter of this ECAL candidate is the dynamic range of the SiPMs. This
study investigates the SiPM dynamic range required for the CEPC scintillator
ECAL. A model is developed on the basis of the operation principles of SiPMs to
describe the response of an SiPM to light pulses within one recovery period by
considering the cross-talk effect, photon detection efficiency, and number of
pixels. The response curve of a 10000-pixel SiPM predicted by the model is
consistent with the measured curve within 2% for an incident light pulse of up
to 12000 photons. The intrinsic fluctuations of the SiPM response naturally
exist in this model, and the correction of the saturation effect in the SiPM
response is investigated. Monte Carlo (MC) simulation shows that the algorithm
can restore the response linearity of an SiPM for an incident light pulse in
which the number of photons is up to around six times the number of SiPM
pixels. The model and correction program are implemented for full simulation of
the ZH production Z->vv, H->yy channel to evaluate the impact of the SiPM
dynamic range of the CEPC scintillator ECAL on the reconstructed Higgs boson
mass and the sensitivity to the Higgs signal in this channel. The results show
that the CEPC scintillator ECAL equipped with no less than 4000 SiPM pixels and
operated with a light yield of 20 photon-electrons per channel for a single
minimum ionizing particle can meet the requirements for Higgs boson precision
measurement in the di-photon channel at the CEPC.
