LHC collisions reveal oxygen and neon's shifting nuclear geometry

The Large Hadron Collider has produced new insights into the internal structure of oxygen and neon atoms through high-energy collisions, revealing previously unknown aspects of their nuclear geometry. Researchers using data from the CMS detector observed distinct flow patterns in oxygen-oxygen and neon-neon collisions, offering a clearer picture of how these elements' nuclei are structured. These findings, detailed in a study published in Physical Review Letters, suggest that the nuclei of oxygen and neon do not maintain fixed, rigid shapes but instead shift dynamically based on their energy states and quantum probabilities. The experiment took place at the CERN facility, where the LHC accelerates beams of protons and heavy ions to near-light-speed before colliding them. In this case, the collisions involved oxygen and neon nuclei, each composed of multiple protons and neutrons arranged within a nucleus. Unlike heavier nuclei such as uranium, which have been studied extensively in previous experiments, oxygen and neon offer a unique opportunity to examine the effects of nuclear geometry due to their relatively simpler compositions. The study focused on analyzing the collective flow of particles emitted during these collisions, which can act as a signature of the initial shape of the nuclei before they break apart. When atomic nuclei collide at extreme energies, they momentarily transform into a highly energetic state known as quark-gluon plasma, a phase of matter believed to have existed shortly after the Big Bang. As this plasma cools and expands, it emits particles that carry information about the dynamics of the collision. By measuring the direction and velocity of these outgoing particles, physicists can infer the initial configuration of the nuclei. In the case of oxygen and neon, the researchers found that the flow of charged particles varied depending on the central nature of the collision, suggesting that the nuclei had different initial geometries. The study compared experimental results with theoretical models of nuclear structure. Previous nuclear calculations had suggested that oxygen-16 might have a tetrahedral arrangement of its nucleons, while neon-20 could resemble a more elongated, "bowling-pin" shape. The new data supports these hypotheses, showing that the flow patterns in oxygen-oxygen and neon-neon collisions differ significantly. These differences, according to the researchers, primarily stem from variations in the initial geometry of the nuclei, reinforcing the idea that the structure of atomic nuclei is not static but influenced by their internal dynamics. The analysis was conducted using data collected from collisions at a center-of-mass energy of 5.36 TeV per nucleon pair. The researchers employed advanced fluid-dynamics simulations to model the behavior of the quark-gluon plasma and compare it with the observed particle flows. The results indicate that the collective motion of particles in these collisions aligns with predictions based on the assumed nuclear geometries, further validating the models used in nuclear physics. Looking ahead, the findings open new avenues for studying the structural properties of light nuclei. Future experiments may explore how these geometric characteristics influence other physical phenomena, such as the behavior of nuclear matter under extreme conditions. The work also highlights the importance of precision measurements in understanding the fundamental forces that govern the structure of matter.