LHCb实验利用电弱探针与光诱导过程研究核物质效应的进展  

Advancements in the nuclear matter studies using electroweak probes and photon-induced processes at LHCb

作　　者：李衡讷 Hengne Li(Key Laboratory of Atomic and Subatomic Structure and Quantum Control(MOE),Guangdong Basic Research Center of Excllence for Structure and Fundamental Interactions of Matter,Institute of Quantum Matter,South China Normal University,Guangzhou 510006,China;Guangdong-Hong Kong Joint Laboratory of Quantum Mater,Guangdong Provincial Key Laboratory of Nuclear Science,Southern Nuclear Science Computing Center,South China Normal University,Guangzhou 510006,China)

机构地区：[1]华南师范大学量子物质研究院,原子亚原子结构与量子调控教育部重点实验室,广东省高等学校物质结构与相互作用基础研究卓越中心,广州510006 [2]华南师范大学南方核科学计算中心,粤港量子物质联合实验室,广东省核物质科学与技术重点实验室,广州510006

出　　处：《科学通报》2024年第31期4611-4619,共9页Chinese Science Bulletin

基　　金：国家自然科学基金(12061141007);广东省自然科学基金(2021A1515010033)资助。

摘　　要：本文介绍了LHCb实验中的两项重要研究,旨在以电弱相互作用玻色子为工具探索原子核中的部分子分布函数(nuclear parton distribution functions,n PDFs).第一项研究利用质子-铅核对撞数据测量了Z玻色子的产生,用Z玻色子作为探针研究量子色动力学(quantum chromodynamics,QCD)和nPDFs.通过测量Z玻色子的产生截面,研究人员可以更准确地确定和理解部分子在核物质环境中的分布,从而完善现有的QCD理论并提高nPDFs的精度.第二项研究在铅核-铅核超周边对撞中研究了J/ψ和ψ(2S)介子的光致产生.这种对撞中,两个铅核通过光子和核内胶子的相互作用产生粲夸克偶素.相干光致产生涉及光子与整个原子核的胶子相互作用,能量交换较小,原子核保持完整.该研究验证了现有的微扰QCD和胶子交换模型,并提供了关于核遮蔽效应和核内胶子分布的重要信息.LHCb实验首次测量了粲夸克偶素随横动量变化的相干光致产生截面,并观测到了衍射效应,为未来高能核物理研究提供了宝贵数据.The LHCb experiment at CERN's Large Hadron Collider has made significant progress in studying nuclear parton distribution functions(nPDFs)through two key investigations:The production of Z bosons in proton-lead collisions and the photoproduction of J/ΨandΨ(2S)mesons in ultra-peripheral lead-lead collisions.The study of Z boson production in proton-lead collisions has provided crucial insights into the behavior of quarks and gluons within nucleons.Z bosons,which are neutral electroweak gauge bosons,serve as excellent probes for studying quantum chromodynamics(QCD)because their production and decay processes are dominated by weak interactions and do not involve strong interactions.By measuring the production cross-section of Z bosons,researchers can accurately determine the distribution of partons(quarks and gluons)within nucleons in a nuclear environment.This measurement helps refine the existing QCD theory and improve the precision of nPDFs.The experimental results showed good agreement with theoretical predictions,particularly in the forward direction,providing valuable constraints on nPDFs and enhancing our understanding of nuclear effects on parton distributions.In the second study,LHCb researchers investigated the coherent photoproduction of J/ΨandΨ(2S)mesons in ultraperipheral lead-lead collisions.These heavy quarkonia,composed of charm-anticharm quark pairs,are produced through photon-induced interactions without direct contact between the nuclei.Coherent photoproduction involves minimal momentum exchange,preserving the integrity of the nuclei and providing a unique opportunity to study gluon distributions within the nucleus.The transverse momentum(pT)of the produced mesons is determined by the size of the nucleus,following the uncertainty principle.The LHCb experiment s forward design allowed for effective capture and analysis of particles traveling in the forward direction,distinguishing signal events from background noise.The results of the photoproduction study revealed differential cross-sections o

关 键 词：LHCb实验 Z玻色子 J/ψ介子 量子色动力学 原子核部分子分布函数 光致产生 

分 类 号：O572.214[理学—粒子物理与原子核物理]