  This study is part of a project to investigate the transverse momentum
dependence in parton distribution and fragmentation functions, analyzing
(semi-)inclusive high-energy processes within a proper QCD framework. We
calculate the transverse-momentum-dependent (TMD) multiplicities for $e^+e^-$
annihilation into two hadrons (considering different combinations of pions and
kaons) aiming to investigate the impact of intrinsic and radiative partonic
transverse momentum and their mixing with flavor. Different descriptions of the
non-perturbative evolution kernel are available on the market and there are 200
sets of flavor configurations for the unpolarized TMD fragmentation functions
(FFs) resulting from a Monte Carlo fit of Semi-Inclusive Deep-Inelastic
Scattering (SIDIS) data at Hermes. We build our predictions of $e^+e^-$
multiplicities relying on this rich phenomenology. The comparison of these
calculations with future experimental data (from Belle and Babar
collaborations) will shed light on non-perturbative aspects of hadron
structure, opening important insights into the physics of spin, flavor and
momentum structure of hadrons.
