Search for squarks and gluinos at the ATLAS experiment

在 ATLAS 实验中寻找夸克和胶子

• 批准号: ST/G006717/1
• 负责人: Monica D'Onofrio
• 金额: $ 55.47万
• 依托单位: University of Liverpool
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FG006717%2F1
• 关键词: Search; squarks; gluinos; ATLAS; experiment

The aim of Particle Physics is to understand the nature of the constituents of matter and the forces that bind them together. In the early part of the last century our knowledge grew from concepts of atoms to the discovery of the nucleus and its constituent, protons and neutrons. Later it was discovered that the protons and neutrons also had a sub-structure of quarks held together by gluons. A picture emerged of 6 different quarks, up and down, charm and strange, top and bottom (and their antiparticles), arranged into 3 families, and 4 different forces, strong nuclear force, electromagnetic force, weak nuclear force and gravity. A similar structure was found among leptons, the particles that do not interact via the strong force: electron, muon and tau and their corresponding neutrinos. The Standard Model (SM) of particle physics describes how these particles and forces interact, but ignores the gravitational force. Although high-precision experiments have verified its predictions, the SM is often regarded as a low energy effective theory for several open questions. Among others, it does not explain the origin of particle masses and the Higgs boson, the postulated particle necessary to generate elementary particle mass, has not been observed yet and its own mass is unspecified. Several theoretical scenarios have been proposed to describe physics at very high energies, of which SuperSymmetry (SUSY) and Extra-Dimension (ED) are the most compelling ones. In the large majority of cases, these scenarios foresee the existence of new particles. In SUSY inspired models, for example, the usual particle spectrum is at least doubled and every particle has a 'superpartner' differing in spin by a half unit, possibly much heavier in mass. This solves one of the difficulties in the SM of keeping the Higgs mass stable. The best way to explore the 'Beyond Standard Model' territory is to study collisions between fundamental constituents of matter at extremely high energies, to the TeV scale and beyond. To accomplish this, the High Energy Physics community has designed the most powerful accelerator: the Large Hadron Collider (LHC). Built at CERN, the LHC will collide protons at unprecedented energies. ATLAS, one of the two general purpose experiments at the LHC, will try to find the fingerprints of unknown particles, which might manifest themselves as resonances or through various complex signatures hidden underneath large SM background processes. The primary aim of my proposed programme is to discover new physics with the ATLAS detector at the earliest stage of the LHC turn-on, while simultaneously performing measurements of SM processes in preparation for more detailed longer term searches over the next 5 years. Precision SM measurements are not only important in their own right but also constitute unavoidable backgrounds to searches for SUSY particles. Furthermore, they provide the essential means to optimize the calibration of the detector. Exploiting the knowledge acquired from these studies in terms of detector performances, I shall carry out searches for squarks and gluinos, the superpartner of quarks and gluons, in final state events including jets of hadrons, leptons and large unbalanced transverse momentum. If SUSY is discovered, I will measure the kinematics of squark and gluino decay chains and evaluate their fundamental parameters. The beginning of the LHC era represents a milestone in particle physics and it is imperative to have a well-defined analysis search strategy in the aim of maximizing the potential to find new physics. My research will largely benefit from the combination of the experience I gained at the Tevatron collider and the Liverpool group expertise. This is an exciting time for our field. We have the unique ability to explore the uncharted territory at the energy frontier, and I am eager to be at the forefront of the ATLAS physics programme.

粒子物理学的目的是了解物质组成成分的性质以及将它们结合在一起的力。在上个世纪早期，我们的知识从原子的概念发展到原子核及其组成部分质子和中子的发现。后来人们发现，质子和中子也有一种由胶子结合在一起的夸克的子结构。出现了6种不同的夸克，上夸克和下夸克，粲夸克和奇夸克，顶夸克和底夸克（以及它们的反粒子），分为3个科，以及4种不同的力，强核力、电磁力、弱核力和引力。在轻子（不通过强作用力相互作用的粒子）中也发现了类似的结构：电子、介子和τ以及它们对应的中微子。粒子物理学的标准模型（SM）描述了这些粒子和力是如何相互作用的，但忽略了引力。虽然高精度的实验已经证实了它的预测，但对于一些悬而未决的问题，SM通常被认为是一个低能量有效的理论。其中，它没有解释粒子质量的起源，而希格斯玻色子（假定产生基本粒子质量所必需的粒子）尚未被观察到，其自身的质量也未确定。已经提出了几个理论场景来描述非常高能量的物理，其中超对称（SUSY）和超维（ED）是最引人注目的。在大多数情况下，这些设想都预示着新粒子的存在。例如，在受超对称性启发的模型中，通常的粒子谱至少翻倍，每个粒子都有一个自旋不同半单位的“超级伙伴”，质量可能要重得多。这解决了SM中保持希格斯粒子质量稳定的难题之一。探索“超越标准模型”领域的最好方法是研究极高能量的物质基本成分之间的碰撞，达到TeV或更高的尺度。为了实现这一目标，高能物理团体设计了最强大的加速器：大型强子对撞机（LHC）。在欧洲核子研究中心建造的大型强子对撞机将以前所未有的能量碰撞质子。ATLAS是大型强子对撞机的两个通用实验之一，它将试图找到未知粒子的指纹，这些指纹可能表现为共振，或者隐藏在大型SM背景过程之下的各种复杂特征。我提出的计划的主要目的是在大型强子对撞机启动的最初阶段用ATLAS探测器发现新的物理现象，同时对SM过程进行测量，为未来5年更详细的长期搜索做准备。精确的SM测量不仅本身很重要，而且为寻找超对称性粒子提供了不可避免的背景。此外，它们还为优化探测器的校准提供了必要的手段。利用从这些研究中获得的关于探测器性能的知识，我将在包括强子、轻子和大不平衡横向动量射流在内的终态事件中搜索夸克和胶子，夸克和胶子的超级伙伴。如果超对称性被发现，我将测量方克和胶子衰变链的运动学，并评估它们的基本参数。大型强子对撞机时代的开始代表了粒子物理学的一个里程碑，为了最大限度地发掘新物理学的潜力，必须有一个明确定义的分析搜索策略。我的研究将在很大程度上受益于我在Tevatron对撞机上获得的经验和利物浦团队的专业知识。这是我们这个领域激动人心的时刻。我们有独特的能力在能源前沿探索未知的领域，我渴望成为ATLAS物理项目的最前沿。

项目成果

Search for nonpointing photons in the diphoton and E T miss final state in s = 7 TeV proton-proton collisions using the ATLAS detector

使用 ATLAS 探测器在双光子和 E T 中搜索非指向光子，在 s = 7 TeV 质子-质子碰撞中错过最终状态

• DOI: 10.1103/physrevd.88.012001
• 发表时间: 2013
• 期刊: Physical Review D
• 影响因子: 5
• 作者: Aad G

Search for top and bottom squarks from gluino pair production in final states with missing transverse energy and at least three b-jets with the ATLAS detector

• DOI: 10.1140/epjc/s10052-012-2174-z
• 发表时间: 2012-07
• 期刊: The European Physical Journal C
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