Is the existence of a J/ψJ/ψbound state plausible?  

J/ψJ/ψ束缚态的存在合理吗?

作　　者：Xiang-Kun Dong Vadim Baru Feng-Kun Guo Christoph Hanhart Alexey Nefediev Bing-Song Zou 董相坤;Vadim Baru;郭奉坤;Christoph Hanhart;Alexey Nefediev;邹冰松(CAS Key Laboratory of Theoretical Physics,Institute of Theoretical Physics,Chinese Academy of Sciences,Beijing 100190,China;School of Physical Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Institut für Theoretische Physik Ⅱ,Ruhr-Universität Bochum,Bochum D-44780,Germany;Institute for Theoretical and Experimental Physics NRC“Kurchatov Institute”,Moscow 117218,Russia;Institute for Advanced Simulation,Institut für Kernphysik and Jülich Center for Hadron Physics,Forschungszentrum Jülich,Jülich D-52425,Germany;P.N.Lebedev Physical Institute of the Russian Academy of Sciences,Moscow 119991,Russia;Moscow Institute of Physics and Technology,Moscow 141700,Russia;School of Physics,Central South University,Changsha 410083,China)

机构地区：[1]CAS Key Laboratory of Theoretical Physics,Institute of Theoretical Physics,Chinese Academy of Sciences,Beijing 100190,China [2]School of Physical Sciences,University of Chinese Academy of Sciences,Beijing 100049,China [3]Institut für Theoretische Physik Ⅱ,Ruhr-Universität Bochum,Bochum D-44780,Germany [4]Institute for Theoretical and Experimental Physics NRC“Kurchatov Institute”,Moscow 117218,Russia [5]Institute for Advanced Simulation,Institut für Kernphysik and Jülich Center for Hadron Physics,Forschungszentrum Jülich,Jülich D-52425,Germany [6]P.N.Lebedev Physical Institute of the Russian Academy of Sciences,Moscow 119991,Russia [7]Moscow Institute of Physics and Technology,Moscow 141700,Russia [8]School of Physics,Central South University,Changsha 410083,China

出　　处：《Science Bulletin》2021年第24期2462-2470,M0003,共10页科学通报（英文版）

基　　金：supported in part by the Chinese Academy of Sciences(CAS)under Grants No.XDPB15,No.XDB34030000,and No.QYZDB-SSW-SYS013;the National Natural Science Foundation of China(NSFC)under Grants No.11835015,No.12047503 and No.11961141012;the NSFC and the Deutsche Forschungsgemeinschaft(DFG)through the funds provided to the Sino-German Collaborative Research Center‘‘Symmetries and the Emergence of Structure in QCD”(NSFC Grant No.12070131001,DFG Project-ID 196253076–TRR110);supported by Ministry of Science and Education of Russian Federation under Grant 14.W03.31.0026。

摘　　要：In a recent measurement LHCb reported pronounced structures in the J/ψJ/ψspectrum.One of the various possible explanations of those is that they emerge from non-perturbative interactions of vector charmonia.It is thus important to understand whether it is possible to form a bound state of two charmonia interacting through the exchange of gluons,which hadronise into two pions at the longest distance.In this paper,we demonstrate that,given our current understanding of hadron-hadron interactions,the exchange of correlated light mesons(pions and kaons)is able to provide sizeable attraction to the di-J/ψsystem,and it is possible for two J/ψmesons to form a bound state.As a side result we find from an analysis of the data for theψ/(2 S)J/ψππtransition including bothππand KK final state interactions an improved value for theψ(2 S)→J/ψtransition chromo-electric polarisability:|αψ(2 S)J/ψ|=(1.8±0.1)GeV-3,where the uncertainty also includes the one induced by the final state interactions.得益于世界各大高能物理实验在强子谱研究中的进展,奇特强子态的研究是近20年来强子物理领域的热点.区别于传统夸克模型中三夸克构成的重子和正反夸克对构成的介子,奇特强子态包括由更多夸克构成的多夸克态、夸克胶子构成的混杂态、完全由胶子构成的胶球等.2020年,LHCb合作组公布了质子质子对撞中产生的J/ψJ/ψ不变质量分布,宣布测到了由4个粲夸克cccc构成的粒子X(6900).在随后的一项研究工作中,本文作者通过拟合实验数据发现了J/ψJ/ψ阈值附近存在一个分子态的迹象.这个态的存在最近也被另一课题组证实.那么这个J/ψJ/ψ分子态是由什么束缚在一起的呢?对低能强相互作用已有的认知能够解释它吗?本文作者研究了J/ψJ/ψ之间交换软胶子的相互作用,其长程部分可以由双π介子和双K介子交换来描述.他们发现,在合理的参数范围之间,这种介子交换的相互作用可以为J/ψJ/ψ形成束缚态提供很大一部分束缚力.这意味着J/ψJ/ψ之间的相互作用可能已经强到足以形成束缚态,而不像大家之前认为的那样小.这个J/ψJ/ψ分子态可以在今后的实验中进行寻找.如果得到证实,那么可以预期现实中会存在一系列类似的分子态,比如ηcηc以及对应的全底四夸克态.

关 键 词：Fully-charm tetraquark Hadronic molecule Exotic hadron Dispersion relation 

分 类 号：O572.3[理学—粒子物理与原子核物理]