Publication

Precise Measurement of Matter-Antimatter Asymmetry with Entangled Hyperon-Antihyperon Pairs

2026

Abstract

A search for CP violation with an entangled system of Ξ-Ξ¯+ pairs is performed, using (10,087±44)×106 J/ψ events collected with the BESIII experiment. A nine-dimensional helicity amplitude is used to fit e+e-→J/ψ→Ξ-Ξ¯+ and its subsequent decays. The Ξ- and Ξ¯+ decay parameters are determined with higher precision compared to the best results reported so far. Furthermore, the strong phase difference, (δP-δS)=(0.3±1.2±0.2)×10-2 rad, and the weak phase difference, (ζP-ζS)=(-0.2±1.2±0.1)×10-2 rad, are directly determined. These are the most precise measurements to date. The CP asymmetry observables ACPΞ=(-7.8±4.8±0.8)×10-3 and ΔφCPΞ=(0.6±5.1±0.2)×10-3 rad are determined, which are consistent with CP conservation. In addition, independent measurements of the Λ decay parameter and CP asymmetry ACPΛ=(-2.9±4.3±0.7)×10-3 are also obtained, which are in agreement with the previous measurements, but with much improved precision.

Official source

https://infoscience.epfl.ch/entities/publication/a994f278-ddea-46dd-aa79-61c68694c533

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2026

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/a994f278-ddea-46dd-aa79-61c68694c533

About this result

Related concepts (32)

CP violation

In particle physics, CP violation is a violation of CP-symmetry (or charge conjugation parity symmetry): the combination of C-symmetry (charge symmetry) and P-symmetry (parity symmetry). CP-symmetry states that the laws of physics should be the same if a particle is interchanged with its antiparticle (C-symmetry) while its spatial coordinates are inverted ("mirror" or P-symmetry). The discovery of CP violation in 1964 in the decays of neutral kaons resulted in the Nobel Prize in Physics in 1980 for its discoverers James Cronin and Val Fitch.

Baryon asymmetry

In physical cosmology, the baryon asymmetry problem, also known as the matter asymmetry problem or the matter–antimatter asymmetry problem, is the observed imbalance in baryonic matter (the type of matter experienced in everyday life) and antibaryonic matter in the observable universe. Neither the standard model of particle physics nor the theory of general relativity provides a known explanation for why this should be so, and it is a natural assumption that the universe is neutral with all conserved charges.

Baryogenesis

In physical cosmology, baryogenesis (also known as baryosynthesis) is the physical process that is hypothesized to have taken place during the early universe to produce baryonic asymmetry, i.e. the imbalance of matter (baryons) and antimatter (antibaryons) in the observed universe. One of the outstanding problems in modern physics is the predominance of matter over antimatter in the universe. The universe, as a whole, seems to have a nonzero positive baryon number density.

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Precise Measurement of Matter-Antimatter Asymmetry with Entangled Hyperon-Antihyperon Pairs

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