LHCb实验上底强子衰变直接CP破坏的测量  

Measurements of direct CP violation of B hardon decays at the LHCb experiment

作　　者：钱文斌 杨友华 张宇 周晓康 Wenbin Qian;Youhua Yang;Yu Zhang;Xiaokang Zhou(Institute of Physics and Sciences,University of Chinese Academy of Sciences,Bejing 100049,China;Department of Physics,University of Genova e Istituto di Nazionale di Fiscia Nucleare,Genova 16146,Italy;School of Nuclear Science and Technology,University of South China,Hengyang 421001,China;College of Physical Science and Technology,Central China Normal University,Wuhan 430079,China)

机构地区：[1]中国科学院大学物理学院,北京100049 [2]Department of Physics,University of Genova e Istituto di Nazionale di Fiscia Nucleare,Genova 16146,Italy [3]南华大学核科学技术学院,衡阳421001 [4]华中师范大学物理科学与技术学院,武汉430079

出　　处：《科学通报》2024年第31期4590-4600,共11页Chinese Science Bulletin

基　　金：国家重点研发计划(2022YFA1601901);国家自然科学基金(12375087);中央高校基本科研业务费专项资金;小米青年学者项目资助。

摘　　要：CP破坏是解释宇宙中观测到的正反物质不对称的必要条件之一.粒子物理标准模型中CP破坏的唯一来源CKM矩阵给出的CP破坏远不足以解释宇宙中正反物质不对称的程度,亟需寻找新的CP破坏来源.通过底强子直接CP破坏的测量和精确检验CKM矩阵的幺正性,寻找超出标准模型的新机制是理解上述问题的重要途径.LHCb实验有目前世界上最大的底强子数据样本,为精确测量CP破坏提供了理想研究场所.本文介绍了LHCb实验上底强子直接CP破坏研究的前沿进展,包括CKM相角γ和底强子非粲衰变直接CP破坏的最新测量结果及理论实验所关注的热点问题等.Symmetry,particularly transformations involving charge conjugation(C)and parity(P),plays a fundamental role in modern physics and is indispensable in the development of the Standard Model.While strong,electromagnetic,and gravitational forces remain invariant under C and P transformation,weak interactions violate them,leading to CP violation.This phenomenon was initially observed in K meson decays during the 1960s,a pivotal discovery that greatly contributed to our understanding of the matter-antimatter asymmetry in the universe.Within the Standard Model,CP violation is introduced by the CKM matrix,a 3×3 unitary matrix defining the transformation between quark mass and weak interaction eigenstates.This matrix,determined by three rotation angles and one complex phase,accounts for CP violations but falls short in explaining the observed magnitude of matter-antimatter asymmetry,prompting the search for new sources of CP violation.Weak decays of quarks play a crucial role in investigating these fundamental issues.Research focuses on testing the CKM matrix's unitarity and measuring CP violation in decays sensitive to new physics.The LHCb experiment at CERN's Large Hadron Collider stands at the forefront of this research,amassing high statistics data on b-hadron decays.It provides optimal conditions for studying CP violation.In this review,recent results from the LHCb experiment on two key aspects are discussed.Firstly,it explores the measurements of CKM angleγ,one of the main bottlenecks in the unitarity test of the CKM matrix.Secondly,it addresses charmless b-decays,which are important for searching for new sources of CP violation.The CKM angle y is directly measured through interference in tree-level b→u and b→c processes.Various experimental methods have been developed,each with unique approaches and challenges.Strong parameters of D meson decays are crucial in these measurements,obtained through quantum-correlated■meson pairs produced in electronpositron collisions.LHCb's measurements have significantly con

关 键 词：CP破坏 味物理 CKM矩阵 LHCb实验 

分 类 号：O572.33[理学—粒子物理与原子核物理]