Hadron Physics at COMPASS
Dr. Boris Grube (CERN)

COMPASS is a multi-purpose fixed-target experiment at the CERN Super Proton Synchrotron aimed at studying the structure and spectrum of hadrons using high-intensity muon and hadron beams with energies ranging from 160 to 190 GeV.

One main goal is the search for new hadronic states, in particular hybrid mesons and glueballs. Its large acceptance, high resolution, and high-rate capability make the COMPASS experiment an excellent device to study the spectrum of light-quark mesons in diffractive and central production up to masses of about 2.5 GeV. COMPASS is able to measure final states with charged as well as neutral particles, so that resonances can be studied in different reactions and decay channels.

During 2008 and 2009 COMPASS took a large data sample using negative and positive hadron beams on various targets. The presented overview of the first results from this data set focuses in particular on the search for spin-exotic mesons in diffractively produced final states and the analysis of central-production reactions in order to study glueballs in the scalar sector.

On heavy nuclear targets COMPASS also measures pion-photon processes via the Primakoff effect which is isolated by the identification of very small momentum transfers to the target nuclei. These reactions allow to study chiral dynamics in various final states. Results for the polarizability of the pion and a first measurement of the three-pion production cross section in pion-photon collisions will be presented.