Measurement of the $\Lambda$ Electric Dipole Moment with an Entangled Baryon-Antibaryon System

Abstract

The dominance of matter over antimatter in the universe has consistently driven the pursuit of new physics beyond the Standard Model that violates charge-parity symmetry. Strange baryons (hyperons) remain a largely unexplored territory in which interactions between hyperons and particles from new physics could induce a nontrivial electric dipole moment (EDM). However, direct measurements of hyperon EDMs through spin precession are highly challenging owing to their short lifetimes. In this work, we introduce a method to extract the EDM of the lightest hyperon, $\Lambda$, using the entangled $\Lambda$$\overline{\Lambda }$ system. Our result is consistent with zero, achieving a three-orders-of-magnitude improvement over the previous upper limit established in the 1980s with comparable statistics, providing stringent constraints on potential new physics.