  Polarization and spin effects are useful for probing the Standard Model, in
both the electroweak sector and the strong sector, where the spin decomposition
of the nucleon is still a hot topic, with important new data on the net
polarizations of the gluon and the strange quarks. Spin phenomena are also
useful in searches for new physics, for example via measurements of the
anomalous magnetic moment of the muon and searches for electric dipole moments.
The cross sections for the direct detection of dark matter may also have an
important spin-dependent component, related to the spin decomposition of the
nucleon, that could be an important diagnostic tool. Polarization effects are
also important diagnostic aids for high-energy experiments at electron-proton,
proton-proton and electron-positron colliders.
