Speaker
Description
Recent measurements of the proton’s flavor asymmetry by the SeaQuest/E906 experiment challenge earlier results from NuSea/E866 at large momentum fraction $x$ , underscoring the need for a deeper understanding of the nonperturbative structure of the nucleon sea. A widely invoked theoretical framework is the pion cloud model -- yet it is typically treated perturbatively, despite the intrinsically strong pion-nucleon coupling. In this talk, I demonstrate that physics beyond the one-pion exchange approximation is both significant and highly nontrivial when treated nonperturbatively. Using a simplified scalar version of chiral effective field theory (EFT) formulated on the light front, we perform a fully nonperturbative calculation that consistently incorporates dynamics and renormalization. The results indicate that a complete nonperturbative treatment of chiral EFT is essential to achieve robust, quantitatively reliable predictions -- crucial for meaningful comparison with modern experimental data on the proton’s $\bar{d}/\bar{u}$ asymmetry.