The Dilemma of Baryon Asymmetry in the Cosmos: State of the Art and Research Frontiers in December 2025

Version 1.1: Updated to include the recent breakthrough from the ALICE Collaboration (Nature 648, 2025) regarding deuteron formation via $\Delta$-resonance decay, establishing a phenomenological precedent for resonant shielding mechanisms. ************************************************************************************************************************************************* The observable universe presents a fundamental enigma that challenges the foundations of contemporary physics: the almost absolute predominance of matter over antimatter. This work reviews the state of the art of the Baryon Asymmetry of the Universe (BAU) as of late 2025 (η_B ≈ 6.1 × 10⁻¹⁰). We analyze recent tensions in primordial nucleosynthesis (EMPRESS collaboration) and neutrino asymmetry, as well as the consolidation of leptogenesis following the joint results from T2K and NOvA. Finally, we discuss the prospects for detecting new physics through searches for Electric Dipole Moments (ACME III, n2EDM) and intensity frontier experiments such as SHiP and MATHUSLA.