  We explore the complete cross-section for the production of unpolarized
hadrons in semi-inclusive deep-inelastic scattering up to power-suppressed
$\mathcal{O}(1/Q^2)$ terms in the Wandzura-Wilczek-type (WW-type)
approximation, which consists in systematically assuming that
$\bar{q}gq$-correlators are much smaller than $\bar{q}q$-correlators. Under the
applicability of WW-type approximations, certain relations among transverse
momentum dependent parton distribution functions (TMDs) and fragmentation
functions (FFs) occur which are used to approximate SIDIS cross-section in
terms of a smaller subset of TMDs and FFs. We discuss the applicability of the
WW-type approximations on the basis of available data.

High Energy Physics - Phenomenology