"The Hadron Program at COMPASS"

"The physics of bound systems of strongly interacting particles is studied at the
COMPASS experiment using high energy pion, kaon and proton beams impinging on liquid
hydrogen as well as different nuclear targets. At small momentum scales the hadron
spectrum is governed by the spontaneously-broken chrial symmetry of QCD and the dynamics
of the resulting goldstone bosons, the pions and kaons. Using large-Z nuclei as sources
of quasi-real photons in Primakoff-kinematics basic quantities such as the pion and kaon
polarizabilities, for which solid theoretical predictions from chiral dynamics exist,
can be studied. A first-of-its kind study at COMPASS has recently shown that also the
production of multi-body final states like $\pi^-\pi^+\pi^-$ at low pion-momenta is
governed by chiral dynamics. Diffractive hadron scattering provides a source of the
spectrum of excited mesonic states which is still poorly understood theoretically. The
topics that are being studied with the large data sets collected at COMPASS range from
the search for glueballs and hybrid mesons, the study of diffractive production
mechanisms to the exploration of larger symmetries in the meson spectrum. This talk will
give an overview of the hadron program at COMPASS and present recent results."