Search for new physics on the FASER experiment at the LHC

前向搜索实验（FASER）是一项突破性的基于CERN的计划，作为大型强子对撞机（LHC）运行3的一部分，于2022年夏季开始采集数据。FASER位于ATLAS实验使用的质子-质子相互作用点下游480米处，专门设计用于探索光和弱相互作用的超标准模型（BSM）粒子，其特征是具有相当长的寿命，称为长寿命粒子（LLP）。FASER的仪器配置包括一个圆柱形光谱仪，配备有跟踪器和量热计，浸没在0.6特斯拉的磁场中。这项新的实验已经积累了大约40/fb的数据，预计到2025年运行3结束时将积累超过200/fb的数据。这些粒子表现出一种独特的特征，其特征是两个带相反电荷的高能轨道，起源于探测器内的一个共同顶点。这些轨道具有一个组合的动量，通过10米的混凝土和90米的岩石指向ATLAS交互点。利用基本技术进行的初步数据分析将已经完成，并将提供初步结果。该项目将涉及加强这些初步分析，以提高对暗光子的灵敏度，并探索其他新的物理模型，包括类轴子粒子，将采用先进的多元技术，如神经网络，开发旨在优化信号选择和背景减少的复杂分析。这包括综合来自各个探测器组件的信息，以建立一个全面的粒子识别框架，大大加强信号和背景事件的分离，此外，还将对拟议的FASER实验升级进行可行性研究，这涉及在一个最先进的设施中安装一个全新的探测器。这个升级后的FASER实验将在高亮度LHC上收集更大的数据集，为粒子物理领域的突破性发现开辟新的途径。

The Forward Search Experiment (FASER) is a ground-breaking CERN-based initiative that commenced data-taking during the Summer of 2022 as part of Run 3 of the Large Hadron Collider (LHC). Positioned 480 meters downstream of the proton-proton interaction point used by the ATLAS experiment, FASER is specifically designed for the exploration of light and weakly-interacting Beyond Standard Model (BSM) particles characterized by a substantial lifetime, known as Long-Lived Particles (LLPs). FASER's instrumental configuration comprises a cylindrical spectrometer equipped with a tracker and calorimeter, submerged in a 0.6 Tesla magnetic field. This novel experiment has already accumulated approximately 40/fb of data and is anticipated to amass more than 200/fb by the end of Run 3 in 2025.The primary focus of this research is to analyse the data obtained by FASER, concentrating on the quest for Long-Lived Dark Photons. These particles exhibit a distinctive signature characterised by two oppositely charged, high-energy tracks, originating from a common vertex within the detector. These tracks possess a combined momentum pointing back through 10 meters of concrete and 90 meters of rock to the ATLAS interaction point. Initial data analysis utilizing basic techniques will have already been conducted, with preliminary results made available. The project will involve enhancing these preliminary analyses to increase the sensitivity to dark photons and to explore other novel physics models, including axion-like particles.Advanced multivariate techniques, such as neural networks, will be employed to develop sophisticated analyses aimed at optimizing signal selection and background reduction. This includes the integration of information from individual detector components to establish a comprehensive particle identification framework, significantly enhancing the separation of signal and background events.Furthermore, feasibility studies will be conducted for a proposed FASER experiment upgrade, which involves the installation of an entirely new detector in a state-of-the-art facility. This upgraded FASER experiment will collect a substantially larger dataset at the High-Luminosity LHC, opening new avenues for ground-breaking discoveries in the realm of particle physics.