出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：The physics program of the COMPASS experiment at CERN focuses on the investigation of the
hadron structure and spectroscopy, using both leptonic and hadronic probes. The COMPASS
experiment has collected so far mostly data with polarized muon beams of 160 GeV, but also a
pilot data taking with negative hadron beams of 190 GeV has been successfully completed at the
end of the 2004 run.
The main physics objectives of this pilot run are the study of soft pion-nuclei interactions. The
predictions of the Chiral Perturbation Theory for the electric and magnetic polarizabilities of the
pion will be verified through the study of the Primakoff scattering of 190 GeV pions on thin lead
targets. A sample corresponding to an integrated beam flux of more than 1011 pions has been
collected for this purpose, and an equivalent sample with the muon beam of 190 GeV has been
collected in the same experimental conditions to correct possible systematic effects.
In parallel to the polarizability measurements, first data have also been collected for the study
of the diffractive production of exotic non-qq states. Such states, although predicted by QCD,
still require a confirmation from the experimental side. This measurements are part of a wider
research program, which includes the study of gluon-rich states produced in central proton-proton
collisions, that will be addressed by the COMPASS experiment in the forthcoming years.
The performances of the apparatus during the pilot COMPASS run with hadron beams will be
presented, and the preliminary results of the analysis of the collected data will be discussed. The
future perspectives of the proposed measurements will also be briefly outlined.
