Nuclear Stopping from $0.09A$ to $1.93A\mathrm{GeV}$ and Its Correlation to Flow

We present a complete systematics (excitation functions and system-size dependences) of global stopping and side flow for heavy ion reactions in the energy range between $0.09A$ and $1.93A\mathrm{GeV}$. For the heaviest system, $\mathrm{Au}+\mathrm{Au}$, we observe a plateau of maximal stopping extending from about $0.2A$ to $0.8A\mathrm{GeV}$ with a fast drop on both sides. The degree of stopping, which is shown to remain significantly below the expectations of a full stopping scenario, is found to be highly correlated to the amount of side flow.

Figure 1

Left panels: global side flow as a function of the scaled impact parameter (triangles: Erat selection; crosses: multiplicity selection). Right panels: global scaled transverse and longitudinal rapidity distributions for the Erat selection $b^{(0)}<0.15$. Data for three indicated system energies are shown. Systematic errors are discussed in the text.

Figure 2

Excitation functions (left) and size dependences (right) of the degree of stopping (upper panels) and maximal global side flow (lower panels). The dashed curves result from a correction for statistical fluctuations in the reaction plane orientation. The curve labeled “hydro” is an estimate of the hydrodynamic limit for the side flow. See the text.

Figure 3

Correlation between the maximal directed side flow and the degree of stopping. The line is a linear least squares fit to the data, which extend from $0.15A$ to $1.93A\mathrm{GeV}$.