In-plane retardation of collective expansion in Au + Au collisions

Using charged-particle-exclusive measurements of Au + Au collisions in the Bevalac’s EOS time projection chamber, we demonstrate the advantages of an alternative representation of the squeeze-out phenomenon where the speed of collective expansion is slowest in the plane of the reaction, and is modulated sinusoidally according to fragment azimuth relative to this plane. This simpler representation facilitates a highly comprehensive description of light fragment spectra and the three main categories of collective motion: sideward flow, squeeze-out, and radial expansion.