  Azimuthal asymmetries in high-energy processes, most pronounced showing up in
combination with single or double (transverse) spin asymmetries, can be
understood with the help of transverse momentum dependent (TMD) parton
distribution and fragmentation functions. These appear in correlators
containing expectation values of quark and gluon operators. TMDs allow access
to new operators as compared to collinear (transverse momentum integrated)
correlators. These operators include nontrivial process dependent Wilson lines
breaking universality for TMDs. Making an angular decomposition in the
azimuthal angle, we define a set of universal TMDs of definite rank, which
appear with process dependent gluonic pole factors in a way similar to the sign
of T-odd parton distribution functions in deep inelastic scattering or the
Drell-Yan process. In particular, we show that for a spin 1/2 quark target
there are three pretzelocity functions.
