LSoft hadronic interactions in the COMPASS experiment

The COMPASS experiment at the CERN SPS complex is planning for the year 2004 its first run with a hadron beam. Two physics subjects will be addressed: the study of pion polarizabilities by means of the Primakoff scattering, and the study of diffractively producedηπ ^?-systems. The analysis of η-meson production is related to the search of hybrid mesons, of which no conclusive evidence exists so far.The concept of the Primakoff and diffractive trigger systems and the proposed modifications to the COMPASS muon setup are described in detail. The estimate of event rates for the two measurements shows that COMPASS can provide a statistical accuracy significantly higher than existing data from other experiments.