LHCb实验上前向区域的电弱物理测量  

Electroweak measurements in the forward region at LHCb

作　　者：尹航 徐梦琳 Hang Yin;Menglin Xu(Institute of Particle Physics,Central China Normal University,Wuhan 430079,China;University of Warwick,Coventry CV47AL,UK)

机构地区：[1]华中师范大学粒子物理研究所,武汉430079 [2]University of Warwick,Coventry CV47AL,UK

出　　处：《科学通报》2024年第31期4601-4610,共10页Chinese Science Bulletin

基　　金：国家自然科学基金(12275101)资助。

摘　　要：电弱统一理论是粒子物理标准模型的重要组成部分.精确测量电弱理论的基本参数是检验标准模型和间接寻找超标准模型新物理的重要途径.大型强子对撞机上的LHCb探测器是一个覆盖前向接受度区域的单臂探测器.LHCb实验在前向快度区域的电弱物理测量和质子部分子分布函数测量与ATLAS、CMS实验在中心快度区域的相关测量形成良好互补,能够有效提升电弱物理参数的测量精度、降低系统不确定性.本文介绍了电弱物理及其重要性,综述了LHCb实验上最新的电弱精确测量,包括以下结果:利用第一和第二运行期内采集的质子-质子对撞数据,对W质量、弱混合角等基本参数进行了精确测量,对前向区域的Z玻色子产生截面以及极化进行了测量,为质子部分子分布函数的全局拟合提供了重要且独特的输入;在玻色子伴随粲夸克的产生过程中发现了质子内部存在内秉粲夸克组分的迹象;在Z/W玻色子的稀有衰变方面进行了初步探索.这些实验结果表明LHCb实验在电弱物理方面发挥了极其重要的作用.未来LHCb探测器升级后获取的更多实验数据将进一步提升我们对电弱理论以及质子部分子分布函数的理解.The electroweak theory is an essential component of the Standard Model of particle physics.Precision measurements of electroweak physics observable,through different decay modes and approaches,could not only provide stringent tests on the Standard Model,but also be used to search for new physics indirectly.The LHCb detector is a forward spectrometer in the Large Hadron Collider.Compared to general-purpose detectors,such as the ATLAS and CMS detectors,it covers a unique acceptance region,and provides comprehensive and complementary information.Therefore,the data collected by the LHCb detector could provide stringent constraint on the parton distribution functions of the proton,which is also an important input for the global fit of parton distribution functions.For many important measurements,the LHCb results combined with those from ATLAS and CMS experiments could significantly reduce the systematic uncertainty.This paper introduces the importance of the electroweak physics of the Standard Model and reviews the most recent electroweak results from the LHCb experiment.In the Standard Model,the W mass and weak mixing angle are the fundamental parameters of the electroweak theory.However,tensions between results from different experiments are seen.In 2022,the CDF collaboration published its result on the W mass,which has a large tension between measured results and the electroweak global fit expectation,indicating the existence of new physics.However,tensions between the CDF result and results from other experiments are also seen.Therefore,it is important to have more experimental results to either confirm or exclude the CDF result.As a proof-of-principle,the LHCb collaboration performed the W mass measurement with part of its Run-2 dataset.The measured result is consistent with the electroweak global fit expectation,while an update with more data in the future is expected to have higher precision.The LHCb collaboration also performed the first measurement of the weak mixing angle in the forward region using the Run-

关 键 词：电弱物理 大型强子对撞机 标准模型 质子部分子分布函数 W玻色子质量 弱混合角 

分 类 号：O572.214[理学—粒子物理与原子核物理]