Beautiful Flavours: Discovering New Physics with B-hadrons and Tau-leptons

粒子物理学是研究宇宙的基本性质的学科。我们几十年前就知道，我们用来描述大能量、小长度物理的最好理论--标准模型--是不完整的。例如，该理论缺乏任何粒子来解释我们从天体物理学研究中知道的暗物质的存在。超越标准模型的物理学的基本性质--所涉及的粒子和力--是未知的。尽管标准模型已经有近50年的历史了，但该领域的关键悬而未决的问题仍然是“标准模型之外还有什么物理学？”大型强子对撞机(LHC)以高能碰撞质子束，目的是暴露这一新的物理，用于专门的受控研究；我将在LHC的LHC美(LHCb)探测器收集数据，并解决这个关键问题，试图发现新的基本粒子。我将使用创新的新技术来更好地理解支配我们周围宇宙的物理学。最近，一系列测量提供了一些线索，表明在非常罕见的过程中，标准模型预测的偏差，这些过程考虑了特定粒子(美夸克)衰变成其他粒子(奇怪夸克和缪子或电子)的频率。提出的对这些效应的解释需要标准模型中没有的额外基本粒子。我将在相关的美夸克衰变中寻找这些新粒子的影响；具体地说，我将研究美夸克的衰变，这种衰变涉及到被称为牛轻子的粒子(可以被认为是更重版本的介子和电子)。提出的解释现有反常结果的理论通常会预测在这些轻子过程中会产生更大的影响。因此，我的研究提供了发现新粒子和超越标准模型的物理学的机会，为我们理解宇宙的方式提供了一场潜在的革命。然而，探测和测量这些轻子极具挑战性；创新的新技术至关重要。到目前为止，对类似过程中的牛轻子的测量依赖于找到牛轻子本身衰变到的单个粒子。相反，我将应用机器学习技术，这将使我能够重建牛轻子本身和正在研究的整个系统的性质，利用一种将LHCb探测器的额外输出与更传统的信息相结合的整体方法。这将使我能够更有效地在数据中找到感兴趣的信号，并更好地拒绝可以模拟信号过程的背景。我将使用这些方法对涉及到轻子的美夸克衰变进行一系列测量，并对新现象的出现实现高灵敏度。我将把这种方法整合到LHCb的数据获取和记录哲学中，第一次明确地寻找在LHCb的每一次质子-质子碰撞中，这些美丽夸克衰变到反轻子的过程。我的学习将提供新的知识，让我们更好地了解大自然。如果我的结果与标准模型不一致，我将观察到新粒子的影响；我的测量将对比目前已知的基本粒子重得多的新粒子敏感。这样的发现将重塑我们看待宇宙的方式，潜在地为了解物质本身的性质提供了新的见解。然而，如果我的结果被证明与标准模型一致，我仍然将探索跨越许多不同能量和质量的物理学的广阔图景，并将对标准模型之外的物理行为施加极其强烈的约束。我的研究将使我们对宇宙如何运行有一个新的、更好的理解。

Particle Physics is the study of the fundamental nature of the universe. We have known for decades that our best theory to describe physics at large energies and small lengths, the Standard Model, is incomplete. The theory lacks, for example, any particle that can explain the dark matter that we know exists from astrophysics research. The fundamental nature of the physics beyond the Standard Model - the particles and forces involved - is unknown. Despite the Standard Model being nearly 50 years old the key open question in the field remains 'what physics lies beyond the Standard Model?'. The Large Hadron Collider (LHC) collides proton beams at high energies with the goal of exposing this new physics for dedicated, controlled study; I will collect data at the LHC-beauty (LHCb) detector at the LHC and address this crucial question, seeking to discover new fundamental particles. I will use innovative new techniques to provide a greater understanding of the physics that governs the universe around us.Recently, a series of measurements have provided hints for deviations from Standard Model predictions in very rare processes that consider how often specific particles ('beauty quarks') decay into other particles ('strange quarks' and 'muons' or 'electrons'). Proposed explanations for these effects require additional fundamental particles not present in the Standard Model. I will search for the effects of these new particles in related beauty quark decays; specifically, I will study decays of beauty quarks that involve particles known as 'tau-leptons' (which can be thought of as a heavier version of muons and electrons). Proposed theories that explain the existing anomalous results typically predict much larger effects in these tau-lepton processes. My research therefore offers the opportunity to discover new particles and the physics beyond the Standard Model, offering a potential revolution in the way we understand the universe.However, detecting and measuring these tau-leptons is extremely challenging; innovative new techniques are crucial. To date, measurements of tau-leptons in similar processes have relied on finding the individual particles that the tau-leptons themselves decay to. I will instead apply Machine Learning techniques that will enable me to reconstruct the properties of the tau-leptons themselves and the full system under study, making use of a holistic approach that combines additional output from the LHCb detector alongside the more traditional information. This will enable me to find interesting signals in the data more effectively, and better reject background that can mimic the signal processes. I will use these methods to make a series of measurements of beauty quark decays that involve tau-leptons and achieve high sensitivity to the presence of new phenomena. I will integrate this approach into the data acquisition and recording philosophy of LHCb, searching explicitly for the first time for these beauty quark decays to tau-leptons in every proton-proton collision at LHCb. My studies will provide new knowledge and let us understand nature better. If my results are inconsistent with the Standard Model, I will have observed the effects of new particles; my measurements will be sensitive to new particles much heavier than the currently known fundamental particles. Such a discovery would reshape the way we view the universe, potentially offering new insight into the nature of matter itself. However, should my results prove consistent with the Standard Model, I will still have explored a vast landscape of physics across many different energies and masses, and will have placed extremely strong constraints on the behaviour of the physics that lies beyond the Standard Model. My research will give us a new and greater understanding of how the universe works.