Harnessing the Power of B -> D(Multi-body)K Decays at LHCb for a Precise Measurement of the CKM Angle Gamma

据信，宇宙起源于一种被科学家称为“大爆炸”的宇宙学模型。它描述了时间和空间是如何被创造出来的，从而诞生了一个原始的“火球”，后来它扩展并演变成了今天的宇宙。已经获得了各种有力支持宇宙大爆炸模型的证据；然而，有一个奇特之处仍然没有得到解释。根据该模型，除了我们所说的日常普通物质外，大爆炸还应该产生等量的反物质。反物质，顾名思义，可以说是普通物质的对立面。当一个物质粒子具有一定的质量和电荷时，它的反物质对除了相反的电荷外，将具有相同的特性。尽管大爆炸模型预测了什么，但科学家们发现，今天所有可观测到的宇宙几乎都是由物质组成的。因此，问题是，所有的反物质都去了哪里？这仍然是现代物理学中最大的未解之谜之一。如果物质和反物质是等量产生的，那么在物理定律中一定存在某种过程，导致了我们今天所看到的不对称。其中一个过程就是所谓的“CP违规”。如果自然以平等的方式对待物质和反物质，那么对称性Cp将被保留下来。然而，很明显，自然界并不保留这种对称性，因此物质和反物质的物理定律一定是不同的。也就是说，违反了CP。在粒子物理学领域，物理学家已经发展出一种数学理论，它描述了与物质的基本粒子相互作用的四种基本力中的三种(引力是未被解释的力)。到目前为止，几乎所有由粒子物理的标准模型(SM)描述的三种力的实验测试都产生了与其预测一致的结果。因此，它被认为是现代科学的一次胜利。在它的基础上，SM是基于量子力学(QM)的理论，该理论将每个基本粒子视为波。当用数学表示时，得到的“波函数”描述了粒子将如何在遵守QM定律的情况下随时间演化。SM实际上允许在某些类型的粒子衰变中存在CP破坏，并且这种类型的对称性破坏已经得到了实验验证。然而，仍然存在的问题是，CP破坏的来源不足以解释巨大的物质-反物质不对称。由于这一原因和其他原因(如重力不能被纳入的事实)，人们相信一定存在SM所描述的以外的物理；即所谓的新物理学(NP)。虽然已经观测到了CP破坏，但SM中几乎所有的CP破坏参数都还没有得到精确的测量。事实上，对这些参数中的一个进行世界上最好的测量，称为伽马，构成了我研究提案的主要目标。如果没有伽马的精确测量，就不可能在潜在的NP内识别CP违例的来源。因此，伽马受到彻底的限制是至关重要的。通过分析在粒子衰变链中产生的被称为D介子的粒子的衰变特性来获取伽马是最好的。由于这些是量子粒子，它们的行为受QM支配，就像任何其他波一样，D介子波函数具有幅度和相位信息。为了访问参数伽马，必须详细了解这两个属性。然而，只有结合分析两个不同实验的数据集：LHCb和CLEO-c，才有可能同时提取幅度和相位信息。只有到那时，才有可能精确地确定SM参数伽马，并朝着发现NP迈出一步。

The universe is believed to have begun according to a cosmological model that scientists refer to as the 'Big Bang'. It describes how both time and space were created giving birth to a primordial 'fireball' that has since expanded and evolved into today's current universe. A variety of evidence has been obtained that strongly supports the Big Bang model of the universe; however, there is one peculiarity that remains unexplained. According to the model, in addition to the 'stuff' we refer to as every day ordinary matter, the Big Bang should have produced equal amounts of something called antimatter. Antimatter, as the name implies, can be described as the opposite of ordinary matter. Whilst a matter particle will have a definite mass and electric charge, its antimatter partner will possess the same characteristics except for an opposite electric charge. Despite what the Big Bang model predicts, scientists find that almost all of today's observable universe is made up of matter. The question is, therefore, where has all the antimatter gone? This remains one of the greatest unsolved mysteries in modern day physics. If matter and antimatter were created in equal quantities, then there must exist some process within the laws of physics that results in the asymmetry we see today. One such process is that referred to as 'CP-violation'. If nature treats matter and antimatter in equal ways then the symmetry, CP, would be preserved. Quite clearly, however, nature does not preserve this symmetry and so the physical laws must be different for matter and antimatter. That is, CP is violated. Within the field of particle physics, physicists have developed a mathematical theory which describes three of the four fundamental forces seen to interact with the elementary particles of matter (gravity being the unaccounted force). To this present day, almost all experimental tests of the three forces described by this 'Standard Model' (SM) of particle physics have produced results that agree with its predictions. It is, therefore, regarded as a triumph of modern day science. At its foundation, the SM is based on the theory of Quantum Mechanics (QM) which considers each fundamental particle as a wave. When represented mathematically, the resulting 'wavefunction' describes how the particle will evolve in time whilst obeying the laws of QM. The SM actually permits the existence of CP-violation within certain types of particle decays, and this type of symmetry breaking has been experimentally verified. The problem that remains, however, is that this source of CP-violation is insufficient to explain the huge matter-antimatter asymmetry. Due to this and other reasons (such as the fact that gravity is unable to be incorporated), it is believed there must be physics beyond that described by the SM; so called New Physics (NP). Although CP-violation has been observed, almost all CP-violation parameters in the SM have yet to be precisely measured. In fact, making a world's best measurement of one of these parameters, called gamma, forms the main objective of my research proposal. Without a precision measurement of gamma it will not be possible to identify sources of CP violation within potential NP. It is, therefore, critical that gamma is thoroughly constrained. Gamma is best accessed by analysing the decay properties of particles called D mesons that have been produced in the particle decay chain B->DK. Since these are quantum particles, their behaviour is governed by QM and, just like any other wave, the D meson wavefunction possesses amplitude and phase information. Detailed knowledge of both these properties is necessary in order to access the parameter gamma. However, it is only possible to extract both amplitude and phase information by analysing in conjunction the datasets of two different experiments: LHCb and CLEO-c. Only then will it be possible to precisely determine the SM parameter gamma and provide a step towards discoveries of NP.