High baryon and energy densities achievable in heavy-ion collisions at $\sqrt{s_{NN}}=$ 39 GeV

TL;DR

This paper estimates that central Au+Au collisions at 39 GeV achieve extremely high baryon and energy densities, indicating a deconfinement transition and complex fragmentation dynamics in heavy-ion collisions.

Contribution

It provides the first detailed estimates of baryon and energy densities at 39 GeV using a three-fluid dynamics model, highlighting the effects of deconfinement transition.

Findings

Initial baryon density about 10 times nuclear saturation density.

Energy density approximately 40 GeV/fm^3 in the central region.

Deconfinement transition increases system opacity and influences fragmentation regions.

Abstract

Baryon and energy densities, which are reached in central Au+Au collisions at collision energy of $\sqrt{s_{NN}}= 39$ GeV, are estimated within the model of three-fluid dynamics. It is shown that the initial thermalized mean proper baryon and energy densities in a sizable central region approximately are $n_B/n_0 \approx$ 10 and $\varepsilon\approx$ 40 GeV/fm$^3$, respectively. The study indicates that the deconfinement transition at the stage of interpenetration of colliding nuclei makes the system quite opaque. The final fragmentation regions in these collisions are formed not only by primordial fragmentation fireballs, i.e. the baryon-rich matter passed through the interaction region (containing approximately 30\% of the total baryon charge), but also by the baryon-rich regions of the central fireball pushed out to peripheral rapidities by the subsequent almost one-dimensional expansion of the central fireball along the beam direction.