Oerview:The nuclear theory and phenomenology group aims to explore properties of hadrons and nuclear matter under normal and extreme conditions as governed by the Quantum Chromodynamics (QCD) with close connection to related experiments and phenomenology.

Members:Heng-Tong Ding, Qin-Hua Fu, Defu Hou, Chen Ji, Weiyao Ke, Sheng-Tai Li, Fuming Liu, Long-gang Pang, Guang-You Qin, Hai-Tao Shu, Xin-Nian Wang, Yuan-fang Wu, Ming-mei Xu, Chun-bin Yang, Ben-Wei Zhang, Hanzhong Zhang, Daimei Zhou.

The fundamental theory for nuclear physics, quantum chromodynamics (QCD), describes the interactions among quarks and gluons. However, the intricate nature of QCD at low energy often makes it difficult to understand nuclear phenomena in terms of quarks and gluon as fundamental degrees of freedom in the Standard Model. In physical systems, new symmetries, effective degrees of freedom, and many-body dynamics may emerge, which brings the field of nuclear physics a great many surprises. Research of the nuclear theory and phenomenology group aims to

• Explore the phase matters formed under strong interactions.

• Study the properties of nuclear under extreme conditions (high temperature, density, rotation, and magnetic field).

• To understand their behavior from first principle QCD, as well as effective theories.

• To interact with experiments to examine the theory and propose new measurements.

Phenomenology of relativistic heavy-ion collisions 

Colliding heavy nuclei at relativistic energies creates a new form of matter called the quark-gluon plasma (QGP). It has an extremely high temperature and density, comparable to those achieved in the early universe. Experimental measurements at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory and the Large Hadron Collider at CERN reveal striking behavior of the QGP, such as the near-perfect fluidity, the emergence of constituent quark degrees of freedom, the quenching of energetic quarks and gluons. The theoretical calculation, machine learning techniques, and dynamical modeling of the entire collision process help to understand the experimental data and to build a deeper understanding of the system. These include the initial-state wave function of the collision, the QGP equation of state, its quasi-particle excitations, collective behavior, and its interaction with QCD jets.

In collider experiments, the quark-gluon plasma expands and cools down and will eventually undergo a phase transition to a system of hadrons (such as protons and pions). It is conjectured that there is a critical endpoint (CEP) of such a phase transition at Finite baryon chemical potential. Identifying the CEP from experiments has a profound impact on understanding the phase diagram of QCD. To achieve this, theoretical models and dynamical simulations of phase transitions must be developed to connect CEP physics to experimentally measurable quantities, such as multi-particle correlations and fluctuations.

Team members：Jinghua Fu, Weiyao Ke, Fu-Ming Liu, Long-Gang Pang, Guang-You Qin, Enke Wang, Xin-Nian Wang, Yuan-Fang Wu, Ming-Mei Xu, Chun-Bin Yang, Ben-Wei Zhang, Hanzhong Zhang, Dai-Mei Zhou.

Phenomenology of Electron-ion Collisions 

An electron-ion collider (EIC) is a power microscope of the inner workings of partonic dynamics in the proton and nuclei environment. The production of hadrons and jets at EIC is a primary way to extract the transverse-momentum-dependent (TMD) parton distribution of the nuclei and properties of the cold nuclear matter. We develop effective theories and Monte-Carlo simulation techniques that include nuclear medium effects to facilitate future programs at the EIC.

Team members：Weiyao Ke, Enke Wang, Xin-Nian Wang.

Lattice QCD

The Lattice QCD group focuses on advancing our understanding of the strong interaction using lattice QCD, a first-principles approach to Quantum Chromodynamics (QCD). We study the properties of strongly interacting matter under extreme conditions, such as high temperature, density, and strong magnetic fields, relevant to the early universe, neutron stars, and heavy-ion collisions at RHIC and LHC. Our research explores the QCD phase diagram, chiral phase transition, in-medium hadron properties and transport properties of quark-gluon plasma as well as hadron structure. For more information please visit：http://www.ccnulqcd.net

Team members：Heng-Tong Ding, Sheng-Tai Li, Hai-Tao Shu.

Holography and Strongly-coupled QCD 

The QCD matter at the temperature reached in collider experiments is strongly coupled. Furthermore, in regions of the postulated first-order phase transition, the finite baryon chemical potential makes it difficult to access from lattice QCD. The holography theory establishes a duality between a strongly-coupled gauge field theory and a higher-dimensional weakly-coupled gravity theory. Such a correspondence provides alternative ways to gain insights into strong-coupled QCD systems in those interested regions, including the phase diagrams, and the responses of the QGP to rotation and magnetic fields.

Team members：Defu Hou.

Nuclear Structures and Fundamental Symmetry 

Nuclear structure theory investigates the internal structure and dynamic properties of atomic nuclei, constituting a fundamental aspect of low-energy strong-interaction studies.

Research in few-body nuclear theory calculations involves integrating quantum few-body models with effective field theory to rigorously examine the internal structures of few-nucleon systems, providing theoretical insights and predictions for experimental studies. This work is connected with nuclear astrophysics and precision atomic measurements to address fundamental physical questions. Effective field theory is employed to analyze the structural characteristics of light halo nuclei, aiming to elucidate their role in nuclear astrophysical evolution and cosmic abundance. Additionally, ab initio calculations are used to study the impact of nuclear structure on the precision spectroscopy of hydrogen-like systems. This approach provides high-precision theoretical inputs for the determination of nuclear charge and magnetic moments from atomic spectroscopies, while also testing bound-state quantum electrodynamics.

Other research efforts employ relativistic hydrodynamics, hadronic transport, and high-energy parton transport to explore novel forms of nuclear matter under extreme conditions produced by relativistic heavy-ion collisions. Machine learning techniques, such as artificial neural networks, are integrated to extract the equation of state of nuclear matter and initial nuclear structure information—such as nuclear deformation, alpha clustering, and nucleon-nucleon correlations—from extensive and complex nuclear collision data.

Team members：Chen Ji, Longgang Pang.