基于美国布鲁克海文国家实验室sPHENIX实验对新型电磁量能器的性能和底夸克偶素质量谱的模拟研究

Over the past decade, while RHIC and LHC have acquired higher statistics and more precise experimental data, various theoretical tools have been continuously improved and developed, and we have a deeper understanding of the high temperature and high-density nuclear matter, i.e. quark-gluon plasma (QGP). But many important problems still need to be solved urgently, such as the composition of QGP and how quarks and gluons form the hydrodynamic properties of QGP like ideal liquids. In order to establish the relationship between QGP micro-structure and macro-structure, in the next era, we need to use a variety of analytical scales of micro-probes to explore the internal mechanism of QGP, especially the important probes, such as particle jets and heavy quarkonium. The sPHENIX experiment on RHIC can accurately measure high-energy QGP probes in multiple dimensions, including Jet, photon Jet pairs and Upsilon particles, and study the interaction between QGP and various high-energy probes, the evolution of QGP and its internal structure. . The sPHENIX experiment plans to measure one of the unique probes, bottom quarkonium. The three quantum states (1S, 2S, and 3S) of the Upsilon meson can be observed and distinguished simultaneously by detecting the positron-electron pairs at final states of its decay. The differential suppression effect of QGP medium on Upsilon particles during heavy ion collision can be studied. The simulation work related to the sPHENIX experiment is one of the main tasks of the international cooperation group of sPHENIX. Its main purpose is to quantify the design objectives and physical performance of detectors. This application is based on the sPHENIX experimental framework to carry out simulation studies of electromagnetic calorimeter performance and bottom quark mass spectrum. The first is to quantify the performance of the electromagnetic calorimeter, especially to evaluate its ability to detect electrons in the di-electron decay channel. The second is to carry out simulation studies of background estimation and electronic recognization, to evaluate the separation ability of electromagnetic calorimeter for the three quantum states of Upsilon meson in its mass spectrum, and then to evaluate the performance of the measurement of the differential suppression effect of Upsilon meson in QGP medium.

将在RHIC上计划运行的sPHENIX实验可以精确测量多个维度下的高能QGP探针，包括喷注、光子喷注对和底夸克偶素等，研究QGP与各种高能探针间的相互作用和QGP的演化及其内部结构等。关于sPHENIX实验相关的模拟工作是sPHENIX国际合作组主要工作之一，其目的主要是确定量化探测器设计目标和物理性能。本申请项目拟基于sPHENIX实验框架开展电磁量能器性能和底夸克偶素质量谱的模拟研究。一是通过模拟分析量化电磁量能器的性能指标，特别是评估其对双电子衰变道中电子的探测能力。二是进行背景估计和电子识别的模拟研究，评估电磁量能器对Upsilon介子质量谱三个量子态的分离能力，进而分析评估对Upsilon介子在QGP介质中的微分压制效应的测量的性能。

将在RHIC上计划运行的sPHENIX实验可以精确测量多个维度下的高能QGP探针，包括喷注、光子喷注对和底夸克偶素等，研究QGP与各种高能探针间的相互作用和QGP的演化及其内部结构等。关于sPHENIX实验相关的模拟工作是sPHENIX国际合作组主要工作之一，其目的主要是确定量化探测器设计目标和物理性能。本项目的研究工作主要基于sPHENIX实验探测器的整体设计框架以及电磁量能器基本结构，通过模拟分析了高能核核对撞事件的末态粒子在探测器上的响应数据，确定了电磁量能器有对电子测量良好的响应性能、能量分辨及鉴别能力，进而研究了sPHENIX实验对Upsilon粒子双电子衰变的重构技术及其背景大小估计等，验证了sPHENIX实验可以通过Upsilon粒子的测量研究QGP介质对Upsilon粒子三个量子态的微分抑制效应。本项目对电子鉴别的重点研究表明了sPHENX实验对Upsilon的探测具有显著的信号提取能力。机器学习应用于粒子鉴别具有很大的优势，作为本项目的亮点工作，基于机器学习的算法可以大大提高信号电子的鉴别能力和背景强子的否决能力。这将大大提高对Upsilon粒子信号测量的信噪比，特别是对提取Upsilon(3s)态的信号将发挥决定性的作用。

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