The COMPASS experiment

The Common Muon and Proton Apparatus for Structure and Spectroscopy (COMPASS) experiment is a multipurpose experiment getting beam from CERN’s Super Proton Synchrotron (SPS). The experiment looks at the complex ways in which the elementary quarks and gluons work together: from the proton to a huge variety of more exotic particles. The aim is to study the internal structure of protons and neutrons and to discover more about how the property called spin arises in them, in particular how much is contributed by the motion of quarks or by the gluons that bind the quarks together. To do this the COMPASS team fires muons (particles that are like heavy electrons) and particles called pions at a polarized target.