Nuclear Physics Seminar: Chun Yuen Tsang - Baryon Transport from Light to Strange Quarks

The baryon number (B) is a conserved quantity in quantum chromodynamics (QCD). Baryons carry one unit (B = 1), while mesons carry zero (B = 0). Since baryons consist of three valence quarks, each is conventionally assumed to carry 1/3 unit of baryon number. An alternative theory instead assigns the entire unit to the baryon junction, a non-perturbative Y-shaped gluon topology connected to all three valence quarks. Although there are good theoretical reasons to suggest the existence of junctions, many physical processes evolve similarly regardless of which carries the baryon number, so neither theory has been experimentally verified. In this talk, we present four experimental results that distinguish the two pictures: (1) net-baryon vs. net-electric charge in isobar collisions, (2) net-proton yield in photonuclear collisions, and (3) net-proton and (4) net-hyperon yields versus rapidity in hadronic Au + Au collisions. These observables allow us to disentangle the two pictures by exploiting the two key differences between gluon junctions and valence quarks: it is easier to stop a junction in a collision, and junction stopping is independent of quark flavor. All evidence so far favors the baryon junction picture. This will be followed by a discussion of future prospects for baryon junction studies.