PERTURBATIVE AND NON-PERTURBATIVE ASPECTS OF HADRONIC PHYSICS

This thesis presents a combined theoretical and phenomenological investigation of QCD dynamics, focusing on two complementary aspects. First, the method of multiparticle fields is employed to construct models for multiquark scattering processes. These models reproduce key qualitative features of experimental data, such as the non-monotonic behavior of the proton elastic scattering cross section as a function of squared momentum transfer. Spin effects are identified as a critical ingredient in explaining these phenomena. To approximate loop diagram contributions within this framework, the Laplace method is utilized, offering a practical but improvable computational tool. Second, an affinity-based methodology is developed to explore the kinematic transition between transverse momentum dependent (TMD) and collinear factorization regimes in semi-inclusive deep inelastic scattering (SIDIS). A transition from binaveraged to event-by-event affinity calculations preserves essential correlations among non-perturbative parameters, yielding a more reliable classification of kinematic regions. The analysis reveals that the TMD region is broader than previously estimated, particularly within the JLab12 kinematics, while the collinear region becomes well accessible at higher JLab22 energies. A distinct TMD-Collinear Matching Region is identified, providing new opportunities to study the interplay between factorization regimes. The findings of this work offer both theoretical insights and practical tools for future studies of nucleon structure and hard scattering processes. Recommendations for further development include incorporating higher-order loop diagrams into the multiparticle field framework, refining computational methods, extending affinitybased analyses to other processes, and guiding experimental efforts through targeted kinematic cuts.