Figure: Schematic diagram of nuclear structure studies using low-energy measurements and high-energy nuclear collisions.

Supported by grants from the National Natural Science Foundation of China (Grant Nos. 11890710, 12147101, 12025501), Professor Yugang Ma’s group at Fudan University, in collaboration with Stony Brook University, has made a significant breakthrough in studying nuclear structure via high-energy nuclear collisions for the first time. This approach is crucial for exploring the initial conditions of quark-gluon plasma (QGP) and offers a novel and independent experimental tool for investigating nuclear structure across energy scales. The study, titled “Imaging Shapes of Atomic Nuclei in High-Energy Nuclear Collisions”, was published online in Nature on November 7, 2024. The article link can be found at https://www.nature.com/articles/s41586-024-08097-2).

The geometric shape of atomic nuclei, along with the intrinsic fundamental interactions and dynamical symmetries within, has long been a frontier topic in the study of many-body quantum systems and strong interaction physics. Currently, investigations of nuclear structure are primarily conducted in low-energy nuclear physics, which is measured over longer time scales. In high-energy nuclear collisions, the nuclei undergo the Lorentz contraction, with interaction exposure time on the order of yoctoseconds (~10⁻²⁴ seconds), shorter than zeptosecond-scale (~10⁻²¹ seconds) zero-point quantum fluctuations of nuclei. This enables instantaneous inverse imaging of nuclear shapes, offering new opportunities to explore the properties of QGP, nuclear shapes, and many-body correlations within nuclei.

The research group introduced the collective-flow-assisted nuclear shape-imaging method, and analyzed observables of final-state hadrons in high-energy heavy-ion collision experiments through elliptic flow, mean transverse momentum fluctuations, and their correlation coefficient (see figure). The finding revealed a large deformation with a slight deviation from axial symmetry in the ground state of uranium-238 nuclei, aligning broadly with previous low-energy experiments. This approach offers a new method for imaging nuclear shapes and critical insights for refining nuclear theoretical models and improving their accuracy. It enhances our understanding of QGP initial conditions and addresses the important issue of nuclear structure evolution across energy scales, potentially crucial for topics such as nucleosynthesis, nuclear fission, and neutrinoless double beta decay. Additionally, it fosters the development of interdisciplinary research at the intersection of high-energy nuclear collisions, low-energy nuclear physics, and nuclear astrophysics.