BESIII Sets World Record Limit On Lambda Hyperon Electric Dipole Moment: Institute Of High Energy Physics Chinese Academy Of Sciences Leads Collaboration Quantum-Entangled Lambda Anti-Lambda Pairs From J/Psi Decays Used 10 Billion J/Psi Events Upper Limit 6.5 × 10⁻¹⁹ e cm At 95% Confidence Level
According to Phys.org/Science, the BESIII Collaboration, led by the Institute of High Energy Physics of the Chinese Academy of Sciences, has achieved the world’s most precise measurement of the electric dipole moment of the Lambda hyperon, improving experimental sensitivity by about three orders of magnitude over the previous best measurement, in a study published in the journal Science.
The collaboration used quantum-entangled Lambda–anti-Lambda pairs produced in J/ψ (J/psi) decays, analysing ten billion J/ψ events collected at the BEPCII collider. A global fit to the joint decay distributions yielded the Lambda EDM as Re(d_Λ) = (−3.1 ± 3.2 ± 0.5) × 10⁻¹⁹ e cm and Im(d_Λ) = (2.9 ± 2.6 ± 0.6) × 10⁻¹⁹ e cm, both consistent with zero. The resulting upper bound is |d_Λ| < 6.5 × 10⁻¹⁹ e cm at 95 per cent confidence level, compared with the previous best limit from a Fermilab fixed-target experiment.
An electric dipole moment of an elementary particle arises from flavour-diagonal CP violation, a breaking of the combined symmetry between charge conjugation and parity. One of the most profound mysteries in modern physics is why the observable universe is dominated by matter rather than antimatter. Although the Standard Model has been remarkably successful in describing elementary particles and their interactions, its known sources of CP violation are insufficient to account for this cosmic imbalance.
The strategy can be extended to other members of the hyperon family; Sigma and Xi baryons, establishing a systematic programme of EDM searches across the strange-baryon sector and testing physics beyond the Standard Model.
The universe chose matter over antimatter. We still do not know why. BESIII just narrowed the search. Check out our previous coverage of science and physics on The Trusted Times.
