Understanding electroweak symmetry breaking from LHC data

粒子物理学的标准模型(SM)描述了迄今为止已知的所有粒子和力。在过去的50年里，它经过了精准的测试。标准模型的理论描述是基于优雅的对称性原理。它允许仅用三个参数来描述所有的相互作用，即规范耦合常数。然而，同样的原理预言SM的所有粒子都应该是无质量的。事实并非如此，这意味着对称必须以某种方式被打破。这种现象被称为电弱对称破缺(EWSB)，造成这种现象的物理机制在很大程度上是未知的，揭开它是过去二三十年来高能物理的主要任务之一，无论是理论上的还是实验上的。目前在瑞士日内瓦附近的欧洲核子研究中心运行的大型强子对撞机就是考虑到这一目标而建造的。这是一个圆周长达27千米的圆形加速器，可以让两束能量非常高的质子相撞(每束质子现在的能量为4TeV)。两台记录碰撞复杂结果的探测器最近发现了似乎是希格斯玻色子的东西，这一发现的宣布于2012年6月公布，这一发现引起了极大的兴奋，特别是对粒子物理学家来说，对普通公众也是如此。虽然希格斯场提供了对EWSB的很好的描述，但完全理解它的探索远未结束。例如，只有一个希格斯玻色子的SM需要非常精确的参数微调。此外，它也没有解释暗物质的观测，也没有解释SM粒子的不同质量和混合的结构。我的研究计划试图通过提出EWSB的替代理论来理解其中的一些问题。例如，我正在研究超对称模型和小希格斯模型。这些理论预测了在大型强子对撞机上可以看到的新粒子和/或力。在各种研究项目中，我提议建立新的模型，为SM的缺陷提供解决方案，并研究它们对大型强子对撞机可能观察到的结果的影响。

The Standard Model(SM) of particle physics gives a description of all the particles and forces known to date. Over the past 50 years it has been tested to exquisite precision. The theoretical description of the Standard Model is based on an elegant symmetry principle. It allows to describe of all interactions in term of only three parameters, namely the gauge coupling constants. However, the same principle predicts that all the particles of the SM should be massless. This is not the case, which means that the symmetry must somehow be broken. This phenomenon is called electroweak symmetry breaking(EWSB) and the physics responsible for it remains to a large extend unknown and uncovering it has been one of the main quests of high energy physics, both theoretical and experimental for the past two or three decades. The Large Hadron Collider now in operation in CERN near Geneva Switzerland has been built with this objective in mind. It is a circular accelerator with a circumference of 27km that collides two beams of protons with very high energy (each beam has now an energy of 4 TeV). Two detectors that record the complicated results of the collisions have recently discovered what seem to be the Higgs boson and the announcement of this discovery was made public in June of 2012, creating a lot of excitement, for particle physicists in particular, but for the general public as well. While the Higgs field offers a good description of EWSB, the quest to fully understand it is far from over. For example, the SM with a single Higgs boson requires a very precise fine-tuning of parameters. It also, among other things, doesn't give an explanation for the observation of dark matter, or explain the structure of the different masses and mixing of the SM particles.My research program tries to understand some of these issues by proposing alternatives theories of EWSB. For example, I am studying supersymmetric models and Little Higgs models. Those theories predict new particles and/or forces that could be seen at LHC. In various research projects I propose to build new models that offer solutions to the shortcomings of the SM, and study their consequences for what the LHC might observe.