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上享有很高的声誉，并推动了我们对亚原子世界如何工作的理解。首先，我们尝试在被称为标准模型的理论框架内进行非常准确的计算，我们认为该模型正确地描述了我们在高能加速器上看到的粒子及其通过自然的强、弱和电磁力的相互作用。这些精确的计算与实验结果之间的差异将为我们超越现有框架，进入更全面地描述基本粒子物理的更深层次的理论指明道路。第二种方法关注的是，如果其中一个更深层次的理论是正确的，我们可能会在与大型强子对撞机(LHC)(不久将在欧洲核子研究中心运行)相关的新实验中看到什么。我们必须确保优化这些实验的分析，以尽可能多地了解情况。标准模型中的精确计算往往是在如何处理强力这一难题上失败的。这种力在构成原子核的粒子、质子和中子以及在高能碰撞中产生的一系列被称为强子的类似粒子中非常重要。这些粒子的成分是夸克，通过强力的行为，它们被困在强子内部。这种“禁闭”使我们很难计算出强力对强子的影响。唯一实用的方法就是对理论进行数值模拟，这是非常具有挑战性的。最近取得了重大进展--我们首次用与实验一致的答案准确地计算了大量不同强子的质量。格拉斯哥在这方面发挥了很大作用，并继续引领着这一进展，特别是在含有b夸克和c夸克的强子结果方面。这些都是从大型强子对撞机目前和未来的实验中对上述标准模型进行测试的关键。例如，实验可以测量b或c强子通过弱力介导的反应转变为其他强子的速率，类似于核β衰变。有了格拉斯哥团队现在将在数值模拟中进行的精确计算，我们可以与实验进行比较，并确定允许物质和反物质之间的对称性破坏的弱力参数。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上发现的新粒子的理论。我们预计至少会发现希格斯粒子，它会产生其他粒子的质量，甚至可能会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作用力的统一理论。为了实现这一目标，需要对新的物理模型进行精确的计算和系统的研究，而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做出理论预测，以便我们可以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准确的比较。我们还研究了额外的信号和改进现有方法以发现新物理的方法。对于理论粒子物理学来说，未来五年将是非常激动人心的时期，格拉斯哥的目标是走在这一领域的前沿。

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.