Improved limit on the electric dipole moment of the electron
Improved limit on the electric dipole moment of the electron
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DOI：
10.1038/s41586-018-0599-8
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发表时间：
2018-10-18
期刊：
影响因子：
64.8
通讯作者：
Wu, X.
中科院分区：
文献类型：
--
作者：
Andreev, V.;Ang, D. G.;Wu, X.
粒子物理的标准模型准确地描述了迄今为止在实验室中进行的所有粒子物理测量。然而，它无法回答宇宙学观测中出现的许多问题，比如暗物质的性质，以及为什么整个宇宙中物质比反物质占主导地位。包含粒子和超越标准模型的相互作用的理论，例如包含超对称的模型，可以解释这些现象。这种粒子出现在真空中，并与普通粒子相互作用以改变它们的性质。例如，非常大的粒子的存在，其相互作用违反了时间反转对称性，这可以解释宇宙物质-反物质的不对称性，可以在电子的自旋轴上产生电偶极矩。没有观测到基本粒子的电偶极矩。然而，偶极矩仅略小于目前的实验界限，已经被预测从比任何已知存在的更大的粒子中产生。在这里，我们提出了一个改进的电子电偶极矩的实验极限，该极限是通过测量在巨大的分子内电场作用下电子量子态叠加中的电子自旋进动得到的。我们测量的灵敏度比以往任何测量都高出一个数量级以上。这一结果表明，如果有一大类猜想粒子存在，并且时间反转对称性被极大地违反，那么它们的质量将大大超过大型强子对撞机直接测量到的质量。
The standard model of particle physics accurately describes all particle physics measurements made so far in the laboratory. However, it is unable to answer many questions that arise from cosmological observations, such as the nature of dark matter and why matter dominates over antimatter throughout the Universe. Theories that contain particles and interactions beyond the standard model, such as models that incorporate supersymmetry, may explain these phenomena. Such particles appear in the vacuum and interact with common particles to modify their properties. For example, the existence of very massive particles whose interactions violate time-reversal symmetry, which could explain the cosmological matter-antimatter asymmetry, can give rise to an electric dipole moment along the spin axis of the electron. No electric dipole moments of fundamental particles have been observed. However, dipole moments only slightly smaller than the current experimental bounds have been predicted to arise from particles more massive than any known to exist. Here we present an improved experimental limit on the electric dipole moment of the electron, obtained by measuring the electron spin precession in a superposition of quantum states of electrons subjected to a huge intramolecular electric field. The sensitivity of our measurement is more than one order of magnitude better than any previous measurement. This result implies that a broad class of conjectured particles, if they exist and time -reversal symmetry is maximally violated, have masses that greatly exceed what can be measured directly at the Large Hadron Collider.