Precision Cross Section Measurements and Searches for New Physics with ATLAS

物质的基本成分及其相互作用的性质启发了人类，至少从古希腊哲学家提出不可分割的基本粒子的想法开始。今天，最著名的理论-标准模型(SM)-在过去30年里在大型粒子加速器的许多实验中以非常高的精度得到了测试。尽管SM已经能够描述所有已发现的效应，但仍有许多奇迹有待解决。例如，天体物理观测表明，到目前为止，我们所知道和研究的物质只占宇宙物质含量的二十分之一。大型强子对撞机(LHC)是有史以来建造的能量最高的粒子加速器。它碰撞质子的能量至少是其他设施的7倍。这项复杂的ATLAS实验旨在记录这些剧烈碰撞的结果。在大型强子对撞机和ATLAS的帮助下，我们可能在几年内解决一些悬而未决的问题。一种解决方案可能是所谓的超对称理论，即我们今天所知的每个基本粒子都被分配了一个伙伴。如果这些新粒子存在，它们应该在大型强子对撞机上被发现，并将研究它们的性质。第一个任务将是了解ATLAS实验的特性，这是有史以来建造的最复杂的技术设备之一。它长约26米，高20米，重7000吨。尽管如此，一些内部组件--硅轨探测器--的定位精度必须达到千分之一毫米。我将与利物浦的专家一起确定校正，以实现尽可能最佳的测量精度。他们建造了这些探测器的一部分。下一项任务将是精确测量已知的标准模型粒子的产生，即所谓的W玻色子。这项测量将显示我们对实验仪器、标准模型和基本粒子的质子组成的理解程度。利用我们今天掌握的所有信息，我们能够预测W玻色子的产生速度，这样我们就可以将测量结果与我们的预期进行比较。最后，我将寻找超越标准模型的理论所预测的粒子。如果产生这些新粒子中的任何一个，它们将迅速衰变成其他可由ATLAS登记的已知粒子。我建议将我的研究重点放在衰变上，在衰变中，电子和它的反物质伙伴正电子与其他高能物体(所谓的喷流)和暗物质的候选粒子一起产生。理论家告诉我们，这类事件将发生在许多不同类型的新模型中，但标准模型预测的比率非常低。衰变产物将携带足够的双亲信息，从而可以确定基本理论的性质。我期待着为这一激动人心的科学计划做出贡献，这可能会显著增强我们对基本构成要素和自然规律的理解。

The nature of the fundamental constituents of matter and their interactions have inspired mankind at least since the days, when the idea of indivisible elementary particles was formulated by ancient Greek philosophers. Today we stand at a point, where the best known theory - the Standard Model (SM) - has been tested over the last 30 years with a very high precision in many experiments at large particle accelerators. Even though the SM has been able to describe all discovered effects, many miracles remain to be solved. For example astrophysical observations show, that the matter we know and have studied up to now makes up only 1/20th of the matter content of the universe. The Large Hadron Collider (LHC) is the highest energy particle accelerator ever build. It collides protons at energies at least 7 times higher than in every other facility. The complex ATLAS experiment was designed to register the outcome of these violent collisions. With the help of LHC and ATLAS we may be able to solve some of the open questions within a few years. One solution may be so called Super Symmetric theories, where every fundamental particle we know today is assigned a partner. If these new particles exists, they should be discovered at the LHC and their properties will be studied. The first task will be to understand the properties of the ATLAS experiment, one of the most complex technical devices ever build. It is approximately 26 m long, 20 m high, and weighs 7000 tons. Still, some of the inner components, the silicon track detectors, have to be positioned with an accuracy of a few 1/1000 of a millimetre. Together with the experts in Liverpool, who build a part of these detectors, I will determine corrections to achieve the best possible measuring accuracy. The next task will be accurate measurements of the production of known Standard Model particles, so called W bosons. This measurement will show how well we understand the experimental apparatus, the Standard Model, and the composition of the proton from elementary particles. Using all the information we have today, we are able to predict the rate with which the W bosons are produced, so we can compare the measurements to our expectation. Finally, I will look for the particles predicted by theories that go beyond the Standard Model. If any of these new particles are produced, they will decay rapidly to other known particles which can be registered by ATLAS. I propose to concentrate my search on decays, where an electron and its antimatter partner, the positron, are produced together with other highly energetic objects (so called jets) and the candidate particle for the dark matter. Theorists tell us, that this kind of events will happen for many different types of new models, but the Standard Model predicts very low rates. The decay products will carry enough information of their parents, so the properties of the fundamental theory can be determined. I am looking forward to contributing to this exciting scientific program, which may significantly enhance our understanding about the basic building blocks and laws of nature.