Heavy quarks, a window into New Physics at ATLAS

我提议的目标是粒子物理前沿的基础研究，以及使这项研究成为可能的仪器。我将用多重夸克的签名来寻找新物理学的迹象。粒子物理学，目前正处于十字路口。粒子相互作用的描述称为标准模型。根据我们对这个模型的理解，需要新的粒子和机制才能在高能下始终如一地维持理论框架。到目前为止，标准模型已经非常成功地解释了高能物理实验的现有数据，比如大型强子对撞机(LHC)的ATLAS实验，但它还不完整。它不能解释观测到的暗物质和暗能量，它们占据了我们宇宙的95%。它也没有一个令人满意的答案来解释为什么宇宙中的物质比反物质多。最后，到目前为止，还没有发现一种重要的粒子--希格斯玻色子。欧洲核子研究中心的大型强子对撞机在能源前沿运行。大型强子对撞机以极高的能量碰撞质子。由此产生的能量密度可与大爆炸后不久的能量密度相媲美。在这次碰撞中产生的粒子将允许进一步揭示物质及其相互作用的基本性质。由于与以前的实验相比，能量有了很大的增加，预计会有令人兴奋的新发现。在令人振奋的可能性中，有可能出现暗物质。这项基础性研究将极大地扩展我们的知识范围。大型强子对撞机的最新测量还没有显示出新物理学的直接信号，这指向了一项发现，其中新粒子的质量尺度比预期的要高。与此同时，数据表明，对于丢失的希格斯玻色子，在低质量时有一个小质量窗口。重的新粒子可能会耦合到顶夸克，这是已知的最重的基本粒子。顶部有一个独特的信号，如果它的衰变产物是所谓的底部夸克。为了进行干净的顶部重建，需要识别b型喷气式飞机。这种“b标记”利用了这样一个事实，即b强子寿命很长，并且显示出一个明显移位的次级顶点。传统的b标签并不决定b喷气式飞机的费用。这就是区分b夸克和反b夸克的味道标记领域。对b型喷注电荷的了解可以大大减少组合背景。我将使b-物理味道标记技术适用于新物理探索。ATLAS实验是大型强子对撞机的两个通用探测器之一。这台巨大的仪器具有出色的重建粒子轨迹和顶点的能力，并以高精度测量它们的动量和能量。这些特性使ATLAS探测器成为测试新物理的一个很好的仪器。顶点的重建依赖于跟踪设备。这样的设备本质上是一台8000万通道的大型数码相机，每25纳秒记录一次带电粒子的经过。为了充分利用任何新发现，并扩大稀有过程的物理覆盖范围，大型强子对撞机及其探测器的升级是必要的。ATLAS跟踪器需要升级，以确保随着大型强子对撞机碰撞强度的增加，继续保持良好的跟踪性能。跟踪器的持续良好性能是非常重要的，因为它是从b-Jet重建二次顶点的先决条件。因此，我建议在ATLAS追踪器，特别是像素升级项目中发挥领导作用。在研究过程中，我建议使用ATLAS收集到的带有多个b型喷气机的事件来搜索到目前为止未知的物理现象。此外，我还将领导跟踪设备升级的研发。新的跟踪设备不仅在粒子物理中有广泛的应用，而且在医学成像中也有广泛的应用。

The goal of my proposal is fundamental research at the frontier of particle physics and the instrumentation that makes this research possible. I will search for signs of New Physics using the signature of multiple heavy quarks.Particle Physics, is currently at a cross road. The description of particle interactions is called the Standard Model. From our understanding of this model, new particles and mechanisms are required in order to consistently sustain the theoretical framework at high energies. So far, the Standard Model has been very successful in explaining the existing data from high energy physics experiments, like the ATLAS experiment at the Large Hadron Collider (LHC), but it is not complete. It does not explain the observed dark matter and dark energy, that fill 95% of our universe. Nor does it have a satisfactory answer to why there is more matter than anti-matter in the universe. Lastly, one essential particle, the Higgs boson, has not been found so far. The LHC at CERN operates at the energy frontier. The LHC collides protons at extremely high energy. The resulting energy density is comparable to the energy density shortly after the Big Bang. The particles produced in this collision will allow to further unravel the fundamental nature of matter and its interactions. Due to the large increase in energy with respect to previous experiments, exciting new discoveries are expected. Among the exhilarating possibilities are candidates for dark matter. This fundamental research will significantly extend the boundaries of our knowledge. The latest measurements at the LHC, have not shown a direct signal of New Physics yet, pointing to a discovery, where the mass scale of new particles is higher than anticipated. At the same time the data indicate a small mass window at low mass, for the missing Higgs Boson.Heavy new particles are likely to couple to the top quark, the heaviest known elementary particle. The top has a unique signature, as one if its decay products is a so called bottom-quark. For an clean top reconstruction the b-jets need to be identified. This "b-tagging" makes use of the fact, that b-hadrons are long lived and show a clearly displaced secondary vertex. Traditional b-tagging does not determine the charge of b-jets. This is the realm of flavour tagging that distinguishes b and anti-b quarks. The knowledge of the charge of b-jet can considerable reduce combinatorial background. I will make b-physics flavour tagging techniques applicable to New Physics searches.The ATLAS experiment is one of two general purpose detectors at the LHC. The gigantic apparatus has excellent capabilities to reconstruct the tracks and vertices of particles and measure their momenta and energy with high precision. These properties make the ATLAS detector a great apparatus to test for new physics. The reconstruction of vertices relies on tracking devices. Such a device is essentially a large 80 million channel digital camera, that records the passing of charged particles every 25 nanoseconds. To fully exploit any new discoveries and extend the physics reach for rare processes, an upgrade of the LHC and its detectors is necessary. The ATLAS tracker needs to be upgraded in order to guarantee continuing good tracking performance with increasing intensity of LHC collisions. Continuing good performance of the tracker is very important, as it is a prerequisite for the reconstruction of secondary vertices from b-jets. Therefore I propose to take a leading role in the ATLAS tracker and in particular the pixel upgrade project. During the course of the fellowship I propose to use events with multiple b-jets collected by ATLAS to search for so far unknown physics phenomena. In addition I will lead research and development on the tracking device upgrade. New tracking devices have a wide range of applications, not only in particle physics, but for example also in medical imaging.