Neutron EDM

中子是原子核的基本组成部分。虽然中子总体上是电中性的，但它是由带电粒子组成的。中子电偶极矩（英语：Neutron electric dipole moment，简称nEDM）是中子内部正负电荷分布的量度，就像磁铁有南北两极一样，一个有EDM的中子会有一端稍负，另一端稍正。然而，只有当物理学定律中的某些对称性被轻微打破时，这种情况才会发生-通过与大爆炸时宇宙中物质对反物质的主导作用完全相同的机制。这些机制尚不清楚，但通过测量（并限制）nEDM，我们对试图解释宇宙中所有物质起源的新物理模型施加了极其严格的限制。我们的团队目前在这个基本量的测量精度方面拥有世界上最好的极限。拟议的工作将提高灵敏度的两倍，在第一种情况下，后来更多-也许接近一个数量级。

Neutrons are an elemental part of the nucleus of the atom. Although electrically neutral overall, neutrons are made up of charged particles. The neutron electric dipole moment (nEDM) is a measure of the distribution of positive and negative charge inside the neutron - just as a magnet has north and south poles, so a neutron with an EDM would have one end slightly negative, and the other slightly positive. However, this can only happen if certain symmetries in the laws of physics are slightly broken - by exactly the same mechanisms that were responsible for the dominance of matter over anti-matter in the Universe at the time of the Big Bang. These mechanisms are not understood, but by measuring (and putting limits upon) the nEDM, we put extremely tight constraints upon new models of physics that attempt to explain the origin of all of the matter in the Universe. Our group currently holds the world's best limit in the precision of measurement of this fundamental quantity. The proposed work will improve the sensitivity by a factor of two in the first instance, and later on by much more - perhaps approaching an order of magnitude.