π^(0)介子寿命的实验研究  

Experimental Research of Neutral Pion Lifetime

作　　者：马玲玲[1,2] 杨翠 MA Lingling;YANG Cui(The Key Laboratory of Physics and Photoelectric Information Functional Materials,North Minzu University,Yinchuan 750021,China;College of Electric and Information Engineering,North Minzu University,Yinchuan 750021,China)

机构地区：[1]北方民族大学物理与光电信息功能材料重点实验室,银川750021 [2]北方民族大学电气信息工程学院,银川750021

出　　处：《原子核物理评论》2021年第3期256-264,共9页Nuclear Physics Review

基　　金：中央高校基本科研业务费(2018KYQD01,2020DXXY002)。

摘　　要：QCD(Quantum Chromo Dynamics)手征反常理论主导了π^(0)介子到两个γ光子的衰变。基于手征反常理论和手征微扰论的修正,对π^(0)介子寿命的理论预测精度高达1%。高精度实验测量π^(0)介子的寿命可以严格检验低能区的QCD理论和手征微扰论。本工作重点介绍了三种测量π^(0)介子寿命的实验方法:直接测量法、双光子反应法和Primakoff测量法。2018版的PDG收录了测量π^(0)介子寿命精度最高的5个实验,并以此给出π^(0)介子寿命的平均值。回顾了这5个实验,其中2004年在美国JLab实验室进行的PrimEx-Ⅰ实验的测量精度最高,为2.8%。虽然这些实验结果在误差范围内与理论预测相符合,但实验精度还不足以严格检验精度为1%的理论预测。为了进一步提高实验精度,美国JLab实验室于2010年进行了第二次实验PrimEx-Ⅱ,测量精度为1.57%。将PrimEx实验系列的结果取加权平均,得到总的实验不确定度为1.50%。这是迄今为止对π^(0)寿命最精确的实验测量,在实验误差范围内可以验证QCD手征反常理论的预测。此外,还对PrimEx-Ⅱ的设备布局和数据分析方法做了简单介绍。π^(0)→γγdecay is dominated by chiral anomaly in quantum chromodynamics(QCD).Based on this anomaly and corrections of chiral perturbation theory(ChPT),π^(0) lifetime is predicted in high precision and the estimated uncertainty is on the level of 1%.The experimental measurement ofπ^(0) lifetime in a comparable precision is critical to test the QCD and ChPT at confinement scale energy.The methods ofπ^(0) lifetime measurement and experiments included in PDG of 2018 version forπ^(0) lifetime average are reviewed,in which PrimEx-Ⅰ performed in JLab in 2004 is the most precise experiment and has a total uncertainty of 2.8%.Even though those experimental results are in agreement with theoretical prediction in the range of experimental errors,the precision is not yet sufficient totri sngently test the theoretical prediction.In order to get more precise measurement ofπ^(0) lifetime,PrimEx-Ⅱ was performed in JLab in 2010 with the precision of 1.57%.The weighted average of PrimEx-I and PrimEx-Ⅱ results has a total uncertainty of 1.50%and confirms the prediction based on the chiral anomaly in QCD.Moreover,the experiment setup and data analysis approach of PrimEx-Ⅱ are also reviewed in this article.

关 键 词：π^(0)介子寿命 π^(0)介子衰变宽度 Primakoff效应 PrimEx-Ⅱ 

分 类 号：O572.2[理学—粒子物理与原子核物理]