September 4, 2026
The BESIII international collaboration has announced a landmark experimental achievement. Leveraging the quantum-entangled Lambda-antilambda hyperon pairs produced from J/ψ particle decay at the Beijing Electron-Positron Collider, researchers have accomplished the world’s most precise measurement of the Lambda hyperon Electric Dipole Moment (EDM). The measurement sensitivity has been enhanced by approximately three orders of magnitude compared with previous best global results, providing critical and authoritative experimental data for exploring CP symmetry violation in the strange quark system and searching for new physics beyond the Standard Model. The findings have been officially published in the top international journal Science.
The matter-antimatter asymmetry of the universe remains one of the most fundamental and unsolved puzzles in modern particle physics and cosmology. The CP symmetry violation predicted by the Standard Model of particle physics is far insufficient to explain the observed cosmic phenomenon where matter dominates the universe while antimatter is nearly absent. The scientific community widely recognizes that undiscovered physical laws exist in the universe. As one of the most sensitive and essential experimental probes, the permanent particle EDM enables the detection of time-reversal symmetry breaking and traces potential signals of new physics.
As a key research object for hadron physics and CP violation studies, the Lambda hyperon contains strange quarks but features an extremely short lifespan, making traditional measurement methods based on external magnetic field spin precession completely inapplicable. For more than four decades, the global physics community lacked high-precision experimental data on the Lambda hyperon EDM, leaving long-term stagnation in this research field.
To tackle this global technical challenge, the Chinese BESIII research team developed an innovative experimental scheme. Massive J/ψ particles are generated through electron-positron collisions, which further decay into quantum-entangled Lambda and antilambda hyperon pairs with highly correlated and constrained spin states. Without relying on large external electromagnetic fields, researchers accurately reconstruct and analyze hyperon spin information by capturing the precise angular distribution of hyperon weak decay products. This breakthrough overcomes the experimental bottlenecks caused by short-lived hyperons and establishes an innovative technical route for hyperon EDM measurement.
Supported by massive high-quality datasets, the experiment analyzed 10 billion J/ψ events and precisely screened 3 million high-purity Lambda-antilambda candidate events with a signal purity of 99.9%. The study sets a strict upper limit on the Lambda hyperon EDM at 95% confidence level: <6.5\times10^{-19}\ e\cdot cm. While the result is consistent with zero and no non-zero EDM signal has been observed, it improves the measurement sensitivity of this field by 1,000 times, setting a new global record. It delivers the strictest experimental constraints to date for the study of CP symmetry violation in the strange quark sector and enables effective verification and screening of mainstream new physics theoretical models, including supersymmetry and the two-Higgs doublet model.
This achievement marks a landmark application of quantum entanglement technology in high-precision collider particle physics measurements. It validates an innovative paradigm for high-energy physics experiments, provides mature technical references for subsequent high-precision EDM measurements of Ξ, Σ and other hyperons, and lays a solid methodological foundation for frontier physical research at China’s next-generation large scientific facility, the Super Tau-Charm Facility (STCF).
Industry authorities commented that this significant breakthrough further consolidates China’s leading global position in tau-charm physics. It fills the long-standing international research gap in high-precision measurement of strange quark hyperons, expands the boundary of human understanding of the fundamental laws of matter from an entirely new dimension, and contributes crucial Chinese scientific research strength to unraveling the core mystery of cosmic matter origin and exploring new breakthroughs in fundamental physics.