Tracking the baryon number with nuclear collisions
- B. E. Aboona
- J. Adam
- L. Adamczyk
- I. Aggarwal
- M. M. Aggarwal
- Z. Ahammed
- A. K. Alshammri
- E. C. Aschenauer
- S. Aslam
- J. Atchison
- V. Bairathi
- X. Bao
- P. Barik
- K. Barish
- S. Behera
- R. Bellwied
- P. Bhagat
- A. Bhasin
- S. Bhatta
- S. R. Bhosale
- J. Bielcik
- J. Bielcikova
- J. D. Brandenburg
- C. Broodo
- X. Z. Cai
- H. Caines
- M. Calderón de la Barca Sánchez
- D. Cebra
- J. Ceska
- I. Chakaberia
- P. Chaloupka
- Y. S. Chang
- Z. Chang
- A. Chatterjee
- D. Chen
- J. Chen
- J. H. Chen
- L. Chen
- Q. Chen
- W. Chen
- Z. Chen
- J. Cheng
- Y. Cheng
- W. Christie
- X. Chu
- S. Corey
- H. J. Crawford
- M. Csanád
- G. Dale-Gau
- A. Das
2026-08-13
Baryon quantum number is found to be conserved since baryogenesis in the early Universe. Conventionally, each fractionally charged valence quark is understood to carry one-third of a baryon number. An alternative hypothesis posits that baryon number is instead carried by a baryon junction—a nonperturbative, Y-shaped gluonic configuration. Neither scenario has been verified experimentally. The STAR Collaboration reports measurements at mid-rapidity of baryon number ( B ) over the electric charge number difference (∆ Q ) in isobar nuclear collisions, and the net-proton yield along rapidity in photonuclear collisions. A larger B /∆ Q ratio and less asymmetric net-proton yield are observed than predicted from models assigning baryon number to valence quarks. These findings, corroborated by previous measurements in Au+Au collisions, disfavor the valence quark picture.