  We consider the cross section in Fourier space, conjugate to the outgoing
hadron's transverse momentum, where convolutions of transverse momentum
dependent parton distribution functions and fragmentation functions become
simple products. Individual asymmetric terms in the cross section can be
projected out by means of a generalized set of weights involving Bessel
functions. Advantages of employing these Bessel weights are that they suppress
(divergent) contributions from high transverse momentum and that soft factors
cancel in (Bessel-) weighted asymmetries. Also, the resulting compact
expressions immediately connect to previous work on evolution equations for
transverse momentum dependent parton distribution and fragmentation functions
and to quantities accessible in lattice QCD. Bessel-weighted asymmetries are
thus model independent observables that augment the description and our
understanding of correlations of spin and momentum in nucleon structure.
