The initial energy density of gluons produced in very high energy nuclear collisions

TL;DR

This paper numerically computes the initial gluon energy density in high-energy nuclear collisions, providing key insights for RHIC and LHC experiments.

Contribution

It presents a non-perturbative numerical calculation of the gluon energy density function for SU(2), extrapolating results to SU(3) relevant for real collisions.

Findings

Function f(g^2μL) decreases rapidly at small g^2μL

f(g^2μL) varies by about 25% over a wide range

Estimated initial energy densities for RHIC and LHC collisions

Abstract

In very high energy nuclear collisions, the initial energy of produced gluons per unit area per unit rapidity, $dE/L^2/d\eta$, is equal to $f(g^2\mu L) (g^2\mu)^3/g^2$, where $\mu^2$ is proportional to the gluon density per unit area of the colliding nuclei. For an SU(2) gauge theory, we perform a non--perturbative numerical computation of the function $f(g^2\mu L)$. It decreases rapidly for small $g^2\mu L$ but varies only by $\sim 25$%, from $0.208\pm 0.004$ to $0.257\pm 0.005$, for a wide range 35.36--296.98 in $g^2\mu L$, including the range relevant for collisions at RHIC and LHC. Extrapolating to SU(3), we estimate the initial energy per unit rapidity for Au-Au collisions in the central region at RHIC and LHC.