The Matter-Antimatter Asymmetry Problem: From Dirac's Prediction to Modern Baryogenesis

The observable universe is composed almost entirely of matter, despite theoretical expectations that the Big Bang should have produced matter and antimatter in equal quantities. This profound imbalance constitutes one of the most fundamental unresolved problems in modern cosmology. This paper examines the matter–antimatter asymmetry from Dirac’s 1931 prediction of antimatter through recent LHCb observations of CP violation in baryons reported in 2025. We analyze Sakharov’s three necessary conditions for baryogenesis, review key experimental milestones ranging from Wu’s discovery of parity violation to contemporary results in high-energy accelerator physics, and critically assess leading theoretical frameworks proposed to explain the asymmetry. These include electroweak baryogenesis, grand unified theory (GUT) scenarios, and leptogenesis mechanisms. Recent measurements of CP violation in the quark sector—and emerging evidence suggesting possible CP violation in the lepton sector—are discussed in detail, along with their quantitative inadequacy to account for the observed cosmic matter excess of approximately one baryon per billion photons. The paper concludes by examining ongoing searches for large-scale antimatter regions using experiments such as AMS-02, and by discussing the broader implications of these findings for physics beyond the Standard Model.