Antihydrogen Physics

反氢，一个正电子和一个反质子的束缚状态，最近在实验室的受控条件下产生。该提案寻求通过促进在中性陷阱(即所谓的磁梯度陷阱)中进行的新一代反氢实验来利用这一进展。这是一种磁场的排列，作用于反原子的小磁矩，产生捕获力。然而，这种陷阱很浅，目前只能将反氢保持在基态，动能相当于1开尔文以下的温度。因此，我们需要用这些低动能形成反氢，这是一项尚未完成的任务。一旦被捕获，我们希望能够利用电场和激光进行实验来操纵反氢。在未来，我们希望能够产生非常冷的反氢，使测量反物质的引力相互作用成为可能。然而，所有的反氢实验都是困难的，所以我们在这里要解决的问题是：为什么要费心呢？我们将用对称性的例子来解释这一点。很明显，根本的不对称性隐藏在自然界的深处。例如，在20世纪50年代的S发现，弱的核相互作用违反宇称守恒。然而，有缺陷的宇宙镜大部分可以通过添加所谓的电荷共轭来修复，粗略地说，这意味着当每个粒子被其反粒子取代时，相互作用不受影响。有一段时间，人们相信自然规律将遵循宇称反转和电荷共轭相结合的规律。但到了20世纪60年代中期，S发现，对于一小类被称为K介子的不寻常的、转瞬即逝的粒子的反应，这是不正确的。从那时起，人们一直认为电荷共轭/宇称反转镜中的小瑕疵可以通过应用时间反转来纠正。然而，这种三向开关不同于三个离散对称或它们的任意双向组合，因为电荷/宇称/时间组合作为一个定理存在，可以用量子场论的基本假设来证明。这些理论是我们目前对宇宙理解的基石，但被广泛认为是不完整的。因此，测试这种独特的三向开关是我们理解自然的核心。我们目前对宇宙起源的描述与大爆炸有关，大爆炸被认为是一个能量事件，创造了等量的物质和反物质。那么，为什么它们不都互相毁灭，留下一个没有物质的宇宙呢？到目前为止，对宇宙中大量剩余反物质的搜索都没有找到任何踪迹。目前，人们认为我们的宇宙是物质主导的，换句话说，是不对称的。另一个补充的事实是，我们目前通过大量对转瞬即逝的稀有粒子的研究所确定的不对称量不足以解释物质宇宙的存在。因此，只有通过探索最基本的对称性，我们才能开始了解我们观察到的宇宙是如何形成的。

Antihydrogen, the bound state of a positron and an antiproton, has recently been created under controlled conditions in the laboratory. The proposal seeks to exploit this advance by facilitating a new generation of experiments on antihydrogen held in a neutral trap, a so-called magnetic gradient trap. This is an arrangement of magnetic fields that acts upon the small magnetic moment of the anti-atom to produce a trapping force. However, such traps are shallow, and are currently only capable of holding antihydrogen in its ground state with kinetic energies equivalent to a temperature below 1 Kelvin. Thus, we need form antihydrogen with these low kinetic energies, a task not yet achieved. Once trapped, we hope to be able to do experiments to manipulate the antihydrogen, using electric and laser fields. Further into the future we hope to be able to produce very cold antihydrogen to make it possible to measure the gravitational interaction of antimatter. However, all experiments with antihydrogen are difficult, so the question we address here is; why bother? We will explain this using the example of symmetry.It has been apparent for a while that fundamental asymmetries are hidden deep within nature. For example, in the 1950's it was discovered that the weak nuclear interaction violates parity conservation. However, the defective parity mirror can be mostly repaired by adding so-called charge conjugation, which, loosely speaking, means that interactions are unaffected when every particle is substituted by its antiparticle. For a while it was believed that the laws of nature would obey the combination of parity reversal and charge conjugation. But by the mid-1960's this was found to be untrue for a small class of reactions involving unusual, fleeting, particles called K-mesons. Since then it has been assumed that the small blemish in the combined charge conjugation/parity reversal mirror can be corrected by the application of time-reversal.However, this 3-way switch differs from the three discrete symmetries, or any 2-way combination of them because the charge/parity/time combination exists as a theorem that can be proved using the basic postulates of quantum field theory. Such theories are the cornerstone of our current understanding of the Universe, but are widely recognised as being incomplete. So testing this unique 3-way switch is going to the heart of our understanding of nature. Our current picture of the beginning of the Universe involves the Big Bang, which is thought to have been an energetic event that created equal amounts of matter and antimatter. Why then did they not all annihilate one another and leave a Universe devoid of matter? Searches for large amounts of remnant antimatter in the Universe have, thus far, failed to find any trace. Currently it is thought that our Universe is matter dominant; in other words asymmetric. The other fact to add to this is that the amount of asymmetry we can currently identify via numerous studies of fleeting and rare particles isn't enough to explain the existence of the material Universe.Thus, it is only by probing the most basic symmetries that we can begin to understand how the Universe we observe came to be.