Investigations in Quantum Chromodynamics and Physics Beyond the Standard Model

格拉斯哥理论小组在研究亚原子世界的两种不同方法方面享有很高的声誉，并推动了我们对亚原子世界如何运作的理解。首先，我们尝试在标准模型的理论框架内进行非常精确的计算，我们认为标准模型正确地描述了我们在高能加速器中看到的粒子以及它们通过自然的强、弱和电磁力的相互作用。这些精确的计算结果与实验结果之间的差异，将为我们指出一条超越现有框架的道路，通向更全面地描述基本粒子物理学的更深层次的理论。第二种方法与我们在大型强子对撞机（不久将在欧洲核子研究中心开始运行）的新实验中可能看到的情况有关，如果所提出的更深层次的理论中有一个或另一个是正确的。我们必须确保我们优化这些实验的分析，以尽可能多地学习。标准模型中的精确计算常常建立在如何处理强作用力的难题上。这种力在组成原子核、质子和中子的粒子以及在高能碰撞中产生的一系列类似的强子粒子中非常重要。这些粒子的成分是夸克，它们被强力的作用困在强子里。这种“约束”使得计算强作用力对我们能看到的强子的影响变得非常困难。唯一可行的方法是理论的数值模拟，这是非常具有挑战性的。最近，我们取得了重大进展——我们准确地计算了许多不同强子的质量，并且第一次得到了与实验相符的答案。格拉斯哥在这方面发挥了重要作用，并继续引领进展，特别是在含有b和c夸克的强子的研究结果方面。它们是上述标准模型测试的关键，无论是目前的实验还是未来的大型强子对撞机实验。例如，实验可以测量b或c强子通过弱作用力介导的反应转变为其他强子的速率，类似于核衰变。格拉斯哥研究小组现在将在我们的数值模拟中进行精确计算，我们可以与实验进行比较，并确定弱力的参数，这些参数允许物质和反物质之间的对称性被破坏。这使我们能够非常严格地测试标准模型。格拉斯哥团队还将研究超越标准模型的理论，特别是预测我们可能在大型强子对撞机中发现的新粒子的理论。我们希望至少能找到希格斯粒子，它能产生其他粒子的质量，甚至可能发现与超对称或额外维度等理论相关的奇异新粒子。我们希望发现这些粒子并测量它们的性质将导致基本力的统一理论。为了实现这一目标，需要精确的计算和对新物理模型的系统研究，我们的专业知识使我们处于理想的位置。这使我们能够对标准模型和新物理进行理论预测，这样我们就可以准确地将它们与我们在大型强子对撞机上工作的实验同事的结果进行比较。我们还研究了其他信号和改进现有方法以寻找新物理的方法。未来五年将是理论粒子物理学非常激动人心的时期，格拉斯哥的目标是走在这方面的前沿。

The Glasgow theory group has a strong reputation in two different methods of studying the subatomic world, and pushing forward our understanding of how it works. In the first, we attempt very accurate calculations within the theoretical framework called the Standard Model that we believe correctly describes the particles that we see at high energy accelerators and their interactions, through the strong, weak and electromagnetic forces of Nature. Discrepancies between these accurate calculations and what is seen in experiments will then point the way to going beyond our existing framework to a deeper theory that describes fundamental particle physics more completely. The second method is concerned with what we might see at the new experiments associated with the Large Hadron Collider (LHC) (shortly to start running at CERN) if one or other of the suggested deeper theories is correct. We must make sure that we optimise the analysis of these experiments to learn as much as possible. Accurate calculations in the Standard Model often founder on the difficult problem of how to handle the strong force. This force is important inside particles that make up the atomic nucleus, the proton and neutron and a host of similar particles called hadrons made in high energy collisions. The constituents of these particles are quarks, and they are trapped inside hadrons by the behaviour of the strong force. This `confinement' makes calculations of the effects of the strong force on the hadrons we can see very hard. The only practical method is numerical simulation of the theory, and this is very challenging. Recently significant progress was made - we calculated the masses of lots of different hadrons accurately with answers that agreed with experiment for the first time. Glasgow played a big part in this and continues to lead progress, particularly with results for hadrons containing b and c quarks. These hold the key to the tests of the Standard Model described above both from current experiments and future ones at LHC. Experiments can measure, for example, the rate at b or c hadrons change into other hadrons by a reaction mediated by the weak force, akin to nuclear beta decay. With the precision calculations that the Glasgow team will now do in our numerical simulations we can make a comparison with experiment and pin down the parameters of the weak force that allow for violations of symmetry between matter and antimatter. This allows us to test the Standard Model very stringently. The Glasgow team will also investigate theories that go beyond the Standard Model, in particular theories that predict new particles that we might discover at the LHC. We expect to find at least the Higgs particle, which gives rise to the masses of other particles, and may even discover exotic new particles associated with theories such as supersymmetry or extra dimensions. We hope that discovering these particles and measuring their properties will lead to a unified theory of the fundamental forces. To achieve this goal requires both precision calculations and systematic investigations of new physics models, for which our expertise leaves us ideally placed. This allows us to make theoretical predictions for both the Standard Model and the new physics so that we can accurately compare them with results from our experimental colleagues working on the LHC. We also investigate additional signals and ways of improving existing methods for finding new physics. The next five years will be a very exciting time for theoretical particle physics and Glasgow aims to be at the forefront of this.