The Gluon Exchange Model in proton-nucleus collisions

TL;DR

This paper introduces the Gluon Exchange Model (GEM) for baryon production in proton-nucleus collisions, explaining how multiple gluon exchanges influence baryon stopping and making predictions testable with CERN SPS data.

Contribution

The paper presents a novel color exchange scheme based on effective diquark formation probabilities, linking baryon stopping to gluon exchange complexity rather than energy loss.

Findings

Baryon stopping increases with the number of proton-nucleon collisions.

Probabilities for diquark formation depend on the number of exchanged gluons.

Model predictions are verifiable with existing CERN SPS data.

Abstract

We apply our recently formulated Gluon Exchange Model (GEM) to baryon production in proton-nucleus reactions involving N>1 proton-nucleon collisions. We propose a description scheme for the process of soft color octet (gluon) exchange, based on the assumption that probabilities to form an effective diquark are equal for all allowed pairs of quarks. The latter effective diquark can form either from two valence, one valence and one sea, or from two sea quarks. Consequently we calculate the probabilities for different color configurations involving diquarks of valence-valence, valence-sea and sea-sea type. These probabilities appear to depend on the number of exchanged gluons, which results in increasing baryon stopping as a function of the number of proton-nucleon collisions in the nucleus. As such, the nuclear stopping power appears to be governed by the emergence of new color configurations as a function of N rather than by the energy loss of the original valence diquark. The advantage of our approach lies in its high predictive power which makes it verifiable by the new, precise data on proton and neutron production from the CERN SPS. The latter verification, and a set of predictions for the N-dependence of the baryon stopping process, are included in the letter.