Physicists working with the STAR detector at the Relativistic Heavy Ion Collider have uncovered a new detail regarding how protons maintain their identity. New data published in the journal Science suggests that baryon number, a fundamental quantum property, is not solely carried by the three quarks inside a proton. Instead, evidence points to a Y-shaped junction of gluons as the primary carrier.
This shift in understanding challenges decades of conventional physics models. Researchers, including a team from Rice University, observed that these gluon junctions behave differently than the quarks they connect during high-energy collisions. While the three quarks typically continue along the beamline during an impact, the gluon junctions tend to stop and transform their energy into new baryons that emerge in perpendicular directions.
This behavior provides strong evidence for the gluon junction model. Nicole Lewis, a physicist at Rice University who led the project, noted that the team initially aimed to adapt a new method for the STAR detector. The resulting data contradicted existing predictions, forcing the team to design specific experiments to test the alternative model. The results indicate that this junction configuration is central to how matter persists.
The conservation of baryon number remains one of the significant mysteries in physics. It explains why the total number of protons and neutrons in the universe has remained consistent since the Big Bang, a fact that also relates to the imbalance between matter and antimatter. By identifying that gluons play a central role in this process, scientists are gaining a clearer view of the fundamental structure of matter.
The STAR collaboration utilized the 1,200-ton detector to track thousands of particles generated by ion collisions. This discovery represents a collective effort from institutions including Brookhaven National Laboratory, Kent State University, and several international partners. This new insight into the structure of subatomic particles changes how researchers interpret the building blocks of the universe, providing a refined map for future experiments in particle physics.