Stime di Modello della Violazione di Parità nell'Interazione Forte

One of the enduring puzzles in Nature is the imbalance of matter and antimatter. Nonetheless, the Standard Model, the current most successful theory of particles and their interactions does not manage to provide us with a solution. The most likely explanation for this disproportion is the violation of CP symmetry, \textit{i.e.} the combination of the charge conjugation (C) and parity (P) symmetry. CP symmetry is broken in the electroweak sector of the Standard Model, but the violation is not large enough to account for the observed matter-antimatter imbalance. This opens the possibility of studying the Strong CP Problem: a possible violation of CP symmetry originating from the strong force. In this thesis, we explore the possibility of Parity Violation (PV), since no first principle of QCD guarantees P invariance from a theoretical standpoint. One of the possible measurable effects of CP violation is the generation of permanent electric dipole moments and anapole moments in various particles. Nevertheless, in the last 30 years, no experiments have been able to measure any effects of strong CP violations. In this thesis, we consider more general structures, i.e., parity-violating Parton Distribution Functions (PDFs). Experimental data do not exclude the possibility of small but nonzero PV PDFs, but at present, there exist no model calculations to guide the phenomenological search for this effect. To model these PV PDFs, we adopt a simplified description of the proton based on the “spectator model”. We introduce PV effects in the model and study the features of the resulting PDFs. We constrain the parameters of the model by comparing the results to estimates based on experimental data. The model generates nontrivial features for the new PV PDFs, providing further insight into the structure of the proton and the amount of Strong P Violation in its interior and giving indications on how to search for these intriguing effects experimentally.