Studies of the FASER Calorimeter and Searches for New Physics with LHC Run 3 Data

FASER 热量计的研究以及利用 LHC Run 3 数据寻找新物理

• 批准号: 2573521
• 金额: --
• 依托单位: University of Liverpool
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2573521
• 关键词: Studies; FASER; Calorimeter; Searches; New

FASER is a new experiment at the LHC designed to detect light and weakly-interacting particles predicted by several extensions of the Standard Model of particle physics [1]. It aims to identify new particles belonging to a dark sector, called dark photons, which are possibly long-lived particles (LLPs) produced at the ATLAS interaction point [2]. These dark photons are thought to decay to e+e- (45%), (45%) or (10%). The decay products of such light, weakly-interacting particles are highly collimated and in the very forward region, requiring only a small detector. The FASER detector is located in TI12 - an unused tunnel previously used to connect the Super Proton Synchrotron (SPS) to LEP [2]. Installation will be completed during the current long shutdown ready for data acquisition during Run 3, which is scheduled for 2022. The main components of the FASER detector are the scintillators, the tracking stations, the dipole magnets, and the calorimeter [1]. The initial focus of this project, prior to data acquisition, is the study and simulation of FASER's sampling electromagnetic calorimeter (ECAL) [3]. This is building on previous work that used examples in Geant4 [4] to build a simple simulation setup and evaluated the impact of angular tilt and performing angular scans to investigate the loss of energy in the gap in the calorimeter. Work was also carried out which aimed to implement fast simulations using a more complex setup [5]. Simulation of the ECAL is required for the development of data analysis in the search for new physics. Current work is being performed towards the implementation of a full simulation of the detector, which requires careful evaluation of the impact of materials and geometry on the deposited energies in the ECAL. Additional work will subsequently be carried out to realise a fast simulation to reduce the computational times and make future analysis efficient. Once this is completed, the software needed to analyse the data will be developed and used for scientific results.Initial studies confirm the results previously shown using simple Geant4 simulations in terms of the fraction of deposited energy and behaviour as a function of injected energy. Further simulation studies using FASER's software framework, Calypso [6], are on-going to evaluate the energy dependence more precisely for high momentum particles. The goal is to validate the electromagnetic calorimeter simulation with first data. The ultimate aim is to go on to analyse data taken at FASER in the search for new physics in the form of dark photons or other long-lived particles. In the event that no such discoveries are made, the goal moves towards setting world-best constraints over a range of parameter space that is currently unexplored.References:[1] FASER Collaboration (2019) FASER's Physics Reach for Long-Lived Particles, Phys. Rev. D 10.1103/PhysRevD.99.095011[2] FASER Collaboration (2018) FASER: FORWARD SEARCH EXPERIMENT AT THE LHC, Technical Report arXiv:1812.09139v1[3] Fabjan, C. W., Gianotti, F. (2003) Calorimetry for Particle Physics, CERN[4] Geant4 Calorimetry Example: https://geant4-userdoc.web.cern.ch/geant4-userdoc/Doxygen/examples_doc/html/ExampleB4.html[5] Fellers, D. (2020) FASER Fast Calorimeter Simulation, FASER Offline Meeting 25/05/2020 https://indico.cern.ch/event/918531/ [6] https://gitlab.cern.ch/dcasper/calypso/-/tree/master-ecal-2020Oct28

FASER 是大型强子对撞机的一项新实验，旨在检测通过粒子物理标准模型的几个扩展预测的光和弱相互作用粒子[1]。它的目的是识别属于暗区的新粒子，称为暗光子，它们可能是在 ATLAS 相互作用点产生的长寿命粒子 (LLP) [2]。这些暗光子被认为会衰减到 e+e- (45%)、(45%) 或 (10%)。这种轻的弱相互作用粒子的衰变产物是高度准直的，并且位于非常靠前的区域，只需要一个小型探测器。 FASER 探测器位于 TI12 - 一条未使用的隧道，以前用于将超级质子同步加速器 (SPS) 连接到 LEP [2]。安装将在目前的长期停工期间完成，准备在计划于 2022 年进行的第 3 次运行期间采集数据。FASER 探测器的主要组件是闪烁体、跟踪站、偶极磁铁和量热计 [1]。在数据采集之前，该项目的最初重点是 FASER 采样电磁热量计 (ECAL) 的研究和模拟 [3]。这是建立在之前的工作基础上的，该工作使用 Geant4 [4] 中的示例来构建简单的模拟设置，并评估角度倾斜的影响并执行角度扫描以研究热量计间隙中的能量损失。还开展了旨在使用更复杂的设置实现快速模拟的工作[5]。在寻找新物理学的过程中，数据分析的发展需要 ECAL 仿真。目前正在进行的工作是对探测器进行全面模拟，这需要仔细评估材料和几何形状对 ECAL 中沉积能量的影响。随后将进行额外的工作以实现快速模拟，以减少计算时间并提高未来分析的效率。一旦完成，将开发分析数据所需的软件并将其用于科学结果。初步研究证实了之前使用简单的 Geant4 模拟在沉积能量的分数和作为注入能量的函数的行为方面显示的结果。使用 FASER 的软件框架 Calypso [6] 正在进行进一步的模拟研究，以更精确地评​​估高动量粒子的能量依赖性。目标是用第一批数据验证电磁量热计模拟。最终目标是继续分析 FASER 采集的数据，以寻找暗光子或其他长寿命粒子形式的新物理。如果没有做出这样的发现，目标将转向在当前未探索的一系列参数空间上设置世界最佳约束。参考文献：[1] FASER Collaboration (2019) FASER's Physical Reach for Long-Lived Particles, Phys 。 Rev. D 10.1103/PhysRevD.99.095011[2] FASER 协作 (2018) FASER：大型强子对撞机的正向搜索实验，技术报告 arXiv:1812.09139v1[3] Fabjan, C. W., Gianotti, F. (2003) 粒子物理量热法，欧洲核子研究中心[4] Geant4 量热示例：https://geant4-userdoc.web.cern.ch/geant4-userdoc/Doxygen/examples_doc/html/ExampleB4.html[5] Fellers, D. (2020) FASER 快速量热仪模拟，FASER 离线会议 25 /05/2020 https://indico.cern.ch/event/918531/ [6] https://gitlab.cern.ch/dcasper/calypso/-/tree/master-ecal-2020Oct28