LHCb实验上重夸克偶素产生机制研究进展  

Progress on heavy quarkonium production mechanisms at LHCb

作　　者：安刘攀 李培荣 杨振伟 张艳席 Liupan An;Peirong Li;Zhenwei Yang;Yanxi Zhang(School of Physics,Peking University,Beijing 100871,China;School of Nuclear Science and Technology,Lanzhou University,Lanzhou 730000,China)

机构地区：[1]北京大学物理学院,北京100871 [2]兰州大学核科学与技术学院,兰州730000

出　　处：《科学通报》2024年第31期4558-4569,共12页Chinese Science Bulletin

基　　金：国家自然科学基金国际(地区)合作交流项目(12061141007);国家自然科学基金面上项目(12175005,12375068);国家重点研发计划(2022YFA1601900,2020YFA0406400);国家杰出青年科学基金(11925504)资助。

摘　　要：量子色动力学(quantum chromodynamics,QCD)非微扰机制是尚未完全理解的基本问题,重夸克偶素的产生过程为认识QCD微扰以及非微扰性质提供了理想的途径.理论家提出了色单态模型、色蒸发模型以及非相对论性量子色动力学等方法来计算重夸克偶素的产生截面等特征.自欧洲核子研究中心大型强子对撞机运行以来,LHCb实验对重夸克偶素产生机制进行了广泛的研究,测量了J/、(2S)和(nS)等介子的产生截面和极化,并测量了J/和J/介子、J/和(2S)介子,以及J/和(nS)介子的关联产生截面与有效截面.这些研究结果为深入理解重夸克偶素的产生机制、甄别不同的理论模型以及约束理论模型的参数空间提供了重要的实验信息,大大改进了我们对重夸克偶素产生过程中微扰和非微扰性质的认识.本文将介绍LHCb实验在重夸克偶素产生机制方面的相关研究和未来展望.The strong interaction is one of the fundamental forces of nature.The 20th century witnessed the development of our knowledge of the strong interaction,from nuclear force to quantum chromodynamics(QCD),from the nucleon structure of nuclei to the partonic structure of various hadrons.The evolution of the coupling constant of QCD with energy scale makes the strong force behave very differently at high-and low-energies.At the large momentum transfer,corresponding to high energy domain,the strong interaction becomes so weak that physics processes can be calculated perturbatively in power expansions of the coupling constant.Oppositely,at low energies(<1 GeV),it falls into the nonperturbative regime,which hinders our understanding of the strong interaction through first-principle QCD calculations.Experimentally,quarks and gluons are confined inside color neutral hadrons,namely color confinement.The confinement mechanism of QCD is an unsolved fundamental problem in physics.The hadroproduction of heavy quarkonia involves both perturbative and nonperturbative processes of QCD,such that it is ideal to study QCD properties.The creation of heavy-quark pairs due to interactions of quarks and gluons can be calculated perturbatively,while the hadronization of heavy quark pairs into heavy quarkonia is nonperturbative.Various models have been developed to calculate heavy quarkonium production,differing mainly in the treatment of the hadronization process.In the color single model(CSM),the heavy quark pairs and the final-state quarkonium must have the same quantum numbers.The color evaporation model(CEM) uses parameters,which are independent of the interaction processes and heavy-quark quantum numbers,to describe the hadronization rates.In the nonrelativistic QCD(NRQCD) framework,intermediate heavy-quark pairs with all possible quantum numbers can hadronize into a certain quarkonium.Their transformation probabilities are expressed by long distance matrix elements(LDMEs),which are ranked by the powers of the heavy-quark velocity in

关 键 词：LHCb实验 重夸克偶素 量子色动力学 截面 极化 

分 类 号：O572.33[理学—粒子物理与原子核物理]