Bridging grant for UCN Project

与原子核内的中子不同，超冷中子(UCN)可以自由移动，并且具有有趣的性质。UCN被地球引力场困住，它们从墙上反弹，它们可以储存在磁瓶中。由于UCN可以储存很长时间，并且可以产生许多中子，因此可以高精度地研究中子的性质，如中子寿命和中子β衰变的不对称性。产生高强度中子源的一个动机是，观察到中子的永久电偶极矩(EDM)将意味着新的物理学。当两个电荷相互分离时，产生一个电偶极矩，在标准模型中，中子电火花加工预计为~1e-31e cm。如果发现中子具有更大的EDM，它将在一定程度上有助于解释标准模型所不能容纳的宇宙的物质支配。为了将我们计划测量nEDM的非凡敏感性放在人类的角度来看，如果人们想象一个中子膨胀到地球大小，目前大约1e-26e cm的限制对应于大约1.5微米的电荷中心的间隔。

Unlike the neutrons inside of the nucleus of an atom, Ultra Cold Neutrons (UCN) are free to move around, and they have interesting properties. UCN are trapped by Earth's gravitational field, they bounce off walls, and they can be stored in magnetic bottles. Since UCN can be stored for a long time, and many neutrons can be produced, properties of neutrons can be studies to high precision such as the neutron lifetime, and the neutron beta decay asymmetry. A motivation for producing a high intensity neutron source is that an observation of a permanent Electric Dipole Moment (EDM) of the neutron would imply new physics. An electric dipole moment is created when there are two charges separated from one another, and in the standard model, the neutron EDM is predicted to be ~1e-31 e cm. If neutrons are found to have a larger EDM, it will in part help explain the matter domination of the universe which is not accommodated by the standard model. To put the extraordinary degree of sensitivity to which we plan to measure the nEDM into a human perspective, if one imagines a neutron expanded to the size of the Earth, the current limits around 1e-26 e cm correspond to a separation of the centres of charge of about 1.5 microns.