New Physics at the Large Hadron Collider

欧洲核子研究中心的大型强子对撞机(LHC)是未来十年粒子物理的旗舰研究设施。在2012年大型强子对撞机第一阶段发现希格斯粒子后，从2015年开始的第二阶段的关键科学目标是寻找和探索超越标准模型(SM)的物理。在太电子伏特(TeV)尺度上，即在大型强子对撞机(LHC)的范围内，新物理的存在是由SM留下的两个基本问题推动的：等级问题和暗物质的性质。等级问题指的是希格斯质量在电弱尺度上的不稳定性，它受到源自高尺度物理的量子涨落的影响。例如，可以通过新的TeV级粒子与SM顶夸克配对来解决这个问题。另一方面，暗物质是由稳定的、相互作用弱的粒子与质量接近TeV尺度的粒子自然解释的。这种粒子在SM的许多扩展中都被预测到，这些扩展试图解决层级问题，比如超对称性或具有额外空间维度的模型。在大型强子对撞机上，可以直接寻找新的物理学，例如，在由逃逸的暗物质粒子引起的横向动量不平衡的签名中，或者通过精确度研究，试图在所有现有的实验观测数据的全球理论分析中建立与标准模型的偏差，特别是包括希格斯部分。在大型强子对撞机的新物理研究单元中，我们建议在大型强子对撞机上进行新的物理场景的理论计算和分析，这些场景解决了层次结构问题，暗物质的起源，或者两者兼而有之。它们特别包括新粒子的产生和衰变的精确计算，探索希格斯顶区和暗物质模型，系统研究大型强子对撞机和暗物质的产生和探测，以及希格斯性质和新物理模型的全球拟合。这些理论分析将为解释大型强子对撞机第二阶段新的物理搜索提供基础，对于充分开发其潜力至关重要。

The Large Hadron Collider (LHC) at CERN is the flagship research facility of particle physics for the next decade. After the discovery of a Higgs particle in the first phase of the LHC in 2012, the key scientific goal for the second phase, starting in 2015, is to search for and explore physics beyond the Standard Model (SM). The existence of new physics at the Tera-electronvolt (TeV) scale, i.e. in reach of the LHC, is motivated by two fundamental questions left unanswered by the SM: the hierarchy problem and the nature of dark matter. The hierarchy problem refers to the instability of the Higgs mass at the electroweak scale under quantum fluctuations originating from high-scale physics. It can be solved, for example, through new TeV-scale particles partnering the SM top quark. Dark matter, on the other hand, is explained naturally by stable, weakly interacting particles with masses near the TeV scale. Such particles are predicted in many extensions of the SM, which attempt to solve the hierarchy problem, like supersymmetry or models with extra space dimensions. At the LHC, new physics can be searched for either directly, for example in signatures with a transverse momentum imbalance caused by escaping dark matter particles, or through precision studies which attempt to establish deviations from the Standard Model in a global theoretical analysis of all existing experimental observables, including in particular the Higgs sector.In the Research Unit ¿New Physics at the LHC¿ we propose to pursue theoretical calculations and analyses of new physics scenarios at the LHC which address the hierarchy problem, the origin of dark matter, or both. They comprise, in particular, precision calculations for the production and decay of new particles, the exploration of the top-Higgs sector and models of dark matter, a systematic study of top-partner and dark matter production and detection at the LHC, and global fits of Higgs properties and new physics models.These theoretical analyses shall provide the basis for the interpretation of new physics searches during the second phase of the LHC, and are crucial in order to fully exploit its potential.