Searching for long-lived particles beyond the Standard Model at the Large Hadron Collider
Searching for long-lived particles beyond the Standard Model at the Large Hadron Collider
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DOI：
10.1088/1361-6471/ab4574
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发表时间：
2019-03
期刊：
影响因子：
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通讯作者：
J. Alimena;James Beacham;M. Borsato;Yangyang Cheng;X. C. Vidal;G. Cottin;A. Roeck;N. Desai
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文献类型：
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作者：
J. Alimena;James Beacham;M. Borsato;Yangyang Cheng;X. C. Vidal;G. Cottin;A. Roeck;N. Desai
超出标准模型（SM）的粒子通常具有比弱尺度下的SM粒子更长的寿命。当在CERN的大型强子对撞机（LHC）等实验中产生时，这些长寿命粒子（LLP）可以在远离初级质子-质子碰撞的相互作用顶点的地方衰变。这种LLP特征与LHC中大多数新物理搜索的目标是快速衰变粒子的特征不同，通常需要定制技术来识别，例如，显着移位的衰变顶点，具有非典型属性的轨道和短轨道段。考虑到它们的非标准性质，全面概述LHC的LLP签名有助于确保发现新物理的可能途径不会被忽视。在这里，我们报告了理论家和实验学家社区与ATLAS，CMS和LHCb实验的联合工作-以及那些致力于专门实验的人，如MoEDAL，milliQan，MATHUSLA，CODEX-b和FASER -调查LLP搜索的当前状态在LHC，并为LLP搜索的发展制定未来的路径，无论是在即将到来的运行3和高亮度LHC。这项工作是围绕LHC实验当前和未来的潜在能力来组织的，以普遍发现新的LLP，并采取基于签名的方法来调查产生LLP的模型类别，而不是强调任何特定的理论动机。我们开发了一套简化的模型;评估当前搜索的覆盖范围;记录已知的，往往是意想不到的背景;探索拟议的探测器升级的能力;为搜索结果的呈现提供建议;并展望最新的前沿，即高多重性“暗阵雨”，突出扩大LHC对这些信号的影响范围的机会。
Particles beyond the Standard Model (SM) can generically have lifetimes that are long compared to SM particles at the weak scale. When produced at experiments such as the Large Hadron Collider (LHC) at CERN, these long-lived particles (LLPs) can decay far from the interaction vertex of the primary proton-proton collision. Such LLP signatures are distinct from those of promptly decaying particles that are targeted by the majority of searches for new physics at the LHC, often requiring customized techniques to identify, for example, significantly displaced decay vertices, tracks with atypical properties, and short track segments. Given their non-standard nature, a comprehensive overview of LLP signatures at the LHC is beneficial to ensure that possible avenues of the discovery of new physics are not overlooked. Here we report on the joint work of a community of theorists and experimentalists with the ATLAS, CMS, and LHCb experiments --- as well as those working on dedicated experiments such as MoEDAL, milliQan, MATHUSLA, CODEX-b, and FASER --- to survey the current state of LLP searches at the LHC, and to chart a path for the development of LLP searches into the future, both in the upcoming Run 3 and at the High-Luminosity LHC. The work is organized around the current and future potential capabilities of LHC experiments to generally discover new LLPs, and takes a signature-based approach to surveying classes of models that give rise to LLPs rather than emphasizing any particular theory motivation. We develop a set of simplified models; assess the coverage of current searches; document known, often unexpected backgrounds; explore the capabilities of proposed detector upgrades; provide recommendations for the presentation of search results; and look towards the newest frontiers, namely high-multiplicity "dark showers", highlighting opportunities for expanding the LHC reach for these signals.