Study of transverse-momentum--dependent parton distribution functions.

The dynamics and the interactions between quarks and gluons are governed by the theory of Quantum chromodynamics (QCD), which exhibits asymptotic freedom. Two examples of high-energy processes are the Semi-Inclusive Deep Inelastic Scattering (SIDIS) and the Drell-Yan process. These are very interesting because, thanks to different factorization theorems, we can write their cross-sections in a factorized way by using the Transverse-Momentum--Dependent Parton Distribution Functions (TMD-PDFs) and Fragmentation Functions (TMD-FFs). These functions are crucial in understanding the three-dimensional structure of hadrons, because they give us information about their internal structure. For example, the TMD-PDFs give us the joint probability density of finding a particle with a certain fraction $x$ of nucleon momentum and transverse momentum $k_T$ inside the hadron. Moreover, these functions can be written as a product of a perturbative part, which has already been calculated at different orders, times a non-perturbative part, which can be extracted from the experimental data. We will present some results obtained from the extractions we have done regarding it.