  Atomic nuclei are self-organized, many-body quantum systems bound by strong
nuclear forces within femtometer-scale space. These complex systems manifest a
diverse set of shapes~, traditionally explored via non-invasive spectroscopic
techniques at low energies. Their instantaneous shapes, obscured by
long-timescale quantum fluctuations, are considered not directly observable at
low energy. We introduce a complementary method, collective flow assisted
nuclear shape imaging, to image the nuclear global shape by colliding them at
ultrarelativistic speeds and analyzing the collective response of outgoing
debris. This technique captures a collision-specific snapshot of the spatial
matter distribution in the nuclei, which, through the hydrodynamic expansion,
leaves imprints on the particle momentum distribution patterns observed in
detectors. We benchmark this method in collisions of ground state Uranium-238
nuclei, known for its elongated, axial-symmetric shape. Our findings, while
confirming an overall deformation broadly consistent with prior low-energy
experiments, also indicate a small deviation from axial symmetry in the nuclear
ground state. This approach marks a new way of imaging nuclei, especially those
with uncertain shape characteristics, and refines initial conditions in
high-energy nuclear collisions. It tackles the important issue of nuclear
structure evolution across various energy scales.
