  CMS experiment is using Geant4 for Monte-Carlo simulation of the detector
setup. Validation of physics processes describing hadronic showers is a major
concern in view of getting a proper description of jets and missing energy for
signal and background events. This is done by carrying out an extensive studies
with test beam using the prototypes or real detector modules of the CMS
calorimeter. These data are matched with Geant4 predictions. Tuning of the
Geant4 models is carried out and steps to be used in reproducing detector
signals are defined in view of measurements of energy response, energy
resolution, transverse and longitudinal shower profiles for a variety of hadron
beams over a broad energy spectrum between 2 to 300 GeV/c.
