  A Shashlyk calorimeter prototype for the KOPIO experiment has been
constructed and experimentally tested. The energy resolution of about
4%/sqrt(E(GeV)) for 0.5-2.0 GeV/c positrons was obtained. Based on this results
as well as on the results of special measurements, a Monte-Carlo model of the
Shashlyk module response was developed. This model, including the effects of
shower evolution, light collection in scintillator plates, light attenuation in
fibers, quantum efficiency of the photodetector, thresholds and noises in the
readout system is consistent with experimental results. Possible improvment of
the Shashlyk energy resolution up to 3%/sqrt(E(GeV)), the level required by
KOPIO experiment, are discussed.
