Probing CP symmetry and weak phases with entangled double-strange baryons.
Probing CP symmetry and weak phases with entangled double-strange baryons.
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用纠缠双奇异重子探测 CP 对称性和弱相
DOI：
10.1038/s41586-022-04624-1
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发表时间：
2022-06
期刊：
影响因子：
64.8
通讯作者：
BESIII Collaboration
中科院分区：
文献类型：
--
作者：
BESIII Collaboration
虽然粒子物理学的标准模型非常成功，但它并不能解释为什么我们的宇宙包含的物质比反物质多得多。动态生成的物质-反物质不对称性的关键是存在违反电荷共轭和宇称（CP）对称性的过程。因此，CP对称性的精确测试可以用来寻找标准模型之外的物理。然而，强子的衰变是通过强弱过程的相互作用来实现的，这可以用振幅之间的相对相位来量化。虽然以前的实验构建CP观测值，依赖于强和弱阶段，我们提出了一种方法，连续的两体衰变的纠缠多奇怪重子-反重子对提供这些阶段之间的分离。我们的方法利用了双奇异重子和它的反粒子之间的自旋纠缠，使得能够直接确定弱相位差，（P − P − S）=（1.2 ± 3.4 ± 0.8）× 10−2 rad。此外，三个独立的CP观测量可以从我们的测量参数。在一个给定的数据样本大小的估计参数的精度是几个数量级以上实现与以前的方法。最后，我们提供了一个独立的测量最近争论的Λ衰变参数αΛ（参考文献）。该不对称性与先前最精确的测量一致并且在精度上兼容。使用自旋纠缠的重子-反重子对，BESIII合作报告了强子中潜在电荷共轭和宇称（CP）破坏效应的高精度测量。
Though immensely successful, the standard model of particle physics does not offer any explanation as to why our Universe contains so much more matter than antimatter. A key to a dynamically generated matter–antimatter asymmetry is the existence of processes that violate the combined charge conjugation and parity (CP) symmetry. As such, precision tests of CP symmetry may be used to search for physics beyond the standard model. However, hadrons decay through an interplay of strong and weak processes, quantified in terms of relative phases between the amplitudes. Although previous experiments constructed CP observables that depend on both strong and weak phases, we present an approach where sequential two-body decays of entangled multi-strange baryon–antibaryon pairs provide a separation between these phases. Our method, exploiting spin entanglement between the double-strange Ξ− baryon and its antiparticle , has enabled a direct determination of the weak-phase difference, (ξP − ξS) = (1.2 ± 3.4 ± 0.8) × 10−2 rad. Furthermore, three independent CP observables can be constructed from our measured parameters. The precision in the estimated parameters for a given data sample size is several orders of magnitude greater than achieved with previous methods. Finally, we provide an independent measurement of the recently debated Λ decay parameter αΛ (refs. ). The asymmetry is in agreement with and compatible in precision to the most precise previous measurement. Using spin-entangled baryon–antibaryon pairs, the BESIII Collaboration reports on high-precision measurements of potential charge conjugation and parity (CP)-symmetry-violating effects in hadrons.
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