  Recent data from semi-inclusive deep inelastic scattering collected by the
HERMES collaboration allow for the first time to discuss how the
transverse-momentum dependence of unpolarized distribution and fragmentation
functions is affected by the flavor of the involved partons. A model built with
flavor-dependent Gaussian transverse-momentum distributions fits data better
than the same flavor-independent model. The current analysis is performed for
totally unpolarized scattering of leptons off protons and deuterons, with
detected pions in the final state. There are convincing indications of flavor
dependence in the fragmentation functions, while for parton distribution
functions the evidence is weaker.
