  Nucleon transfer reactions in deuteron-deuteron collisions at energies above
the three- and four-body breakup threshold are described using exact four-body
equations for transition operators that are solved in the momentum-space
framework. Differential cross sections, analyzing powers, polarizations, and
spin transfer coefficients are obtained using realistic two-nucleon potentials
and including the Coulomb repulsion between protons. Overall good agreement
between predictions and experimental data is found. Most remarkable
discrepancies are seen around the minima of the differential cross section at
higher energies and in the outgoing nucleon polarization at lower energies.
