Optimal collision-energy range for realizing macroscopic high-baryon-density matter

TL;DR

This study identifies the optimal collision energy range (around 3-5 GeV) in heavy-ion collisions to produce high-baryon-density matter with large spacetime volume, crucial for understanding dense nuclear matter.

Contribution

The paper determines the optimal collision-energy window for creating high-baryon-density matter using microscopic transport simulations, highlighting the importance of event selection.

Findings

Optimal energy range is around 3-5 GeV.

High baryon density exceeds three times nuclear density.

Large event-by-event fluctuations in density profiles.

Abstract

We investigate the volume and lifetime of the high baryon-density matter created in heavy-ion collisions and estimate the optimal collision-energy range to realize the high baryon-density region over a large spacetime volume. We simulate central collisions of gold ions for the center-of-mass energy per nucleon pair $\sqrt{s_{NN}}=2.4 - 19.6\;{\rm GeV}$ with a microscopic transport model JAM. We discover that the optimal range is around $\sqrt{s_{NN}}=3 - 5\;{\rm GeV}$, where a baryon density exceeding three times the normal nuclear density is realized with a substantially large spacetime volume. Higher and lower energies are disfavored due to short lifetime and low density, respectively. We also point out that event-by-event fluctuations of the spacetime density profile are large, indicating the importance of the event selection in the experimental analysis.