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LHC的一个新实验，旨在探测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]。它旨在识别属于暗扇区的新粒子，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，并且处于非常向前的区域，只需要一个小的探测器。FASER探测器位于TI 12中，这是一个以前用于连接超级质子同步加速器（SPS）和LEP的未使用的隧道[2]。安装将在当前的长时间关机期间完成，准备在运行3期间进行数据采集，该运行计划于2022年进行。FASER探测器的主要部件是双极磁铁、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研究和模拟FASER的采样电磁量热计（ECAL）[3]。这是建立在以前的工作，使用Geant 4 [4]中的示例来构建一个简单的模拟设置，并评估角度倾斜的影响，并执行角度扫描以研究量热计中差距的能量损失。还开展了旨在使用更复杂的设置实现快速模拟的工作[5]。ECAL的模拟是研究新物理学的数据分析发展所必需的。目前的工作正在进行对执行的检测器，这需要仔细评估的材料和几何形状的影响，在ECAL的沉积能量的全面模拟。随后将进行额外的工作，以实现快速模拟，减少计算时间，使未来的分析效率。一旦完成，将开发分析数据所需的软件，并用于科学结果。初步研究证实了先前使用简单的Geant 4模拟所显示的结果，即沉积能量的比例和作为注入能量函数的行为。使用FASER的软件框架Calypso [6]的进一步模拟研究正在进行中，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的数据，以寻找暗光子或其他长寿命粒子形式的新物理。参考文献：[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 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