Transverse-momentum-dependent fragmentation functions in e+e-annihilation

Fragmentation functions are non-perturbative functions used to describe the formation of colorless, observable hadrons starting from a colored, partonic initial state. The knowledge of these functions are based on the experimental data, and a good parameterization of the fragmentation processes can shed light on the confining aspect of QCD, and are also a key ingredient in accessing nucleon parton distribution functions in semi-inclusive deep inelastic scattering and proton-proton collisions. In the last decade, a strong interest has risen about the transverse-momentum-dependent (TMD) fragmentation functions, which can be used as tools to probe the 3D-structure of nucleons, and to investigate the Q2evolution of TMD objects. In this review we will summarize the existing light-quarks fragmentation related measurements from the BaBar, Belle, and BESIII e+e-experiments; in particular, we will focus on the polarized TMD Collins fragmentation functions, emerging from correlations between the transverse polarization of the fragmenting parton and the direction of the resulting hadrons.