Search for baryon junctions in photonuclear processes and isobar collisions at RHIC

TL;DR

This paper investigates the role of gluon junctions in baryon transport during high-energy nuclear collisions, proposing experimental tests at RHIC to detect their signatures and explain baryon excess phenomena.

Contribution

It introduces the concept of gluon junctions as a mechanism for baryon transport and suggests specific experimental approaches at RHIC to identify their signatures.

Findings

Net-baryon rapidity density follows an exponential distribution with slope -0.61±0.03.

Existing data from A+A collisions support the gluon junction transport hypothesis.

Proposes photon-induced processes as a new method to search for baryon junction signatures.

Abstract

During the early development of Quantum Chromodynamics, it was proposed that baryon number could be carried by a non-perturbative Y-shaped topology of gluon fields, called the gluon junction, rather than by the valence quarks as in the QCD standard model. A puzzling feature of ultra-relativistic nucleus-nucleus collisions is the apparent substantial baryon excess in the midrapidity region that could not be adequately accounted for in most conventional models of quark and diquark transport. The transport of baryonic gluon junctions is predicted to lead to a characteristic exponential distribution of net-baryon density with rapidity and could resolve the puzzle. In this context we point out that the rapidity density of net-baryons near midrapidity indeed follows an exponential distribution with a slope of $-0.61\pm0.03$ as a function of beam rapidity in the existing global data from A+A collisions at AGS, SPS and RHIC energies. To further test if quarks or gluon junctions carry the baryon quantum number, we propose to study the absolute magnitude of the baryon vs. charge stopping in isobar collisions at RHIC. We also argue that semi-inclusive photon-induced processes ($\gamma+p$/A) at RHIC kinematics provide an opportunity to search for the signatures of the baryon junction and to shed light onto the mechanisms of observed baryon excess in the mid-rapidity region in ultra-relativistic nucleus-nucleus collisions. Such measurements can be further validated in A+A collisions at the LHC and $e+p$/A collisions at the EIC.