  CERN COMPASS can investigate pion-photon interactions, to achieve a unique
Primakoff Coulomb physics program, centered on pion polarizability and hybrid
meson structure studies. COMPASS uses 100-280 GeV beams (muon, pion) and a
virtual photon target, and magnetic spectrometers and calorimeters to measure
the complete kinematics of pion-photon reactions. The COMPASS experiment is
scheduled to begin data runs in 2001. Pion polarizabilities and hybrid mesons
can be studied via the Primakoff reactions pion + gamma ---> pion + gamma and
pion + gamma ---> Hybrid. The electric (alpha) and magnetic (beta) pion and
Kaon polarizabilities characterize their deformation in an electromagnetic
field, as occurs during gamma-pion Compton scattering. They depend on the
rigidity of their internal structures as composite particles, and are therefore
important quantities to test the validity of theoretical models. The
polarizability measurement will provide an important new test of QCD chiral
dynamics. The studies of quark-antiquark-gluon hybrid mesons would improve our
understanding of these exotic mesons. COMPASS may improve previous Primakoff
polarizability and Hybrid studies by two to three orders of magnitude.
  Appendixes A (Pion and Kaon Polarizabilities at COMPASS) and B (Hybrid Meson
Structure at COMPASS) of this contribution include evaluations submitted to the
APS DNP Town Meeting White Paper Committee. These summarize (1) the fundamental
scientific issues addressed, (2) major achievements since the last DNP long
range plan, (3) the short and long term U.S. outlook, (4) comparison of U.S.
and global effort, (5) other issues.
