Baryon enhancement in high-density QCD and relativistic heavy ion collisions

TL;DR

This paper investigates how high parton densities in high-energy nuclear collisions lead to the breakdown of collinear factorization at low transverse momenta, resulting in gluon recombination dominance and baryon enhancement observed in RHIC data.

Contribution

It introduces a framework for understanding baryon enhancement through gluon recombination in high-density QCD, contrasting with traditional fragmentation models.

Findings

Gluon recombination dominates at low transverse momenta.

The calculated baryon-to-meson ratio aligns with RHIC experimental data.

Breakdown of collinear factorization occurs at $p_T \,\lesssim\, Q_s/g$.

Abstract

We argue that the collinear factorization of the fragmentation functions in high energy nuclear collisions breaks down at transverse momenta $p_T \lesssim Q_s/g$ due to high parton densities in the colliding hadrons and/or nuclei. We find that gluon recombination dominates in that $p_T$ region. We calculate the inclusive cross-section for $\pi$ meson and nucleon production using the low energy theorems for the scale anomaly in QCD, and compare our quantitative baryon-to-meson ratio to the RHIC data.