Time evolution of light nuclei cumulants and ratios with a first-order phase transition in the UrQMD transport model

The UrQMD model with a density dependent equation of state, including a first-order phase transition, isused to study the time dependence of baryon number and proton number susceptibilities up to third order inheavy ion reactions of Elab = 2–3 A GeV. A significant deviation from the Gaussian fluctuations of the baryonnumber fluctuation in coordinate space is observed. The proton number fluctuations are always suppressed asthey constitute only a small fraction of the total baryon number during the dense phase of the collision. It isfound that the only measurable, but small, signal would be an enhancement of the third order (or higher) protoncumulant in a finite rapidity window dy that is larger than one unit of rapidity. In addition, it is found that thecoordinate fluctuations will lead to an enhancement of cluster production due to the correlations in coordinatespace. However, this enhancement is small and mainly occurs during the dense part of the collision before thesystem actually freezes out.