LIVERPOOL REQUEST FOR POSTDOCTORAL RESEARCH ASSISTANTS 2022

基础物理学致力于回答以下重大问题：我们的宇宙是由什么构成的；它是如何演化的；是什么力量支配着它；它们如何塑造我们观察到的现象？在粒子物理学中，我们建立实验来研究宇宙中最小的组成部分，基本粒子，这样我们就可以用我们的发现来解决这些问题。我们关于基本粒子如何行为的知识被封装在一个叫做标准模型的理论中。它具有巨大的预测能力，并为理解宇宙的本质提供了一个简单的框架。然而，我们也知道这一理论是不完整的。最高能量下的实验让我们检验了预测，并确定了我们理论的有效性极限。专门的高精度实验让我们能够探测到令人难以置信的预测准确度。理论和实验数据之间任何不一致的最微弱的痕迹都可能提供新的物理运行规律的第一个线索，这将是在理解宇宙本质方面向前迈出的一步。我们最紧迫的问题之一是，为什么物质在这么大程度上主导着反物质。物质和反物质在早期宇宙中的数量应该是相等的，但现在可以观察到的反物质非常少。我们宇宙的这一决定性特征最终必然是由于物质和反物质行为的不同，但这种不同是一个谜。中微子是最难以捉摸的粒子，它可能掌握着理解为什么会发生这种情况的关键。它们不带电荷，几乎不与物质相互作用，质量非常小，为了探测它们，我们必须建造巨大但非常灵敏的探测器。我们研究的一个重要部分是对中微子进行详细的测量，了解它们的质量，以及它们是否对我们这个以物质为主导的宇宙负有责任。我们寻求解决的另一个谜团与暗物质有关。我们知道在星系中看不到足够多的恒星来解释恒星围绕它们旋转的速度。我们通过假设星系中也含有不可见(暗)物质来解释这一现象。暗物质提供了使恒星保持在轨道上所需的额外引力，但其性质尚不清楚。人们提出了许多解释，从它是由极低质量的粒子形成的，到大质量的黑洞。有些解释已经被排除了，但许多解释无论是从实验上证实还是拒绝都是极具挑战性的。为了解决这个问题，我们开发了更强大的实验，使用广泛的方法和技术，执行最广泛的搜索可能形成这种难以捉摸的暗物质的未知粒子。

Fundamental physics strives to answer the big questions: what is our Universe made of; how did it evolve; what forces govern it and how do they shape the phenomena we observe? In particle physics we build experiments to examine the very smallest constituents of the Universe, fundamental particles, so that we can address these questions with our findings.Our knowledge of how fundamental particles behave is encapsulated in a theory called the Standard Model. It has enormous predictive power and provides a simple framework to understand the nature of the Universe. However, we also know the theory is incomplete. Experiments at the highest energies let us test predictions and determine the limits of the validity of our theory. Dedicated high-precision experiments let us probe predictions to incredible levels of accuracy. The faintest trace of any disagreement between theory and experimental data could provide the first hint of new laws of physicsoperating, which would be a step forward in understanding the nature of the Universe.One of the most pressing questions we have concerns why matter dominates so much over anti-matter. Matter and antimatter should have been created in equal quantities in the early Universe, but very little anti-matter can be observed now. This defining feature of our Universe must ultimately be due to a difference in behaviour between matter and anti-matter, but this difference is a mystery. Neutrinos, the most elusive of particles, may hold the key to understanding why this happened. They have no charge, barely interact with matter, have a very small mass and to detect them we have had tobuild enormous but very sensitive detectors. An important part of our research is to make detailed measurements of neutrinos, to understand their masses and whether they are responsible for our matter-dominated universe.Another mystery we seek to resolve concerns dark matter. We know that there are not enough stars visible in galaxies to explain the speed at which stars rotate around them. We explain this by hypothesizing that galaxies also contain invisible (dark) matter. Dark matter supplies the extra gravitational force necessary to keep stars in their orbits, but its nature is unknown. Many explanations have been proposed, ranging from it being formed of extremely low mass particles to massive black holes. Some explanations have been excluded, but many are extremely challenging to either confirm orreject experimentally. To address this, we develop more powerful experiments using a wide range of approaches and technologies, to perform the broadest search for the unknown particles that may form this elusive dark matter.