Physicists have reached a significant milestone in particle physics by providing new evidence for a theory proposed fifty years ago. The research concerns the nature of protons and neutrons, specifically regarding what carries the baryon number. For decades, the standard assumption was that this number resides with the three valence quarks inside a baryon. However, fresh findings from the STAR Collaboration at the Brookhaven National Laboratory suggest a different mechanism is at play.
The team analyzed data from high-energy particle collisions, specifically comparing isobar nuclear collisions and photonuclear interactions. By tracking how matter moves through a collision zone compared to electric charge, researchers observed that the baryon number travels further than the electrically charged valence quarks. This suggests the number is actually carried by a Y-shaped structure called a baryon junction, which consists of massless gluons.
This distinction is important because it challenges the simple valence-quark model that has dominated the field for years. While the valence quarks carry the charge, the junction acts as the glue holding the subatomic particles together. The research data indicates that the junction model aligns with experimental observations better than the traditional valence-quark picture.
Understanding this mechanism is a step toward solving broader questions about the nature of the universe. Specifically, physicists hope that defining how the baryon number is transported will help explain the imbalance between matter and antimatter. This asymmetry allowed stable matter to form in the early universe, creating the world as we observe it now.
Future experiments at the upcoming Electron-Ion Collider will provide more data to confirm these findings. This work currently represents the most consistent explanation for the observed phenomena, as it remains the only framework that matches all experimental results gathered by the team. The shift in perspective marks a departure from five decades of conventional thinking in subatomic particle research.