The gluon contribution to the nucleon spin and the COMPASS experiment at CERN

A new fixed target experiment is being constructed at CERN. It has the goal to investigate hadron structure and hadron spectroscopy by using either muon or hadron beams. From measurements of various hadron asymmetries in polarised muon-nucleon scattering for the first time it will be possible to determine the contribution of the gluons to the nucleon spin. Main objective of the hadron program is the search of exotic states, and glueballs in particular. This physics programme will be carried out with a new two-stage magnetic spectrometer, with particle identification and calorimetry in both stages, to run at the CERN SPS from the year 2000 onwards. (27 refs).