Large Hadron Collider experiments reveal neon nucleus may be bowling-pin shaped

A recent experimental result from the Large Hadron Collider at CERN suggests that the internal structure of the neon-20 nucleus may not be approximately spherical as commonly depicted in traditional textbooks, but rather closer to a "bowling pin" shape. This finding provides new experimental clues for studying deformation of light atomic nuclei and collective behavior in high-energy nuclear collisions.

Atomic nuclei are composed of protons and neutrons, determining the elemental identity of atoms and carrying most of their mass. Although nuclei are often simplistically depicted as spherical, nuclear physics research has shown that some nuclei exhibit pronounced non-spherical deformation, such as the pear-shaped nuclei mentioned in previous studies. Accurately understanding these shapes helps physicists comprehend the behavior of atomic nuclei under extreme conditions.

Because atomic nuclei are extremely small and quantum states average over different orientations in conventional measurements, directly "seeing" the shape of a nucleus in the laboratory is not easy. The Large Hadron Collider offers an alternative approach: when nuclei collide at high energies, their initial geometric structure influences the flow patterns of matter produced after the collision. By analyzing particle jets and flow patterns, researchers can infer the internal shape of the nucleus in reverse.

In this study, the CMS collaboration compared collision data involving oxygen-16 and neon-20, focusing on differences in particle flow between oxygen-oxygen and neon-neon collisions. These two nuclei were selected because their masses are relatively close, yet theoretical calculations and existing studies suggest their internal structures may differ: oxygen-16 may possess a tetrahedral nuclear structure, while neon-20 is predicted to exhibit a bowling-pin-like deformation.

The researchers focused on particle flow patterns such as elliptic flow and triangular flow. The results show that collective flow produced in collisions is sensitive to the initial geometric shape of the nuclei, with the relative strength of elliptic flow exhibiting features correlated with nuclear deformation, particularly in more central collisions. However, the study also notes that variations in triangular flow do not fully match model predictions quantitatively, and further verification and refinement of models will be needed.

The findings have been published in Physical Review Letters. The researchers believe that this result demonstrates that collective flow in light-ion collisions not only reflects the hydrodynamic medium response, but may also carry information about the spatial arrangement of protons and neutrons within the nucleus, providing new experimental evidence for studying nuclear structure using high-energy particle collisions.