质子偶素:实验发现及理论预言  

Protonium:Discovery and prediction

作　　者：马伯强[1] Bo-Qiang Ma(School of Physics,Peking University,Beijing 10087l,China)

机构地区：[1]北京大学物理学院,北京100871

出　　处：《科学通报》2024年第31期4620-4624,共5页Chinese Science Bulletin

摘　　要：2024年4月9日,北京谱仪Ⅲ(Beijing SpectrometerⅢ,BESⅢ)合作组[1]在Physical Review Letter发表了一篇文章,报道了实验组利用北京正负电子对撞机(Beijing Electron Positron Collider,BEPC)产生的100亿个粲夸克偶素事例,分析由粲夸克偶素衰变到一个光子和三对正负介子对的衰变过程,通过重建三对正负介子对的不变质量并由两个共振态结构X(1840)和X(1880)来拟合数据(图1),发现X(1880)的统计显著性超过10倍标准偏差的偏离.The Beijing Spectrometer(BESⅢ)Collaboration reconstructed the invariant mass of three pairs of positive and negative pions by studying the decay process of charmonium to a photon and three pairs of positive and negative pions.They discovered the resonant structures X(1840)and X(1880),which were initially found in the earlier experimental work of proton and anti-proton spectrum in J/Ψ→γ+p+p decay andη'π~+π~-decay channels in decay by the BES Collaboration in2003 and 2005.The experimental results of this important work further confirm the existence of new particles,which are interpreted as the predicted proton-antiproton bound states,also known as protonium.This paper briefly introduces the experimental discovery processes of these resonant structures and discusses the theoretical explorations inspired by them.The predictions proposed by these theoretical explorations offer a new perspective for studying the nature of these particles and new decay modes.For example,Yan Mulin,along with his collaborators,made significant contributions to the theoretical exploration of the X(pp)structure direction using proton-antiproton bound states.Starting from the theoretical background of viewing protons as skyrmions,this group discussed a system composed of a skymion and an anti-skyrmion,discovering a bound state solution for the skyrmion and anti-skyrmion system,which can explain the bound state of proton and antiproton.They then constructed a phenomenological potential model for a proton and an antiproton,which can calculate the mass and width of the bound state by adjusting parameters,interpreting X(pp)as the bound state of a proton and an antiproton,namely protonium.Additionally,based on experimental phenomena of producing multiple mesons in low-energy proton-antiproton collisions,this group explicitly predicted another decay channel of X(pp)as a protonantiproton bound state,decaying into 4 to 7 mesons instead of 2-3 mesons.The recent analysis by BESⅢCollaboration of the decay process of charmonium to a photon an

关 键 词：粲夸克偶素 BESⅢ 不变质量 衰变过程 理论预言 统计显著性 标准偏差 北京谱仪Ⅲ 

分 类 号：O572.33[理学—粒子物理与原子核物理]