A perspective on describing nucleonic flow and pionic observables within the ultra-relativistic quantum molecular dynamics model  

作　　者：Yang-Yang Liu Jun-Ping Yang Yong-Jia Wang Qing-Feng Li Zhu-Xia Li Cheng-Jun Xia Ying-Xun Zhang 

机构地区：[1]China Nuclear Data Center,China Institute of Atomic Energy,Beijing 102413,China [2]School of Science,Huzhou University,Huzhou 313000,China [3]Institute of Modern Physics,Chinese Academy of Sciences,Lanzhou 730000,China [4]Center for Gravitation and Cosmology,College of Physical Science and Technology,Yangzhou University,Yangzhou 225009,China [5]Guangxi Key Laboratory of Nuclear Physics and Technology,Guangxi Normal University,Guilin 541004,China

出　　处：《Nuclear Science and Techniques》2025年第3期105-118,共14页核技术(英文)

基　　金：supported by the National Natural Science Foundation of China(Nos.11875323,12275359,12205377,12335008,U2032145,11790320,11790323,11790325,and 11961141003);the National Key R&D Program of China(No.2018 YFA0404404);the Continuous Basic Scientific Research Project(No.WDJC-2019-13);the China Institute of Atomic Energy(No.YZ222407001301);the Leading Innovation Project of the CNNC(Nos.LC192209000701 and LC202309000201)。

摘　　要：In this work,we study the impacts of the isospin-independent momentum-dependent interaction(MDI)and near-threshold NN→NΔcross sections(σ_(NN→NΔ))on the nucleonic flow and pion production observables in the ultra-relativistic quantum molecular dynamics(UrQMD)model.With the updated isospin-independent MDI and the near-threshold NN→NΔcross sections in the Ur QMD model,17 observables,which are the directed flow(v_(1))and elliptic flow(v_(2))of neutrons,protons,Hydrogen(H),and charged particles as a function of transverse momentum(p_t∕A)or normalized rapidity(y^(lab)_0),and the observables constructed from them,the charged pion multiplicity(M(π))and its ratio(M(π^(-))∕M(π^(+))),can be simultaneously described at certain forms of symmetry energy.The refinement of the UrQMD model provides a solid foundation for further understanding the effects of the missed physics,such as the threshold effect,the pion potential,and the momentum-dependent symmetry potential.Circumstantial constraints on the symmetry energy at the flow characteristic density 1.2±0.6ρ_(0)and the pion characteristic density 1.5±0.5ρ_(0)were obtained with the current version of UrQMD,and the corresponding symmetry energies were S(1.2ρ_(0))=34±4 MeV and S(1.5ρ_(0))=36±8 MeV,respectively.Furthermore,the discrepancies between the data and the calculated results of v_(2)^(n)and v_(2)^(9)at high p_(t)(rapidity)imply that the roles of the missing ingredients,such as the threshold effect,the pion potential,and the momentum-dependent symmetry potential,should be investigated by differential observables,such as the momentum and rapidity distributions of the nucleonic and pionic probes over a wide beam energy range.

关 键 词：Momentum dependent interaction NN→NΔcross section Symmetry energy Flow andπobservable 

分 类 号：O57[理学—粒子物理与原子核物理]