Speaker
Description
We present a general framework originated from topologically nontrivial configurations, known as instantons in the QCD vacuum, to evaluate the non-perturbative transverse partonic structure of hadrons. Within this approach, we derive the transverse-momentum-dependent parton distribution functions (TMDPDFs) for the pion, kaon, and rho meson, as well as the Collins–Soper (CS) kernel that governs their rapidity evolution. Our results provide a tomographic view of the pion and kaon in both parton momentum fraction $x$ and transverse coordinate space $b_T$. The extracted CS kernel, when combined with perturbative contributions, shows good agreement with recent lattice QCD results and phenomenological fits. Notably, we find that the CS kernel exhibits logarithmic growth at large quark transverse separation, offering an important constraint for its phenomenological parametrization. Lastly, our framework allows direct comparison with lattice calculations in Euclidean signature, providing a novel method to evaluate the soft function and extract the CS kernel via analytic continuation.
